辽河盆地东部凹陷渐新统辉绿岩:特征、识别与成藏规律

Oligocene diabase of Eastern Sag in Liaohe Basin,NE China:characteristics,identification and hydrocarbon accumulation

基于41口钻井3555m辉绿岩井段测录井、岩心岩屑和560km。三维地震资料，通过86件岩石薄片鉴定，建立地质属性～测井／地震响应关系，研究辽河盆地东部凹陷辉绿岩的岩性、岩相和测井识别特征，实现钻井约束一地震填图，探索辉绿岩的空间分布与成藏规律。辉绿岩具全晶质似斑状结构，斑晶为斜长石和单斜辉石，有效储集空间以次生溶蚀孔缝为主。辉绿岩可分为中心和边缘两类亚相，其中有利储层主要发育在边缘亚相。测井特征呈现高阻、低声波时差的平滑或微齿化曲线，地震反射特征为强振幅、中一低频、同相轴连续性较好。纵向上辉绿岩主要分布在沙河街组三段（沙三段）和沙河街组一段（沙一段），岩体存在顺层和穿层两种原始侵入产状，以及碟状与断块两种后期改造形式。辉绿岩的分布受主干走滑断裂（驾掌寺和驾东断裂）控制，有单侧和双侧两种侵入方式，侵入距离为1375—5625m（平均为2572m），岩体厚度为49—165m（平均为112m）。通常辉绿岩体积越大，其上覆地层厚度越大。辉绿岩侵入时代为东营组晚期，是火山一热液作用的产物，流体一围岩相互作用形成的次生溶蚀孔隙是辉绿岩油气成藏的关键因素，“顶面成藏”是辉绿岩的主要成藏规律。

Relationships between geology and logging/seismic responses were established for the study of diabase from Eastern Sag in Liaohe Basin based on 3 555 m logging intervals and core ＆ cuttings of diabase from 41 wells and 560 km2 3D seismic data and observation of 86 thin sections acquired in the area. We investigated the lithology, lithofacies and logging identification features of the diabase, performed well data constraining-seismic mapping, and explored the spa- tial distribution and hydrocarbon accumulation regularity of the rock. Diabase has wholly crystalline porphyric-like texture with phenocrysts of plagioclase and clinopyroxene. The effective reservoir space in the rocks is mainly secondary dissolved pores and fractures. Diabase can be divided into two sub-facies：centrality and border. High-quality reservoirs are inclined to be distributed in border sub-facies. The rocks display themselves as smooth or slight sawtooth logs with high resistivity and low interval transit time , and seismic reflectance signatures of high amplitude, middle- to low-frequency and fine con- tinuity of events. Vertically, the diabase was shown to be mainly distributed in the first and third members of the Shahejie Formation. The rock shows two kinds of original invasion occurrence, namely layer-parallel and translayer invasion and two types of later transformation, i. e. saucer-shaped and fault-block transformation. Distribution of the diabase was mainly controlled by the main strike-slip fault （Jiazhangsi fault and Jiadong fault） of two intrusive manners associated with faul- ting of unilateral and bilateral invasion. The invasion distance were measured to be 1 375 m to 5 625 m and averaged at 2 572 m and thickness of the intrusions was 49 m to 165 m （ averaged 112 m）. Generally,larger volume of diabase means larger thickness of overlying strata. The intrusive age of diabase is dated back to late Dongying period as the result of vol- canic-hydrothermal effects. Secondary pores caused by fluid-rock interaction is suggested to be a critical factor for the for- mation of diabase reservoirs and ＂interface reservoirs＂ is proposed to be the main reservoiring pattern of the rock.