准噶尔盆地腹部地层压力异常特征与控制因素

Formation pressure anomalies and controlling factors in central Juggar Basin

应用钻井地层压力实测资料、测录井资料和地震速度资料等,结合盆地地层沉积结构分析,对准噶尔盆地腹部地区地层超压异常的横、纵向空间分布特征及其成因控制因素进行综合研究。研究表明:1)超压异常在盆地腹部地区普遍存在,其出现的顶界面具有穿层性,整体具有向西北方向超压顶面埋深变浅、向凹陷内埋藏变深的特点;超压顶面在莫索湾地区为侏罗系三工河组,顶面埋深在4 400 m左右,向西到夏盐-达巴松和玛湖地区超压顶面为三叠系,埋深在3 500 m左右,在莫南凸起的永进油田超压顶面在白垩系底部,埋深在5 800 m左右。2)莫索湾地区的侏罗系以下地层都存在超压异常,侏罗系的异常压力值最高,在二叠系-石炭系有所降低;同时,根据压力系数结构剖面特征分析,将超压异常划分为两种类型。3)分析盆地腹部超压异常的空间特征,认为不同层系、不同构造位置的超压异常形成具有不同的控制因素。

Formation pressure measurements and logging and seismic data were combined with basin sedimentary texture to analyze the spatial distribution of formation overpressure and its controlling factors. The results show that 1) overpressure zone is widely distributed in the central part of the basin. It has a diachronous top surface,shallows overall in NW direction and deepens toward the centre of the sag. In Mosuwan area,the top surface of the overpressure zone corresponds to the Jurassic Sangonghe Formation and has a burial depth of about 4 400 m. In Xiayan-Dabasong and the Mahu areas to the west,it corresponds to the Triassic and shallows to 3 500 m. In an oil field called Yongjin in Munan uplift,it corresponds to the bottom of the Cretaceous and deepens to about 5 800 m. 2) Overpressure can be observed in layers at and below the Jurassic in Mosuowan area with the highest values measured in the Jurassic and some lower values measured in the Permian-Carboniferous. Two types of overpressure are classified based on profile characteristics of pressure coefficient structure. 3) Spatial characteristics of the overpressure anomalies in central Basin reveal the roles of different controlling factors upon the forming of overpressure in different tectonic locations in the basin.