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| 液态CO2前置压裂地面管线堵塞模拟及抑制方法 |
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罗明良1,2,罗帅2,李钦朋2,司晓冬2,李靖3,高燕3
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(1.非常规油气开发教育部重点实验室(中国石油大学(华东)),山东青岛 266580;2.中国石油大学(华东) 石油工程学院,山东青岛 266580;3.中国石油川庆钻探长庆井下技术作业公司,陕西西安 710018)
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| 摘要: |
| 应用自制管道流动安全可视化评价装置模拟液态CO2前置压裂管线或放空阀门附近水合物及干冰生成过程,结合CO2相态预测,明确液态CO2前置压裂地面管线潜在堵塞类型及因素,优选适应液态CO2前置压裂的管线堵塞物抑制剂,并通过数值模拟方法考察地面管线中堵塞物抑制剂驱替液态CO2过程,改进液态CO2前置压裂泵注流程。结果表明:地面管线压力为3.0 MPa时,液态CO2直接放空会在阀门及附近管线中形成干冰;当液态CO2泵注结束后连续注入水基压裂液时,潜在堵塞物为水基压裂液结冰及少量CO2水合物形成的混合物;优选的堵塞物抑制剂冰点低于-30 ℃,与水基压裂液及液态CO2配伍良好;通过向地面压裂管线泵注0.53 m3堵塞物抑制剂循环约1 min驱替残余液态CO2,管线温度可迅速恢复至0 ℃以上;矿场应用表明,一套压裂机组即可实现液态CO2与水基压裂液连续泵注,施工过程未出现管线及阀门堵塞,施工时间由3～4 d缩短至0.5 d,降低了液态CO2前置压裂施工风险。 |
| 关键词: 液态CO2 前置压裂 堵塞物 抑制剂 数值模拟 |
| DOI：10.3969/j.issn.1673-5005.2020.02.012 |
| 分类号: |
| 文献标识码:A |
| 基金项目:国家自然科学基金项目(51874334,51674278);山东省自然科学基金项目(ZR2018MEE010); “十三五”国家科技重大专项(2017ZX005030005) |
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| Simulation of surface pipeline plugging during liquid CO2 pre-fracturing and its inhibition method |
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LUO Mingliang1,2, LUO Shuai2, LI Qinpeng2, SI Xiaodong2, LI Jing3, GAO Yan3
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(1.Key Laboratory of Unconventional Oil ＆ Gas Development (China University of Petroleum (East China)), Ministry of Education, Qingdao 266580, China;2.School of Petroleum Engineering in China University of Petroleum(East China), Qingdao 266580, China;3.Changqing Downhole Technical Operation Company, Chuanqing Drilling Engineering Company Limited, PetroChina, Xi 'an 710018, China)
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| Abstract: |
| A visual device that can evaluate the flow of fracturing fluid in pipeline was used to investigate the formation of hydrate and dry ice at the venting valve and in nearby pipeline. The forms of the potential blockage of the pipeline and their influence factors in the process using liquid CO2 for pre-fracturing were studied combined with the prediction CO2 phases at different conditions. Plug inhibitors for liquid CO2 fracturing pipeline were selected. The process of plug inhibitors displacing liquid CO2 was investigated by a numerical simulation method and the pumping procedure of liquid CO2 was also modified. The results show that, when the pipeline pressure with liquid CO2 is around 3.0 MPa, dry ice can be formed at the valve and in its nearby pipeline if liquid CO2 is directly released. When a water-based fracturing fluid is continuously injected after liquid CO2 injection, the blockage of the surface pipeline is mainly caused by the freezing of the water-based fracturing fluid and a small amount carbon dioxide hydrate. The preferred plug inhibitor should have a freezing point below -30 ℃ and is compatible with the water-based fracturing fluid and liquid CO2. The residual liquid CO2 can be displaced by pumping about 0.53 m3 plug inhibitor in the surface pipeline for around 1 min, and the temperature in the pipeline can be quickly increased to above 0 ℃. A pilot testing shows that a single set of fracturing facility can be used to conduct continuous pumping of liquid CO2 and water-based fracturing fluid. There was no pipeline blockage during the fracturing process and the operation time was shortened from 3-4 d to 0.5 d. The blockage risks of liquid CO2 fracturing can be significantly reduced. |
| Key words: liquid CO2 pre-fracturing blockage inhibitor numerical simulation |
