Study On The Meso-mechanism Of The Sand Production Of The Weakly Cemented Sandstone Reservoir

Weakly cemented sandstone is our main reservoir,the sand production is widespread in the process of oil exploitation.The sand production often causes many engineering disasters,such as sand buried reservoir and wellbore sand plug.The sand production in a appropriate amount can enhance the permeability of the reservoir and enhance the recovery rate.Thus the study of the sand production mechanism of weakly cemented sandstone and reasonable control of sand production not only be useful to the disaster prevention but also be useful to the recovery rate.This paper takes the weakly cemented sandstone as the research object. Firstly, study its meso-structure characteristic by using the image processing technique.Then establish the statistical damage constitutive model by using the method that combines the theory and experiment.At last study the process of sand production in the numerical simulation method. The main work as follows:(1) Select typical weakly cemented sandstone sampled and conduct CT scans to get its meso-structure image;separate the pore structure by the image processing technique,which is based on MATLAB Image Processing Toolbox;analyses the pore structure in statistical methods to get the statistical parameters;study the method of rebuild of meso-structure based on the Monte- Carlo stochastic simulation techniques.(2) Considering the heterogeneity in mechanical property of the weakly cemented sandstone,to assume the strength of the sandstone element obey the Weibull distribution, and build the statistical damage constitutive model based on the Drucker-Prager model,Then pull the expression and distribution parameters,such as m and F0;Test the effectiveness of the established statistical damage constitutive model,which is based on the theory curve and uniaxial test curve.(3) Build the sandstone model that include different porosity on the basis of the building method of meso-structure model; analyses the effect of porosity to hydraulic conductivity on the basis of ABAQUS.(4) To achieve the damage constitutive model in programming by the using UMAT,which is a constitutive property model interface of ABAQUS;Then on the basis of the work above,to study the dynamic progress of the micro-crack initiation and crack propagation.