摘要
四川页岩气井随着施工区块由威202向威204区块转移,水基钻井液在二开普遍出现了CO_(3)^(2-)和HCO_(3)^(-)污染问题。污染发生地层主要为长兴组、龙潭组、茅口组,表现为黏度和切力快速上升且难以控制。针对这一问题,首先对污染来源进行了探讨,分析认为CO_(2)侵入长兴组、龙潭组地层钻井用钻井液,部分井浆中含有大量HCO_(3)^(-)(大于10000 mg/L)。对预防措施和2种处理方案进行了讨论,提出用CaCl_(2)处理更适合该区块钻井液。最后对威204H23-5井和黄206井钻井液CO_(2)污染的处理工艺进行探索。2口井在采用CaO处理不理想情况下,改用CaCl_(2)方案处理。威204H23-5井钻井液中HCO_(3)^(-)含量由15420 mg/L降低至1120 mg/L,黏度大于300 s降低至污染前状态的54 s;黄206井钻井液受污染后黏度为180 s,处理后黏度降至污染前状态的57 s。该方法具有高效、经济、针对性强等优点,但应落实好技术措施,避免钻井液受Ca^(2+)和HCO_(3)^(-)双重污染。
Shale gas drilling in Sichuan basin is moving from the block Wei-202 to block Wei-204,where the water based drilling fluids used in the second interval were generally contaminated with CO_(3)^(2-)and HCO_(3)^(-).The source of the contamination is the Changxing,Longtan and Maokou formations.Contamination of the drilling fluids resulted in fast increase in viscosity and gel strengths,and it was difficult to bring under control the increase in viscosity and gel strengths.To deal with this problem,the source of CO_(3)^(2-)and HCO_(3)^(-)was first analyzed.It was believed that CO_(2)invasion took place in drilling the Changxing and Longtan formations,and some mud materials contain high concentration of HCO_(3)^(-)(>10,000 mg/L).Measures have been taken to prevent the contamination from mud materials.Using pH meter,the concentrations of CO_(3)^(2-)and HCO_(3)^(-)can be accurately measured.Preventing measures and two treatment methods(CaO and CaCl_(2))were discussed,and it was concluded that CaCl_(2)is the best additive to deal with the contamination.Previously CaO had been used to treat out the CO_(2)contamination on well Wei-204H23-5 and well Huang-206,but the results were not satisfactory.After using CaCl_(2)to treat out the CO_(2)contamination,the concentration of HCO_(3)^(-)was reduced from 15,420 mg/L to 1120 mg/L,and the viscosity of the mud was reduced from above 300 sec to 54 sec,which was the viscosity of the mud before HCO_(3)^(-)contamination.The viscosity of the mud in well Huang-206 was 180 sec after HCO_(3)^(-)contamination,and was reduced to 57 sec,as that before the contamination.This method of eliminating CO_(2)contamination has the advantages of is high efficiency,cost-effective and strong pertinence.Keep in mind that the technical measures should be well prepared to avoid contamination of the mud by both Ca^(2+) and HCO_(3)^(-).n recent years,with the transfer of the construction block from Wei202 to Wei204,the pollution problem of carbonate/bicarbonate in the water base drilling fluid was widely enc
作者
李文涛
LI Wentao(Great Wall Drilling Co.Southwest Project,Weiyuan,Sichuan 642450)
出处
《钻井液与完井液》
CAS
北大核心
2022年第1期53-58,共6页
Drilling Fluid & Completion Fluid
关键词
水基钻井液
页岩气
碳酸根
碳酸氢根
Water based drilling fluid
Shale gas
Carbonate
Biocarbonate
