SCALMAN - SCAL Data Management

Rock property data input to petrophysical and reservoir engineering models requires reliable special core analysis (SCAL) data acquired from laboratory contractors. The full value of SCAL has often not been realized because the data have not been effectively audited and interpreted or reconciled with available well and log data. Many oil company personnel do not have the time nor the expertise to effectively specify, supervise, and interpret increasingly sophisticated core analysis programs. In many cases, operators have been forced to carry out additional and expensive core analyses because an inconsistent or inappropriate approach to the design and implementation of the core analysis program has been adopted. Too often SCAL data are overlooked, lab reports may lie around unopened for years before being used, and there is no audit trail. This results in unacceptable uncertainties in reservoir models.

Developing an effective relationship between the end user of core data and the data acquisition laboratory is critical to the success of any core analysis program. This demands a high level of expertise in the supervision of service contractors, and the critical analysis and interpretation of data.

Weatherford's SCALMAN services provide an integrated solution to SCAL data management and ensures a more authoritative, yet cost effective utilization of rock property data in reservoir exploitation and management strategies. The overriding objective is to reduce the value gap in hydrocarbons in place and reserves through the following key SCAL data management processes:

• SCAL program design
• Data acquisition
• Data quality control
• Data output
• Data interpretation
• Reservoir model data input

Weatherford's independence, experience and expertise will guarantee that you benefit from:

• Quality assured, fully documented, and traceable core test data
• Cost savings through the elimination of wasteful or inappropriate testing
• "Fast track" data application through continuous quality control during test program
• Direct cost savings through a reduction in the time your own staff spend in supervising SCAL programs and interpreting the data

Figure 1: SCALMAN Key Processes

SCAL Data Management Services

Effective design and supervision of SCAL programs are crucial. Weatherford works with you and your preferred core analysis service contractors to ensure an innovative and cost effective solution to the acquisition of reliable data.

• Design: Initially, the detailed objectives of the core data acquisition programs are defined and agreed upon. In partnership with your engineers and petrophysicists, Weatherford designs the SCAL program following an initial review to assess the validity and applicability of the current core database in relation to log, well and relevant reservoir data. Any limitations and omissions in the database, and any anomalous or inconsistent data that must be addressed in the core analysis programs are identified. We will advise on coring interval selection, core bit selection, potential application of mud invasion profiling using tracers, optimum drilling fluid selection, core sample preservation and conventional core analysis sampling, and testing procedures.
• Specification: Weatherford provides detailed core preparation procedures, test procedures, and quality-control and data reporting procedures to be adopted by the service laboratories. These are the foundation of the core audit trail.
• Tender Evaluation: If the work is put out to tender, Weatherford's technical evaluation will allow you to select the most appropriate contractor for any particular suite of tests, based on their technical capability and price, rather than contracting a single laboratory to perform the entire work program. This provides a more cost effective means of acquiring reliable SCAL data.

Data Acquisition

• Supervision: Ongoing lab supervision and test data quality control checks ensure that any problems or unusual, anomalous or inconsistent results can be identified during the test program, so that they can be rectified before the work is completed. Thereafter, it is too late, and costs will be incurred in retesting.
• Audit: We will ensure that complete records of the test methods and procedures together with laboratory experimental data are retained, so that there is a complete audit trail. These are not normally provided by service laboratories but are essential to a detailed understanding of the results of the core tests and will prove invaluable in future reservoir evaluation.

Data Quality Control

Weatherford's management of the data acquisition stage ensures the most reliable data during staged field development. However, our expertise also allows you to benefit when evaluating your current SCAL database such as: asset evaluation or re-evaluation, farm-ins, unitization and equity determinations. These data have been typically acquired from a number of different wells, usually by different laboratories, and are of varying vintage and quality.

Weatherford's SCAL data review will enable identification and elimination of suspect, anomalous, and inconsistent data which otherwise would adversely affect reservoir models.

Initially lab reports are scanned and data are provided in digital format. The test data are organized by well, by lab, by date, by type of test, and by geological zone, a process which aids data quality control. The subsequent data review includes:

• An assessment of core data sensitivity to experimental techniques and interpretation methods
• An assessment of the suitability of the data with specific reference to static and dynamic reservoir models

Diagnostic plots, data comparisons, and experimental data are used to identify anomalous, suspect, or plainly erroneous data. For example:

Figure 2: J Function Used to QC Capillary Pressure Data

Figure 3: Porosity Reduction Ratio Plot

Data Output

All suspect data are eliminated from the data acquisition database and we provide you with a digital database of quality-controlled SCAL data that can be used in data interpretation.

The SCAL data are categorized as:

• Only available
• Best available
• Fit for purpose

Data Interpretation

Data interpretation will depend on your requirements but might typically include:

• Reservoir zonation into different flow/hydraulic units
• Determination of effective reservoir stress at initial and final conditions
• Porosity compaction correction
• Archie or Shaly Sand log interpretation parameters (e.g. m, n, m*, n*)
• Averaging and normalization of capillary pressure data obtained using different fluid and test systems
• Development of a saturation-height model and comparison of the model results with direct core measurements and log water saturation estimates
• Assessment of the reliability and applicability of the current relative permeability database in relation to data requirements for reservoir simulation and available field and production data
• Endpoint data including S_wirr and ultimate S_ro
• Averaging and normalization of relative permeability data
• Integration of the core test results with other relevant well and log data, and the existing SCAL database
• Comparison and correlation of different data sets with a range of petrophysical parameters (e.g. S_wirr versus permeability, S_oi versus S_wirr, Archie parameters) by zone, facies or other relevant discriminator

Figure 4

We will provide you with a digital SCAL database which will allow future updates as and when new data are acquired. We will recommend opportunities, including further analysis work, for improvement of the reservoir models.

Reservoir Model Data Output

SCAL data are integrated with logs and other well and core data to provide the following data input to reservoir models:

Static Models

• Porosity correction and compaction factors
• Water saturation interpretation parameters
• Saturation-height functions

Dynamic Models

• Absolute to effective permeability transforms
• Initialization curves (Pc and kr) for ECLIPSE Ô and other simulators
• Upscaled (pseudoised) relative permeability curves

Figure 5

SCAL Data Management Expertise

Weatherford's staff are some of the foremost experts in core analysis in the industry, with many years of practical experience in the acquisition and interpretation of core data. The consultancy expertise which Weatherford can provide has been enhanced by giving many training courses in core analysis and petrophysics all over the world.

Weatherford offers the multi-disciplinary capability required to address the technical challenges in core analysis data acquisition and its integration with petrophysical and well data. Staff within Weatherford have extensive experience in core analysis, geomechanical analysis, petrophysics, well test analysis, in-place and reserves evaluation, production engineering, and reservoir simulation.

Recent SCAL Data Management Projects

• Role as expert in major North Sea equity redetermination which involved rigorous review of SCAL data. Resolved disputes centering around water saturation interpretation, porosity compaction corrections and saturation-height models.
• Review, audit, and interpretation of SCAL data for field development evaluations worldwide.
• Project management of the core analysis programs related to the development of major North Sea fields. Each involved review of the existing core database, preparation of detailed test specifications and reporting protocols, contractor supervision, preparation of fully-documented interpretative reports, and the integration and reconciliation of core data with other well and reservoir data.
• A field-wide petrophysical study to quantify the effects of wettability contamination on core-derived Archie parameters used in water saturation estimation. Re-interpretation of the core and log data, in the light of wettability-controlled data sensitivity, in conjunction with material balance studies, indicated that gas reserves could be effectively increased by 10%.
• Several integrated production log, core analysis, and petrophysical studies to validate residual gas saturation in sandstone and chalk reservoirs as a result of aquifer influx.

Further Pseudo Upscaling consultancy can also be delivered. Read More ...