辉绿岩热液作用对围岩储层影响的机理研究

Currently, oil and gas reservoir are discovered in the metamorphic zone, where the rocks surrounded by diabase rock have been reformed through hydrothermal action. The evolution and distribution of these reservoirs is closely related to hydrothermal fluid, which played an important role on surrounding rocks. Thus, aimed at the surrounding rocks distributed in Jiyang depression of Bohai bay basin, Gaoyou depression of Subei basin and Beishan area in Bejing district, different studies are carried out as follows: First study comparison between surrounding reservoirs influenced by hydrothermal fluid and not referred through by the rock characteristics, physical characteristic, pore type and pore structure, the crack development characteristics, diagenesis, and the evolution of characteristics of clay minerals, cement types and distribution characteristics, then study effects on surrounding reservoirs caused by different occurrence of diabase intrusions, influence of hydrothermal fluid on the surrounding reservoirs at different combination of sand and shale wall rock reservoir, and influence of hydrothermal fluid on the surrounding reservoirs at different diagenetic stages. Different temperature effects as clay mineral inversion, temperature measuring of cementing fluid inclusion and apatite fission track in authigenic minerals are considered to trace the fluid activity. According to the reactions between fluid and rock, the study of mechanism how hydrothermal action reacted on surrounding rock is conducted to provide theoretical reference for further assessment on unconventional reservoir and prediction for favorable area in contact metamorphic zone.

近年来，在辉绿岩的围岩经过热液改造形成的变质带内发现了油气藏，其形成与分布与热液对围岩储层的改造关系密切。本项目以渤海湾盆地的济阳坳陷、苏北盆地的高邮凹陷和北京北山地区侵入岩的围岩为研究对象，首先通过岩石学特征、物性特征、孔隙类型和孔隙结构、裂缝发育特征、成岩作用、粘土矿物的演化特征、胶结物类型及分布特征等研究开展被热液改造围岩储层与未受热液改造储层特征的差异分析，其次，进行辉绿岩侵入热液对不同的砂泥岩组合围岩储层的影响差异性研究、不同产状辉绿岩侵入体（岩墙和岩床）对围岩储层影响的差异研究和辉绿岩热液对处于不同成岩阶段的围岩储层改造差异研究，在此基础上探索粘土矿物转化、胶结物流体包裹体测温、自生矿物中磷灰石裂变径迹等温度效应进行流体活动示踪，通过流体-岩石反应效应，探讨热液作用对围岩储层的影响机理，为深化特殊油气储层评价、预测接触变质带有利储层发育区提供重要的理论依据。

岩浆侵入能够形成多种不同类型油气储层。深入研究岩浆侵入对围岩储层的影响机理对扩展油气勘探领域具有重要意义。本课题主要以受辉绿岩侵入影响的油田和露头（苏北盆地高邮凹陷、团山子采石场及北京北山）为研究实例，对上述科学问题进行了探索。高邮凹陷北斜坡古近系阜宁组辉绿岩及其热接触变质带发育广泛，根据储层岩石的变质程度，将辉绿岩热接触变质带划分为中级和低级变质带。其中泥岩变质主要形成板岩和角岩，砂岩变质成为变质砂岩。变质泥岩储集空间主要由晶间微孔、微裂缝、微溶孔和构造缝构成；而变质砂岩中发育原生粒间孔、粒间溶孔、粒内溶孔、铸模孔和超大孔。辉绿岩侵入带来的高温，高压以及释放的热流体是影响变质带储层发育的主要因素。岩石经过改造后储集性能不同，其中变质泥岩（尤其是角岩）物性比正常泥岩好，为有利储层；而变质砂岩物性整体比正常砂岩差。综合以上研究建立了接触变质带储层发育模式。对松辽盆地南部团山子采石场辉绿岩侵入露头进行研究，采用连续密集取样，利用常规分析和碳、氧稳定同位素等测试手段，对围岩成岩及变质特征进行了全面分析。岩浆侵入对角岩围岩影响包括：（1）自生绢云母随距侵入体越远，其含量越少；（2）粘土矿物主要为成岩晚期的伊利石和绿泥石；（3）角岩中发育特殊“气孔-杏仁”构造。岩浆侵入对上覆砂岩影响表现为：（1）造成自生石英的特征分布；（2）造成粘土矿物的不均匀分布；（3）形成反映应力挤压特征的颗粒结构。角岩中浊沸石发育和高岭石不发育反应了碱性环境，不利于热液微裂缝中碳酸盐矿物被溶蚀。因此尽管角岩发育微孔、微缝等少量储集空间，但渗透能力很低。侵入活动对研究露头砂岩储层物性造成不利影响，主要由于挤压作用和热液流动作用影响，导致自生矿物不均匀分布，从而造成或是加剧了砂岩储层的非均质性。对北京北山虎峪露头裂缝特征进行初步探索，结果表明辉绿岩侵入对砂岩围岩裂缝的发育具有积极作用，在一定程度上改善储集性能。