Evaluation Of Caprock Sealing Ability Of Cambrian In Tarim Basin

A large number of hydrocarbons have been discovered in the carbonate rock strata of the Tarim Basin.With the improvement of the exploration level and the discovery of deep oil and gas reservoirs,higher requirements for ultra-deep geological exploration have been put forward.This paper studies the Cambrian based on the Tazhong area of the Tarim Basin.The research on the sealing ability of carbonate cap rock is the focus.Based on laboratory analysis,combined with physical analysis,triaxial stress analysis,breakthrough pressure analysis,microscopic identification,CT analysis,scanning electron microscopy and other technical means,the analysis is focused on The lithological composition,lithological micro-characteristics,and lithologic sealing ability of the strata have established a set of quantitative and qualitative quantitative evaluation methods for the sealing performance of the Cambrian seal,and which is used to comprehensively evaluate the closure of Cambrian caprocks..Taking the analysis of the lithological micro-characteristics of the ultra-deep layer of the Tarim Basin as the starting point,the Cambrian lithology should be divided into muddy limestone,granular limestone,mud-grained amphibolite,porphyrite,granitoid,and cloud.There are eight types of rock,ointment and salt rock.The sealing ability of carbonate rocks is mainly affected by the structure of rock particles,the content of paste,and the development level of micro-fractures.Mudstone,oolitic,gypsum,and salt rock can be used as the dominant lithologies closed by cap rocks.On the basis of laboratory analysis,it was found that the relationship between the microscopic parameters of the Cambrian rocks was lithologically different.The macro-characteristics analysis found that brittle rock and salt rock undergoes brittle-plastic transformation below the stratum depth of less than 1000 m,and the faults affect the salt and salt rocks.In addition,the sealing effect of caprock in dolomite is not obvious,and it has a great influence on the sealing of mudstone dolomite.On the basis of lithologic analysis,through the establishment of a developmental geologic model of pastes and salt rocks combined with earthquake predictions,the Cambrian cream and salt rocks in the Tarim Basin are distributed in a “bull's eye” pattern.The middle part is salt rock,and the outer layer is the cream in sequence.Rock,oolitic,pure dolomite.The salt rock has the largest area of distribution,and the gypsum rock has a narrow band around the salt rock.Based on the analysis of macro and micro parameters of rock,three evaluation methods for rock sealing capacity were established,namely porosity calculation model,permeability calculation model,and impedance-like calculation model,to quantitatively evaluate cap sealing ability.Finally,through a comprehensive evaluation of the caprock qualitative and quantitative,the capping capability can be divided into three types of areas,with the best sealing ability in the area of Class I,which is the development of salt rock area in the central part of the basin,and the type II area is the gypsum rock in the central area.The oolitic cloud development area and the mudstone development area in the Tadong area are relatively poor in the sealing capacity in the area of class III,which is the development area of the dolomite in the Lundong-Gucheng area.