柴达木盆地德令哈坳陷石炭系页岩气系统评价

石炭系是柴达木盆地油气勘探的新层系，油气勘探程度低，但发育厚度大的高有机质丰度泥页岩，具有很好的页岩气资源潜力。通过对德令哈坳陷石炭系露头剖面进行实测和钻井岩心分析，明确石炭系泥页岩空间展布特征。测定样品有机地球化学参数、孔渗特征，并且进行等温吸附和渗流实验，分析其储集特征。结合德参1井盆地模拟分析，研究石炭系页岩气成藏事件，划分德令哈坳陷石炭系页岩气系统。研究表明：石炭系泥页岩广泛发育，埋深较大但未发生变质；泥页岩有机质丰度较高，有机质类型主要为Ⅱ2型和Ⅲ型，处于成熟-高成熟演化阶段；上石炭统泥页岩发育优于下石炭统；泥页岩表现为低孔低渗特征，孔隙度在1.89%~5.48%，渗透率为(0.115~2.7)×10-7 μm2；上覆地层发育厚层泥页岩可以提供良好的盖层条件；古近纪末-现今为页岩气系统形成的关键时期；上石炭统克鲁克组钻遇天然气显示，证实了德令哈坳陷石炭系页岩气系统的存在。在泥页岩厚度、埋深、TOC含量、成熟度等条件综合评价基础上，将德令哈坳陷划分为德令哈页岩气系统与埃北页岩气系统。

Carboniferous shale gas system evaluation for the Delingha depression in Qaidam Basin

As one of petroleum exploration frontier formations in Qaidam Basin, Carboniferous has great shale gas source potentialities but at a relatively immature exploration stage presently. Based on field geological survey and drilled well analyses, the distribution of Carboniferous shale for the Delingha depression in Qaidam Basin was clarified. The characteristics of organic geochemistry, porosity and permeability for Carboniferous shale samples were tested. We also made isothermal adsorption tests and seepage experiments for studying the shale accumulation conditions. Combined with basin modeling analysis of Well Decan 1, this paper evaluated Carboniferous shale gas system for the Delingha depression in Qaidam Basin. Carboniferous shale is widely distributed in the depression with various thickness and buried depth. Most shale has higher organic matter richness and organic matter types of Ⅱ2 and Ⅲ, and is at the thermal stage of maturity and high maturity. Upper Carboniferous shale has large thickness and organic matter richness than that of Lower Carboniferous. Carboniferous shale shows the reservoir characteristics of low porosity of 1.89%5.48% and low permeability of (0.1152.7)×10-7 μm2. Thick shale of overlying formations provides favorable cap condition for Carboniferous shale gas. Basin modeling indicates that from the end of the Paleogene to present is the critical moment for the Carboniferous shale gas system in the Delingha depression. Natural gas shows of Keluke Group of Upper Carboniferous indicate that Carboniferous shale gas system exists in the Delingha depression. In light of shale thickness, buried depth, TOC, thermal maturity and other geological conditions comprehensive evaluation, this paper divided the Delingha depression into two shale gas systems, i.e., Delingha shale gas system and Aibei shale gas system.