In this paper we examine the use of simultaneously recorded pressure and flow rate obtained from short duration transient tests performed during perforating operations. Of primary interest in this work is the application of the technique to evaluate the addition of perforated intervals to a thick, partially completed pay zone. The study describes in detail the objectives, test design, data acquisition and analysis of transient tests performed on four producing wells in Uinta. County, Wyoming, before, during and after reperforation operations. A field example presents data along with their interpretation for one of the wells to illustrate the analysis techniques. Estimates of the permeability and skin effect from these short-term tests and subsequent production logging measurements are compared to those obtained from earlier conventional tests to assess the effectiveness of the recompletion operations. The results demonstrate the validity of the tests conducted and their utility in completion evaluation.
Pressure buildup testing as a means to estimate reservoir parameters and to evaluate completion effectiveness is widely practiced in the oil and gas industry. A typical buildup test procedure involves producing a well to stabilization and shutting it in while measuring the downhole pressure. The measured pressures are then analyzed using various graphical techniques, e.g., type-curve analysis, Horner plot, MDH plot, etc. The reservoir pressure response in such tests can often be masked by wellbore storage effects at early times. As a result, correct system identification and reservoir parameter estimation require that tests be conducted long enough for the storage effects to dissipate. In recent years, practical methods have been developed for combining measured downhole flow rates with transient pressure data in order to correct for the wellbore storage effect.1–3 One method available for analysis of simultaneously acquired flow rate and pressure is convolution, which involves continuous superposition of the pressure response based on an assumed reservoir model and measured flow history. 1,2 The use of convolution and its derivative4,5 has proven effective in correctly identifying system response and estimating reservoir parameters from early-time data. Field examples1,3 using production logging sensors have shown that the application of the convolution analysis technique, in conjunction with diagnosis,6 allows the ability to perform a valid well test of relatively shorter duration.
In this study, we show that the Measurement. While Perforating (MWP) tool, with pressure and flow rate measurement capability, can be used during perforating operations to acquire transient data which may be analyzed as a well test for determination of reservoir parameters.7,8 Also presented is a case study illustrating the interpretation of simultaneously acquired pressure and flow rate in a series of short duration tests before, during and after the addition of perforated intervals to a thick, partially completed pay zone.
The tests were performed on four producing wells in the SW Wyoming Thrustbelt Province of Uinta County. Test data and interpretation are presented for only one of hese wells, the others being quite similar. Results are compared with those from previous conventional tests, and are interpreted in conjunction with other production logging measurements to assess the effectiveness of the reperforating operations.
