太原西山煤田多期次异常热事件“时-空-温”配置关系及其对煤储层孔-裂隙系统的影响

It is a common phenomenon that sedimentary basins experienced multiple abnormal thermal events, which significantly controlled the mineralization/accumulation of oil, nature gas, coal and coal-measure gas. Exploration and development practice of coal bed methane in Xishan coalfield, Taiyuan indicated rapidly varying coal rank and strong heterogeneity of reservoir properties. It also indicated that the coalfield underwent multiple thermal events since Triassic period. Spatial and temporal distribution of these abnormal thermal events and their impact on differential pore-fracture system evolution become a research topic requiring immediate attention. Take Xishan coalfield as a research object, this proposed research will start with identification of multiple thermal events. Based on the organic matter vitrinite reflectance measurements, fission-track and U-Th/He of minerals (i.e. apatite, zircon and sphene), authigenic minerals and vein minerals dating as well as fluid-inclusion analysis will be performed and used in combination to establish the time-space-temperature configuration of multiple abnormal thermal events. Then, pore-fracture system with different configuration of thermal events will be investigated to understand the controlling mechanism of thermal on reservoir heterogeneity. The research is expected to provide a feasible approach to reconstruct the thermal history of sedimentary basins with multiple thermal events, and to provide new insights on the factor and mechanism of coal reservoir heterogeneity.

沉积盆地多期次异常热事件共存是一种普遍现象，其对油气、煤及煤系气等多种能源矿产的成矿（藏）有重要的控制作用。太原西山煤田煤层气勘探开发实践表明，煤田煤级变化快、储层非均质性强。三叠纪以来，煤田经历了多期次异常热事件，这些异常热事件的时空分布及其对煤储层孔-裂隙系统差异性发育的影响亟待探究。本项目以太原西山煤田为研究对象，从盆地多期次异常热事件识别入手，在有机质镜质组反射率分析的基础上，应用磷灰石/锆石/榍石矿物裂变径迹和U-Th/He定年、自生温标矿物定年、脉体矿物定年和流体包裹体分析等多种方法结合，研究多期次异常热事件“时-空-温”分布特征及配置关系，进而探讨不同异常热事件配置方式对煤储层孔-裂隙发育的影响，揭示煤储层非均质性成因的热控制机理，从而为多期次异常热事件共存盆地热演化史恢复提供可行的途径，为煤储层非均质性成因机理提供新的视角。

沉积盆地多期次异常热事件共存是一种普遍现象，其对油气、煤及煤系报等多种能源矿产的成矿（藏）有重要的控制作用。本项目以太原西山煤田为研究对象，开展了以下工作：（1）利用有机质成熟度、矿物结晶度指数、流体包裹体测温等多种温标耦合的方法，确定煤田所经历的最大古地温，进而识别异常热事件的期次；（2）通过锆石/磷灰石裂变径迹、锆石U-Th/He等低温热年代学方法，结合脉体矿物和流体包裹体地球化学特征分析，确定构造热事件年龄，恢复了煤田构造热演化史，建立了构造热事件的“时-空-温”配置关系；（3）对不同 “时-空-温”配置条件下的煤储层特征进行了分析，揭示了异常热事件对储层的影响，进而探讨了煤系气富集的影响。取得了如下研究成果：（1）煤田存在晚侏罗世-早白垩世、晚三叠世-早侏罗世和中侏罗世多期次异常热事件；（2）煤田西部煤变质作用主要受晚侏罗世-早白垩世岩浆活动的影响，煤田东部煤级定型时间为晚三叠世-早侏罗世和中侏罗世；（3）中生代以来，煤田东北部和西南部具有相同的抬升史，而西山煤田核心区与西北部边缘表现为差异性抬升，表现为煤田核部抬升时间早、西北边缘抬升时间晚的特点；（4）煤田存在多期多类流体，表现为碳酸盐（方解石、白云石）脉和黄铁矿脉的形式充填在煤层裂隙中。白云石脉主要分布在2# 煤层，而方解石脉主要发育在8# 煤层顶板；黄铁矿脉广泛分布于2# 煤层和8# 煤层，这些脉体矿物的充填导致了煤储层渗透率降低；（5）综合流体包裹体和地层埋藏-抬升史，认为煤田存在多阶段烃的充注；（6）煤田热演化程度和流体活动的差异性是导致煤系气非均质性分布的关键。依托本项目发表学术论文9篇，培养博士研究生2名，硕士研究生2名。