Use of Transient Testing in Reservoir Management

Abstract

Summary Transient tests can be used throughout the life of the reservoir to manage and to optimize recovery of hydrocarbon fluids. This paper shows applications of various well-testing methods during the exploration, appraisal, and primary and secondary recovery phases of field projects. Single-well tests [e.g., drillstem tests (DST's) and buildup tests] are primarily used during the various stages of field development and primary recovery, whereas multiple-well tests (e.g., interference tests) are most often used during secondary recovery. A clear understanding of the type of information obtained from well tests is essential if this information is to be used properly in managing the reservoir. Examples are the different values of permeabilities calculated from single-vertical-well, horizontal-well, and multiple-well tests; the values of average reservoir pressures; and the double-porosity parameters calculated from tests in naturally fractured reservoirs. The state of the art of testing and measurement tools, acquisition systems, and interpretation methods affects the type of information obtained from well tests and should be considered by the petroleum engineer before results are used. The paper presents information to help the engineer use transient tests properly and to their fullest extent. Field examples are used when appropriate. Introduction The main difference between petroleum engineering and most other engineering disciplines is that the systems that petroleum engineers work with are given to them, whereas in other engineering disciplines the engineers design their systems. For example, the car engine is designed by a mechanical engineer and the structure of a building is designed by a civil engineer. Oil and gas fields are not designed or developed by petroleum engineers. They are given to them. As a matter of fact, the biggest challenge petroleum engineers face is to characterize these systems. In this regard, petroleum engineers have the same problem as mining and meteorological engineers and groundwater hydrologists. However, petroleum engineers have the added complexity, which mining and meteorological engineers do not have, of being unable to see the in-situ properties of our systems physically and measure them directly. Therefore, to obtain the physical properties of hydrocarbon-bearing formations, petroleum engineers rely on indirect measurements, such as inferring formation permeability from production data, calculating porosity from a sonic log, or determining the distance to a fault from a buildup test.