摘要
鄂尔多斯盆地临兴地区上古生界致密砂岩气藏资源勘探潜力巨大，但是成藏规律及运移方式较为模糊。基于构造、沉积相和砂体展布特征，临兴地区上古生界源-储组合关系可分为源内、近源和远源3种类型。利用岩石热解、热成熟度测定、岩心描述、薄片鉴定、扫描电镜观察，物性分析以及地震和测井等资料，对烃源岩、储层、充注动力及断裂的发育进行分析。结果表明：临兴地区发育煤、炭质泥岩和暗色泥岩3套烃源岩，干酪根类型为Ⅲ和Ⅱ型，有机质丰度较高，普遍进入成熟-高成熟阶段，生气潜力较大；储层岩石类型以成熟度中等的长石岩屑砂岩为主，非均质性强，孔喉类型多样，包括原生粒间孔、溶解粒间孔、溶解粒内孔、晶间孔和微裂缝。物性以低孔-低渗为主，平均孔隙度为6.81%，平均渗透率为0.610×10 μm，属于典型致密储层；地层超压普遍发育，气体膨胀力是源内、近源组合成藏的关键动力；断裂十分发育，既可为天然气垂向充注至远源组合提供运移通道，又能改善储层品质，提高天然气横向运移能力。在此基础上，对建立起的成藏模式进行物理模拟实验，发现储层非均质性及断裂的发育是影响气水关系的主要因素，源内组合处于成藏优势区，可作为后期勘探开发的重点。
Abstract
The exploration potential of the Upper Paleozoic tight sandstone gas reservoirs in Linxing area, Ordos Basin is huge, but the accumulation patterns and migration pathways are relatively controversial.Based on the characteristics of structure, sedimentary facies and sand-body distribution, the source-reservoir combination relationship of the Upper Paleozoic in Linxing area can be categorized into three types:in-source-, near-source- and far-source-reservoir combinations.Using the data of rock pyrolysis, thermal maturity measurement, core description, thin-section observation, scanning electron microscopy, petrophysical property analysis, seismic and well logging interpretation, we analyzed the development characteristics of the source rock, reservoir, charging dynamics and faults.The results show that there are three sets of hydrocarbon source rocks in Linxing area, including coal, carbonaceous mudstone and dark mudstone source rocks with Type Ⅲ and Ⅱ kerogens.The source rocks have high abundance of organic matter and are mostly mature to highly mature, thus are large in hydrocarbon generation potential.The reservoir rocks are dominated by feldspar lithic sandstone of moderate maturity, and are characterized by high heterogeneity and multiple pore throat types, including primary intergranular pores, dissolved intergranular pores, dissolved intragranular pores, intercrystalline pores and micro-cracks.The reservoirs mostly have low porosity and low permeability, with an average porosity of 6.81% and an average permeability of 0.61×10 μm, which reflects a typical tight reservoir.Overpressure is common and gas expansion force is the main driving force for gas accumulation of the in-source- and near-source-reservoir combinations.The well-developed faults can serve as the migration pathways for the natural gas vertically charging to the far-source-reservoir combination and can also improve the reservoir quality and strengthen the lateral migration ability of natural gas.Physical simulation experiments were carried out on the established accumulation model, and it was found that reservoir heterogeneity and faults are the main factors affecting the gas-water relationship.The in-source-reservoir combination is the favorable area for hydrocarbon accumulation, and can be selected as the focus of later exploration and development.
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