准噶尔盆地腹部超压层分布研究

Study into the distribution of overpressure stratum in the hinterland of Jungar basin.

准噶尔盆地腹部普遍发育深层(大于4 000 m)超压系统,很多钻井都钻遇超压。通过对超压段钻井、地质、测井、地震特征的系统研究发现,超压段泥浆密度大幅增加,具有高声波时差、低电阻率以及地震低速的超压响应特征。利用Dix公式计算地震层速度和利用Fillippone公式计算地层压力,得到超压数据体。准噶尔盆地腹部超压在白垩系及其以下沉积地层中均有分布,超压层的深度范围不同。盆1井西凹陷较浅,其次是东道海子北凹陷和昌吉凹陷东部,昌吉凹陷中部和西部最深。超压层大多顺层分布,只是在凹陷边缘以及昌吉凹陷西南有穿层现象。超压顶面分布的层位由北往南、从东到西逐渐变浅,从三叠系顶部到白垩系底部。深部超压对油气分布和富集有着重要的控制作用,准噶尔盆地腹部超压层分布的研究将对本区油气勘探起到积极的推动作用。

Deep zone overpressure system is commonly developed in the hinterland of Junggar basin (deeper than 4, 000 meters) and so many drillings met the overpressure zone. The analysis of drilling, geology, logging, and seismic data in the overpressure section shows that the slurry density of overpressure zone has a great increase, and is characterized by the overpressure response of high a-coustic travel time, low resistivity, and low seismic velocity. Based on this model, the seismic interval velocity was calculated by the Dix formula and the strata pressure was computed by the Fillippone formula for the overpressure data volume. The overpressure zone in the hinterland of Junggar basin distributes in Cretaceous formation and the sedimentary formations under the Cretaceous formation. The depth of the overpressure stratums differs in different sags, with the west sag of Penl well being shallowest, the north sag of Dongdaohaizi and the east part of Changji sag being the second shallowest, and the centre and west of Changji sag the deepest. Most of the overpressure stratums are along-bed distributed, except the margin area of the sag and the southwest of Changji sag where layer penetration can be found. The stratums distributed on the top of the overpressure zone become shallow from north to south, from east to west, and from the top of Triassic to the bottom of Cretaceous. The deep overpressure has a significant control effect on hydrocarbon distribution and accumulation. The study of overpressure distribution in the hinterland of Junggar basin will promote the hydrocarbon exploration in this area.