The Crucial Theoretical Research On The Short-term-fracturing Technique For Injection Wells In BN Offshore Oilfield

Precise prediction of fracture initiation pressure from candidate wells and the research on long-term stretch pattern of fracture are the most pivotal technology for short-term-fracturing project design.For deviated wellbores and the corresponding well completion methods,based on transformation theory of coordination,in-situ stresses distribution around wellbores can be obtained and this paper presents a model of stress distribution during water injection process through the theory of elasticity which considers the casing and wellbore as a two-layer cylinder.To further simplify the perforation as a cylinder and in consideration of the damage zone,similarly the stress distribution of perforation could be acquired through the theory of percolation by considering short-term-fracturing fluid filtration stress filed.Calculating the initiation pressure requires the circumferential stress of perforation tunnel through the principle of superposition.The hydro-mechanical coupling effect of long-term water injection is considered in this model.The effect of pore elasticity is caused by the extrusion of the fluid entering the pore space of the rock.Then the process of fluid flow not only reflects the ability of seams,but also embodies the function of energy transfer.It is also one of the direct causes of rock deformation.Finally,based on the calculation results,the two aspects of the fracture morphology and the effect of increasing injection are analyzed,and the following conclusions are obtained:(1)Different stress regimes influence the fracture pressure.The deviated angle and inclination do also have a great impact on initiation pressure.Thus the ODP plan often has an incorrect prediction on initiation pressure.(2)During the long-term waterflooding,the polluted zone did also influence the initiation pressure.The casing has its elasticity,patio ratio and with,these factors do also influence the initiation pressure.(3)The water saturation increases and the oil saturation decreases,the pore pressure increases as the long-term waterflooding proceeding.As the project time goes by,the length of the fracture increases.The more the pore pressure is,the shorter the fracture length will be.(4)For X well,during the process of micro-fracturing,the hydraulic fracture will not communicate the fault,thus it will not pose a risk to the development of the oil field.