苏北盆地海安凹陷下白垩统层序地层和沉积相研究

Characteristics and Evolution of Late Cretaceous Sequence Stratigraphy and Sedimentary Facies in Hai'an Sag

运用地震、测井和分析化验等资料,对苏北盆地海安凹陷下白垩统泰州组进行了层序地层和沉积相研究,将泰州组划分为2个三级层序(泰一段构成层序I1和泰二段构成层序I2)和5个体系域,其中,层序I1沉积于盆地断陷期,由于受仪征运动的影响该层序多与下伏浦口组为角度不整合接触,彼此间为典型的层序界面,发育辫状河冲积平原相、辫状河三角洲前缘相、滨—浅湖相和半深湖相沉积;层序I2形成于盆地拗陷期,主要发育辫状河三角洲前缘相、半深湖—深湖相沉积,湖泊沉积范围广,湖相暗色泥岩沉积是盆地主要烃源岩。指出海安凹陷生油层主要发育于沉积层序I2中部湖侵体系域的泥灰岩段,该生油层本身又是良好盖层;而储集层则主要发育在沉积层序Ⅰ1和I2顶部的高水位晚期;海安凹陷中心发育的辫状河三角洲前缘及前三角洲砂体是油气的有利勘探区。

This article studies the sequence stratigraphy and sedimentary facies of the Taizhou Formation in the Hal ＇an sag in the Subei basin using seismic data, well log data, and assaying data. The Taizhou Formation can be divided into 2 third-order sequences and 5 system fields. Sequence I1 consists of the member 1 of the Taizhou Formation, sequence I2 consists of the member 2 of the Taizhou Formation. The sequence I1 was deposited during the faulting period of the basin, during the period when the plain of braided delta, the front of braided delta and shoreshallow lake subfacies were developed. Sequence I2 was deposited during the depression period and the shrinking period of the basin, during this period, the front of braided delta and deep facies were developed. The main source rocks were developed in the middle of the TST sequence I2 which is also good capping formation. The sand body reservoirs of lake 2 delta and fan delta were developed during the later period of the HST sequences I1 and I2, and are the potential areas for oil and gas.