川东北YB地区陆相地层超压特征及压力预测

摘要

In YB area of the northeastern Sichuan Basin, several sets of pressure systems exist. From the upper Triassic to Jurassic, especially in continental strata, overpressure and strong overpressure are common. Based on DST ( drill stem test) and logging data, the present pressure features in YB area and the logging responses of mudstone overpressure sections in 3 typical wells are analyzed. The pressure coefficient of continental strata from the Upper Triassic to Jurassic in YB area ranges from 1.3 to 2. 2, indicating overpressure or strong overpressure. The top burial depth of overpressure zones locates at 3 600-4 000 m. The logging responses of mudstone overpressure sections show that the resistance of mudstones changes obviously while DT and mudstone density do not change very much. It might be related to the obvious difference between ancient and present burial depth and the high saturation of gas. The formation pressures converted from mudstone DT by means of Eaton formula are close to field testing results. A pressure prediction model to revise mudstone acoustic logging based on tested pressure has been made and might achieve good prediction results.%川东北YB地区存在多套压力系统,上三叠统—侏罗系陆相地层普遍发育超压及强超压.根据钻杆测试和测井资料,分析了YB地区现今压力特征和3口典型井泥岩超压段的测井响应特征,结果表明,YB地区陆相地层上三:叠统—侏罗系压力系数分布在1.3～2.2之间,该区普遍发育超压至强超压,超压的顶界面约在3600～4000 m左右;超压段泥岩测井响应特征显示,声波时差和泥岩密度变化相对较小,泥岩电阻率变化较大,这可能与超压段古埋深与现今埋深差别较大、地层含气饱和度较高有关.采用Eaton公式利用泥岩声波时差换算出的地层压力与实测结果接近.研究认为,利用实测压力校正泥岩声波测井的压力预测模型,有可能取得更好的预测效果.