Study On The Time-Varying Law Of Fracture Pressure In High Temperature And High Pressure Wells

As the world ’s energy demand continues to increase and conventional oil and gas resources continue to decrease,people gradually turn their attention to high-temperature and high-pressure oil and gas reservoirs.The Yingqiong Basin gas field in the western South China Sea is a typical high-temperature and high-pressure oil and gas field.Its formation pressure is high,the temperature is high,the formation conditions are complex,and a series of complex situations are prone to occur during drilling.Aiming at the limitation of the high-pressure and high-pressure well fracture pressure calculation model in the XX Basin,this paper established a set of fracture pressure shear calculation model based on the Mohr-Coulomb criterion by analyzing the formation stress state and the shape of the borehole wall cracks.Different from other fracture pressure shear models,the influence of temperature is introduced in this shear model,making the model more suitable for high temperature and high pressure wells in the XX Basin,and compared with conventional fracture pressure models.Using the change law of the wall temperature of the high-temperature and high-pressure well with the drilling fluid circulation time,the time-varying law of the fracture pressure of the high-temperature and high-pressure well was studied.The fracture pressure of segment decreases continuously with the increase of drilling fluid circulation time.During the drilling fluid circulation,the damage pattern of the borehole wall may also change.Aiming at the crack initiation and extension of high-temperature and high-pressure wells in XX area,this paper uses the ABAQUS software as a platform and uses a cohesive unit to establish a two-dimensional model to simulate the experimental process of high-temperature and high-pressure well floor leakage.This paper simulates the fracture initiation pressure and propagation pressure with different drilling fluid circulation time,heat conduction coefficient,elastic modulus and thermal expansion coefficient,and analyzes the variation rules of fracture initiation pressure and propagation pressure.Simultaneously,the fracture morphology changes under different drilling fluid injection time and circulation stop conditions were simulated,and the fracture morphology changes under different conditions were observed.Different from other fracture extension numerical simulation models,the influence of temperature is added to this numerical simulation model,making the model more suitable for the actual situation of high temperature and high pressure well formations.Through the above research,a set of calculation models suitable for high temperature and high pressure wells and considering a more comprehensive fracture pressure is established to guide the safe and rapid drilling of high temperature and high pressure wells.