Research On Temporary Diverting Fracturing Technology In The Tight Sand Formation Of High Stress Difference

It is more and more important of the oil and gas resources in the tight formation,and hydraulic fracturing method may be used to exploit these recourses effectively.The production may largely determined by the complexity of the hydraulic fracture,but winged fracture often occurs when stress difference is high.So the research on temporary diverting fracturing technology in the tight sand formation of high stress difference should be carried out to improve the product.The main research work contains the following several points.1.The research on the fracturing ability of the tight formation.The influence on the fracturing ability of rock brittleness,fracture toughness,natural weak surface was analyzed;Based on in-situ stress field and fracture tip stress field,the research on the influence on the fracture propagation path of natural fracture attitude,mechanical parameters,and the quantitative analysis of critical conditions aimed at hydraulic fracture blunting,penetration,nature fracture opening,shear sliding was carried out;Based on the work introduced,the model to evaluate the fracturing ability of the tight formation was established.2.Temporary diverting fracturing model.Hydraulic fracture diverting mainly occurs when the net pressure was improved.The research on the mechanism of temporary diverting fracturing was carried out,and it turned out that two conditions should be met when fracture diverting occurs.The first one is that pressure in the fracture tip should be dissipated because of the leak-off behavior.The second one is the stress intensity factor which influenced by the change of net pressure distribution caused by the plugging should be less than the formation fracture toughness.Based on the mechanism research,temporary diverting fracturing model was established,and analyzed the factors which influent the efficiency of plugging such as the plugging location,plugging length,compact level,filtration and so on.3.The true tri-axial plugging simulation experimentsTo understand the plugging effect,a true tri-axial plugging experimental set-up was developed to carry out a series of plugging experiments.The experimental programs of plugging effect contains the types,diameter,and concentration of plugging agents.It turned out that with respect to inert material,the crosslinking material was better at the plugging efficiency,and the fiber material can help form the blocking effectively;It was recommend that two different diameters of the agents working together can improve the plugging efficiency;The permeability of plugging would decline as the percent of fine particle increases.