A New Method for Evaluating the Recoverability of Geothermal Fluid Under In Situ Conditions Based on Nuclear Magnetic Resonance

Abstract

Aiming to solve the problems of unclear pore structure, unknown fluid storage and seepage pattern, and inaccurate fluid recoverability evaluation under in situ high pressure of thermal storage, a new method based on in situ high pressure nuclear magnetic resonance displacement test is proposed for evaluating the seepage capacity and recoverability of geothermal fluid under in situ stress. Based on the study of in situ pore structure and movable water content under different displacement pressures, a new prediction method for the recoverable heat of geothermal reservoir fluids is established. This study finds that significant changes in the pore structure of the samples are observed in the in situ test environment. The pore volumes of macropores and mesopores decrease significantly, while the influence of stress on transition pores and micropores is relatively small. Movable water content increases as a logarithmic function with increase in displacement pressure. Considering in situ stress and fluid mobility, the recoverable heat of geothermal fluids predicted under the new assessment methodology is 27.26% of the static predicted resource. Through the establishment of the above model, accurate prediction of recoverable resources can be realized under different in situ stress.