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China Surfactant Detergent & Cosmetics ›› 2022, Vol. 52 ›› Issue (10): 1062-1071.doi: 10.3969/j.issn.1001-1803.2022.10.005

• Development and application • Previous Articles     Next Articles

Evaluation of efficient and economical Ba/Sr scale remover and descaling technology for offshore oil wells

Wu Shaowei1,*(),Cheng Limin1,Wan Xiaojin1,Liang Yuzhu2,Zhang Liang2,3,Kang Wanli2,3   

  1. 1. Zhanjiang Branch, CNOOC, Zhanjiang, Guangdong 524057, China
    2. School of Petroleum Engineering, China University of Petroleum (East China), Qingdao, Shandong 266580, China
    3. Key Laboratory of Unconventional Oil and Gas Development (China University of Petroleum (East China)), the Ministry of Education, Qingdao, Shandong 266580, China
  • Received:2021-11-26 Revised:2022-09-15 Online:2022-10-22 Published:2022-10-24
  • Contact: Shaowei Wu E-mail:wushw1@cnooc.com.cn

Abstract:

Due to the difficulty in removing BaSO4/SrSO4 scale from offshore oil wells and the high operating costs, it is necessary to optimize the formula of descaling agent and the descaling process to reduce the scale removal cost. A series of descaling experiments were conducted referring to the typical bottom-hole conditions of the oil wells in Weizhou Oilfield. New formulas of descaling agent were developed, and the descaling agent currently used in field was improved, from the point of view of maintaining the descaling effect to reduce the amount of descaling agent or maintaining the amount of descaling agent to improve the descaling effect. A novel concept to improve the descaling process was proposed, in which the descaling operation was combined with the workover operation, and the feasibility thereof was preliminarily assessed. The results show that, the dosage of the current agent SD-132 and the preferred new agent DTPA can be reduced to 8% and still meet the descaling index requirements. The amount of scale dissolved by the developed new formula containing DTPA can be increased by 13.08% compared with the current agent SD-132 at the same mass fraction (16%). After adding 2%-4% DTPA to the current agent SD-132, the amount of scale dissolved can also be increased by 14.49%. The new formula is applicable to different types of scale samples. The combination of descaling agent and workover fluid has a certain feasibility. The combined fluid can still maintain good descaling and formation protection performance. If the workover can achieve descaling at the same time, the cost for descaling agent and operation will be greatly reduced. The economy of the Ba/Sr scale descaling process for offshore oil wells will be greatly improved.

Key words: BaSO4/SrSO4 scale, descaling agent, scale dissolving ability, descaling process, workover fluid

CLC Number: 

  • TE423