高温高压油气藏试产期间固井水泥环力学完整性——以准噶尔盆地南缘高探1井为例

准噶尔盆地南缘超深层勘探已成为中国石油天然气勘探的重点领域,钻完井工程面临诸多高温高压环境的挑战.在完井试产期间,井筒温度和压力的大幅度且快速下降会改变水泥环应力,易导致套管和水泥环收缩不平衡,产生微间隙.为此,采用厚壁圆筒弹性力学理论,建立了套管-水泥环-地层组合体弹性力学模型,利用有限差分程序求解.研究认为,高温高压油气藏试产期间,水泥环的主要失效形式为收缩微间隙失效.以准噶尔盆地南缘高泉背斜高探1井试产为例,评价试产过程中水泥环失效时井筒压降及温度变化临界值,以及两者与水泥石力学参数的相互关系.该力学评价方法的研究对于高温高压油气藏试产期间水泥环完整性评价具有较高的应用价值.

Research on Cement Sheath Mechanical Integrity during Trial Production of HTHP Oil and Gas Reservoir: A case Study from Gaotan-1 Well in the South Margin of Junggar Basin

Ultra deep exploration in the southern margin of Junggar basin has become a key field of oil and gas exploration in China, and the drilling and completion engineering is facing many challenges of high temperature and pressure environment. During well completion and trial production, the large and rapid decrease of wellbore temperature and pressure will change the stress of cement sheath, which will easily lead to unbalanced shrinkage and micro gap of casing and cement sheath. Therefore, based on the theory of thick wall cylinder, the elastic mechanics model of casing cement sheath formation combination is established and solved by the finite difference program. It is considered that the main failure mode of cement sheath is shrinkage micro gap failure during the trial production of high temperature and high pressure (HTHP) oil and gas reservoir. Taking the production test of Gaotan-1 well in Gaoquan anticline in the southern margin of Junggar Basin as an example, the critical values of wellbore pressure drop and temperature change in the process of cement sheath failure, and the relationship between them and the mechanical parameters of cement stone are evaluated. The study of the mechanical evaluation method has a high application value for the integrity evaluation of cement sheath during the trial production of HTHP gas reservoir.