渝东北地区五峰组—龙马溪组页岩气保存条件分析

发布时间：2018-05-01 04:29

本文选题：页岩气保存条件 + 断层封闭性　；参考：《成都理工大学》2017年硕士论文

【摘要】：本论文以渝东北地区上奥陶统五峰组—下志留统龙马溪组页岩为研究对象,分析其页岩气保存条件。研究区受多期次构造活动的影响,地质构造复杂、断裂及褶皱均较为发育,势必会影响页岩气富集保存。因此,本文拟通过区内断层封闭性、盖层封盖性以及水文地质条件等研究来讨论该地区的五峰组—龙马溪组页岩气保存条件,以期为今后的页岩气研究及勘探工作提供一定的参考。本文主要通过断裂带内方解石脉的碳氧同位素及石英脉内的包裹体特征来研究断层封闭性:据方解石脉的碳氧同位素可知区内断裂带内流体基本来源于碳酸盐岩围岩,但也有外源流体混入的特征,且跟大气降水的渗入有关;据流体包裹体的成分及均一温度,可知大巴山前陆构造带是气体逸散的主要通道,且城口断裂经历了较高的热演化,往南方向其热演化程度呈逐渐降低趋势;计算出区内古大气水的下渗深度:城口断裂与坪坝断裂之间,下渗深度达2400m;坪坝断裂至鸡鸣寺断裂间,下渗深度1800~2000m;鸡鸣寺断裂以南下渗深度1200~1600m。综合分析认为坪坝断裂以南地区的流体封闭性受区域构造运动的影响有限,断层封闭性良好,仅叠瓦断层带内地区封闭性较差。本文通过研究盖层类型及厚度、岩石学特征、目的层厚度及埋深、底板条件等来综合分析区内盖层封盖性。结果显示研究区内发育三套盖层,志留系盖层、二叠系盖层、中下三叠统盖层;坪坝断裂到鸡鸣寺断裂之间断裂比较发育,地层产状多呈高陡形态,上覆地层已基本失去保存意义;鸡鸡鸣寺断裂—沙市隐伏断裂地区断裂相对较少,背斜核部和向斜核部地层产状较平缓,除田坝背斜核部出露剥蚀区外,上覆盖层主要为二叠系—三叠系地层,断裂较少,且埋深在2800~4000m之间,普遍小于4500m。本文通过地下水的氘氧同位素值分析其来源,通过地下水特征系数分析其水文地质封闭条件。结果显示研究区内地下水来自大气降水;深层地下水矿化度高、变质系数低,处于还原的、稳定的水体环境。温泉水温度推算而得的循环深度在500~710m,表明710m以下地层进入水文地质封闭条件相对较好的交替阻滞带,大气水下渗作用减弱,保存条件好。通过断层封闭性、盖层封盖性及水文地质条件综合分析,对五峰组—龙马溪组页岩气保存有利区进行预测。鸡鸣寺断裂以北地区保存条件差。鸡鸣寺断裂以南、沙市隐伏断裂以北划分出三个保存有利区,分别为岩水、巫溪宁厂、巴东沿渡河附近三个地区,保存有利区面积分别为218km~2、132 km~2、89 km~2。
[Abstract]:In this paper, the shale of the Upper Ordovician Wufeng formation and Lower Silurian Longmaxi formation is taken as the research object, and its shale gas preservation conditions are analyzed. The study area is affected by multi-stage tectonic activity, the geological structure is complex and the faults and folds are relatively developed, which will inevitably affect the accumulation and preservation of shale gas. Therefore, through the study of fault sealing, capping and hydrogeological conditions in this area, this paper intends to discuss the shale gas preservation conditions of Wufeng formation and Longmaxi formation in this area. In order to provide some reference for shale gas research and exploration in the future. Based on the carbon and oxygen isotopes of calcite veins in fault zones and the characteristics of inclusions in quartz veins, the fault sealing properties are studied in this paper. According to the carbon and oxygen isotopes of calcite veins, the fluid in the fault zone is basically derived from the surrounding rocks of carbonate rocks. According to the composition and homogenization temperature of fluid inclusions, the Foreland tectonic belt of Dabashan is the main channel of gas emission, and the Chengkou fault has undergone a relatively high thermal evolution. The depth of infiltration of paleo-atmospheric water in this area is calculated as follows: the depth of infiltration between Chengkou fault and Pingba fault is 2400m; the depth between Pingba fault and Jimingsi fault is 2400m; The depth of infiltration is 1800 ~ 2000m, and the depth of infiltration is 1 200 ~ 1600m south of Jimingsi fault. The comprehensive analysis shows that the fluid sealing in the south of Pingba fault is limited by the regional tectonic movement and the sealing property of the fault is good only in the imbricate fault zone. In this paper, the types and thickness of caprock, the petrological characteristics, the thickness and depth of the target layer, and the condition of the bottom plate are studied to analyze comprehensively the capping property of the caprock in the area. The results show that there are three sets of caprocks, Silurian caprock, Permian caprock, middle and lower Triassic caprocks, and the faults between Pingba fault and Jimingsi fault are relatively developed, and the formation forms are mostly high and steep. The overlying strata have basically lost the significance of preservation, there are relatively few faults in the Jijimingsi fault-Shashi concealed fault area, and the formation of the anticline nucleus and syncline nucleus is relatively smooth, except for the exposed and denuded area of the Tianba anticline core. The overburden is mainly Permian-Triassic strata with less faults, and the buried depth is between 2800m and 4000m, generally less than 4500m. In this paper, the source of deuterium and oxygen isotopes of groundwater is analyzed, and the hydrogeological closure conditions of groundwater are analyzed by the characteristic coefficient of groundwater. The results show that the groundwater in the study area comes from atmospheric precipitation, the deep groundwater has high mineralization, low metamorphic coefficient, and is in a reduced and stable water environment. The circulation depth calculated from the temperature calculation of the hot spring water is 500 ~ 710m, which indicates that the strata below 710m enter the alternate block zone with relatively good hydrogeological sealing conditions, and the atmospheric underwater permeability is weakened and the preservation conditions are good. Through comprehensive analysis of fault sealing, capping and hydrogeological conditions, the favorable area of shale gas preservation in Wufeng formation and Longmaxi formation is predicted. The preservation conditions of the area north of the fault of Jimingsi are poor. To the south of Jimingsi fault and north of Shashi hidden fault, there are three favorable preservation areas, namely, Yanshui, Wuxi Ningchang and Badong near the Badu River. The area of the favorable preservation area is 218km~2132 KMU 22 ~ (89) km / m ~ (2).
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P618.13

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