Fracture Propagation By Hydraulic Fracturing In Offshore Fields

With the more severe energy situation in China,the development of medium and high permeability reservoirs in offshore oil and gas fields and the decrease of high quality oil and gas resources make tight and low permeability reservoirs become the main force in exploration and development.This paper is based on the finite element software ABAQUS using the method of cohesive element and extended finite element method to study the hydraulic fracture expansion in tight sandstone reservoir.The research contents are as follows:Firstly,a 3D hydraulic fracturing model is established to study the single-seam expansion pattern in tight sandstone reservoir during hydraulic fracturing,and its parameter sensitivity analysis is carried out to discuss the influence of various factors on fracture morphology;Then,a 2D plane hydraulic fracturing model of hydraulic fracture intersecting with natural fracture is established to study the inter-seam interference of natural fracture to hydraulic fracture,and finally,a 2D plane strain model of three hydraulic fractures is established.Sequential fracturing and staggered fracturing are used to study the inter-seam interference of multiple hydraulic fractures.The results show that,in the process of hydraulic fracture propagation,a tendency of high pressure concentration is formed in the fracture,the pore pressure gradually decreases from the fracture center to the boundary on both sides,the soil on both sides of the fracture keeps compaction,and the fracture appears elliptical vertical fractures with wide middle and narrow sides,and the length of the fracture is much larger than the width and height of the fracture.The tensile strength of the rock,the in-situ stress difference of the reservoir,and the viscosity and displacement of the fracturing fluid have significant effects on the fracture morphology.The larger the tensile strength,the smaller the in-situ stress difference,and the higher the viscosity of the fracturing fluid,the more likely the fracture is to form a "short and wide fracture";the larger the fracturing fluid displacement is,the more likely the fracture is to form a "long and wide fracture".When the hydraulic fracture intersects with the natural fracture,the tip of the hydraulic fracture tends to the far end of the natural fracture,and at the same time,the width of the fracture at the intersection will change.The progressive Angle,stress difference and fracturing fluid viscosity between hydraulic fracture and natural fracture can change the propagation morphology after the intersection of the two fractures,while the change of fracturing fluid displacement will not change the propagation morphology after the intersection of the two fractures,but can significantly increase the fracture width and speed up the intersection time of the hydraulic fracture and natural fracture.Simulation of the vertical well staged fracturing,the interference phenomenon between seam can be observed clearly,main show is early fracturing horizon of fracture is pressed,the late fracturing process of bottom hole pressure increased significantly,by optimizing the fracturing of different order,found the wrong order fracturing 132 way can effectively avoid the interference between seam,the greatest degree of communication within the reservoir.