Zhang Rui, Wang Junhao, Liu Shujie, Zhang Zizhen, Ma Lei, Meng Wenbo, Wang Zhiyu, Huang Yi, Liu Hexing, Xu Fabin
Key Laboratory of Unconventional Oil & Gas Development (China University of Petroleum (East China), Ministry of Education), Qingdao 266580, China.
School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China.
ACS Omega. 2021 Sep 10;6(37):23943-23951. doi: 10.1021/acsomega.1c02960. eCollection 2021 Sep 21.
Deepwater gas wells usually have high production rates, which result in high-speed sand movement along with the gas flow and acid components such as CO in the gas flow. The erosion and corrosion effect intensifies the damage to sand screens and can further lead to sand control failures, which endanger the safety of production operations. In this paper, using a differential rotation device to simulate erosion, corrosion, and erosion-corrosion, experiments observing the impacts of several factors on sand screens were carried out. The factors include CO partial pressure, temperature, flow velocity, sand content, and sand particle size. Their impacts on erosion, corrosion, and erosion-corrosion rate are inspected independently, and the sensitivity of factors to the erosion-corrosion rate of a sand screen was determined using the range method. Traditional erosion models involving flow rate, sand content, and sand grain size and traditional corrosion models involving CO partial pressure and temperature are taken as references, and an erosion-corrosion coupled model of sand screens is established based on the experimental results using the multivariate regression analysis. With critical damage thickness taken as the failure criterion of a sand screen, a prediction method for sand screen failure is formed and is applied to the case study of the S deepwater gas field. The results show that under the experimental conditions, the screen loss rate due to erosion-corrosion is significantly higher than that of erosion only or corrosion only and is even higher than the sum of both. The erosion-corrosion rate increases with the increase of CO partial pressure, temperature, flow velocity, sand content, and sand particle size. It has an exponential relationship with the negative reciprocal of temperature, a linear relationship with the partial pressure of CO, and power fitting relationships with flow velocity, sand content, and sand particle size. The ranking of sensitivities to the erosion-corrosion rate of high-quality screens is as follows: sand content > flow velocity > temperature > sand particle size > CO partial pressure. The error between the predicted results by the proposed model and the experimental results is in the range of 0.44-9.47%. The erosion-corrosion rate of sand screens in each production well of the S gas field is in the range of 0.0111-0.0521 mm/a, while the durability of the screens is 14-68 years. The erosion-corrosion rate model of a sand screen and the prediction method for sand screen failure proposed in this paper provide theoretical support to the durability evaluation of sand screen in deepwater gas wells, which is of great significance for ensuring the safe and efficient development of offshore oil and gas resources.
深水气井通常具有较高的产率，这导致高速砂粒随气流移动，并且气流中含有酸性成分，如二氧化碳。冲蚀和腐蚀作用加剧了对防砂筛管的损害，并可能进一步导致防砂失败，危及生产作业安全。本文利用差动旋转装置模拟冲蚀、腐蚀以及冲蚀 - 腐蚀，开展了观察多种因素对防砂筛管影响的实验。这些因素包括二氧化碳分压、温度、流速、含砂量和砂粒尺寸。分别考察了它们对冲蚀、腐蚀以及冲蚀 - 腐蚀速率的影响，并采用极差法确定了各因素对防砂筛管冲蚀 - 腐蚀速率的敏感性。以传统的涉及流速、含砂量和砂粒尺寸的冲蚀模型以及涉及二氧化碳分压和温度的腐蚀模型为参考，基于实验结果利用多元回归分析建立了防砂筛管的冲蚀 - 腐蚀耦合模型。以临界损伤厚度作为防砂筛管的失效准则，形成了防砂筛管失效预测方法，并应用于S深水气田的案例研究。结果表明，在实验条件下，冲蚀 - 腐蚀造成的筛管损失率显著高于单纯冲蚀或单纯腐蚀造成的损失率，甚至高于两者之和。冲蚀 - 腐蚀速率随二氧化碳分压、温度、流速、含砂量和砂粒尺寸的增加而增大。它与温度的负倒数呈指数关系，与二氧化碳分压呈线性关系，与流速、含砂量和砂粒尺寸呈幂函数拟合关系。优质筛管对冲蚀 - 腐蚀速率的敏感性排序为：含砂量＞流速＞温度＞砂粒尺寸＞二氧化碳分压。所提模型的预测结果与实验结果之间的误差在0.44% - 9.47%范围内。S气田各生产井中防砂筛管的冲蚀 - 腐蚀速率在0.0111 - 0.0521mm/a范围内，筛管的耐用年限为14 - 68年。本文提出的防砂筛管冲蚀 - 腐蚀速率模型及防砂筛管失效预测方法为深水气井防砂筛管的耐久性评价提供了理论支持，对确保海洋油气资源的安全高效开发具有重要意义。
