Research On Temperature Field Model Of Fractured Well Considering The Coupling Effect Of Temperature And Pressure

Distributed temperature testing(DTS)is gradually being used for downhole monitoring of fracturing Wells,aiming to solve the common technical problems such as fracture propagation morphology and fracturing effect evaluation in the fracturing process.Temperature prediction model is the basis of fracture diagnosis based on DTS monitoring,but it is still a difficult problem to quantitatively predict the temperature distribution in the fracturing process at present.In the process of fracturing,the temperature and pressure in the wellbore and fracture are affected by the external fluid,and the temperature and pressure also affect the fluid characteristics.This coupling effect is a factor that cannot be ignored in the calculation of fracture morphology.The physical properties of the fluid will directly affect the flow rate of the fluid to the bottom hole and into the fracture,thus affecting the fracturing volume.Aiming at the temperature distribution of wellbore and reservoir during fracturing,a pseudo-threedimensional(P3D)fracture propagation model is established in this paper.Considering the influence of temperature and pressure on different parameters,such as fluid volume,fracture volume and fluid density,the pressure drop in the fracture containing different fluids is analyzed,and the fracture morphology parameters are given.The accuracy of the model is confirmed by comparing with existing fracture morphology simulation methods.At the same time,the temperature distribution model of simulated wellbore,near fracture zone and reservoir is established.By coupling solving the flow and heat transfer models of wellbore,fracture and reservoir,the fracture size in the process of fracture expansion and closure is simulated,and the temperature distribution of wellbore,fracture wall and reservoir in the process of fracturing is calculated.The cooling of the reservoir during pumping and the warming of the reservoir after the pump is stopped.The above model is used to calculate 7 cases,and the accuracy of the fracture propagation model is confirmed by the calculation of 5 cases.The influence of fracturing process on reservoir temperature field was analyzed by two examples,and the influence of DTS sensor installation position on test results was analyzed.The research results will provide theoretical support for fracturing dynamic analysis,fracturing reconstruction effect evaluation and optimization design based on DTS data.The results show that there is an obvious "cooling" and "warming" process in the reservoir around the fracture during the injection process of fracturing fluid,while the fracturing fluid has an obvious warming and then stabilizing phenomenon.Through simulation,it is found that the temperature of crack surface changes obviously in the direction of crack height,and the position of DTS optical fiber has a great influence on the test results.The distance between DTS and crack entrance can be determined by temperature simulation,so that the crack initiation position can be accurately inferred from the temperature data.