https://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&feed=atom&action=historyOR/15/066 Hydraulic fracturing - Revision history2024-03-29T10:40:18ZRevision history for this page on the wikiMediaWiki 1.41.0https://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44308&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:37:02Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:37, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name="<del style="font-weight: bold; text-decoration: none;">></del>API 2009">API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name="API 2009">API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44307&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:36:31Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:36, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, <del style="font-weight: bold; text-decoration: none;"> </del>2009<ref name=">API 2009"<del style="font-weight: bold; text-decoration: none;"><</del>API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<ins style="font-weight: bold; text-decoration: none;">></ins>API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44306&oldid=prevAjhil: /* State of stress */2019-12-03T12:35:32Z<p><span dir="auto"><span class="autocomment">State of stress</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:35, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Predicting pore pressure range with depth is more complex. Generally, a hydrostatic pore pressure (''u'') can be defined by the weight of a water column equal to depth, giving a pore pressure gradient of 10&nbsp;MPa/km. Therefore pore pressure is likely to range between 10 and 50 MPa in European shale gas operations. However in basins that are bound by low permeability barriers, such as shale cap rock or faults with high clay content, deformation can result in a raised pore pressure, referred to as overpressure. Overpressure can also be observed in shale gas units, Charpentier & Cook (2011)<ref name="Charpentier 2011"></ref> report that it is a desirable attribute in shale gas reservoirs.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>Predicting pore pressure range with depth is more complex. Generally, a hydrostatic pore pressure (''u'') can be defined by the weight of a water column equal to depth, giving a pore pressure gradient of 10&nbsp;MPa/km. Therefore pore pressure is likely to range between 10 and 50 MPa in European shale gas operations. However in basins that are bound by low permeability barriers, such as shale cap rock or faults with high clay content, deformation can result in a raised pore pressure, referred to as overpressure. Overpressure can also be observed in shale gas units, Charpentier & Cook (2011)<ref name="Charpentier 2011"></ref> report that it is a desirable attribute in shale gas reservoirs.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The introduction of pore-fluid under pressure has a profound effect on the physical properties of porous solids (Hubbert & Rubey, 1961<ref name="Hubbert 1961">Hubbert, M K, and Rubey, W W. (1961) Role of fluid pressure in mechanics of overthrust faulting; reply to discussion: ''Geological Society of America Bulletin'', '''72''', pp.1445–1451.</ref>; Terzaghi, 1943<ref name="Terzaghi 1943">Terzaghi, K. (1943). ''Theoretical Soil Mechanics''. New York, John Wiley.</ref>). In a saturated porous system, the fluid supports some proportion of the applied load, creating fluid-pressure (''u''), which acts in the opposite direction to load lowering overall stress exerted through mineral grains. The addition of ''u ''lowers available stress by an amount that is proportional to the pore pressure. The law of effective stress thus dictates that strength is determined not by confining pressure alone, but by the difference between confining and pore-pressures. In simple drained tests, ''u ''remains constant and the observed effective stress is similar to the applied load. Conversely, if the pore-fluid system is closed, ''u ''rises in proportion to the applied load as pore space is reduced, significantly lowering the overall effective stress. Thus, the mechanical response of rocks to applied load is significantly affected by the ability of fluids to drain. Many rocks have been shown to follow the law of effective stress, including shale (Handin ''et al.'', 1963<ref name="Handin 1963">Handin, J, Hager, R V, Jr, Friedman, M, and Feather, J N. (1963). Experimental deformation of sedimentary rocks under confining pressure; pore pressure tests. ''Bulletin of the American Association of Petroleum Geologists'', '''47''', pp.717–755.</ref>; Kwon ''et al.'', 2001<ref name="Kwon 2001">Kwon, O, Kronenberg, A K, Gangi, A<del style="font-weight: bold; text-decoration: none;">.</del>F<del style="font-weight: bold; text-decoration: none;">.</del>, and Johnson, B. (2001) Permeability of Wilcox Shale and its effective pressure law. Journal of Geophysical Research, B, Solid Earth and Planets, 106, pp. 19,339-19,353.</ref>). Kwon ''et al. ''(2001)<ref name="Kwon 2001"></ref> showed that the effective pressure coefficient χ was equal to 0.99&nbsp;±&nbsp;0.06 for Wilcox shale. This value is indistinguishable from unity and demonstrates that the law of effective stress is obeyed in this particular shale formation. The poroelastic effect (after Biot, 1941<ref name="Biot 1941">Biot, M A. (1941). General theory of three-dimensional consolidation. ''Journal of Applied Physics'', '''12''', pp.155–164.</ref>) is added to the law of effective stress to account for the partial transfer of pore-pressure to the granular framework. Therefore at the target depth range for shale gas the effective stress is likely to range between 3.8 and 65 MPa, assuming no overpressure.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The introduction of pore-fluid under pressure has a profound effect on the physical properties of porous solids (Hubbert & Rubey, 1961<ref name="Hubbert 1961">Hubbert, M K, and Rubey, W W. (1961) Role of fluid pressure in mechanics of overthrust faulting; reply to discussion: ''Geological Society of America Bulletin'', '''72''', pp.1445–1451.</ref>; Terzaghi, 1943<ref name="Terzaghi 1943">Terzaghi, K. (1943). ''Theoretical Soil Mechanics''. New York, John Wiley.</ref>). In a saturated porous system, the fluid supports some proportion of the applied load, creating fluid-pressure (''u''), which acts in the opposite direction to load lowering overall stress exerted through mineral grains. The addition of ''u ''lowers available stress by an amount that is proportional to the pore pressure. The law of effective stress thus dictates that strength is determined not by confining pressure alone, but by the difference between confining and pore-pressures. In simple drained tests, ''u ''remains constant and the observed effective stress is similar to the applied load. Conversely, if the pore-fluid system is closed, ''u ''rises in proportion to the applied load as pore space is reduced, significantly lowering the overall effective stress. Thus, the mechanical response of rocks to applied load is significantly affected by the ability of fluids to drain. Many rocks have been shown to follow the law of effective stress, including shale (Handin ''et al.'', 1963<ref name="Handin 1963">Handin, J, Hager, R V, Jr, Friedman, M, and Feather, J N. (1963). Experimental deformation of sedimentary rocks under confining pressure; pore pressure tests. ''Bulletin of the American Association of Petroleum Geologists'', '''47''', pp.717–755.</ref>; Kwon ''et al.'', 2001<ref name="Kwon 2001">Kwon, O, Kronenberg, A K, Gangi, A F, and Johnson, B. (2001) Permeability of Wilcox Shale and its effective pressure law. Journal of Geophysical Research, B, Solid Earth and Planets, 106, pp. 19,339-19,353.</ref>). Kwon ''et al. ''(2001)<ref name="Kwon 2001"></ref> showed that the effective pressure coefficient χ was equal to 0.99&nbsp;±&nbsp;0.06 for Wilcox shale. This value is indistinguishable from unity and demonstrates that the law of effective stress is obeyed in this particular shale formation. The poroelastic effect (after Biot, 1941<ref name="Biot 1941">Biot, M A. (1941). General theory of three-dimensional consolidation. ''Journal of Applied Physics'', '''12''', pp.155–164.</ref>) is added to the law of effective stress to account for the partial transfer of pore-pressure to the granular framework. Therefore at the target depth range for shale gas the effective stress is likely to range between 3.8 and 65 MPa, assuming no overpressure.</div></td></tr>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44305&oldid=prevAjhil: /* Description of the hydraulic fracturing process */2019-12-03T12:34:17Z<p><span dir="auto"><span class="autocomment">Description of the hydraulic fracturing process</span></span></p>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In recent years effort has been made to increase fracture populations through various advanced hydraulic fracturing techniques. These include the Zipper and Texas Two-Step methods. In the Zipper technique two horizontal wells are stimulated simulateously to maximize stress perturbations near the tips of each fracture (Rafiee et al., 2012<ref name="Rafiee 2012">Rafiee, M, Soliman, M Y, and Pirayesh, E. (2012). Hydraulic fracturing design and optimization: a modification to zipper frac. In ''SPE Annual Technical Conference and Exhibition''. Society of Petroleum Engineers.</ref>). This technique has been adapted into the Modified Zipper technique where fractures are initiated in a staggered pattern, creating a more complex fracture pattern (Rafiee et al., 2012<ref name="Rafiee 2012"></ref>). In the Texas Two-Step method (Soliman et al., 2010<ref name="Soliman 2010">Soliman, M Y, East, L E, and Augustine, J R. (2010). Fracturing design aimed at enhancing fracture complexity. In ''SPE EUROPEC/EAGE Annual Conference and Exhibition''. Society of Petroleum Engineers.</ref>) repeat stimulation is performed in an alternate sequence. In conventional stimulation, as described above, the well can be considered as stimulations sites numbered 1 to 10. Conventionally stimulation occurs in order of 1, 2, 3, etc. With Texas Two-Step the stimulation sequence is 1, 3, 2, 4, 6, 5, etc. Any change in fracturing sequence alters the stress in the area between fractures and activates stress-relieved fractures, which can create a complex network of fractures connected to the main hydraulic fractures (Rafiee et al., 2012<ref name="Rafiee 2012"></ref>). This method has been shown to create a more complex fracture network (Roussel & Sharma, 2011<ref name="Roussel 2011">Roussel, N P, and Sharma, M M. (2011). Optimizing fracture spacing and sequencing in horizontal-well fracturing. ''SPE Production & Operations'', '''26'''(02), pp.173–184.</ref>).</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>In recent years effort has been made to increase fracture populations through various advanced hydraulic fracturing techniques. These include the Zipper and Texas Two-Step methods. In the Zipper technique two horizontal wells are stimulated simulateously to maximize stress perturbations near the tips of each fracture (Rafiee et al., 2012<ref name="Rafiee 2012">Rafiee, M, Soliman, M Y, and Pirayesh, E. (2012). Hydraulic fracturing design and optimization: a modification to zipper frac. In ''SPE Annual Technical Conference and Exhibition''. Society of Petroleum Engineers.</ref>). This technique has been adapted into the Modified Zipper technique where fractures are initiated in a staggered pattern, creating a more complex fracture pattern (Rafiee et al., 2012<ref name="Rafiee 2012"></ref>). In the Texas Two-Step method (Soliman et al., 2010<ref name="Soliman 2010">Soliman, M Y, East, L E, and Augustine, J R. (2010). Fracturing design aimed at enhancing fracture complexity. In ''SPE EUROPEC/EAGE Annual Conference and Exhibition''. Society of Petroleum Engineers.</ref>) repeat stimulation is performed in an alternate sequence. In conventional stimulation, as described above, the well can be considered as stimulations sites numbered 1 to 10. Conventionally stimulation occurs in order of 1, 2, 3, etc. With Texas Two-Step the stimulation sequence is 1, 3, 2, 4, 6, 5, etc. Any change in fracturing sequence alters the stress in the area between fractures and activates stress-relieved fractures, which can create a complex network of fractures connected to the main hydraulic fractures (Rafiee et al., 2012<ref name="Rafiee 2012"></ref>). This method has been shown to create a more complex fracture network (Roussel & Sharma, 2011<ref name="Roussel 2011">Roussel, N P, and Sharma, M M. (2011). Optimizing fracture spacing and sequencing in horizontal-well fracturing. ''SPE Production & Operations'', '''26'''(02), pp.173–184.</ref>).</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> </div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div> </div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>The complete fracturing process may be repeated when the flow of hydrocarbons begins to decrease, necessitating the well to be re-stimulated. Re-fracturing is typically carried out when the production rates have declined beyond the expected reservoir depletion rate (ICF, 2009<ref name="ICF 2009"><del style="font-weight: bold; text-decoration: none;">ICF. (2009). Technical assistance for the draft Supplemental Generic EIS: Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to develop the Marcellus Shale and other low permeability gas reservoirs. Agreement No.9679. Submitted to NYSERDA. Albany, NY: ICF Incorporated.</del></ref>). In examples from the Barnett shale, wells were re-stimulated when production declined by between 50–85% of the original production rate (ICF, 2009<ref name="ICF 2009">ICF. (2009). Technical assistance for the draft Supplemental Generic EIS: Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to develop the Marcellus Shale and other low permeability gas reservoirs. Agreement No. 9679. Submitted to NYSERDA. Albany, NY: ICF Incorporated.</ref>). However, experience in the states has shown that re-stimulation is likely to be infrequent; either once every 5–10 years, if at all (NYSED, 2011<ref name="NYSED 2011">NYSDEC. (2011). Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high- volume hydraulic fracturing to develop the Marcellus Shale and other low-permeability gas reservoirs. Revised draft. Albany, NY: ''New York State Department of Environmental Conservation''.</ref>). Economics will drive the decision on re-stimulation.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>The complete fracturing process may be repeated when the flow of hydrocarbons begins to decrease, necessitating the well to be re-stimulated. Re-fracturing is typically carried out when the production rates have declined beyond the expected reservoir depletion rate (ICF, 2009<ref name="ICF 2009"></ref>). In examples from the Barnett shale, wells were re-stimulated when production declined by between 50–85% of the original production rate (ICF, 2009<ref name="ICF 2009">ICF. (2009). Technical assistance for the draft Supplemental Generic EIS: Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to develop the Marcellus Shale and other low permeability gas reservoirs. Agreement No. 9679. Submitted to NYSERDA. Albany, NY: ICF Incorporated.</ref>). However, experience in the states has shown that re-stimulation is likely to be infrequent; either once every 5–10 years, if at all (NYSED, 2011<ref name="NYSED 2011">NYSDEC. (2011). Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high- volume hydraulic fracturing to develop the Marcellus Shale and other low-permeability gas reservoirs. Revised draft. Albany, NY: ''New York State Department of Environmental Conservation''.</ref>). Economics will drive the decision on re-stimulation.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The process of hydraulic fracturing will be tailored for each different geological formation. The properties of the formation and the ''in situ ''pressure conditions will govern much of the process, such as the fluid injection pressure and the number of stages needed. Shale formations can be heterogeneous and anisotropic so the physical properties of the shale will need to be defined accurately in order for the hydraulic fracturing process to be appropriately managed and as cost effective as possible.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>The process of hydraulic fracturing will be tailored for each different geological formation. The properties of the formation and the ''in situ ''pressure conditions will govern much of the process, such as the fluid injection pressure and the number of stages needed. Shale formations can be heterogeneous and anisotropic so the physical properties of the shale will need to be defined accurately in order for the hydraulic fracturing process to be appropriately managed and as cost effective as possible.</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44304&oldid=prevAjhil: /* Stages of shale gas extraction */2019-12-03T12:33:41Z<p><span dir="auto"><span class="autocomment">Stages of shale gas extraction</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:33, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Shale gas extraction consists of three stages (Mair ''et al.'', 2012<ref name="Mair 2012"><del style="font-weight: bold; text-decoration: none;">Mair, R, Bickle, M, Goodman, D, Koppelman, B, Roberts, J, Selley, R, Shipton, Z, Thomas, H, Walker, A, Woods, E, and Younger, P L. (2012). Shale Gas Extraction in the UK: a Review of Hydraulic Fracturing. ''Royal Society and Royal Academy of Engineering'', London, pp.76.</del></ref>):</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Shale gas extraction consists of three stages (Mair ''et al.'', 2012<ref name="Mair 2012"></ref>):</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* '''Exploration. '''A small number of vertical wells (perhaps only two or three) are drilled and fractured to determine if shale gas is present and can be extracted. This exploration stage may include an appraisal phase where more wells (perhaps 10 to 15) are drilled and hydraulically fractured to characterize the shale; examine how fractures will tend to propagate; and establish if the shale could produce gas at commercially viable rates. Further wells may be drilled (perhaps reaching a total of 30) to ascertain the long-term economic viability of the shale.</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>* '''Exploration. '''A small number of vertical wells (perhaps only two or three) are drilled and fractured to determine if shale gas is present and can be extracted. This exploration stage may include an appraisal phase where more wells (perhaps 10 to 15) are drilled and hydraulically fractured to characterize the shale; examine how fractures will tend to propagate; and establish if the shale could produce gas at commercially viable rates. Further wells may be drilled (perhaps reaching a total of 30) to ascertain the long-term economic viability of the shale.</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44303&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:33:09Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:33, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"><del style="font-weight: bold; text-decoration: none;">report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</del></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 (King 2012)<ref name="King 2012"></ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44302&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:32:24Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:32, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 King <del style="font-weight: bold; text-decoration: none;">(</del>2012<ref name="King 2012"> report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref><del style="font-weight: bold; text-decoration: none;">) </del>metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 <ins style="font-weight: bold; text-decoration: none;">(</ins>King 2012<ins style="font-weight: bold; text-decoration: none;">)</ins><ref name="King 2012">report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44301&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:31:36Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:31, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000<ref name="King 2012"><del style="font-weight: bold; text-decoration: none;">King (2012) </del>report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000 <ins style="font-weight: bold; text-decoration: none;">King (2012</ins><ref name="King 2012"> report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref><ins style="font-weight: bold; text-decoration: none;">) </ins>metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44300&oldid=prevAjhil: /* Fracturing fluids */2019-12-03T12:29:25Z<p><span dir="auto"><span class="autocomment">Fracturing fluids</span></span></p>
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:29, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{| class="wikitable"</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>{| class="wikitable"</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><span id="Table 1"></span></div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div><span id="Table 1"></span></div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>|+ Table 1&nbsp;&nbsp;&nbsp;&nbsp;Fracture fluid additives (From NYSDEC, 2011<ref name="NYSDEC 2011">NYSDEC. (2011). Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to develop the Marcellus Shale and other low-permeability gas reservoirs. Revised draft. Albany, NY: ''New York State Department of Environmental Conservation''.</ref>; Broomfield & Donovan, 2012<ref name="Broomfield 2012"><del style="font-weight: bold; text-decoration: none;">Broomfield, M, and Donovan, B. (2012). Evidence: Monitoring and control of fugitive methane from unconventional gas operations. ''The Environment Agency'', Bristol, UK, pp.134.</del></ref>)</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>|+ Table 1&nbsp;&nbsp;&nbsp;&nbsp;Fracture fluid additives (From NYSDEC, 2011<ref name="NYSDEC 2011">NYSDEC. (2011). Supplemental Generic Environmental Impact Statement on the Oil, Gas and Solution Mining Regulatory Program. Well permit issuance for horizontal drilling and high-volume hydraulic fracturing to develop the Marcellus Shale and other low-permeability gas reservoirs. Revised draft. Albany, NY: ''New York State Department of Environmental Conservation''.</ref>; Broomfield & Donovan, 2012<ref name="Broomfield 2012"></ref>)</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|- style="vertical-align:top;"</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>|- style="vertical-align:top;"</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>| style="background-color: #dcdcdc;" | '''Additive type'''</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>| style="background-color: #dcdcdc;" | '''Additive type'''</div></td></tr>
</table>Ajhilhttps://earthwise.bgs.ac.uk/index.php?title=OR/15/066_Hydraulic_fracturing&diff=44299&oldid=prevAjhil: /* Direction of drilling */2019-12-03T12:29:00Z<p><span dir="auto"><span class="autocomment">Direction of drilling</span></span></p>
<table style="background-color: #fff; color: #202122;" data-mw="interface">
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<td colspan="2" style="background-color: #fff; color: #202122; text-align: center;">Revision as of 12:29, 3 December 2019</td>
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<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Direction of drilling==</div></td></tr>
<tr><td class="diff-marker" data-marker="−"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #ffe49c; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000<ref name="King 2012">King (2012) report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"><del style="font-weight: bold; text-decoration: none;">Arthur, J D, Bohm, B, Coughlin, B J, and Layne, M. (2008). Evaluating the environmental implications of hydraulic fracturing in shale gas reservoirs. Tulsa, OK: ALL Consulting.</del></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td><td class="diff-marker" data-marker="+"></td><td style="color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #a3d3ff; vertical-align: top; white-space: pre-wrap;"><div>Hydraulic fracturing requires the drilling of a borehole to the target depth. Advances in drilling techniques have meant that it is now possible to drill both vertically and horizontally (created by deviating a vertical well until horizontal). The advantage to horizontal drilling is that there is a larger surface area in contact with the target formation, meaning there is the potential for a greater reservoir drained volume achieved and increased flow of hydrocarbons into the well. Hydraulic fractures tend to propagate perpendicularly to the direction of least principal stress, following the direction of maximum principal stress (API, 2009<ref name=">API 2009"<API. (2009). Hydraulic fracturing operations: well construction and integrity guidelines. API guidance document HF1, ''American Petroleum Institute:'' Washington DC.</ref>). As a result, horizontal wells are drilled in the direction of the minimum principal stress. Experience in the Marcellus Shale in Pennsylvania shows that horizontal wells may extend up to 3,000<ref name="King 2012">King (2012) report typical horizontal lengths ranging from 2,000 ft to 6,000–ft (600–1830&nbsp;m), with extremes of 12&nbsp;000 ft or more (3,660&nbsp;m).</ref> metres laterally from the well pad (Arthur ''et al.'', 2008<ref name="Arthur 2008"></ref>). Therefore the total length of the well could be in the region of depth + 3,000&nbsp;m, therefore up to 6,000 metres in length.</div></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><br></td></tr>
<tr><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td><td class="diff-marker"></td><td style="background-color: #f8f9fa; color: #202122; font-size: 88%; border-style: solid; border-width: 1px 1px 1px 4px; border-radius: 0.33em; border-color: #eaecf0; vertical-align: top; white-space: pre-wrap;"><div>==Stages of shale gas extraction==</div></td></tr>
</table>Ajhil