Numerical Simulation And Experimental Study On Rock Electrical Property Of Thin Shaly Sandstone Reservoir

Formation resistivity is an important parameter for oil and gas interpretation and evaluation.The shaly sandstone formation has strong non-uniformity,many influencing factors,and complex conductive mechanism.The measured resistivity is obviously affected by the inclination angle when the structure inclination angle exists.The existing electrical measurement technology and interpretation theory cannot meet the site requirements.The electrical property and conductive mechanism of the shaly sandstone formation need to be studied.This thesis study the electric properties and mechanism of the thin shaly sandstone formation in a constant current field based on numerical simulation by the finite element software COMSOL.It provides a theoretical basis for the interpretation and evaluation of electric logging.The main research content includes the following sections.The first part analyzes the numerical simulation method of the rock electrical properties in shaly sandstone formation Firstly,the finite element simulation software COMSOL and sand shale formation numerical simulation methods were introduced,including the principles and methods of numerical simulation,the construction of formation models,and the grid meshing methods.Second,various factors of affecting rock resistivity are discussed.They include the rock lithology,water in pore,porosity,the saturation of oil and gas,and the shale inside the rock.They lay the foundation for the study of electrical properties of the shaly sandstone formations.The second part numerically studies the influence of dip angle on the measured resistivity of the layered rock samples.Firstly,the effects of layered thickness and resistivity are studied under different dip angles.Second,the effect of dip angle on the resistivity of layered rock sample is studied.By observing the current line and current density distribution of the layered rock sample,the electric properties and conductive mechanism of the interlayer rock samples with dip are analyzed.The results show that in addition to the influence of interlayer thickness and interlayer resistivity on the resistivity of the rock sample under a given electrode arrangement,the measured resistivity is also related to the location of the interlayer and the size of the measured rock sample.For the layered rock sample,the dip angle increases,and the measured resistivity decreases nonlinearly.From the view of the circuit,it can be regarded as the equivalent series and parallel transition.The closer is the resistivity between the layers,the smaller is the influence of the dip angle on the measured resistivity.The third part is the numerical simulation of the rock properties of the layered shaly conglomerate formation.The relationship between shale,porosity,fluid in the pores,and formation resistivity in the layered shaly conglomerate formation is calculated.The applicability of Archie's formula is discussed from the view of numerical calculation.The calculation results show that the fluid resistivity in the pores is the main factor affecting the resistivity of the formation.The resistivity of shaly conglomerate formations with different fluid resistivities varies.The applicable range of the Archie formula is that the rock matrix must be insulated with respect to the fluid.The fourth part is the numerical simulation study on the influence factors of the resistivity of dispersed and structural shaly conglomerate formations.The influence of various factors on the apparent resistivity of dispersed shaly conglomerate formations is calculated.The relationship between the position,the resistivity of shale and the apparent resistivity of the formation is studied.The results show that the difference between the resistivity of the pure conglomerate formation and the dispersed mud conglomerate formation decreases nonlinearly with increasing porosity.In structural mud conglomerate formations,the apparent resistivity of the formation has a certain relationship with the pore connectivity between the matrix particles.The apparent resistivity increases non-linearly with the increase of the structure resistivity when the conglomerate particle and structure shale particle are arranged by a staggered way.The fifth part is the numerical simulation of the rock electrical properties of shaly sandstone formation with fault.The effects of thickness,resistivity,dip of the fault,and fault distance on the electrical resistivity of the rock sample and the mechanism are analyzed.The results show that the resistivity of the layered rock sample of the fault structure is related to the relative position relationship between the fault and the surrounding rock.The resistivity of the rock sample is linear with the thickness of the fault,the resistivity of the fault when the faces of fault contact with each other.When the section is not in contact,the relationship is nonlinear.The resistivity of the rock sample is the comprehensive influence of all media through which the current line can flow.The sixth part is the experimental study with the tensor resistivity meter to verify the influence of layer bed with dip angle.Through the use of YXZL-RII type tensor resistivity meter to measure the resistivity of the object in the sandwich tape inclination angle,the existence of the influence of the measured dip angle is verified,and the measurement object is both modeled and simulated.The numerical calculation result is compared with the experimental data and the rationality of the simulation calculation is verified.