Interference Testing and Pulse Testing in the Kenli Carbonate Oil Pool--A Case History

Abstract

Summary This comprehensive study of the geological characteristics of a carbonate oil pool involves multiwell testing, interference testing, and pulse testing. From the calculation and analysis of 32 well-testing curves, sketches are drawn showing the distribution of various parameters of the whole area. On the basis of the parameters of the whole area. On the basis of the permeability (k) distribution chart, the anisotropic permeability (k) distribution chart, the anisotropic heterogeneity of permeability and its distributional pattern are analyzed. Pulse testing data are presented and pattern are analyzed. Pulse testing data are presented and compared with those of interference testing. A rough distributional chart for permeability is proposed for use in numerical simulation. Introduction Multiwell transient testing includes interference testing and recently developed pulse testing. Kamal has given an introduction to the combined use of the different well test methods in the study of formations and Earlougher has reviewed the techniques of interpretation of various parameters. parameters. The type-curve matching method is generally used in the analysis of interference testing data. Type-curve matching, as a characteristic line method with its high accuracy, may eliminate the errors from the use of different characteristic-point methods, caused by the irregular distribution of points actually measured. Pulse testing is a new form of multiwell testing recently developed by Johnston et al. With the use of pressure transients of the initial stage, the method gives results similar to those of interference testing but in a shorter duration than the latter, so that the influence of pressure trend of the oil pool may be avoided. Pierce and Kamal have proposed several charts for interpretation of parameters from the curves. Kamal's chart is particularly useful for unequal pulse and shut-in periods, particularly useful for unequal pulse and shut-in periods, simple and practical for both pulse-test design and data interpretation. Applications of multiwell testing in the study of oil fields are many. Matthies' application of interference tests in the Wolfcamp field, McKinley et al.'s detailed reservoir description of an oil field by pulse testing, and Pierce's study of the distribution of faults in the Kelsey Pierce's study of the distribution of faults in the Kelsey field are among the most illustrative. Ramey's analysis of well pairs in a nine-spot pattern for a homogeneous anisotropic system deserves particular mention. He provides a complete set of data for an oil province provides a complete set of data for an oil province valuable for the interpretation of its anisotropic characteristics and useful for further study of the province. There are plenty of instances describing the province. There are plenty of instances describing the techniques of study--e.g., Ramey et al.'s study on the effect of faults and Vela et al.'s study on reservoir heterogeneity. However, as Kamal pointed out, while there are some ways to interpret data pertaining to homogeneous anisotropic or isotropic formations and to multiwell testing of different kinds of bounded systems, none is available for the heterogeneous formations. The only solution is to try numerical simulations of hypothetical models. In interference or pulse testing at the oil field, a highly sensitive pressure gauge is the most important tool. The measuring system of Johnson and Raynor rendered useful service in the pulse tests. The recently developed quartz pressure gauge is also an efficient instrument for pulse testing, The CY-733 differential pressure gauge for multiwell testing enables us to gather a considerable amount of relevant data. This bottomhole instrument uses a glass piston-cylinder as the pressure-sensitive element, with piston-cylinder as the pressure-sensitive element, with sensitivity of about 0.14 psi [0.97 kpa] in wells 6,560 ft [2000 m] deep and 0.014 psi [0.97 kpa] in shallow wells 660 ft [200 m] deep. The instrument can work continuously for more than 10 days in one run. It is simple in structure and suitable for measuring small pressure variations at specific spots. This paper presents a case of a limestone oil pool that is trapped by a faulted and weathered surface. It describes the multiwell testing program, shows the distribution of reservoir parameters, and gives essential data obtained from interference and pulse testing, interpreted according to the method recommended in the literature. Principles and Methods Principles and Methods What is Multiwell Testing? The multiwell testing technique is a method of studying the formation by observation of the transmission of pressure transients in an elastic system (i.e., a reservoir). A well pair is used as the unit of interference testing (see Fig. 1). Pulse testing and interference testing are analogous in method, and both use well pairs as the units of testing. JPT