ARC Group’s "ResQ^TM" Approach and Methodology to Reservoir Characterization

Our 25-year experience in oil and gas production and field re-development and reactivation services is offered to perspective clients through our ResQ^TM approach to reservoir characterization. ResQ^TM is focused on increasing the recovery efficiency of mature oil and gas fields through thorough integrated reservoir characterization programs and includes determination of the reservoir architecture as a framework within which to evaluate petrophysical, production, saturation, and production data. Recent advances in industry’s understanding of sequence stratigraphy, depositional systems, diagenesis and porosity evolution, geophysics, and production analysis—much of which were pioneered by our ResQ^TM technical staff—have made reservoir characterization an extremely sophisticated enterprise.

Principal ResQ^TM project objectives and services are to delineate the location and the volumes of in-situ and remaining oil and gas reserves, and to develop the appropriate advanced recovery strategies for maximizing recovery efficiency in these reservoirs. Critical to this effort is identification of primary and secondary fluid flow paths, as well as the characterization of intrareservoir flow. Detailed knowledge of regional and local structure, genetic sequence-stratigraphic stacking patterns, reservoir lithofacies architecture, diagenetic overprint, and resulting reservoir compartments, combined with production information, is essential to ResQ^TM achieving the goal of increased production.

ResQ^TM Approach

Our ResQ^TM approach is a multi-task ResQ^TM workflow service program (Figure 1). The following is a discussion of the ARC Group’s services that are provided to the client both internationally in the clients offices and/or at our head offices in Austin, Texas. This overview of the ResQ^TM services is provided to the client prior to beginning the program so that both the client and ARC Group can define the pathway that will be followed from the beginning of the project, to include milestones reached and scheduled tasks accomplished. Both the client and ARC Group can monitor the progress to date and achievements and project goals.  

Figure 1. ARC Group’s trademark “ResQ^TM” approach will define the flow paths and activities planned in field characterization studies.

ResQ^TM Activity I: The structural and stratigraphic framework of the field area must be defined and quantified. Because reservoir attributes and drainage are facies controlled, their three-dimensional extent and distribution will be governed by facies architecture. Definition of facies composition and extent (reservoir architecture) facilitates prediction of the spatial arrangement of reservoir properties and the location of the original (and remaining) oil and/or in the field. This activity integrates stratigraphic, sedimentological and seismic analyses.

ResQ^TM Activity II: This part of the project is designed to delineate and quantify the residency and volume of oil by delineating spatial variation of petrophysical attributes—in particular, permeability, porosity, oil/gas saturation and hydrocarbon pore volume.

ResQ^TM Activity III: The specific objective of the production-engineering phase of the study is to determine primary and secondary fluid flow trends through development of pressure, watercut, and cumulative production maps of completion intervals.  These maps will support the development of optimum recovery strategies.

ResQ^TM Activity IV: In this activity all data and interpretations will be integrated into a quantified geological, geophysical, petrophysical and engineering model of the reservoirs. The integrated model will be the basis for the construction of a geologically constrained numerical model of the reservoir.

ResQ^TM Activity V: In this activity the quantified reservoir model determined in Activity IV will be used to determine a multi-component portfolio of reservoir development opportunities including recompletions, new infill wells, advanced drilling technologies such as vertical and multilateral wells, and secondary recovery.
           

ResQ^TM ACTIVITY I:
Geologic and Seismic Characterization of the Structural and Stratigraphic Framework

This phase of the study involves stratigraphic, sedimentological and seismic analysis of reservoirs.  The purpose of this activity is to identify the stratigraphic and structural architecture of the area through detailed seismic and stratigraphic study; the integration of the results of these studies; and the use of seismic attributes to constrain the mapping of the reservoir system at the exploration, field and between-well scale. 

Focus Area 1. Correlation and high-resolution genetic stratigraphic framework
A series of stratigraphic and structural cross sections are constructed and used to determine the stratigraphic framework complexity. Correlation is based on sequence stratigraphic characteristics, with an emphasis on through-going shale sections that correspond to condensed sections (equivalent to maximum flooding surfaces) and to unconformities. Particular attention is given to sediment stacking patterns and to identifying genetic units.  Well-based sections and the associated tops and fault cuts are tied to equivalent seismic data sections to identify fault and sedimentary stacking patterns. Sandstone content and depositional trends are mapped within each of the correlated intervals established in the sequence stratigraphic framework. Depositional environments interpreted from core descriptions are calibrated to petrophysical log patterns and interpolated between cored wells. Depositional systems tract architecture and reservoir stacking patterns are identified. Map products include net sandstone-isopach maps and log-facies maps for delineation of depositional facies for each of the major reservoir intervals.  Mapping of sedimentological facies is constrained by seismic attribute maps.

ResQ^TM SEDIMENTOLOGICAL SERVICES PROVIDED

1. Establish correlation framework
2. Construction of stratigraphic database necessary for depositional history and sand distribution analysis
3. Description of available cores and comparison with well logs for facies analysis and reservoir property prediction
4. Extrapolation of cored well data to those wells without cores
5. Net sand and log facies mapping of all reservoirs.
6. Paleoenvironmental interpretations of each reservoir

Focus Area 2. Seismic structural framework
The structural framework is determined by integrating well log correlations with available seismic data. Based on data available, all 2 and/or 3 D seismic data is processed and interpreted. Structure maps are prepared for all principal reservoir surfaces.

The task structure of this activity is as follows:

ResQ^TM GEOPHYSICAL SERVICES PROVIDED

1. Review of geophysical information
2. Seismic Interpretation
   1. Synthetic seismograms
   2. Identification and correlation of all major seismic horizons                                             
   3. Interpretation of seismic horizons          
   4. Faults patterns
   5. Building velocity model and
   6. Mapping in time and depth of seismic horizons. Maps will be constructed at the top and base of the seismic horizons
3. Analysis of seismic attributes
   1. Correlation and mapping of attributes
   2. Integration of seismic attributes and petrophysical properties
   3. Integration of mapped horizons with seismic attributes

ResQ^TM ACTIVITY II:
Advanced Petrophysical Analysis

This step is of critical importance as it is the basis for all aspects of resource quantification including volumetrically, stratigraphically, and areally. Typical petrophysical services would involve the following:

ResQ^TM PETROPHYSICAL SERVICES PROVIDED

1. Assemble database of all available production, salinity, and pressure data
2. Depth shift all curves to match geological top reference curve
3. Correct all key curves for environmental effects
4. Provide edited curves to geologists for correlation framework
5. Integrate available core and production data with well log data on key wells
6. Calibrate porosity, shale volume, water saturation, and permeability to core data
7. Calibrate permeability to well test or production decline data
8. Normalize remaining field wells to key reference wells
9. Analyze wells for porosity, shale volume, water saturation, permeability, and net pay
10. Provide team with results of analyses to integrate with maps

To the extent the petrophysical data allow, the time-tested petrophysical analysis procedure and services that we apply consists of the following primary objectives.  

1. Quality control of geophysical and petrophysical logs
2. Construct and validate petrophysical models tied to core
3. Compile permeability and porosity diagrams by facies, reservoir and log character
4. Apply petrophysical information to maps

ResQ^TM ACTIVITY III:
Reservoir Engineering

The goal of the production engineering activity is to quantify volumes and locations of original oil in place, both aerially and by reservoir, in order to develop a predictive reservoir flow model based on the reservoir facies tracts determined in Activity 1. Production trends such as time-series analyses of production, pressure and watercut information are critical in determining fluid flow paths in the reservoir. Should sufficient data be available, by-well production will also be related to reservoir facies using petrophysical attributes.

Engineering analyses of pressures, fluid flow (oil and water) and production volumes, within the context of the geological framework, are the major focus of this activity.

Specific activities of this activity are as follows:

ResQ^TM ENGINEERING SERVICES PROVIDED: ANALYSIS OF PRODUCTION HISTORIES AND DETERMINATION OF REMAINING VOLUMETRICS

1. Relate well histories (completion histories, workovers) to historical production curves.
2. Update production database in OFM based on revised correlation framework.
3. Determine relations of production of fluid (oil, water and gas) to pressure variation in the reservoir
4. Review water injection history and relate to production
5. Determine if secondary recovery pilot programs are a viable option
6. Compile summary tables of petrophysics and cumulative production per reservoir and per well.
7. Bubble maps of oil, water, and gas production
8. Calculate original volume of oil and/or gas for all reservoirs

ResQ^TM ACTIVITIES IV:
Integration of Geology, Seismic, Petrophysical and Engineering Analyses

The primary goal of this stage of the investigation will be to use the geologic framework and resource interpretations to identify those parts of the targeted field that are most prospective for maximizing production through waterflood redesign, the drilling of new conventional wells, designing advanced drilling scenarios such as multilaterals, and recompleting existing wells. These resource-targeted infill locations are optimized for either conventional vertical wells or advanced technologies such as horizontal and multilateral wells.  We also evaluate existing wells to determine which oil/gas productive zones have “oil/gas-behind-pipe” and are therefore candidates for recompletion. The ResQ^TM task structure of actions that will be undertaken in this part of the project is shown in Figure 3.

The basis for the development of the portfolio of advanced recovery strategies are maps of hydrocarbon pore volume (SoPhiH) for each reservoir, which are developed through synthesis of the results of the geological analysis (Activity 1) and the petrophysical analysis (Activity 2). Sand distribution, determined in Activity 1, guides the mapping of SoPhiH, original oil/gas in place, and watercut trends (determined in Activity 3) for each reservoir.  This activity, integration of all results, is the most important of activities carried out in a reservoir characterization study, and is, of course, dependent on successful conclusion of the preceding activities.  This integrated reservoir model developed through ResQ^TM applications can become the foundation for numerical modeling of reservoir performance.

Specific services to be carried out in these activities are:

ResQ^TM INTEGRATION SERVICES PROVIDED: COMPLETE INTEGRATION OF ALL SEISMIC, SEDIMENTALOGIC, PETROPHYSICAL AND ENGINEERING ANALYSIS

1. Generate maps of reservoir properties for each of the targeted reservoirs.  Reservoir property mapping will be computer generated, but will be guided by the net sand and log facies maps generated in Activity I including:
1. Porosity maps
2. Permeability maps
3. Structural maps with original and current oil, water, and/or gas contacts
4. Water saturation maps
5. Net pay maps
6. Hydrocarbon pore volume (hydrocarbon index – net pay*porosity*oil saturation) maps
2. Estimation of original volumes of oil/gas in place by reservoir and fault block.

ResQ^TM ACTIVITIES V:
Development of a Portfolio of Extended Development Opportunities

ResQ^TM DEVELOPMENT OPPORTUNITIES SERVICES PROVIDED: PORTFOLIO OF ADVANCED RECOVERY STRATEGIES FOR EXTENDED DEVELOPMENT

1. Identification of behind-pipe opportunities for recompletions
2. Use of net sand, log facies, hydrocarbon-pore volume and production maps to identify optimum areas for geologically targeted, conventional infill wells
3. Use of net sand, log facies, hydrocarbon-pore volume and production maps to identify optimum areas for horizontal wells
4. Use of net sand, log facies, hydrocarbon-pore volume and production maps to identify optimum areas for multilateral wells
5. Use assessment of past injection to determine if water flooding is appropriate, and if so, identify which part of the field would be best suited for deployment of a pilot waterflood
6. If waterflooding is feasible, determine optimum reservoirs for waterflooding based on reservoir facies composition (for example: are channels the best suited for waterflooding?) and facies architecture

ResQ^TM ACTIVITIES VI:
Technology Transfer

Service Activity 1. Monthly progress reports
A monthly summary of activities, including progress toward key milestones, will be provided to Pemex by the ARC Group at the end of each month.  A draft of this monthly report will be available for review prior to the end of the month and it will be finalized and provided to Pemex by the end of the month. Subtasks to be completed during the following month will also be included in the monthly report. 

Service Activity 2. Final Report
A comprehensive final report, including digital copies of all interpretative displays, will be developed at the conclusion of the project. 

Service Activity 3. Technology transfer workshop
A two to five day technology-transfer presentation at which the Team will summarize the results of the project, and discuss at length recommendations for the development of the field, will be presented on site at the conclusion of the project.