莺琼盆地高温高压井地层温度计算方法研究与应用

南海西部海域莺琼盆地地质环境非常复杂, 地层温度分布范围较广, 最高地层温度超过240℃。目前探井地质设计时地温计算沿用的方法大多是利用最大测井温度或完井测试温度计算的地温梯度来预测井底温度, 存在较大的局限性和误差。为了降低井底温度的预测误差, 优化勘探开发地质设计, 对随钻测量温度和电缆测井温度的影响因素进行了分析, 利用外推法建立了地层温度的计算模型, 与测试所得的静止温度基本一致。此外, 利用外推法计算得到区域单井的井底温度数据, 建立了莺琼盆地不同地质层组的地温梯度模型, 同时, 采用地质分层组地温梯度累加计算井底温度的方法, 对单井井底温度进行预测, 预测结果与测试静止温度误差较小。结果表明, 利用外推法计算地层温度是正确且可行的, 可以用于钻前井底地层温度的预测。

The geologic environment in the Yingqiong Basin, the western South China Sea is very complex, where formation temperature covers a wide range and exceeds 240℃ at its maximum.For the geologic design of an exploratory well, bottom-hole temperature 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 design, 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.