从断裂带内部结构探讨断层封闭性

断裂带内部结构具有分带特征，包括破碎带和裂缝密集带，破碎带中有黏结力断层岩带低孔低渗有效阻止油气穿越断层侧向运移，断层岩发育的断层侧向应该是封闭的。裂缝密集带和无黏结力断层岩带都有可能保持较高的孔渗性，成为油气垂向运移的有利通道，因此断层垂向封闭的条件是：裂缝封闭，同时无黏结力断层岩带高含断层泥使孔渗性低于围岩。一条断层同时断开储层和盖层，由于储层和盖层岩性不同，其变形特征不同，断裂带内部结构特征存在差异。盖层往往是由塑性的岩石组成，其内断裂具有塑性断层特征，断裂带内部结构表现为裂缝密集带不发育的软泥充填的大裂缝组合，有效阻止油气穿越盖层散失，断层垂向封闭。

Study on Fault Closure Based on Interior Structure of Fracture Belt

Fracture belt has interior zoning characteristic,including fault rock belt,cracking belt and thick fractures belt.Low porosity and permeability of fault rock belt prevents oil and gas from lateral migration traversing through faults.Lateral fault where fault fractures develop should be closed.Both thick fractures belt and cracking belt can probably keep high porosity and permeability and become favorable channels for vertical migration of oil and gas.So the conditions for vertical closure of faults are: fracture is closed,and cracking belt contains high content of mud making porosity and permeability lower than surrounding rock.One fault simultaneously cut reservoir and cap rock.Because of different lithology between reservoir and cap rock,they have different deformation characteristic and different interior structure of fracture belt.Cap rock is often composed of plastic rock and its fracture has plastic fault characteristic.The interior structure appears as large fractures combination filled with soft mud and without thick fractures developed.This can prevent oil and gas escaping through cap rock.Fault is vertically closed.