BOREHOLE IMAGING SIG

Vision Statement:

The purpose of this SIG is to provide a forum for those interested in borehole imaging to conduct technical discussions concerning tool design, data acquisition and delivery, applications, interpretation, and to develop/promote industry standards.

Meet the Board:
Chair: Christian Rambousek, NiMBUC Geoscience
Vice Chair: Chandramani Shrivastava, Schlumberger 
Secretary: Alex Kaye, Lloyd's Register 
Treasurer: Peter Barrett, Halliburton

All of the BHI SIG board members can be contacted via this single email alias: [email protected]


SPWLA Borehole Imaging SIG: initial discussion

Present: Tegwyn Perkins, Peter Barrett and Bernd Ruehlicke
Date: 13-Oct-2021
Location: Houston, TX
Time: 12:00-14:00.

The SPWLA Borehole Imaging SIG was founded over lunch by Peter, Bernd and Tegwyn.  First on the agenda was to begin to establish a framework for Dip pick results inspired by the talks at the regional EAGE workshops in April and  September from Christian Rambousek.

The draft By-Laws for this SIG were crafted by Tegwyn Perkins.

Background (from Christian):

Introduction:
In 2020 the initiative to establish a standardization for borehole image log related data has been established by a number of geoscience consultancies, geoscience specialists from O&G operators who are involved with BHI Data, software companies and service companies. The kick-off of this initiative was presented at the first EAGE borehole Geology Workshop Asia Pacific in early 2021 and received very positive feedback and further interest to participate in this initiative.

Borehole image logs (BHI) are one of the key sources for determining structural models, depositional environments and flow units. Their ability to record bedding and fracture geometries along with petrophysical properties make BHI a unique data source for a variety of disciplines. Stratigraphy, Reservoir Engineering, Geomechanics, Hydrodynamics, and Discrete Fracture Network (DFN) modeling each have their own requirements for BHI derived data. DFN models, for instance, require fracture geometry and bedding relationship, as well as BHI geophysical data that can be used to understand fracture aperture, size, and hydrodynamic properties.

Currently, a lack of data processing and reporting standards limits the usefulness of many expensive and complex BHI logging records. Valuable fracture geometry and geophysical attributes data can be lost in transferring between data formats. Worse, ambiguity in fracture coding can lead to significant errors in geological, geomechanical, and hydrodynamic models built on BHI data.

Motivation:
This paper presents an example of how such BHI standardization could benefit the community by improving dip data – including fracture and bedding feature identification, truncation, and interpretation of complete and incomplete sinewaves. Currently, without standards transferring bedding dip data from one software to another can be error prone, time consuming and problematic. If successful, this consortium will improve how bedding dip data and attributes are defined, stored, and transferred.

Similarly, fractures also come with their own unique properties, i.e., complete, partial, age (hierarchy), width etc. Whilst not all attributes may be defined during an analysis, a data standard is needed which recognizes both the level of confidence in assigned attributes, and provides a mechanism for dealing with missing data. Consistent standards will enable maximum (and consistent) use of BHI derived fracture data.

BHI also are used to derive valuable attributes including stress related failures, such as borehole breakouts and drilling induced tensile fractures. The consortium will also

seek to improve how this information is processed, stored, and transferred.

Conclusions:
This abstract is designed to gauge interest for this initiative and add new members to the consortium to work on a timeline for definitions of non-proprietary, cross-industry standards. After receiving input from various disciplines, working with borehole image log data (e.g. geoscientists, reservoir engineers, geo-modelling experts, geomechanical experts or petrophysicists) we would also like to invite more software companies, programmers, and professional organizations such as EAGE, SPWLA or other relevant organizations. The most relevant issues of data transfer will be identified and documented to highlight the key features needed for a successful BHI data standard. The objective is the smooth transfer of vital reservoir properties between all relevant packages, increasing accuracy and reducing time spent on format conversions. At this early stage, opinions and potential volunteers are sought and will be connected to the existing consortium to discuss a possible roadmap and milestones of this process.

This presentation is designed to build the awareness of the issue of BHI data standards and to attract a diverse group of professionals developing, interpreting, and applying BHI data.

Initial Agreement: The vehicle for data delivery must be a comma separated human readable ascii file, as this is the most versatile. To allow adding Log and curve attributes in a consistent matter, the best compromise is to use LAS3 with comma a delimiter. For consumers not able to load a LAS3 they can still just cut off the header and read the bulk data as a standard CSV file.


Thoughts on what should be included on a "standard" dip data set.

All results are TRUE NORTH referenced. Partial sine depth is the depth of the center of the partial sine and not the depth of the theoretical full sine.

Header must contain:

MDEC (Magnetic declination) MINC (Magnetic inclination) MFIN (Magnetic Field intensity) LAT (decimal with sign) LONG (decimal with sign) Definition of dip data types

Relevant Customer and Well Information (Names, Field, API etc.)

Curves to be exported:

Measured Depth: unit ft/m

DIP : True dip  unit deg (not this dega nonsense.  Temperature is degC or degF or degK but azimuthal values are simply   deg.)

AZIM: True azimuth. Unit deg DIPTYPE : Ascii diptype used QUALITY: 0 to 1, 1 is best.

BDIP: Apparent dip rel to borehole  Unit deg BAZI : Apparent azimuth rel to borehole Unit deg

HEIGHT: Used for Breakouts and Tensile failures to tell over how long an interval parallel to the borehole they were picked. Suggested unit is IN. (Inches) WIDTH: Also for Breakouts and Tensile failures, defining the width in deg relative to the borehole circumference the features was picked,. Unit deg OMEGA: The angle of the Tensile relative to the borehole axis.  
Exact definition still open for discussion. Unit deg (between 0-180)

GR: Gamma from the image log unit GAPI HAZI  Unit deg

DEVI,  Unit deg

P1AZ [never ever ever use P1NO]  Unit deg

RB : 0 for LWD tools oriented to wards H-S (or a constant depending if left, center to right edge of first sector used). Unit deg

CALI :  A caliper used for picking. Unit IN

DOI:   Depth of investigation used for that particular pick. Note, the dip picks could have been based on 3 different tools over the same interval (a LWD density, a WL resistivity and a WL acoustic) causing 3 different DOIs , Unit IN.  CALI+2 * DOI is the actual diameter used for the particular pick.

DIPAUX: Some form of apparent Left and apparent right azimuth NULL data is -999.25