Study Of Stress Correct Resistivity Method Of Tight Sandstone In KeShen Structure

The tight sandstone reservoir of Cretaceous Bashijiqike group in Keshen area is in an abnormal high pressure and strong stress state,and therefore the stress influence on formation resistivity is remarkable.It often gives a false appearance of high resistivity reservoir,and then conventional reservoir fluid property discrimination methods can't correctly evaluate this kind of reservoir.How the ground stress affects the resistivity of the formation is still unclear.In addition,how to use the ground stress data to correct the resistivity of the formation is currently lacking methods that can be used for reference.In this paper,by simulating the stress-resistivity experiment under the ground conditions,the relationship between stress and resistivity is deduced theoretically,and the relationship between the stress and resistivity under the actual formation conditions is analyzed.From these three aspects,understands the causes and mechanism of the formation resistivity influenced by the ground stress.Based on the accurate calculation of the ground stress,model of the stress corrects the resistivity in the Keshen area was established,The layer-by-point calibration of the deep detection resistivity curve provides an accurate electrical parameter for accurate identification of the fluid-bearing properties of the reservoir.Has achieved the following results and understanding:(1)By analyzing the stress-resistivity experiments under high temperature and high pressure,and know that the variation law of resistivity,resistivity increase coefficient with horizontal stress difference,and effective stress,which provides a solid experimental theoretical basis for analyzing the mechanism of the stress affecting resistivity and establishing a resistivity model.(2)Based on reservoir rock mechanics,the theoretical relationship between porosity and m-index with stress increase is derived,with the increase of the in-situ stress,the decrease of the porosity and the increase of the pore structure index.Archie's formula shows that the formation resistivity increases.From the rock mechanics theory,it is deduced and confirmed that "the increase of the in-situ stress will cause the formation resistivity to increase".(3)From the relationship between formation pore pressure,vertical effective stress,horizontal stress difference,horizontal principal stress direction,lateral pressure coefficient and resistivity,the relationship between stress increment and resistivity increment,horizontal stress difference and horizontal and vertical resistivity The relationship between the seven aspects of the analysis of the formation resistivity changes with the ground stress.Among them,the horizontal stress difference,effective stress,Lateral pressure coefficient is the main influencing factor.(4)An experimental study of the increase in resistivity as the stress increases in the form of an e-index,Theoretical studies of resistivity increase with in-situ stress,and in practical strata,resistivity increases with the increase of horizontal stress difference,effective stress,and lateral pressure coefficient,and also increases in the form of e-index.The influence mechanism of the formation resistivity is increased.When the stress increases,the particles of the rock contact tightly,the rock pores and throat radius decrease,the ion flow is hindered,the electrical conductivity is weakened,and the resistivity increases.(5)Starting from the different factors and mechanisms of the in-situ stress affecting the resistivity,four models of the in-situ stress-affecting resistivity correction are proposed and established.Each model has its advantages and disadvantages.Based on the comprehensive theoretical analysis and practical application,the segmented geostress correction resistivity model based on the stress resistivity increasing coefficient is respected as the correction model of the in-plane stress resistivity affecting the high-steep tectonic strong stress block in the Tarim Basin.(6)Based on the Forward platform,a correction program of geostrophic resistivity has been developed.When using this program to process well logging data,it is necessary to accurately calculate lithologic and physical parameters of stratigraphy,three-direction geostress,horizontal stress difference and vertical Effective stress,and then sub-block optimize parameters,the use of the fifth model for the impact of stress on the ground stress correction,and the calibration results of other models as a reference curve.Calculated using the corrected resistivity of gas saturation,compared with the test results,explain the coincidence rate increased significantly.Through the above research,the formation mechanism(mechanism)of formation resistivity affected by geostress is clarified,the quantitative relationship between geostress and formation resistivity(electrical effect of geostress)is clarified,A reasonable and perfect calibration model and plate of the resistivity affecting the geostress are established,and finally a set of logging processing technologies that are suitable for the correction of the resistivity of the geostress due to the reservoir characteristics in the work area is formed.In order to accurately identify the reservoir properties and storage Accurate modeling of layer parameters provides reliable electrical data and improves the accuracy and quality of pore-water saturation parameter evaluation in low-porosity and low-permeability reservoirs,which is worthy of popularization and application...