库车坳陷逆掩断层封闭性及流体运移

【作者】 付晓飞；

【导师】 吕延防； 刘银河；

【作者基本信息】 大庆石油学院 ， 矿产普查与勘探， 2002， 硕士

【摘要】 本文通过逆掩断层发育特征研究，分析了逆掩断层封闭机理，在断裂带填充物性质与断层封闭性定量关系模拟实验和膏泥岩变形特征模拟实验基础上建立了断层封闭性评价标准及评价方法，以此对库车坳陷几个典型构造上逆掩断层垂向封闭性进行了评价，结果表明现今断层多是封闭的，这是库车塌陷天然气和异常孔隙流体压力得以保存的主要条件。利用生长三角带和平衡剖面技术对断裂形成时期和活动时期进行了研究，结果表明，不同构造带断裂形成时期存在很大差异，基本规律是从北到南断裂形成时间越来越晚，但断裂主要活动时期则在库车期—第四系。在此基础上对逆掩断层垂向封闭性演化史进行了恢复，认为断裂自吉迪克组沉积时期以来均有活动，但这种活动是间歇性的，活动时期断层开启，静止时期断层多是封闭的。建立了逆掩断层泄压的地质模型和数学模型，选取参数后进行了模拟计算，结果表明逆掩断层活动开启释放压力，但要将地层压力释放到正常地层压力需要时间较长，在断裂活动时期不足以将圈闭中超压释放掉，这是库车坳陷超压能够保存的另一主要原因。分析了断裂在天然气成藏中的作用，认为不同类型的断裂在天然气成藏过程中的作用是不同的：贯通生、储、盖层的穿盐断层对油气散失和泄压作用；贯通源岩和储层的盐下断层对抽气运聚的充注作用；不连接源岩的滑脱断层对油气聚散无作用；储层内调整断层对油气分布起调整层位作用。总结了库车坳陷存在的四种断层组合输导模式：即盐下断层通过断层与穿盐断裂相连的组合输导模式；盐下断层通过储层与穿盐断裂相连的组合输导模式；盐下断裂通过储层和圈闭顶部突破断层与穿盐断裂相连的组合输导模式；单一穿盐断层输导模式。并利用该模式对库车坳陷几个典型构造天然气成藏过程进行了研究，并对失利井进行了分析，结果认为第一种和第二种模式有利于天然气藏形成，第三种模式因圈闭顶部发育突破断层不会形成大气田，第四种模式因缺乏天然气充注通道很难形成气藏。在此基础上分析了库车坳陷天然气成藏特征，总结出三种天然气成藏模式，即克拉2型成藏模式、克拉3型成藏模式和吐孜洛克型成藏模式。该模式对库车坳陷下一步勘探具有重要指导作用。更多还原

【Abstract】 Through the research on the development character of overthrust fault, we analyzed its sealing mechanism. We also established evaluation standard and method of fault sealing ability through the following two simulation experiment: experiment on the quantitative relationship between property of fracture zone filler and fault sealing ability; experiment on the deformation character of cream shale. Based on these work, we evaluated sealing ability of overthrust faults on several typical structure in Kuche depression. The result is that most current faults are sealed. This is the main condition for natural gas and abnormal pore pressure to preserve in Kuche depression. We have also studied fracture formation and moving period by means of growth triangle zone and equilibrium section technology. The result is that fracture formation period in diffirentt struture zone are very d’rffirent. The basic law is that from the north to the south, the fracture formation period is later and later. But the main fracture moving period is Kuche - Quaternary. Based on these research, we recovered the evolution history of overthrust faults vertical sealing ability and considered that there always have fracture activity ever since Jidike formation deposition period. But this kind of activity is not always continuous. During moving period, fault is open. During static period, fault is dosed. We established geological and mathematic model for the relief of overthrust fault and earned out simulation computation after selecting factors. The result is that pressure can be released when fault is open. But ft will take a long time for the formation pressure to be relieved to normal formation pressure. This is not enough for the superpressure in the trap to be relieved. This is the other main reason for the overpressure in Kuche depression to be preserved. We analyzed the effect of fracture in the gas deposit formation and hold that different kinds of fracture have different effect: hydrocarbon dissipation and relief effect of crossing salt bed faults that run through source rock, reservoir, and caprock; filling effect of under salt bed faults that run through source rock and reservoir; slippage faults that did not connect source rock have no effect to hydrocarbon accumulation and dissipation; adjusting faults in reservoir have effect of adjusting formations for hydrocarbon distribution. We also summed up four kinds of faults combination transportation model: the model that under salt bed fault and crossing salt bed fault are connected by faults; the model that under salt bed fault and crossing salt bed fault are connected by reservoir, the model that under salt bed fracture and crossing salt bed fracture are connected by reservoir and breakthrough faults at the top of the trap; single crossing salt bed model. We studied gas deposit formation process of several typical structure in Kuche depression by these models. Failure wells were also analyzed. The result is that the first and second model are favorable to gas deposits formation. The third model can not formbig gas deposit because breakthrough faults developed at the top of the trap. The fourth model are very drfficuft to form gas deposit because the short of gas filing passage. Based on these research, we analyzed gas deposit formation character of Kuche depression and concluded three kinds of gas deposit formation model. They are: Kela 2 model, Kela 3 model; Tuzfluoke model. The models are important guide for next step exploration in Kuche depression.更多还原