IMPROVING OIL RECOVERY USING INTEGRATED EVALUATION TECHNIQUES

Based on a workshop sponsored by North Midcontinent PTTC, held on April 23, 2002 in Wichita, Kansas

BOTTOM LINE

The Kansas Geological Survey has developed new technologies and strategies to improve oil recovery from Kansas's oil fields. The focus has been to provide increased access to public data through online digital programs, development of software to evaluate electric logs, improved reservoir characterization, modeling and computer simulations. The key to better management of oil fields is integration of all available data with economic analysis strategies.

PROBLEM ADDRESSED

The Kansas Geological Survey (KGS) carries a responsibility to the independent operators in Kansas to provide data and advanced evaluation and interpretation techniques for hydrocarbon exploration and production. Individual operators do not have the facilities or manpower to accumulate and access all the public data collected by the state of Kansas. KGS researchers are able to improve means of access to data, and demonstrate new technologies and best practices through development of software, methodologies and case studies applicable to Kansas oil fields.

KEY WORDS:

Core Analysis, Digital Data/Online Access, Modeling, Pressure Transient Testing, PfEFFER Software, Reservoir Characterization

SPEAKERS

From Kansas Geological Survey:
Accessing Kansas Digital Data
Tim Carr
Evaluating Electric Log Data
John Doveton
Mapping reservoir properties including determining original oil in place and estimating recovery factors
Lynn Watney
Economic Analysis
Marty Dubois
Additional reservoir properties needed to develop reservoir model using special core analysis and transient testing
Alan Byrnes and Rodney Reynolds, PTTC Regional Director

Computer simulations to identify the most efficient recovery process
Bill Johnson, Discovery Capital, LLC

TECHNOLOGY OVERVIEW

Advanced technologies and access to data provided by the Kansas Geological Survey (KGS) is designed to assist Kansas independent operators to increase oil production through improved management strategies based on increased understanding of available data, interpretative software programs, reservoir analysis, modeling and integrated economic analysis. 

Accessing Kansas Digital Data
A key to improved oil field exploration and development is knowledge of what data are available and the most efficient, cost-effective means of gathering and using this data. The Kansas Digital Online Database is designed for easy access and fast response to queries based on standardized forms and menus. Data included in the digital database include: well information, production data, electric logs, cuttings, cores, and maps. The main menu of the Kansas Oil and Gas Information Page lists contacts for major projects, staff, maps and publications, tutorials and short courses, databases, and other oil and gas web resources. A standardized web query Master List of Wells is designed to easily access data from wells throughout Kansas, by Township and Range, field name or county locality. Standard well completion reports for each well are available, along with digital logs, and core data and photographs. Landgrid data allows one to click on by county to find wells and field data. The Internet tutorial assists those who are unfamiliar with database searching, besides making working from local or home offices fast and efficient. The database is not static. In addition to new well data, plans are to add pressure transient data, add new links between well and leases, add links to adjoining states, and improve the data flow. 

Evaluating Electric Log Data
Digital techniques for wireline log data developed by KGS provide a means of evaluating the paper and raster log images available through the Survey archive files and database. The logs are in ASCII format, a simple digital log format than can be read by word processors or software spreadsheet programs, such as EXCEL. EXCEL can be used to store large amounts of data on worksheets and to plot the log data on graphs. The log analysis program developed by KGS, PfEFFER, is an EXCEL-based spreadsheet program. Features include the ability to convert ionic composition data into water resistivity. Pickett plots show the relationship of resistivity and porosity. Crossplots for neutron-density, composition profiles can also be made from spreadsheet data. KGS offers one-day courses on how to use PfEFFER, and the software is available through them at a moderate cost.

Mapping reservoir properties including OOIP and estimating recovery factors
Geo-Engineering Modeling through Internet Informatics (GEMINI) is a reservoir property mapping public web-application developed by KGS. GEMINI is an application of web-based analysis software for petroleum databases, logs, rock properties and fluid production. Reservoir characterization involves integrating properties, which vary widely in scale. Geological models must be validated with a variety of architectures and data, which require flexible analysis tools. Some of the common reservoir properties, which can be mapped and integrated include: methodology of field study, data collection, log and core analysis, cross sections and grids, contouring, volumetrics, material balance, production data, decline curves, recovery factors, optimized solutions, and simulation parameters. Important considerations in reservoir management include cost benefits, teamwork, partnerships, integration and compatibility of databases, compatibility of hardware and software, portability of digital results and archiving and future use of data. 

GEMINI is capable of integrating stratigraphic, sedimentologic, structural, and diagenetic data to build a framework for modeling. Tutorials demonstrate how to work through problems in well-level analysis, field-level analysis, develop modules and catalog reservoir properties. Projects developed in GEMINI are password protected. Well analysis modules allow selection of log tops, core analysis, and profiles and incorporate PfEFFER spreadsheet capabilities. The rock catalogue provided by GEMINI includes extensive petrophysical data: porosity, permeability, capillary pressure properties, electrical properties, mechanical properties, lithologic properties and geologic properties. A high-resolution correlation software package, Correlator, for building cross-sections of well log data enables excellent graphic presentation. Volumetric and material balance analyses serve as an important intermediate step toward reservoir simulation. GEMINI is designed to use petrophysical data and pore properties with volumetrics to optimize solutions. Future plans for upgrading GEMINI include additional modules for cross sections and correlation, more tutorial information about how to use the program, additional material balance and integration abilities, and the ability to work in partnership with companies for feedback and testing. Workshops for using GEMINI are planned. 

Reservoir properties from core analysis and pressure transient testing
Reservoir models change with time as new data, new technologies and more efficient recovery methods change the needs of the reservoir manager. The fundamental properties of reservoir models are the basic architecture, reservoir properties (porosity, permeability, saturations), and fluid properties (pressure, viscosity, bubble point, formation volume factor) derived through special core analysis. Examples demonstrated various special core analysis techniques using Kansas field data. Equations for capillary pressure and information on properties, which influence the shape of a capillary pressure curve (maximum pore throat size, pore throat size distribution, surface area), were illustrated. Graphs demonstrate the effect that changes in pressure have on permeability related to overburden pressures from increases in grain angularity, ductile grain content, grain sphericity, heterogeneous grain size, and the number of induced core fractures. Better understanding of the properties of the reservoir rocks allows construction of more accurate geomodels, improved models of remaining oil-in-place, and improves reservoir management and efficient oil recovery. 

Pressure transient testing (PTT) can answer many operator questions on well productivity related to wellbore damage, depleted pressure, communication between injectors and producers, and flow behavior in the reservoir. PTT consists of making rate changes in wells, monitoring how reservoir pressure changes with time and relating these pressure changes to reservoir properties. The main types of PTT's are drillstem, buildup, drawdown, falloff, and multiple well interference or pulse testing. PTT samples a large reservoir volume, and averages responses from a large area. The basic steps for PTT are to create a diagnostic log-log plot, identify flow regimes, create specialized plots to help identify flow regimes (Horner, Miller-Dyes-Hutchinson), calculate the parameters from the specialized plots, select the basic reservoir and well model and calculate the type curve, check the model for consistency.

Computer simulation
Two types of reservoir models are (1)exploration models used for geophysics, basin analysis and analogies and (2) development models, which build off existing models, have more data available and can include more detail than exploration models. Reservoir models can help with decisions on buying and selling, costs, drilling, planning infilling drilling, and selecting improved oil recovery methods. Reservoir models can be used to substantiate geology, understand fluid flow, prove a technical point, predict future potential, and compare depletion alternatives. Reservoirs are inherently complex and modeling is the tool to understanding the complexities and solving problems. All kinds of data from historical data, digitized maps, land grid data, and well constraints can be input into models to visualize and display the information to assist in optimizing field production. Using a reservoir model to optimize a gas field will address considerations such as: how many well are needed, acceleration rate, where to drill new wells, that is the throughput, and how much compression is required. Reservoir modeling should be applied throughout the life of the reservoir to improve the economics. 

Economic Analysis
Economic analysis is a critical element in project evaluation. Economic analysis in the planning stage can answer questions on the risk of a project, is there a better project, under what conditions would you do the project, how reasonable are your underlying assumptions. Economic terminology includes definitions of a number of terms: internal rate of return, net present value, years to pay out, times of pay out, discount rates, and capital investment. Economic analysis requires the use of a spreadsheet program like EXCEL, which can handle several metrics types (IRR, NPV, YTPO, XPO) for strategic planning. As an example, strategic planning of CO₂ floods in Kansas necessitates understanding of geologic models and simulations, knowledge of the potential resource size as a function of the price of oil and the cost of CO₂. Scenario building, using risk management and evaluating several different scenarios to select the most likely outcome, is an important part of economic analysis. Scenarios allow the operator to use risk-weighted economics to make decisions on reservoir development and management. 

CONNECTIONS:

Kansas Geological Survey
1930 Constant Ave
Lawrence, KS 66047-3726 
Phone: 785-864-3965 Fax: 785-864-5317 
Alan Byrnes abyrnes@kgs.ku.edu
Tim Carr tcarr@kgs.ku.edu
John Doveton doveton@kgs.ku.edu
Marty Dubois mdubois@kgs.ku.edu
Lynn Watney lwatney@kgs.ku.edu

Rodney Reynolds
Tertiary Oil Recovery Project
KU Energy Research Center
1930 Constant Ave
Lawrence, KS 66047
Phone: 785-864-7398 Fax: 785-864-7399
Email: reynolds@ku.edu 

Bill Johnson
Discovery Capital, LLC
453 S. Webb Rd, Suite 100
Wichita, KS 67207
Phone: 316-681-2542
Email: discap@earthlink.com


For information on PTTC's North Midcontinent Region and it's activities contact:
Rodney R. Reynolds, Project Manager, Kansas University Energy Research Center
1930 Constant Ave., Lawrence, KS 66047-3726
Phone: 785-864-7398, Fax 785-864-7399, Email: reynolds@ku.edu

Disclaimer: No specific application of products or services is endorsed by PTTC. Reasonable steps are taken to ensure the reliability of sources for information that PTTC disseminates; individuals and institutions are solely responsible for the consequences of its use.

The not-for-profit Petroleum Technology Transfer Council is funded primarily by the US Department of Energy’s Office of Fossil Energy, with additional funding from universities, state geological surveys, several state governments, and industry donations.

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