Pressure Analysis of Multiple-Sealing-Fault Systems and Bounded Reservoirs by Type-Curve Matching (1979)

Abstract Previously, if a multiple-boundary situation was Previously, if a multiple-boundary situation was suspected in a hydrocarbon reservoir, about the best one could hope to do was to obtain an estimate of the distance to the nearest boundary. Also, although a well in a closed rectangular drainage area presents a very important flow problem in conventional reservoir engineering, no comprehensive method existed in the literature to determine the location of the well relative to each of the sealing boundaries of the drainage area. This study presents a type-curve matching technique, based on the time rate of change of dimensionless pressure, for interpreting the pressure transient behavior of a well located in pressure transient behavior of a well located in various multiple-sealing-fault systems and inside closed rectangular reservoirs. Type-curve plots generated in this manner may be used to match drawdown curves, based on the time rate of change of field pressure data, to determine several essential reservoir parameters such as the kh and phi c products, extent of drainage area, and distance to surrounding seating boundaries. In multiple-sealing-fault systems, buildup curves are similar to drawdown curves for long producing times. Introduction Because the presence of a fault in a reservoir is of great importance, a considerable number of pressure analysis techniques dealing with this situation have been proposed in the literature. However, very little attention has been given to the case of a multiple-boundary situation. The first application of the image method to multiple-sealing-fault systems was made by Jones. He considered a flowing gas well in an areally extensive quadrant formed by two linear no-flow boundaries that intersect at 90 deg. and showed that, after a sufficient number of producing days, the slope of the drawdown curve ultimately would be four times the initial value. Later van Poollen showed how drawdown curves from a well located between two intersecting faults can be used to find the angle between the two boundaries. Both Jones and van Poollen implied that the rate of change of pressure with time might be useful for analyzing the pressure with time might be useful for analyzing the pressure behavior of a well in a two-fault block. pressure behavior of a well in a two-fault block. Prasad presented an analytical solution for Prasad presented an analytical solution for calculating the well pressure distribution in a wedge reservoir system. Tiab and Kumar demonstrated that for a well between two parallel sealing faults, the time rate of change of pressure provides a unique behavior to detect and determine the distance to each fault. Pressure transient testing also has been applied extensively to study the case of a well in a closed drainage area. In 1937, Muskat developed a method to determine the eventual static pressure of a well in a closed circular reservoir. In the late 1940's, van Everdingen and Hurst published a fundamental study of the unsteady pressure distribution for both finite and infinite reservoirs. These two publications laid the foundation for two major reports by Horner and Miller et al. Horner presented a method of analysis of pressure buildup data obtained from a well in an infinite reservoir. He also reported the influence of a sealing fault on pressure buildup curves and the behavior of a well at the center of a finite circular reservoir. About the same time, Miller et al. published the results of a study in which they compared the effects of no-flow and constant-pressure conditions existing at the external boundary of a circular reservoir. In 1954, Matthews et al. presented a technique for estimating both the average reservoir pressure and pressure distributions within a large variety of pressure distributions within a large variety of bounded geometric shapes. SPEJ P. 378