Impacts of Environmental Factors on LWD Curves and Calibration Techniques in Horizontal Shale Gas Wells

LWD curves can not fully represent the actual characteristics of shale formations due to environmental factors,and so to improve the accuracy of geosteering and to improve the rate of drilling in high-quality shale formations,real-time calibration is needed.Taking horizontal wells with LWD data in Weiyuan Shale Gas Industry Demonstration Zone as research objects,the characteristics of LWD curves under different environment were evaluated quantitatively and qualitatively to construct calibration charts.Optimal fitting,numerical iterative and other techniques were deployed to establish calibration models for relevant charts.Feasibilities of such operations were analyzed by using core data from laboratories.In this way,one complete package of calibration techniques for impacts of environmental factors on LWD curves of shale formationa was obtained.The newly-developed techniques were used in the LWD data processing from shale formation of 12 horizontal wells in the Weiyuan Area.Relevant results showed that such calibration can effectively eliminate the negative impacts of stratigraphic electrical anisotropy,relative angle,borehole environment,instrument deviation,drilling fluid density and other environmental factors to obtain the features of penetrated formations more accurately.