Difference between revisions of "OR/19/049 Geophysical (wireline) logs"

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Latest revision as of 10:01, 21 January 2020

Kearsey, T, Gillespie, M, Entwisle, D, Damaschke, M, Wylde, S, Fellgett, M, Kingdon, A, Burkin, J, Starcher, V, Shorter, K, Barron, H, Elsome, J, Barnett, M, and Monaghan, A. 2019. UK Geoenergy Observatories Glasgow: GGC01 cored, seismic monitoring borehole — intermediate data release. British Geological Survey Internal Report, OR/19/049.

Geophysical logging is the process of measuring the properties of a formation using sensors attached to a winch cable (wireline) suspended in the borehole. Measurements are made continuously down the borehole by raising or lowering the sensor tools. The property measurements are then converted to a standard series of geophysical logs including: Density, P-Wave Transit Time, Neutron Porosity etc.

Description of geophysical logging technology is beyond the scope of this report, there are a number of textbooks which cover the acquisition and interpretation of wireline logs including: Serra (1983)[1]; Hearst et al. (2000)[2] and Ellis and Singer (2007)[3]. Wireline logs have also been used extensively as part of the Integrated Ocean Drilling Program with a number of resources available online[note 1].

LAS format for conventional log data[edit]

File name: GGC01_Composite_Certified.las and 6 similar named files
Conventional geophysical logs are provided in LAS format[note 2], version 2.0. This is a column separated ASCII format. Almost all specialist logging software is capable of loading and interpreting geophysical log data in LAS format. In addition to this LAS files can also be viewed in any software capable of manipulating an ASCII text file, including Notepad (Windows), VI (Unix) or spreadsheets (e.g. Microsoft Excel).

Data provision of borehole imaging data in dlis fomat[edit]

File name: GGC01_Acoustic_2.dlis
Acoustic borehole image logging was acquired for borehole GGC01. When processed using specialist software this file provides an unwrapped interior borehole wall image. The image facilitates visualisation of the physical condition of the borehole’s wall, such as presence of breakouts, open fractures etc. and also some details of geological features visible on the borehole wall, such as intersections of some beds with the borehole and some types of discontinuity which are not open.

Borehole imaging data is provided in the form of Digital Log Interchange Standard (DLIS) files. This binary format cannot be read with anything other than specialist borehole imaging software, which is required to interpret the data files. The file was acquired and processed by Robertson Geo Ltd using the WellCAD software and the associated DLIS file integrity has been checked by BGS scientists using Schlumberger Techlog borehole imaging software.

Note: The Robertson Geoscience AWS imaging tool DLIS format is not supported by all specialist borehole imaging software and so additional processing stages may be needed to load the data. DLIS files contain array-formatted data, which prevented their conversion into the LAS (Log ASCII Standard) format used to report the other logging parameters. The borehole image logging data can however be viewed in the field prints, ‘GGC01_acoustic updated.pdf’.

Log acquisition metadata[edit]

Three LAS files are supplied with a standard metadata package defining the well metadata and acquisition (Table 7).

Table 7    Simplified well metadata header from LAS files.
PARAMETER UNIT VALUE DESCRIPTION
STRT M 0 First reference value
STOP M 198.856 Last reference value
STEP M 0.004 Step increment
NULL -9999 Missing value
WELL GGC01 Well name
FLD Glasgow Field
LOC Project_ GGERFSNS66SW
BJ 3754BGS ID_20650619
Location
PROV N/A Province
DATE 17-Dec-18 Date
COMPANY BGS Operator
Completion_date 14-Jan-19 DD-MMM-YYYY
CTRY Scotland COUNTRY
EGL M 9.66 Ground Level Elevation
EKB M 9.66 Datum Elevation
DREF MSL Permanent Datum
FL Glasgow Geographical area name
LCNM Robertsons Logging contractor
LMF GL Log Datum
LATI deg 55.8411448 Latitude
LONG deg -4.2213957 Longitude
ORIGINALWELLNAME GGC01 Well Name
OPER BGS British Geological Survey
SPDA 15-Nov-18 Spud Date
TD M 199 Drillers’ Depth
UNKNOWN GGC01 Full well title
WELL-ID 20650619 UNIQUE WELL
IDENTIFIER (BGSID)
WELL-NAME NS66SW/3754 Single Onshore Borehole
Index
Water_depth M 0 Water Depth
X M 260915 Easting
Y M 663109 Northing
TYPE_FLUID_IN_HOLE Water Drilling Fluid
TOP_LOGGED_INTERVAL 0.0 m Top Logged Depth
BTM_LOGGED_INTERVAL 198.86 m Bottom Logged Depth
RECORDED_BY KO Logging Engineer
WITNESSED_BY IJ Observer

GGC01_composite_certified.LAS[edit]

This file contains the main geophysical logs that define the geological succession that would typically be included in an industry composite plot.

Table 8    Contents of GGC01_Composite_Certified.
Parameter Units Description
DEPT M DEPTH
INC DEG Inc
CONDUCTIVITY US/CM Conductivity
TEMPERATURE DEGC Temperature
CAL_X MM Cal X
CAL_Y MM Cal Y
GAMMA API Gamma
AZ DEG Az
DENSITY GM/CC Density
BRD CPS BRD
HRD CPS HRD
PORS LPU Pors
NEAR CPS Near
FAR CPS Far
TX1-RX1 µS TX1-RX1
TX1-RX2 µS TX1-RX2
SLOWNESS µS/FT Slowness
RESISTIVITY OHMM Resistivity

GGC01_Flowmeter_Certified.LAS[edit]

This file contains the flowmeter outputs that show the fluid ingress into the well bore.

Table 9    Contents of GGC01_Flowmeter_Certified.LAS.
Parameter Units Description
DEPT M DEPTH
RATE_D4 RPM RATE d4
CABL_D4 M/MIN CABL d4
RATEU4 RPM RATEu4
CABLU4 M/MIN CABLu4
RATEU6 RPM RATEu6
CABLU6 M/MIN CABLu6
RATED6 RPM RATEd6
CABLD6 M/MIN CABLd6
RATED8 RPM RATEd8
CABLD8 M/MIN CABLd8
RATEU8 RPM RATEu8
CABLU8 M/MIN CABLu8

GGC01_Full_Waveform_Sonic_Certified.LAS[edit]

This is the full wave form sonic including the interval transit time between the multiple source receiver pairs that allow the detailed sonic profile to be constructed.

Table 10    Contents of GGC01_Full_Waveform_Sonic_Certified.LAS.
Parameter Units Description
DEPTH M Depth
SVEL µs/ft 5 Interval Transit Time
TA µs 1 Transit Time TX1-RX1
TB µs 2 Transit Time TX1-RX2
TC µs 3 Transit Time TX2-RX1
TD µs 4 Transit Time TX2-RX2

Summary composite log image files[edit]

File names: GGC01_Comp_Plot_1_200.pdf and GGC01_Comp_Plot_1_500.pdf
Two composite log image files are included in the data pack at scales of 1:200 and 1:500.

Footnote[edit]

References[edit]

  1. SERRA, O E. 1983. Fundamentals of well-log interpretation. Elsevier.
  2. HEARST, J R, NELSON, P H, PAILLET, F L. 1999. Well logging for physical properties: a handbook for geophysicists, geologists and engineers. 2nd Edition. Wiley.
  3. ELLIS, D V, and SINGER, J M. 2007. Well Logging for Earth Scientists. 2nd Edition. Springer. https://doi.org/10.1007/978-1-4020-4602-5