Study On Rule Of Cement Sample Damage By Blast Wave

Low permeability reservoir plays an increasing important role in petroleum exploitation with the development of petroleum industry, but the stimulation technology for low permeability reservoir by explosion method can not meet the demand for the development of petroleum industry. The main reason is that the theoretic research for the stimulation technology by explosion method is imperfect, and many theoretic problems should be deeply studied, and the rule of rock damage by exploding load is one of which should be essential studied. So the rule of cement sample damage by blast wave is studied in this thesis, and the rule acquired from which has theory sense and utility value to accelerate the development of the stimulation technology by explosion method.The cement damage experimental programs of explosive away from small cement sample and explosive hugging closely on big cement sample are proposed, and the operational scheme is also designed. The blast wave velocity in water is within 1500~1550 m/s, and the attenuation rule in water is also gained, which settle the bases for the experiment study of cement sample damage. The fracture distribution rule in the cement sample abaft blast wave by-passing is observed, and blast wave spreading process and the fracture initiation & propagation mechanism are analyzed. The attenuation rule of the blast wave in cement sample is deduced. The relationship between blast wave pressure and blast wave velocity is deduced, which can calculate the blast wave pressure indirectly. It is found that the damage zone dimension has a linear relationship with the explosive load equivalent radius.On the bases of experiment study, the blast wave spreading process and reflection & transmission effect on boundary between water and cement sample are analyzed by numerical simulation method. Blast wave velocity gained in water by numerical simulation is coincided with which gained in experiment. Comparing the result gained from the numerical simulation with which gained from experiment, it is found that they coincide with each other well.Quantitative evaluation for the cement sample damage after exploding is studied. Based on relative damage, fracture porosity and fracture permeability, the quantitative evaluation method for the cement sample after exploding is established, and the tensile damage zone is confirmed as the chief evaluation zone. The parameters need in the evaluation study is gained by experiment research, and it is found that the cement samples are high homogeneous. It is found that the ratio of maximum blast wave pressure and dynamic tensile strength is the main factor influence on elastic wave velocity of cement sample after exploding, and the relationship between the tensile stress in annular direction and blast wave pressure is also deduced. The rules between dimensionless elastic wave velocity, relative damage and dimensionless tensile pressure are obtained. The rules between relative damage, fracture permeability and fracture porosity are also gained. Using the result above-mentioned, the rule between fracture permeability and dimensionless tensile pressure is obtained, and the optimum dynamic load creating enough micro-fracture and enhancing the permeability greatly is studied.