Technical Progress and Developing Trends in Unconventional Oil and Gas Mud Logging in China

Unconventional oil and gas pose new challenges to mud logging,including detection resolution,data quality,the completeness of acquired parameters,the effectiveness of evaluation methods etc.Through the study of the "12th Five-Year Plan Period",four innovative logging technologies,namely element logging,on-line logging of drilling fluid NMR,portable 3D NMR logging with high resolution and front setting gas logging with high resolution were developed,and improved the resolution of detecting the elements from 12 kinds to over 20 kinds in the element logging,which fills the gap of on-line detecting the oil content in drilling fluids.In addition,pore throat resolutions of core has been raised 10 times as high as the past,and the detection dimensions changed from 1D to 3D.At the same time,resolution for gas component was improved from C5 to C8 or C10.Three kinds of comprehensive evaluation methods,including geosteering for horizontal wells,tight sand reservoir evaluation and gas shale evaluation,were established.With the increase of geological complexity and requirements for reducing cost,increasing production and efficiency,there is an incentive for developing technologies including microstructure detection,carbon isotope analysis,integration of logging instruments,3D geosteering in horizontal wells,MWD of pore pressures in fractured shale etc.