基于破坏接近度的储气库井壁稳定性分析

Analysis of Wellbore Stability of Gas Storage Based on Failure Proximity

摘要: 为了研究储气库注采过程中井壁的稳定性，合理评价井壁危险程度或损伤程度，提出了基于破坏接近度的储气库井壁稳定性分析方法。结合H储气库的地质条件及注采参数，构建了三维模型，采用Abaqus有限元分析软件，计算了H储气库典型井在注采作用下井壁的破坏接近度，并考察注气温度、注气压力、地应力不均匀系数、套管水泥环刚度及围岩参数对井壁稳定性的影响。研究结果表明：① 通过对比塑性区及破坏接近度等值云图，表明破坏接近度理论在储气库井壁稳定性分析中是可行且合理的；② 破坏接近度不仅可以定性地给出井壁围岩的弹性区、塑性区及破坏区，也能定量地反映井壁未屈服区域的危险程度或屈服区域的损伤程度；③ 注采周期内采气阶段稳定性略小于注气及关井阶段，地应力不均匀系数和围岩参数对井壁稳定性影响最大，套管水泥环影响次之，注气温度会产生一定影响，在一定压差范围内注采压差对井壁稳定性影响较小。④ 在保持经济性下提高注气温度对于保护井壁围岩稳定是有益的，地应力不均匀系数的提升、套管水泥环刚度的降低、地层参数的降低对于保护井壁围岩稳定是不利的。本文提出了在经济性的前提下提高注气温度以保护井壁围岩稳定的建议。同时，指出了地应力不均匀系数的提升、套管水泥环刚度的降低以及地层参数的降低对井壁稳定性的潜在不利影响。这些发现对于储气库的工程设计和安全管理具有重要的指导意义。

Abstract: In order to study the stability of the well wall and reasonably evaluate the danger degree or damage degree of the well wall, the stability analysis method of the gas storage well wall based on the damage proximity is proposed. Combined with the geological conditions and injection and production parameters of H gas storage, the three-dimensional model is constructed, and Abaqus finite element analysis software is used to calculate the damage proximity of well wall of typical H gas storage well under injection and production, and investigate the influence of gas injection temperature, gas injection pressure, stress uneven coefficient of ground, casing cement ring stiffness and surrounding rock parameters on the stability of well wall. The results show that: (1) By comparing the equivalent cloud map of the plastic zone and the destruction proximity, it shows that the failure proximity theory is feasible and reasonable in the stability analysis of gas reservoir well wall; (2) The damage proximity can not only qualitatively give the elastic area, plastic area and damage area of the well wall surrounding rock, it can also quantitatively reflect the risk degree of the unyield area or the degree of damage in the yield area; (3) The stability of gas production stage in the injection and production cycle is slightly less than that of gas injection and shutdown stage, the ground stress uneven coefficient and surrounding rock parameters influence the stability of the well wall, Cannshing cement ring affects secondary, Gas injection temperature can have some effect, the injection and production pressure difference within a certain pressure range has little influence on the stability of the well wall; (4) Improving the gas injection temperature under the condition of maintaining economy is beneficial to protect the stability of the surrounding rock of the well wall, while the increase of the ground stress uneven coefficient, the reduction of the stiffness of the casing cement ring, and the reduction of the formation parameters are unfavorable to protecting the stability of the surrounding rock of the well wall. This study improves the gas injection temperature to protect the surrounding rock. At the same time, the potential adverse effects of the stiffness and the decrease of the formation parameters on the stability are pointed out. These findings have important guiding significance for the engineering design and safety management of gas storage.