What Is Reservoir Management?

Abstract

Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Summary This paper describes practical aspects of reservoir management and new approaches being used today, with emphasis on the multidisciplinary team approach. Case studies are presented that illustrate the effectiveness of this approach. In addition, specific attributes of a successful reservoir-management organization and program are highlighted. Definition Reservoir management has been defined by a number of authors.1–4Basically, sound reservoir-management practice relies on use of financial, technological, and human resources, while minimizing capital investments and operating expenses to maximize economic recovery of oil and gas from a reservoir. The purpose of reservoir management is to control operations to obtain the maximum possible economic recovery from a reservoir on the basis of facts, information, and knowledge.3 History and Current Status Before 1970, many considered reservoir engineering to be of major technical importance in reservoir management. Wyllie5 emphasized the fundamental concepts of reservoir mechanics and automation with computers. Essley6 emphasized the advancement in technical aspects of reservoir engineering, yet warned that vital engineering considerations are often neglected or ignored. During the 1970's and 1980's, synergism between geoscientists and reservoir engineering proved to be very successful. Craig et al.7emphasized the value of detailed reservoir description with geological, geophysical, and reservoir-simulation techniques. Harris and Hewitt8presented a geological perspective of the synergism in reservoir management. Even though the synergism provided by the interaction between geoscientists and reservoir engineering was quite successful, the values of other disciplines(e.g., production operations and drilling) and other engineering functions like facilities engineering were not realized to their fullest extent. Reservoir management has now matured to the point where great emphasis is placed on working as a cross functional team, involving all technical areas, management, economics, legal, and environmental groups. This type of reservoir-management model has proved to be quite successful.9–20This paper highlights the major contributions to this model. Data Collection and Management Data collection and management are very important to project success, and they must be carefully planned and carried out. A clear understanding of the purpose and application of the data is necessary (i.e., a definition of why the information is needed and how it is to be used). A cost/benefit analysis of the data (i.e., the cost of data collection and management and the benefits to be derived) is mandatory. Justification, priority, timeliness, quality, and cost-effectiveness should be the guiding factors in data collection and analysis. Fig. 1 shows an efficient data-flow diagram. Proper timing of data collection is very important because early initiation of a well-coordinated data-collection program not only provides a better monitoring and evaluation tool, but also costs less in the long run. For example, a few early drillstem tests could help decide if and where to set pipe. Sometimes these data can also provide the same type of information normally available by complex and expensive cased-hole, multiple-zone testing. An extra log or an additional hour's time on a drillstemtest may provide better information than could be obtained from more expensive core analysis. A market research found that geologists and engineers spend up to half their time collecting and processing data.17 As a result, they have lesstime available for analysis and making future recommendations. The data-management issue is not an easy task. We all look forward to the result of a joint-study project, sponsored by the Petrotechnical Open Software Corp., in developing industry data standards. Integration of Geoscience and Engineering In 1977, Halbouty19 advised, "It is the duty and responsibility of industry managers to encourage full coordination of geologists, geophysicists, and petroleum engineers to advance petroleum exploration, development, and production." Since then, considerable progress has been made in this integration effort. Sessions and Lehman20 presented the concept of increased interaction between geologists and reservoir engineers through multifunctional teams and cross training between the disciplines. Sneider21recommended that geologists, geophysicists, petroleum engineers, and others work together on a project more effectively and efficiently as a team rather than working as a group of individuals. Traditionally, data of different types have been processed separately, leading to several disparate approaches: a geologic, a geophysical, and a production/engineering model. The industry has made considerable progress in integrating these models as the importance of geology and geophysics in predicting reservoir performance is better recognized by reservoir engineers. With the advent of 3D geologic modeling programs, automating the generation of geological maps and cross sections from exploration data is practical. In addition, the geologic picture (including the qualitative interferences) is being transferred into a simulation model.22,23 Using numerical simulation, the reservoir engineer today seeks more data, both in quantity and quality, from the geoscientists. On the other hand, history matching of the reservoir's performance and utilization of a numerical simulation model can lead to feedback of geological information to the geologist. Better tools and data, along with the advent of new technology, such as workstations and integrated software packages, can minimize remaining barriers between reservoir-management disciplines. Integrated data-storage and-retrieval systems that use workstations and interactive technologies provide abridge between geoscientists and engineers. By integrating the work of geoscientists and engineers, it is possible to check and to validate seismic and geologic interpretations. Team members are able to correct contradictions as they arise, minimizing costly errors later in the field's life. In a broader sense, current reservoir-management approaches look not only at integration of geosciences and engineering, but also at integration of data, tools, technology and people, as Fig. 2 shows.