页岩气藏经验产量递减分析方法研究现状

A review of empirical production decline analysis methods for shale gas reservoir

为深入研究和推动经验产量递减分析方法在页岩气藏中的应用,对国内外现有经验产量递减分析方法进行了深入广泛调研。从方法来源、基本模型、典型图版、适用条件、局限性及改进方法等方面,对Arps递减、幂指数递减、扩展指数递减和Duong递减等分析方法进行了详细阐述,同时还给出了今后页岩气藏经验产量递减分析方法的研究重点。研究表明:经验产量递减分析方法都具备产量预测和最终可采储量预测功能,只能对井底流动压力恒定或近似恒定条件下的生产数据进行分析,且要求生产数据连续稳定避免长时间关井。不同经验递减分析方法之间最主要的差异是适用流态不同,其中Arps递减和改进双曲递减仅适用于边界主导流,扩展指数递减和Duong递减适用于线性流,改进Duong递减、幂指数递减和改进幂指数递减适用于线性流和边界主导流。准确识别和划分页岩气井流态是经验产量递减分析方法推广应用的关键。国内页岩气井难以实现井底流动压力恒定或近似恒定的生产方式,如何准确将生产数据校正为定压生产条件下的生产数据是下一步经验产量递减分析方法的研究重点。

The empirical production decline analysis methods inside and outside China were investigated extensively for further understanding these methods and promoting their application in development of shale gas reservoirs. The Arps, power exponential, stretched exponential and Duong decline analysis methods were elaborated in terms of source, decline model, typical curve, application condition, limitation and improved method, and finally the key issues related to empirical production decline analysis methods in future study were proposed. The study results indicate that all the empirical production decline analysis methods are capable of forecasting both production and EUR, but they can only analyze the production data under constant or approximately constant bottom-hole flowing pressure, and require continuous and stable production data without long-term shut-in. The difference in these empirical production decline analysis methods lies in different flow regime. Arias decline model and modified hyperbolic decline model are only available to boundary-dominated flow regime. Stretched exponential decline model and Duong decline model are useful for linear flow regime. Modified Duong decline model, modified power exponential decline model and power exponential decline model are applicable for both linear and boundary-dominated flow regimes. It is critical to identify and classify the flow regime in a shale gas well for application of empirical production decline analysis. In shale gas wells in China, it is hard to keep constant or approximately constant bottom-hole flowing pressure during production, then how to correct such production data to the data under constant or approximately constant bottom-hole flowing pressure is the emphasis in future study on empirical production decline analysis methods.