Study On Quaternary Particles Grading Model Based On Fuzzy Comprehensive Evaluation

As the oil field developed in depth to all kinds of low pressure and leakage formations，the cementing proposed more requirements for both density and strength of the slurry.Compounding cement and various admixtures with high efficiency provided an effectivemethod for low-density high-strength cement slurry design, and the quaternary system, as acomplex system in applications, has presently become an important cement slurry system withbroad space for development. Although some previous grading models can provide certaintheoretical guidance for the cement slurry design, it’s still not ideal in aspect of strength andpermeability of cement stone if beyond their scopes of application. Therefore, theestablishment of a new quaternary grading model to guide the quaternary low-density andhigh-strength cement system design is of great significance.Through theoretical analysis and experimental research, a new quaternary grading modelis studied. By comparing performance of various materials, four components of thequaternary low-density slurry is optimized. By means of image processing technology,Particle morphology influencing the gradation is made quantitative characterization. Asecondary analytic hierarchy structure is constructed with such three levels as target layer,criterion layer and index layer. The weights of each factor and index are objectivelydetermined by combining grey correlation analysis with analytic hierarchy process, thetriangle and trapezoidal membership functions are optimized, and the evaluation standard forquaternary particles grading model is established. Through a solution for the fuzzycomprehensive evaluation model, the quality mixture ratio of four components is eventuallyobtained.By combining a measurement method of packing density with the definition of PVF, an original method of PVF measurement is presented. The rationality of the quaternary particlesgrading model based on fuzzy comprehensive evaluation is verified by comparing the valuesof PVF and such parameters of cement stone as compressive and flexural strength, porosity,and permeability. The research on grading model will provide important guidance significancefor the design of quaternary low-density high-strength cement slurry system, accordingly, itwill also bring a major breakthrough in cementing job for all kinds of complex wells.