基于热弹性理论的含结构面的干热岩井筒变形破坏规律研究

Study on the Deformation and Failure Laws of Hot Dry Rock Wellbore Containing Structure Surface Based on Thermal-elastic Theory

井壁稳定性控制技术是干热岩地热开发的前提条件。以青海共和GR1^#钻干热岩段遇结构面后井筒失稳为工程背景,基于热弹性理论,推导出三维应力状态下干热岩损伤破坏判断表达式,并运用COMSOL有限元软件建立热力耦合作用下干热岩井筒围岩稳定力学模型,研究温度、结构面厚度和倾角对含结构面的干热岩井筒变形破坏规律的影响。研究表明:干热岩井壁的变形量随温度、结构面厚度和倾角的增大而变大,且最大变形量发生在结构面的中部。同一条件下,结构面处的损伤大于花岗岩处,且温度和结构面厚度这2个因素对干热岩损伤影响较为严重;结构面为井筒围岩的弱面,钻井工程施工中应重点关注。

Wellbore stability control technology is the precondition of geothermal development in hot dry rock.The wellbore instability result from the hot dry rock section in GR1^#wellbore containing structure surface in Qinghai Gonghe was taken as an engineering background.Based on the thermal-elastic theory,a formula for judging the damage and failure of hot dry rock under three-dimensional stress state was derived.And a mechanical model for surrounding rock stability of hot dry rock wellbore under the thermo-mechanical coupling effect was established by using COMSOL finite element software.The influences of temperature,structural surface thickness and dip angle on the deformation and failure law of hot dry rock wellbore containing structural plane were studied.The results show that the deformation of hot dry rock increases with the increase of temperature,structural surface thickness and dip angle,and the maximum deformation occurs in the middle of structural surface.Under the same condition,the damage of structural surface is greater than that of granite,and the temperature and structural surface thickness have serious impacts on the damage of dry hot rock.The structural surface is the weak face of the surrounding rock in the wellbore,which should be paid more attention in the construction of drilling engineering.