Challenges and countermeasures of log evaluation in unconventional petroleum exploration and development

Abstract

To promote adaptation of logging evaluation technologies to the development trend of unconventional oil and gas exploration and development era in China, the current situation and challenges of logging evaluation technologies in China are analyzed systematically. Based on the concept of that demand drives technology development, and referring to the international leading technologies, development strategy of logging evaluation technology in China has been put forward. (1) Deepen petrophysics study: mobile 2D NMR laboratory analysis technology for full diameter core should be developed, characteristic charts and evaluation standards of different fluid properties, different pore structures and different core exposure times should be established based on longitudinal and traverse relaxation spectra; in-depth digital rock experiment and mathematical and physical simulation research should be carried out to create innovative logging evaluation methods; acoustic and electrical anisotropy experimental analysis technology should be developed, and corresponding logging evaluation methods be innovated. (2) Strengthen target processing of logging data: precise inversion processing technology and sensitive information extraction technology of 2D NMR logging should be developed to finely describe the micro-pore distribution in tight reservoir and accurately distinguish movable oil, bound oil, and bound water etc. The processing method of 3D ultra-distance detection acoustic logging should be researched. (3) Develop special logging interpretation and evaluation methods: first, mathematical model for quantitatively describing the saturation distribution law of unconventional oil and gas near source and in source should be created; second, evaluation methods and standards of shale oil and deep shale gas “sweet-spots” with mobile oil content and gas content as key parameter separately should be researched vigorously; third, calculation methods of pore pressure under two high-pressure genetic mechanisms, under-compaction and hydrocarbon charging, should be improved; fourth, evaluation method of formation fracability considering the reservoir geologic and engineering quality, and optimization method of horizontal well fracturing stage and cluster based on comprehensive evaluation of stress barrier and lithologic barrier should be worked out.