三轴压缩下实时高温和热处理后碳酸盐岩力学特性的试验研究

Experimental study on mechanical properties of carbonate rocks under real-time high temperature and heat treatment under triaxial compression

高温高应力条件对深层超深层油气的高效开采提出了极大的挑战。为探究实时高温和热处理2种温度作用下储层岩石力学性质变化的区别,通过自主研制的多场耦合试验系统对新疆塔里木油田的碳酸盐岩展开实时高温和热处理后的三轴压缩试验,分析2种试验情况下岩石强度、变形、破坏模式和力学参数的演化规律。结果表明:(1)随温度升高,实时高温下碳酸盐岩脆-延转化的临界围压减小,热处理后岩石的临界围压增大。(2)在2种试验条件下,碳酸盐岩的弹性模量都随温度的增加而减小;泊松比呈现出不同的变化规律;另外实时高温下碳酸盐岩的弹性模量和泊松比与围压的关系可用指数函数来表示。(3)碳酸盐岩的破裂角随围压的增大而减小;实时温度下岩石的破裂角和常温下相比变化不大,热处理后岩石的破裂角有增大的趋势。(4)与常温和加热处理后的岩石相比,实时高温对碳酸盐岩的体积应变和扩容应力影响更为明显,实时高温下的岩石更易进入屈服阶段。此研究结果有助于深入了解深层碳酸盐岩储层受高温影响下力学性质的变化规律,并为深层油气的安全高效开采提供理论依据。

The high temperature and high stress conditions pose great challenges to the efficient exploitation of deep and ultra-deep oil and gas.To investigate the differences in the effects of real-time high temperature and heat treatment on the mechanical properties of reservoir rocks,using a self-designed multi-field coupling test system,real-time high temperature and heat-treated triaxial compression tests were carried out on carbonate rocks in Tarim Oilfield,Xinjiang.Under the two test conditions,the evolution of rock strength,deformation,failure modes,and mechanical parameters were analyzed.The results show that:(1)As the temperature increases,the critical confining pressure of brittle-ductile transformation of carbonate rocks under real-time high temperature decreases,while the critical confining pressure of rocks after heat treatment increases.(2)The elastic modulus of carbonate rock decreases with increasing temperature under both experimental conditions;the Poisson's ratio exhibits different patterns of variation;additionally,the exponential function can be used to describe the elastic modulus and Poisson's ratio at real-time high-temperature.(3)The fracture angle decreases with increasing confining pressure.Compared to room temperature,the fracture angle of rocks exhibits litter variation in real-time temperature,however,there is a trend of increasing after high temperature.(4)Compared to rocks after heat treatment,the influence of real-time temperature on the volumetric strain and dilatancy stress of rock is more obvious.This study contribute to our knowledge of how temperatures affect the mechanical properties of deep carbonate reservoirs under the influence of high temperatures and provide a theoretical basis for the productive and safe extraction of deep oil and gas.