烃源岩排流体特征及对近源油藏成藏的影响——以东营凹陷北部砂砾岩体为例

Characteristics of formation fluids expelled from source rocks and their effects on reservoir forming: taking sand-conglomerate reservoir of northern Dongying Depression as an example

苗春欣

MIAO Chunxin

中国石化胜利油田分公司勘探开发研究院，山东 东营 257015

Research Institute of Exploration and Development, Shengli Oilfield Company, SINOPEC, Dongying 257015, China

文中分析了东营凹陷古近系沙河街组烃源岩排出流体含油饱和度变化特征，以及有机酸和H2S的形成规律，探讨了烃源岩排流体特征对近源砂砾岩体原油富集的影响，及其对储层的改造作用。结果表明：随演化程度增加，沙河街组烃源岩依次进入排水为主、排低含油饱和度流体、排高含油饱和度流体和再次进入排低含油饱和度流体阶段；有机酸形成于烃源岩未熟—低熟阶段至高成熟阶段的整个生烃过程；热化学成因的H2S在东营凹陷普遍存在。北部砂砾岩体原油富集模式分为高压、高饱和度流体充注成藏和低含油饱和度流体、高部位富集2类；烃源岩排出的有机酸及H2S有利于中深部储层次生孔隙形成。推测成熟烃源岩向浅部或侧向泄流通道附近，以及大量汇集烃源岩流体的储层都是次生孔隙发育有利区。

Oil content of formation fluids expelled from source rocks of Eogene of Dongying Depression in different thermal evolution stages were analyzed, and generation mechanism of organic acids and H2S in source rocks were researched also. According to these, the effects of oil-bearing fluids expelled from source rocks on oil accumulation of sand-conglomerate reservoirs near to source rocks were discussed, and the actions of acids generated in source rocks on sand-conglomerate reservoir secondary pore forming were investigated. With the increasing bury depth, the source rocks enter successively into water only expulsion stage, low oil content fluid expulsion stage, high oil content fluid expulsion stage, and again low oil content fluid expulsion stage. The organic acids generated in all source rock evolution stages, from un-matured to low matured to matured stage. The generating of H2S that originated from sulphurous kerogen cracking and thermochemical sulphate reduction occurred commonly in mature source rocks. The oil accumulation mechanisms of near-source rock sand-conglomerate reservoir of northern Dongying Depression can be classified into two main patterns: pistol-like injection model with high pressure and high oil content fluids in middle and deep formation, top reservoir accumulation model with normal pressure and low oil content fluids driving by buoyancy in shallow formation. Organic acid and H2S expelled from mature source rocks are favorable for tight reservoir secondary pore forming. The reservoir that is inner and near to main channels for fluids expelled from source rock migration upward and horizontally, and reservoirs which is relatively far away from source rocks but accepting source rocks origin fluids are all favorable areas for secondary pore forming.

10.6056/dkyqt201604001