A systematic step-wise approach for shale gas assessment in undeveloped prospects: A case study of Lurestan shale gas area in Iran

Abstract

Key parameters and evaluation methods of shale gas show that it is not possible to guarantee the commercial and economic development of shale gas by sorting out geological sweet spots only according to technical indicators. A research method combining technical indicators including total organic carbon content and vitrinite reflectance with economic indicators including internal rate of return and investment payback period is proposed to screen the best technological and economic development sweet spots in undeveloped areas. This method was used to evaluate the best technological and economic development sweet spots in Cretaceous shale gas reservoirs S1 and S2 of Lurestan area, Iran. Twenty-one geologic sweet spots were picked out based on effective reservoir thickness, vitrinite reflectance and gas content. Based on analogy method, the pressure gradient, clay mineral content, buried depth and other parameters were taken as comparative indicators, the Eagle Ford shale as comparison object, recovery factor and production curve were extracted to estimate the technologically recoverable reserves of the study area. On this basis, the economic indexes such as internal rate of return and investment payback period were used to evaluate the economy of the geological sweet spots. In the case of P10 distribution, the total technologically recoverable reserves and economically recoverable reserves are 7875×108 m3 and 4306×108 m3 respectively, 11 geological sweet spots have commercial development value, among which, No. 1 sweet spot has the highest value, with a net present value of 35×108 USD.