Fieldwide Determination of Directional Permeabilities Through Transient Well Testing

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This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 181437, “Fieldwide Determination of Directional Permeabilities Using Transient Well Testing,” by Yan Pan, Medhat Kamal, and Wayne Narr, Chevron, prepared for the 2016 SPE Annual Technical Conference and Exhibition, Dubai, 26–28 September. The paper has not been peer reviewed. Knowledge of the maximum- and minimum-permeability directions in anisotropic reservoirs helps to optimize injector and producer locations and is important for reservoir management, especially under secondary or enhanced recovery of hydrocarbons. The complete paper describes a method using transient-test data rich with dynamic information aiming to provide fieldwide permeability distribution in well-spacing scale, which is relevant for estimating fluid movement and recovery. Introduction The knowledge of flow communication between wells is key information for reservoir management, especially in secondary or tertiary recovery. The surveillance methods to collect dynamic data to gain such knowledge include multiple-well pressure-transient tests and tracer tests. The measurements of tracer agents arriving at producing wells provide direct confirmation of flow communication. Interwell transient tests derive similar information through the measurement of pressure responses (at observation wells) to the production- or injection-rate changes at an active well, and the time required to conduct such tests is much shorter than the time required to conduct tracer tests. For anisotropic reservoirs, such as naturally fractured fields or channel systems, knowing the permeability tensor directions and the ratios of the maximum to the mini-mum permeability in various locations in the field provides better opportunities to make optimal operational decisions. All previously proposed methods in the literature require three sets of interference or pulse tests among wells offset at different azimuths, and the pressure-response data are analyzed simultaneously using type-curve matching to calculate permeability tensors. In practice, there is limited opportunity to conduct all three sets of interference tests through the same well at one time and to analyze them simultaneously to derive a permeability tensor. In the complete paper, a new method is proposed that uses previous test-analysis results directly to estimate the permeability tensor. The analysis results (the permeability and porosity of the fast path linking two wells) from a single set interwell (interference or pulse) test could be obtained using any modern techniques with analytical, semi analytical, or numerical models and would not be limited to conventional type-curve matching. The algorithm uses mathematical matrix operations, and all analysis results can be integrated to generate the field permeability-tensor map. Mathematical aspects of the method, as well as method validation, are discussed in the complete paper.