被断裂破坏的盖层封闭能力评价方法及其应用

断层对盖层的破坏主要表现为两个方面:一是减小了盖层的连续封盖面积,二是减小了盖层的厚度。盖层被断层破坏的主要影响因素有断层的断距、倾角和盖层厚度。通过对影响因素研究,提出了盖层有效断接厚度的新概念和计算方法。根据我国部分与断层有关的大-中型气田气柱高度资料,发现了有效断接厚度与所能封闭的最大气柱高度的对数线性关系,并由此提出了评价被断层破坏的盖层封闭能力的新方法。通过对库车坳陷库姆格列木群膏泥岩盖层的应用研究,所得结论与勘探实践完全吻合,证明所提出的评价方法是可行的。

Evaluation method for seal ability of cap rock destructed by faulting and its application

There were two situations for cap rock destructed by faulting:one was reduce of successive distribution area of cap rock,another was reduce of thickness of cap rock.The main influencing factors of distribution of cap rock destructed by faulting were fault throw,dip angle and thickness of cap rock itself.A new concept,the effective juxtaposition thickness,was presented and discussed.By the study of influence factors,the logarithmic relation between effective juxtaposition thickness of cap rock destructed by fault and gas column height sealed by cap rock was found.Based on it,a new method evaluating seal ability of cap rock destructed by fault was established.Taking the gypsum-mudstone cap rock of the Kumugeliemu Group in the Kuqa Depression,Tarim Basin,as an example,the effective juxtaposition thickness was calculated and an isopleth map was drawn out.The results were well coincident with the exploration practice,which showed our new evaluation method should be useful and practical for oil-gas exploration.