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The Khuff reservoir in South Ghawar, Saudi Arabia is a heterogeneous tight carbonate reservoir. Acid fracturing program has been initiated to enhance gas production from this reservoir to deliver 1.2 BSCFD of gas. The complex nature of the tectonic stresses, geomechanical properties, reservoir geology and quality, coupled with aerially varying fluid properties (H2S) have sometimes reached the limits of reservoir simulation and stimulation.During the early stages of development, numerous diagnostic tests were conducted on every well before, during, and after fracture treatment. These tests include pre- and post-fracture pressure transient analysis, radioactive tracer or temperature log runs during mini and main fracture treatments, production tests, and production logging. Several acid fracturing fluids, such as, 28% HCl, emulsified 28% and 15% HCl, were applied to achieve optimum fracture length and conductivity, and avoid CO2 corrosion. Complete reservoir characterization, history matching of actual fracture treatment and production forecasts were performed for every well. The objective of these tests and detailed evaluation is to optimize future acid fracture design.This paper presents in detail the integrated optimization process of acid fracturing in the Khuff reservoir. The paper demonstrates that early investment in technology, management of uncertainties, and state of the art reservoir and fracture modeling significantly improved the optimization process.The paper presents detailed assessment of several key wells, comparison between various acid fracturing fluids and techniques, and calibration of results of the stress and fracture models. The paper also discusses the need and importance of some of the tests and the quality of the results that may be obtained from them.Finally, the paper presents reservoir modeling and history matching of acid fracture treatment using state of the art coupled geomechanical single well simulation model. Predictions of acid fracture performance versus time under the Khuff abnormal stress conditions are presented. |
