Resistivity correction for drilling fluid invasion using LWD and wire-line logging data: A case from high-porosity and low-permeability carbonate reservoirs, DLL Oilfield, Oman

Abstract

The effect of drilling fluid invasion on the resistivity of oil-bearing zones during the period from penetrating the zone to completion well logging was studied using intergraded logging while drilling (LWD) and wire-line log data. The results indicate that resistivity change during invasion responds to some important factors such as porosity, oil saturation, pressure differential between drilling mud column and formation, mud filtrate salinity and invasion time. It increases as an exponential function of porosity, a logarithmic function of pressure differential, and a power function of invasion time and oil saturation. Based on the LWD and MDT data, the corrected resistivity equation subject to the drilling fluid invasion was acquired. With the equation, the oil saturation (So) increases by 6.3%–20.0%, averaging at 10.2%. 摘 要: 基于阿曼DLL油田高孔低渗碳酸盐岩油藏的随钻测井（LWD）和电缆测井资料，综合研究了从钻开储集层到完井测井时间内钻井液侵入对高孔低渗碳酸盐岩储集层电阻率的影响。结果表明，钻井液侵入对储集层电阻率的影响程度与储集层的孔隙度、钻井液柱与地层压力差、含水饱和度、钻井液矿化度以及侵入时间相关，其与孔隙度增加呈指数增大关系，与钻井液柱和地层压力差呈对数增大关系，与含水饱和度以及侵入时间呈幂指数增大关系。根据DLL油田LWD测井资料和MDT压力资料，得出储集层电阻率受钻井液侵入影响的校正方程。由校正后电阻率计算的含油饱和度比电阻率校正前计算的含油饱和度增加了6.3%～20.0%，平均增加10.2%。图9表4参16 Key words: drilling fluid invasion, resistivity decrease degree, horizontal well, LWD, wire-line logging, high-porosity and low-permeability reservoir, carbonate rock