Fracture-cavity Carbonate Directional Fracturing Simulation Test Research

The fracture-cavity carbonate reservoir is rich in oil and gas resources.It is the main oil-producing area in the western region of Sinopec.There are many pores and caves and natural fractures inside the reservoir,which bring a series of technical difficulties to the on-site fracturing construction..Taking directional fracturing and controlling the hydraulic fracture propagation path is the key to solving this problem.In this paper,artificial specimens containing pores are prepared by using similar criteria for indoor fracturing simulation,and the effect of the existence of pores on the propagation of hydraulic fractures is studied by the indoor true triaxial directional fracturing test.At the same time,combined with Abaqus numerical simulation,the influence of factors such as hole size,horizontal in-situ stress difference,continuous hole distribution pattern,hole pressure and natural fractures on hydraulic fracture propagation was studied.The following results and conclusions were obtained through research:(1)Effect of hole size on hydraulic cracks: There is stress concentration around the hole body,which has a repelling effect on hydraulic cracks.The larger the hole body size,the greater the influence range of stress concentration,and the easier the cracks to turn to bypass the hole body in advance.(2)Effect of horizontal in-situ stress difference on hydraulic fractures: When low in-situ stress difference,the horizontal in-situ stress difference is not enough to overcome the repulsive force generated by the stress concentration of the hole body,the hydraulic crack will undergo non-planar expansion when meeting the hole,and the horizontal in-situ stress difference The smaller the turning distance,the more complicated the fracture shape.When the high-level in-situ stress difference,the horizontal in-situ stress difference will overcome the stress concentration phenomenon of the hole,and the hydraulic crack will directly penetrate and continue to expand after meeting the hole,forming a single crack.(3)The effect of the distribution of continuous pores on hydraulic fractures:When the pores are continuously interspersed and disorderly distributed,the repulsive force generated by the stress concentration near the wellbore will guide the hydraulic fractures to communicate with the more remote pores,and the fracture shape is more complicated.(4)Effect of internal pressure of pores on hydraulic fractures: when the horizontal stress difference is constant,the greater the internal pressure of the pores,the easier it is to overcome the stress concentration phenomenon generated by the pores,and the easier the hydraulic fractures communicate with the pores in the direction of the maximum horizontal principal stress.(5)Effect of natural cracks on hydraulic cracks: When the approach angle of natural cracks is greater than 45°,as the horizontal ground stress difference continues to increase,hydraulic cracks will gradually pass through the natural cracks and continue to expand in the original direction.By obtaining the propagation law of directional fracturing under different influencing factors,combined with the actual measurement data on site,it can better guide the site fracturing construction and serve the project.