Use of Rate Transient Analysis to Enhance the Well Performance of a Mature Gas Field
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The BHA gas field plays a significant role in Oman's gas production. However, production forecasts and reserves estimation in this gas condensate field have shown considerable uncertainty due to the formation complexity and the relatively low permeability (1-5 md). Mismatches between the observed reservoir performance and deterministic performance predictions have resulted in continuous revision of the booked reserves for this field. To address these reserves revisions, we deployed modern time-rate analysis and time-pressure-rate analysis techniques to improve the analysis and interpretation of the reservoir performance data, and thus better constrain the estimated ultimate recovery (EUR) results for the BHA field. Microsoft® Excel® is used to perform "time-rate" or "decline curve" analysis (DCA) on a selected group of fourteen wells. These wells were chosen based on the continuity of the production data (some wells do not have continuously measured pressures). We follow the industry-standard practice for wells in unconventional reservoirs, where the EUR is estimated at 30 years from the forecasted production trend. Specifically, we estimate reserves using both the Modified Hyperbolic (MH) and Power Law Exponential (PLE) methods. In addition to "time-rate" analysis, we also perform "time-rate-pressure" analysis or "rate transient analysis" (RTA) on these same fourteen well cases using the commercial software package Topaze (Kappa Engineering). In the RTA workflow, we first utilize the diagnostic plots to estimate model parameters and then perform a simulation history match using the anazlytical solution for a vertical well with a finite- or infinite-conductivity vertical fracture. Using the history-matched reservoir model, we then generate a forecast of at least 30 years and we use the cumulative production at 30 years as a proxy for EUR for comparison with DCA methods. We tabulate the 30-year EUR values from DCA and RTA, as well as the model parameters used to obtain these forecasts. We provide simplified correlations of EUR results and model parameters for the DCA and estimates of reservoir properties obtained from RTA. The overall goal of this work is to demonstrate the applicability of these methods to improve our confidence in the estimated reserves for the BHA field.
SubjectRate Transient Analysis
Al Lawati, Basayir Hussain Mohsin (2017). Use of Rate Transient Analysis to Enhance the Well Performance of a Mature Gas Field. Master's thesis, Texas A & M University. Available electronically from