致密砂岩气藏地层孔隙压力预测方法

Prediction of Formation Porosity Pressure in Deep Formation

收集新场构造须二气藏的地质、测井、钻井和压裂等相关资料，尝试运用包括等效深度法、Eaton法、有效应力法在内的多种方法对研究区地层孔隙压力剖面进行了预测。根据前人对川西地区异常高压的产生机制的研究分析，认为川西前陆盆地上三叠统地层异常高压的形成主要受欠压实、生烃增压、黏土矿物脱水增压及构造抬升多种机制影响。最终选用Eaton法建立工区的地层孔隙压力剖面。对地层孔隙压力预测模型进行验证与单井评价，结果表明，模型的预测结果精度较高，能够满足工程要求。根据各单井地层深度划分，新场构造地压梯度情况可大致划分为正常压力带、过渡压力带、高压异常带和压力相对平稳带4个压力区间。该成果对指导后续钻井施工作业和区域地应力场等相关研究具有重要的现实意义。

With various data of well logging, drilling and fracture in Xuer gas reservoir of Xinchang structure, predictions were made by using different approaches including equivalent depth method, Eaton method and effective stress method, for the formation porosity pressure section in this area. According to previous studies for the active mechanism of abnormal high pressure in western Sichuan depression, it is shown that the abnormally high pressure in the foreland basin of the Upper Triassic Formation is mainly affected by uncompacted hydrocarbon booster, booster and dewatering of clay minerals, tectonic uplift. Therefore, in this paper, the Eaton method is adopted to establish the formation porosity pressure section. By verifying the predicting model and evaluating single wells, it is indicated that the predicting model has a very high accuracy to meet the demand of production. According to the depth of stratum, the Xinchang structure can be divided into four pressure areas, including the normal pressure belt, the transition pressure belt, the abnormal high pressure belt and the relatively smooth belt. All of above results may provide some guidance for subsequent drilling jobs and regional stress field researches.