Study on the differences in logging responses of dolomite reservoirs in oil-based and water-based mud environments:a case study of the Dengying Formation in the central Sichuan paleo-uplift
The Dengying Formation in the Penglai gas field of the central Sichuan paleo-uplift is an ultra-deep stratum.some wells use oil-based mud drilling to adapt to the high-temperature and high-pressure environment and increase drilling speed.Therefore,it is important to clarify the differences in logging responses between oil-based and water-based mud environments for reservoir logging evaluation.In this study,two wells(well A and well B)were selected to conduct experiments replacing oil-based mud with water-based mud.Combined with core and gas test data,the differences in logging response characteristics under oil-based and water-based mud measurement conditions were clarified for conventional logging and electric imaging logging.The analysis results showed that:(1)Under the condition of oil-based mud,the values of the natural gamma curve,acoustic logging curves and compensated neuron logging curve at the expanded section are not affected by the mud properties;the compensated density logging curve values are slightly lower,and the differences are greater at the expanded section;the values of the compensated neuron curve at the unexpanded section are not affected by the mud environment;(2)Under the condition of oil-based mud,the resistivity logging of the array induction logging is sensitive to the water layer,and there is a negative difference phenomenon in the water layer;(3)Under the conditions of water-based and oil-based mud,the resistivity logging of the dual laterolog is significantly higher than the resistivity logging of the array induction logging;(4)Oil-based mud imaging logging can display the same formation information as water-based mud imaging logging,and it is not easy to identify borehole collapse and stress relief fractures.The conclusion is that in the oil-based mud environment,the compensated density curve values need to be corrected at the expanded section,and imaging logging in the oil-based mud environment can accurately identify geological features and be used for reservoir evaluation.
Differences in mud environmentOil-based mudArray induction loggingDual laterolog
NETL
NSTL
万方数据
