The geologic environment in the Yingqiong Basin,the western South China Sea is very complex,where formation tem-perature covers a wide range and exceeds 240℃ at its maximum.For the geologic design of an exploratory well,bottom-hole tem-perature is generally predicted using the geothermal gradient calculated with the maximum log temperature or temperature tested during well completion;but this method has great limitations and error.To reduce the error of prediction and optimize geologic de-sign,we use an extrapolation method to establish a model for formation temperature calculation based on the analysis of major controls on temperature measurement while drilling and wireline temperature logging;the outputs are basically consistent with static temperature measurements.We also use individual-well bottom-hole temperature data derived from extrapolation to build a geothermal gradient model for different formations in the Yingqiong Basin,and add up geothermal gradients of different formations to predict individual-well bottom-hole temperature.The errors between predicted results and the tested static temperatures are small.The method of extrapolation is demonstrated to be feasible and correct for formation temperature calculation and could be used to predict the bottom-hole temperature before drilling.
formation temperatureextrapolation methodtemperature recovery ratehigh temperature and high pressureYingqiong Basingeothermal gradient
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