Calculation And Process Design Of Co₂ Fracturing Temperature Field In Clastic Reservoir Of Tahe Oilfield

The clastic reservoir in Tahe oilfield has the characteristics of high shale content,strong water sensitivity and condensate gas reservoir.CO₂ fracturing technology has good adaptability to water-sensitive and flowback difficult reservoirs.Therefore,this paper studies the CO₂ fracturing technology of clastic reservoir in Tahe oilfield.Firstly,a literature survey on CO₂ fracturing was conducted to analyze the adaptability of CO₂ fracturing technology in the reservoir reconstruction of Tahe clastic rock.Secondly,physical parameter calculation models suitable for CO₂ fracturing process were selected,and mathematical models of temperature field and pressure field of wellbore and fracture in CO₂ fracturing process were established to analyze influencing factors and laws,and physical parameter and phase state characteristics of CO₂ were calculated.Temperature field,pressure field and phase state of well GK3,THN1 and Huyang 2 in Tahe oilfield were calculated.The results show that at the initial stage of fracturing,the CO₂ in the middle and upper part of the wellbore is liquid state,and the CO₂ in the bottom of the wellbore and fractures is supercritical state.In the middle and late stages of CO₂ fracturing,CO₂ at the wellbore and fracture heel end is liquid state,CO₂ at the toe end of fracture is supercritical state.CO₂ fracturing fluid has high frictional resistance.Considering wellhead pressure,the well depth less than 3800m,recommend 3/2in tubing;Within4500m,recommend 4in oil pipe;Up to 5200m,recommend 4 1/2in tubing.In the CO₂fracturing design of well Huyang2,the recommended fracture length is about 35m,the conductivity is 40-50D·cm,the recommended 30-50 MLS of ceramsite proppant,the recommended displacement is about 6m³/min and 4 1/2in oil pipe,and the estimated wellhead construction pressure is about 88MPa,and the pumping procedure and equipment requirements are given.