Xinjiang Oilfield Research And Application Of Hydraulic Fracturing With Multiple Fractures

Hydraulic fracturing is a widely used stimulation technique in petroleum industry for enhanced hydrocarbon recovery from low permeable reservoirs.With the development of petroleum industry of Xinjiang Oilfield and the requirement to stimulate reservoirs which is more complicated,more and more people have realized that the theory of single and planar fracture can't give satisfying explain over some complex phenomena and parameter in numerous field setting,the main causation of the emergence premature screen.outs with low proppant concentration and the failure in hydraulic fracturing treatments.So it is urgent to analysis the forming mechanism of multiple.hydraulic fractures and the theory of simultaneous propagation of multiple hydraulic fractures,to understand the diagnostic technologies of multiple.hydraulic fractures and the prevention and cure methods of multiple fractures.So we can get successful stimulation on low permeable or/and complicated reservoirs of Xinjiang Oil field.A set of theoretical models has been established through comprehensive research under the considering of vertical well and the infection of natural fractures in oillayer:1,According to the basic conception of elasticity mechanics and rock mechanics,the mathematical model of initiation pressure of perforated vertical wellbores is established which includes the model of rock breaking itself and the breaking along natural fractures in rock.2,Based on the liquid compressibility inside the well,the propagation mathematical model of multiple 3D.fractures which open and extend one by one is given,the model is also called the pressure increasing model.The feasibility of inartifical fractures' infection on fractures' link.up is studied.The resolution model of the opening up of multiple.hydraulic fractures is set up to simulate the number of fractures which participate distributing the total flow.3,Integrating elasticity mechanics,engineering mechanics,fracure mechanics and finite element method,using the new method of displacement discontinuity in building engineering,this paper established theoretic models of the Displacement Discontinuity Method(DDM)to calculate stress intension coefficient.Several methods are also presented to calculate the turning angel at the end of fracture.The models of the fracture re.orientation,single 3D fracture propagation model,flow distributing among multiple 3D.fractures,the simultaneous propagation model of multiple 3D fractures in the same layer,to study the interference of fracture initiation angel,the number of fractures,the flowing resistance coefficient,the confining stress on total flowing resistance near wellbore.4,The distinguishing methods of flow resistance in the near wellbore which can be divided into perforation pressure drop and flow pressure drop along the fracture which includes the flow resistance in multiple fracture,reorientation fracture and microannulus; through the magnitude of flow resistance,the number of multiple 3D.fractures can be gotten. The model of the magnitude of flow resistance has been build up through multiple step rate tests and transient pressure analysis in mini,fracturing.The "G" function is rebuilded to analyse the velocity of pressure dropping owing to the closing of some fractures.The results of Microseismic Mapping can also be used to understand the number of multiple fractures.5,Many metholds used to decrease high net pressure are summed up and analysed,including perforation in the same orientation,and the proppant slug technique of which this paper give comprehensive research to the grain,the concentration,the number.