水泥环密封安全系数法在稠油热采井的应用

Application of Cement Sheath Sealing Safety Coefficient Method in Heavy Oil Thermal Recovery Well

稠油热采井在注入蒸汽过程中,对水泥环力学性能要求较高,准确评价水泥环密封性是保证热采井正常生产的关键。根据热采井生产特点,建立井筒组合体力学模型,提出一套水泥环密封安全系数评价方法。针对辽河稠油热采典型井进行水泥环密封完整性分析,开展隔热管导热系数、水泥环弹性模量、水泥石峰值强度和井口注汽压力对井筒应力的影响分析。分析结果表明:随隔热系数的减小,井筒温度降低,水泥环弹性模量降低,安全系数明显增加;对于辽河热采井,以15 MPa压力注入350℃蒸汽时,若隔热管完好,则水泥环弹性模量小于9 GPa,峰值强度大于30 MPa,能保证水泥环密封完整性。该方法能满足稠油热采井对固井水泥环力学性能的需求,可为注汽过程的密封完整性提供技术支持。

In the process of steam injection in thermal recovery well of heavy oil,the requirements for the mechanical properties of cement sheath are high,and the accurate evaluation of cement sheath sealing property is the key to ensure the normal production of thermal recovery wells.Based on the production characteristics of thermal recovery wells,the mechanical model of wellbore assembly was built,and a set of cement sheath sealing safety coefficient evaluation method was proposed.The cement sheath sealing integrity analysis was carried out on the typical thermal recovery well of heavy oil in the Liaohe Oilfield,and the influence of thermal conductivity of insulated pipe,elastic modulus of cement sheath,peak strength of hardened cement and wellhead steam injection pressure on wellbore stress was analyzed.The study results show that the wellbore temperature decreases with the decrease of thermal insulation coefficient;as the elastic modulus of cement sheath decreases,the safety coefficient significantly increases;as for the thermal recovery well in the Liaohe Oilfield,when 350℃steam is injected at 15 MPa pressure,if the insulated pipe is in good condition,the elastic modulus of cement sheath is less than 9 GPa,and the peak strength is more than 30 MPa,which can ensure the integrality of cement sheath sealing.This method puts forward mechanical property requirements for cement sheath of thermal recovery well of heavy oil,and provides technical support for the sealing integrity of steam injection process.