Experimental Study On Variation Regularity Of Rock Mechanics Properties Of Saturated Sandstone

In China and the world,unconsolidated sandstone reservoirs have a wide distribution and large reserves,and their oil and gas production occupies an important position,which is the main contradiction of this kind of oil and gas reservoir exploitation.With the development of oil field in the middle and late stage,the sand problem of oil and gas well caused by the rising of water and formation pressure is becoming more and more serious,so the corresponding dynamic sand prediction based on the data of water saturation rise and pressure change is established to provide reasonable basis for determining the reasonable production mode.In order to study the quantitative influence of water-containing conditions on sand production in sandstone reservoir,using triaxial experimental equipment,a series of strength test experiments were carried out,and the parameters of cohesion,internal friction angle,elastic modulus and Poisson Poisson were obtained under the initial conditions,and the intensity parameters were experimentally tested with the changes of saturated time and saturated water degree.The empirical relationship model of rock strength change under the condition of N reservoir saturation in an offshore oilfield is fitted.Through the test of velocity sensitive sand and permeability change under different conditions,the critical velocity of velocity and the change of core permeability under different conditions are obtained,and the XRD mineral component changes of the cores are carried out.The microstructure change of electron microscope scanning particles and the variation of formation sand size distribution explain and reveal the mechanism of velocity sensitivity and sand production in an oilfield,and provide important support for reservoir damage and sand control optimization.The results show that the Young's modulus is 11.9-17.2gpa,average 14.7GPa,Poisson's ratio 0.21-0.35,average 0.296,cohesion(strength)is 14.06 MPa,internal friction angle is 35.67° according to the experimental results.Tensile strength 2.437 MPa.The mechanical parameters of saturated water decreased in different degrees.The fast-sensitive displacement experiment obtains the "speed-sensitive" phenomenon of "permeability jumps",which is due to the rich clay mineral grains produced in the granules,and the dredging pore effect is obvious.The sand prediction shows that the water saturation/water content rises from the initial water cut to the limit water content,and the pressure drop of the critical production is about 24-26%.When the reservoir pressure is reduced and the water content rises,the sand can be intensified.Therefore,in addition to the traditional ground stress,rock strength and production pressure difference,it is necessary to consider the influence of the critical velocity of velocity,the strength of the liquid and the content of shale in the N reservoir.