钱家店凹陷胡力海洼陷下白垩统九佛堂组层序地层特征及其油气勘探意义

以层序地层学理论为指导,以钱家店凹陷胡力海洼陷钻井、测井、地震等资料为基础,结合构造演化、沉积环境、气候条件等层序背景分析,将该区白垩系划分1个Ⅰ级层序、2个Ⅱ级层序、6个Ⅲ级层序。其中,SⅢ1(下白垩统九佛堂组)构型完整、特征典型,分别由低位体系域、湖侵体系域和高位体系域组成。针对研究区层序发育特点,在层序地层单元划分和对比基础上,对层序格架内的沉积相类型和沉积体系分布规律进行研究,总结出胡力海洼陷SⅢ1具有近物源、多物源、快速沉降、快速沉积的特点。SⅢ1高位体系域在西部陡坡带发育近岸水下扇,在东部缓坡带发育扇三角洲,在中央洼陷带则以浅湖—半深湖为主,局部区域分布浊积砂体。由于该层段介于两个级别层序(Ⅱ级和Ⅲ级)的湖侵体系域之间,烃源岩和盖层条件良好,且发育多种有利储集体,是胡力海洼陷寻找岩性油气藏的最有利层段。

Sequence Stratigraphy Characteristics and Its Significance to Petroleum Exploration of Lower Cretaceous Jiufotang Formation in Hulihai Sag,Qianjiadian Depression

Guided by sequence stratigraphy and based on seismic, drilling and well logging data in Hulihai sag of Qianjiadian Depression, analyzing the background of structural evolution and sedimentary environment, climate condition, Cretaceous sequence can be subdivided into one first-order sequence, two second-order sequence, six third-order sequence. S III1 （Lower Cretaceous Jiufotang Formation） develops completely, which is composed of lowstand, transgressive and highstand system tracts. According to the characteristics of sequence development and based on division and comparison of sequence formation units, sedimentary types and system are studied. It is concluded that SIII1 in Hulihai sag features in near and more provenances, rapid subsidence and rapid deposition. The highstand system of S III1 develops nearshore subaqueous fans in the west steep slope belt, and fan delta in the east gentle belt. Shore-shallow lacustrine and deep lacustrine facies are recognized in the central sag; turbidite fan is distributed in some area. The sequence, which is between the transgressive system tract of the second and the third-order sequence, has the best source rocks and sealing conditions as well as various favorable reservoirs. So it is the most favorable target for obtaining discoveries in Hulihai sag.