摘要
煤炭地下气化是对传统物理采煤技术补充的新一代化学采煤技术。气化过程中井筒受到高温和内压载荷的共同作用。针对煤炭地下气化生产井井身结构特点,基于传热理论建立了环空喷淋注水降温条件下的井筒瞬态温度计算模型,结合井筒压力模型基础上,根据弹性力学及壁圆筒理论建立了套管–水泥环–地层围岩组合体温度应力场计算模型。结果表明:高温时,井筒各部分因热膨胀或热收缩受限制而使井筒应力增加。在自然降温条件下套管、水泥环的理论计算最大应力分别为2640.6、151.3 MPa,均超过本身材料许用压应力,在不考虑温度时,套管、水泥环轴向应力分别只有28.4、15.0 MPa,远小于考虑温度时的结果;在环空注水降温方式下,通过控制喷淋腔温度能够有效降低井筒应力;随着套管内压增大,井筒应力也随之增大,且套管内压变化会造成套管和水泥环应力方向发生改变,在对其进行强度校核时需要分情况讨论;在水泥环两侧交面处的应力落差一般较大,水泥环性能参数也与井筒应力密切相关,随着水泥环弹性模量降低或泊松比增加套管-水泥环的应力随之降低,即胶结性能好,高韧性、高泊松比性能的水泥环材料能够降低套管-水泥环应力。上述研究认识可以为煤炭地下气化生产井结构设计及生产工艺提供借鉴。
As a supplement to traditional physical coal mining technology,underground coal gasification(UCG)is a new generation of chemical coal mining technology.During the gasification,the wellbore of UCG production wells is subjected to the combined action of high temperature and internal pressure loads.Targeting the structural characteristics of the wellbore of UCG production wells,this study,based on the heat transfer theory,established a calculation model for the transient temperature of the wellbore under the cooling through annular spray water injection.By combining the wellbore pressure model,as well as the elasticity theory and the wall cylinder theory,this study constructed a calculation model for the temperature and stress fields of the combination of casing,cement sheath,and surrounding rocks in strata.The results of this study indicate that the stresses of various parts of the wellbore increase due to restricted thermal expansion or shrinkage under a high temperature.Under the condition of natural cooling,the maximum stresses of the casing and the cement sheath were theoretically calculated at 2640.6 MPa and 151.3 MPa,respectively,both of which exceeded the permissible compressive stresses of the materials themselves.When the temperature was ignored,the casing and the cement sheath exhibited axial stress of merely 28.4 MPa and 15.0 MPa,respectively,which were far less than those when the temperature was considered.Under the condition of cooling through annular spray water injection,the wellbore stress can be effectively reduced by controlling the temperature of the spray chamber.The wellbore stress increases with an increase in the pressure within the casing.Accordingly,the change in the pressure within the casing will change the stress directions of the casing and cement sheath.These changes should be explored on a case-by-case basis when checking the strength of the casing and cement sheath.The interfaces on both sides of the cement sheath generally exhibit a large stress drop,and the performance parameters of the cement sheath are closely related to the wellbore stress.Furthermore,the contact stress between the casing and cement sheath decreases with a decrease in the elastic modulus of the cement sheath or an increase in its Poisson’s ratio.In other words,the contact stress can be reduced by using the cement sheath material with high cementation,ductility,and Poisson's ratio.The above results can provide a reference for the structural design and production process of UCG production wells.
作者
唐洋
谢娜
熊浩宇
何胤
黄顺潇
TANG Yang;XIE Na;XIONG Haoyu;HE Yin;HUANG Shunxiao(School of Mechanical Engineering,Southwest Petroleum University,Chengdu 610500,China;Energy Equipment Research Institute,Southwest Petroleum University,Chengdu 610500,China)
出处
《煤田地质与勘探》
EI
CAS
CSCD
北大核心
2023年第11期13-23,共11页
Coal Geology & Exploration
基金
中国石油天然气集团有限公司科学研究与技术开发项目[2019E-25(JT)]。
关键词
煤炭地下气化
温度场
温度应力场
井筒完整性
井筒降温
underground coal gasification
temperature field
thermal stress field
wellbore integrity
wellbore cooling
