A Field Application of Pulse-Testing for Detailed Reservoir Description

Abstract

Abstract Johnson et al. have described a new well-testing technique that measures formation flow properties between wells. The technique, called pulse-testing, requires a sequence of rate changes in the flow at one well and measurement of the resulting pressure changes at an adjacent well with a very sensitive differential pressure gauge. This paper describes an extensive application of the technique in a producing oil field. Pulse-tests on 28 of 45 possible well pairs in the field provided a picture of the areal distribution of reservoir hydraulic diffusivity, transmissibility and storage. The primary objective in presenting these data is to demonstrate the potential of the method for reservoir description. A second objective is to show in three ways the qualitative and quantitative accuracy of reservoir parameters determined from pulse-tests:pulse-test data show a nonuniformity in the field, closely correlating with the oil-water distribution as given by production data;pulse-test values for permeability are comparable with core values, andperhaps most important, the field responds to a conventional interference test in the manner in which pulse-test data predict it should. Introduction The pulse-testing technique by Johnson et al. is an ideal source of data for purposes of reservoir description, for it provides a measurement of formation storage S = phi ch, hydraulic diffusivity eta = k/phi c mu and transmissibility T kh/mu between wells. This paper describes an application of this method in a producing oil field. Results were analyzed to give numerical values for the parameters eta, T and S. These values were compared with oil-water production data (for the effect of fluid saturation), with core data and with data from an interference test. The reservoir in which the pulse-test survey was run is the result of a structural trap formed by a fault along the east side of a north-south trending anticline. A down-structure aquifer provides a natural flank water drive for the pool. The producing formation is a dolomitic limestone having mainly vugular permeability; the formation oil has a gravity of 29 degrees API with negligible dissolved gas. The field contains 19 wells, all on pump, arranged on 40-acre spacing along the top of the anticline. Fig. 1 shows the location of all these wells except two at the south end of the field. The dashed line on the righthand side of the figure represents the approximate location of the fault with respect to well positions. Pulse-Test Survey and Analysis of Data A pulse-test requires a pulsing well and a responding well. JPT P. 313ˆ