为提高海上气田外输天然气质量,降低天然气中CO2对长输海管的腐蚀并减少碳排放,基于南海某高碳气田海上平台,首次利用膜脱碳CO2捕集技术建设CO2就地捕集及回注地层埋存工程,基于现场实验及数值仿真模型,从碳埋存可行性分析、膜脱碳系统烃损优化、天然气商品率提升流程改造及能耗优化等方面开展了CO2捕集与封存(Carbon Capture & Storage,CCS)工程实践及运行优化。研究结果表明:从井筒完整性、吸气能力及储层压力变化趋势等方面分析了回注井碳埋存可行性,当注入量为15×104 m3/d时,井底流压增加约1.0 MPa,2030年储层压力预计增加2.4 MPa,压力系数1.02;基于流量关系实验,在膜脱碳系统入口新增JT阀可有效提升膜脱碳系统大处理量下的脱碳效果;通过控制膜脱碳系统JT阀及下海管PV阀开度,可解决CO2定频压缩机的回注量控制问题;海上CCS复杂工程主要用能设备能耗优化后,能耗降幅可达8.2%,并开展了碳排放预测,20年后碳排放量为20 575 556 t/a。研究结果为中国海上油气田CO2捕集与封存处理积累了经验,对类似工程的长效运行具有借鉴价值。

In order to improve the quality of natural gas exported from offshore gas fields, reduce the corrosion of long-distance pipelines caused by CO2 in natural gas, and decrease carbon emissions, a CO2 in-situ capture and reservoir reinjection project was developed for the first time, using CO2 removal membrane based CO2 capture technology on an offshore platform of a high CO2 gas field in the South China Sea. Based on on-site experiments and numerical simulation models, Carbon Capture & Storage(CCS) engineering practice and operation optimization were carried out from the aspects of carbon sequestration feasibility analysis, optimization of hydrocarbon loss in the CO2 membrane capture system, transformation of the natural gas commodity rate improvement process, and energy consumption optimization. The feasibility of carbon sequestration in reinjection wells was analyzed from three aspects: wellbore integrity, inhalation capacity, and reservoir pressure variation trends. The research results indicate that when the injection rate is 0.15×106 m3/d, the bottom-hole flowing pressure increases by approximately 1.0 MPa, and the reservoir pressure is expected to increase by 2.4 MPa by 2030, with a pressure coefficient of 1.02. Based on flow relationship experiments, adding a Joule-Thomson(J-T) valve at the inlet of the CO2 removal membrane system can effectively enhance the CO2 removal performance under high processing capacity. By controlling the opening of the JT valve in the CO2 removal membrane system and the PV valve in the subsea pipeline, the issue of controlling the injection volume of CO2 fixed-frequency compressors can be resolved. After optimizing the energy consumption of the main energy-consuming equipment in the complex offshore CCS project, the energy consumption can be reduced by up to 8.2%. Additionally carbon emission prediction has been carried out, indicating that carbon emissions after 20 years will be 20 575 556 t/a. This study has accumulated experience in the capture and storage of carbon dioxide in offshore oil and gas fields in China, and holds important engineering value as a reference for the long-term efficient operation of similar projects.