鄂尔多斯盆地奥陶系白云岩成因及白云岩储层发育特征  

Origin and reservoir characteristics of Ordovician dolostones in the Ordos Basin

作　　者：包洪平[1,2] 杨帆[1,2] 蔡郑红[1,2] 王前平[1,2] 武春英[1,2] Bao Hongping Yang Fan Cai Zhenghong Wang Qianping Wu Chunying(PetroChina Changqing Oilfield Company, Xi＇an, Shaanxi 710018, China State Engineering Laboratory of Explo- ration and Development for Low-Permeability Oil and Gas Fields, Xi＇an, Shaanxi 710018, China)

机构地区：[1]中国石油长庆油田公司 [2]低渗透油气田勘探开发国家工程实验室

出　　处：《天然气工业》2017年第1期32-45,共14页Natural Gas Industry

基　　金："十三五"国家科技重大专项"大型油气田及煤层气开发"(编号:2016ZX05004-006)

摘　　要：白云岩是鄂尔多斯盆地奥陶系最重要的有效储集岩类,由于岩石结构及产状特征复杂多变,对其成因认识尚存在争议。为此,综合宏观区域地质背景、微观岩石结构、矿物学及岩石地球化学等分析研究成果,将该区奥陶系白云岩划分为泥—细粉晶、粗粉晶、细(中)晶3种类型,指出其分别形成于"蒸发泵吸准同生云化""淡水与富镁卤水混合水云化""回流—渗透云化"3种不同的白云岩化成岩作用环境,并在层位及空间展布上表现出明显的"层控性"及"区位性"分布特征。进而探讨了白云岩的成因,结果认为:① 3种白云岩化作用在时空演化特征上表现出一定的相关性,即均与蒸发背景下的膏盐矿物沉淀有着密切的成因联系;②白云岩中所发育的溶孔、白云石晶间孔及生物格架孔等主要孔隙类型分别形成于3种白云岩类型中,对白云岩类型表现出一定的"专属性",表明孔隙成因与白云岩化成岩作用环境密切相关;③白云岩有效储层的发育与分布主要受原始沉积相带、大区白云岩化的成岩作用环境、相对海平面变化产生的层序界面等3类要素的控制。Dolomite is the most important rock type for the development of the Ordovician effective reservoirs in the Ordos Basin. Its genesis remains controversial due to its complex and variable rock texture and occurrence. In this paper, through analysis of macroscopic regional geological background, microscopic rock texture, mineralogy, and geochemistry, the Ordovician dolomites in this area are divided into three types, i.e. micritic-fine powder crystal, coarse powder crystal, and fine （medium） crystal. It is pointed out that they were formed in three different dolomitization diagenetic environments, namely, penecontemporaneous dolomization by evaporative pumping, mixture dolomitization of freshwater and magnesium-rich brine, and seepage-reflux dolomitization, respectively. In terms of horizon and spatial distribution, they represent the features of ＂strata-controlled＂ and ＂region-specific＂. The analysis of genesis provides the following findings. First, the three types of dolomitization are correlated to certain extent in terms of temporal-spatial evolution. In other words, they were all originated along with the deposition of gypsum mineral under evaporation background. Second, the main pore types, i.e. dissolved pores, intercrystalline pores, and organic framework, were respectively formed in three types of dolomites. They generally dis- tribute in ＂specific＂ type of dolomite, which indicates that the pore genesis is closely related to dolomitization diagenesis environment. Third, the development and distribution of effective dolomite reservoirs is mainly subject to three types of elements, such as primary sed- imentary faices belts, diagenetic environment controlling regional dolomitization, and sequence boundary caused by variation of relative sea level.

关 键 词：鄂尔多斯盆地 奥陶纪 白云岩成因 地球化学 储集层 白云岩分布 层控性 区位性 

分 类 号：P618.13[天文地球—矿床学] P588.245[天文地球—地质学]