The developed geologic model and the collected and analyzed data were used as the basis for a numerical reservoir simulation study to history match the production and pressure performance, and to predict the effect of different oil recovery techniques. A phased approach was utilized to simulate the study area by first performing a single well simulation to determine the sensitivity of the simulation results to various reservoir parameters. Results of the single well simulation and the developed geologic model were then used to model the performance of the full field. The field was simulated to examine the potential for infill drilling and an infill well was drilled and cored. The impact of waterflooding and gas repressurization were also evaluated. Exploration in the Cambrian Rose Run Formation in Ohio resulted in the 1992 discovery of a prolific oil reservoir, the East Randolph field. In the last two and a half years the reservoir produced 450,000 STB and 1,200,000 MCF, and the average reservoir pressure declined from 3,100 psi to 2,200 psi. Declining reservoir pressure, high producing GORs, and operational problems dictated the need for developing a comprehensive reservoir management strategy to improve the operational economics and optimize the oil recovery in the field. Under the Department of Energy Reservoir Management Demonstration Program, a team composed of professionals from Belden & Blake and BDM-Oklahoma was organized to study the potential for improving recovery through infill drilling, waterflooding, and gas repressurization. Further development drilling has confirmed new reservoir limits, and volumetric and material balance analyses indicated potential OOIP exceeding 10 million barrels (compared to the original estimate of 4.4 million barrels). Based on core and log data, a three-layer geologic model was developed to describe the reservoir with the top layer primarily a gas producing zone and the bottom two layers as oil producing zones. Pressure buildup tests, PVT samples, and core relative permeability data were utilized to understand the fluid behavior and develop the reservoir model. Program Objectives BDM-Oklahoma, on behalf of DOE, solicited brief proposals to perform cooperative or cost shared research in developing and implementing reservoir management plans in pursuit of its goal of improving reservoir management understanding through demonstration and technology transfer. Three development projects submitted by small operators of oil reservoirs were selected on the basis of the regional significance of the projects, their potential for economic success, the demonstrated degree of problem identification, the availability and quality of data for addressing the key problem(s), the suggested approaches for solution, and the teaming arrangements suggested by the operators. Once a project is selected, a multidisciplinary team develops a detailed joint work statement delineating the scope of the project, its individual subtasks, the schedule of proposed activities, the need for additional data collection, and the goals and responsibilities of team members. Regular meetings of teams and subteams make optimization of the ongoing work possible through modifications of work plans. Teams are composed of experienced engineers, geoscientists, and other professionals representing BDM-Oklahoma, local operators, service companies, research organizations, state surveys, etc.

Because operators generally have taken a conservative approach to reservoir management, tremendous opportunities exist for increasing production and profitability in domestic reservoirs. Recognizing the potential recovery possible because of sub-optimal reservoir management, the U.S. Department of Energy (DOE) developed a Reservoir Management Demonstration Program to increase reservoir management understanding through demonstration and technology transfer. Three cost-shared projects were launched under cooperative research and development agreements (CRADAs). The first completed project, in East Randolph field, Portage County, OH, was in a small, newly discovered oil reservoir producing from Cambrian marginal marine sandstones of the Rose Run formation. The second completed project addressed a large, mature waterflood in Citronelle field, Mobile County, AL. Substantial progress was made on the third, in Bainville North field, Roosevelt County, MT. Reservoir management strategies were, indeed, developed to increase recovery and profitability. At East Randolph field, gas reinjection was recommended as a secondary recovery technique over waterflood. For Citronelle field, a flow-unit approach to optimizing waterfloods using existing data was developed for the short-term strategy, and recommendations for additional data collection and analysis were developed for the long-term. In the Bainville North field, a reservoir model for simulation aided evaluation of new potential in one of several producing zones. Each project shows the importance of developing reservoir management plans in the context of knowledge of the reservoir system, business environment, and technologies (such as affordable new PC-based programs capable of handling tasks previously requiring a mainframe). Experience also has led to valuable insights on reservoir management methodology, by identifying the general steps and considerations necessary to formulate reservoir management plans for any reservoir. P. 143

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DISCLAIMERThis report was prepared as an account of work sponsoredby an agency of the United StatesGovernment Neither the United StatesGovernmentnor any agency thereof, nor any of their employees,makesany warranty, expressed or implied, or assumesany legal Iiabiliv or responsibilityfor the accuracy, completeness,or usefulnessof any information, apparatus, product, or process disclosed, or representsthat its usewould not infhingepr-watelyowned rights. Availableto thepublicfromthe National TechnicaI Information Service,U.S. Department of Commerce, 5285PortRoyalRd., Springfiel& VA22161-- DISCLAIMERPortions of this document may be illegible in electronic image produced from the document.products. Projects in each of the three reservoir classes currently funded in the program (i.e., FhwialDominated Deltas, ShaIlow Shelf Carbonates, and Slope and Basin Clastics) employed quantitative core-log models to predict foot-by-foot values of reservoir parameters such as porosity and permeability from historically collected wireline data. The approaches to model construction were varied, but led to remarkable success in several instances. The use of core-log models appears to be a readily available and probably underutilized approach that has particular application in desaibing the heterogeneous distribution of petrophysical properties associated with the often complex pore systems of Reservoir Classes I through III. The great potential of this technology for improving recovery on a large scale through better reservoir description is just beginning to be realized because of recent and widespread developments m data processing capabilities. ImagesBorehole imaging is a facet of advanced technology whose utility is rapidly becoming recognized by industry. Acoustic, resistivity, and video imaging tools are being applied enthusiastically m numerous Class Program projects. Imaging tools provide information at resolution higher than most logging tools and generally provide information on the spatial orientation of discontinuities as well as detecting their presence. The continuing trend toward higher costeffectiveness of imaging tools coupled with the wide spectrum of information they can provide on the pore-to-interwell scales suggests that these tools will soon become a part of the logging arsenal routinely applied by all operators.Applications of pging advanced logging tools in Class Program and related projects are demonstrating that many tools designed to measure reservoir properties not previously possible can make substantial contributions to reservoir understanding, but only if care is taken to select the right tools and implement them properly. Project results show that reservoir-specific calibration of tool response to the reservoir property or properties being measured is extremely important. Tools rnaldng substantial contributions in the projects reviewed include nuclear magnetic resonance, acoustic, dielectric, spectroscopy, pulsed neutron, and modular formation tester tools. New tools and technologies under development w...

Citronella field, an aging domestic giant oil field in south Alabama now in its mature waterflood stage, was selected for participation in the U.S. Department of Energy's Reservoir Management Demonstration Program. A reservoir management strategy was developed to extend the economic life of the field through improving operational efficiency and increasing oil production.Waterflood optimization was identified as the primary focus for strategy development. Because the field contains over 450 wells operated by more than 100 individual well operators, the amount of well data for analysis was large and of varying quality. The approach chosen was to fully utilize existing data and select a focus area for improved reservoir characterization.This project demonstrates how a Geographic Information System can efficiently organize and present existing well and reservoir data, Also, techniques were developed to optimize the waterflood on a local scale using a flow unit approach based on previous geological studies. Various production and injection well geometries were developed in order to identify potential wells for recompletion and conversion to injection. Additional areas in the field with recove~potential where the flow unit approach might be applied were identified.