A quantitative relationship between the crustal stress and fault sealing ability

Calculation formula for normal stress and shear stress on fault plane in a triaxial crustal stress state were deduced through establishing mathematical models,and three parameters: fault sealing coefficient,fault tightness index and fault shearing index were taken as indexes to quantitatively evaluate the fault sealing ability.Analysis results demonstrate that the fault sealing ability shows better when the fault sealing coefficient and fault tightness index get greater,while the relationship between the fault shearing index and fault sealing ability is relevant to the property of normal stress that acts on fault plane.When normal stress is a compressive stress,the greater the fault shearing index,the better is the fault sealing ability,while the opening extent of faults gets greater with the increase of the fault shearing index when normal stress is an extensional stress.Moreover,the influence of the magnitude and direction of crustal stress on the fault sealing ability was analyzed.The result indicates that when the included angle between fault strike and the maximum horizontal principal stress changes,both the variation trend of normal stress and shearing stress on fault plane and its influence on the fault sealing ability are contrary,thus in practical application this influence should be synthetically considered.Furthermore,the fault sealing ability of compressive and compresso-shear faults is superior to that of extensional and tenso-shear faults.Numerical simulations of the Tertiary tectonic stress field and analysis of the fault sealing ability in the mid-northern Raoyang Depression demonstrated that the Sha-2 and Sha-3 members should be major targets of exploration,and the Sha-1 member and the Dongying Formation came next.This conclusion is consistent with the exploration and development practice in the Raoyang Depression.