Field Application of Vertical Well Testing Methods With a Case History

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Summary This paper presents information on a field application of vertical well testing techniques and data analyses and summarizes the results of a case history study on vertical pulse testing. The testing program revealed that it is possible to operate and analyze vertical well tests. A modified Prats technique proved adequate for analyzing vertical pulse test data. Introduction Vertical well testing is a type of interference test conducted between two perforations in the same wellbore. The technique, which includes both vertical interference and vertical pulse testing, provides a way to estimate formation vertical and horizontal permeability. Knowledge of those properties can be used to evaluate the extent of vertical communication in a reservoir near a tested well. Such information can be useful in a selective flooding or vertical conformance control program.This paper presents information on a field evaluation of vertical well testing techniques and data analysis, and summarizes the results of a case history study of vertical pulse testing. A companion paper describes vertical well testing techniques, analysis, and design. Vertical pulse testing in Marathon Oil Co.'s Oregon Basin field in Wyoming provided the basis for information presented in this paper. Four vertical pulse tests were conducted in and between Tensleep reservoir zones at Baston A Well 13 in that field. One goat in the program was to evaluate vertical well testing and data analysis techniques. A second goal was to determine the extent of vertical communication in the Tensleep reservoir. The case history study reports results of the field evaluation.On the basis of experience gained, we conclude that one can operate and evaluate vertical pulse tests in most situations. The main difficulty in testing at Baston A Well 13 was the wide difference between sandface and surface injection rates caused by low reservoir pressure and high wellbore storage. That situation created some analysis problems that we were able to overcome for the most part. By appropriate modifications of field procedures, future tests should provide adequate data.We were not too successful in achieving the second goal in the testing program. Analysis results for the first three tests conducted showed an abnormally high vertical permeability. This anomaly - the result of flow behind the casing - caused problems in evaluating vertical permeability in the Tensleep reservoir. However, we were able to estimate vertical permeability using test results plus computer simulation studies. There was no response during the fourth test. That indicates no communication between the tested zones, either through the casing cement or in the reservoir.The testing and analysis procedures used in the four vertical pulse tests were basically the same. With the exception of Test 4, all tests show the same type of response behavior. For this reason, and for the sake of brevity, only Test 1 is discussed in detail in this paper. However, analysis results are presented for all four tests. Vertical Pulse Tests Run in Oregon Basin Field The well used for vertical pulse testing is located on the south flank of the south dome of Oregon Basin field in Wyoming. Testing was done after drilling, logging, and casing the well but before final completion. JPT P. 1113^

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