Rock/Fluid Characterization and Their Integration—Implications on 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. Abstract The flow performance of hydrocarbon reservoirs is controlled largely by rock and fluid properties, their variation, and rock/fluid interactions. In this paper, we highlight the rock- and fluid-data needs for various production processes with an emphasis on quality control (QC) and efficient data management. We stress the need for an integrated and a multidisciplinary approach to rock and fluid characterization to minimize measurement uncertainty. Such an approach will ensure reliable rock and fluid data that are required for the determination of accurate volumes in place, reliable recovery factors, and realistic development plans, thus minimizing technical risks and maximizing the economic value of the hydrocarbon assets. Also discussed are the effects of uncertainties in rock and fluid properties on reservoir-performance prediction. The importance of reservoir surveillance through periodic coring, fluid sampling, and testing as well as reservoir simulation for data validation and refinement is further emphasized. Finally, worldwide field examples of sandstone and carbonate reservoirs containing black oil, volatile oil, and gas/condensates are presented to highlight these points. Introduction The performance of hydrocarbon reservoirs is controlled largely by the rock and fluid properties, their spatial and temporal variations, and rock/fluid interactions (Al-Hussainy and Humphreys 1996). High-quality rock and fluid data are critical for reliable geological modeling, reservoir-engineering calculations, and performance predictions by use of reservoir simulators and for subsequent economic analysis. Many pressure-maintenance and secondary- and tertiary-recovery projects have failed because of inadequate geologic description and lack of reliable rock and fluid data. In the absence of good-quality data in adequate quantity, simulation models with multimillion gridblocks, and sophisticated scaleup methodology, do not add any economic value to the resource. In short, the value of rock and fluid data lies in their potential to guide the selection of the most suitable recovery process and its effect on project economics. Rock characterization involves quantification of porosity, permeability, capillary pressure, and relative permeability associated with various recovery processes. Similarly, fluid characterization quantifies the reservoir phase behavior, fluid compositional changes throughout the reservoir, and changes in fluid properties as a result of production and injection processes. The process of data gathering begins with exploration and continues through the life of the reservoir.