四川页岩气井碳酸根/碳酸氢根污染问题的处理实践

李文涛

doi:10.12358/j.issn.1001-5620.2022.01.009

四川页岩气井碳酸根/碳酸氢根污染问题的处理实践

doi: 10.12358/j.issn.1001-5620.2022.01.009

李文涛

长城钻探钻井液公司西南项目部, 四川威远 642450

详细信息

作者简介:
李文涛，现在主要从事钻井液技术研究工作。电话 17797732300；E-mail：22706407@qq.com

中图分类号: TE254.3
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出版历程
- 收稿日期: 2021-09-28
- 修回日期: 2021-11-07
- 刊出日期: 2022-05-06

Study and Treatment on Carbonate/Bicarbonate Pollution in Shale Gas Wells in Sichuan

LI Wentao

Great Wall Drilling Co. Southwest Project, Weiyuan，Sichuan 642450

摘要

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CO₃²⁻和HCO₃⁻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CO₂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HCO₃⁻（大于10 000 mg/L）。对预防措施和2种处理方案进行了讨论，提出用CaCl₂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CO₂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CaCl₂方案处理。威204H23-5井钻井液中HCO₃⁻含量由15 420 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Ca²⁺和HCO₃⁻双重污染。
- 水基钻井液 /
- 页岩气 /
- 碳酸根 /
- 碳酸氢根
Abstract: 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 CO₃^2- and HCO₃^-. 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 CO₃^2- and HCO₃^- was first analyzed. It was believed that CO₂ invasion took place in drilling the Changxing and Longtan formations, and some mud materials contain high concentration of HCO₃^- (>10,000 mg/L). Measures have been taken to prevent the contamination from mud materials. Using pH meter, the concentrations of CO₃^2- and HCO₃^- can be accurately measured. Preventing measures and two treatment methods (CaO and CaCl₂) were discussed, and it was concluded that CaCl₂ is the best additive to deal with the contamination. Previously CaO had been used to treat out the CO₂ contamination on well Wei-204H23-5 and well Huang-206, but the results were not satisfactory. After using CaCl₂ to treat out the CO₂ contamination, the concentration of HCO₃^- 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 HCO₃^- contamination. The viscosity of the mud in well Huang-206 was 180 sec after HCO₃^- contamination, and was reduced to 57 sec, as that before the contamination. This method of eliminating CO₂ 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 Ca²⁺ and HCO₃^-.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 encountered. The pollution occurred mainly in Changxing, Longtan and Maokou, and the viscosity/shear increased rapidly and was difficult to control. In view of this problem, the sources of pollution were firstly discussed, and the analysis showed that CO₂ intrusion and coal interlayer in Changxing and Longtan were important pollution sources of carbonate/bicarbonate. Some materials contained a large amount of bicarbonate (＞10 000 mg/L), and measures had been taken at present. The accurate test of carbonate/bicarbonate can be achieved by using a pH meter. Secondly, preventive measures and two treatment schemes are discussed, and it is suggested that CaCl₂ treatment is more suitable for this block.Finally, the CO₂ pollution treatment technology of Wei 204H23-5 and Huang 206 was explored. Two wells were treated with the CaCl₂ solution when the CaO treatment was not ideal. HCO₃⁻ in Wei 204H23-5 decreased from 15,420 mg/L to 1120 mg/L, FV ＞300 s decreased to 54 s as pre-pollution state. After the pollution, the FV of Huang 206 well was up to 180 s, and after the treatment, the FV was reduced to 57 s as pre-pollution state. This method has the advantages of high efficiency, economy and strong pertinence, but technical measures should be implemented to avoid the double contamination of drilling fluid by Ca²⁺ and HCO₃⁻.
- Water based drilling fluid /
- Shale gas /
- Carbonate /
- Biocarbonate

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图 1 威204区块H21、23井受污染钻井液的泥饼

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图 2 采用指示剂法和pH计法确定终点

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表 1 威204区块H21、23前期施工井钻井液的性能

井号	井深/ m	ρ/ g·cm⁻³	FV/ s	FL_API/ mL	FL_HTHP/ mL	φ₆/φ₃	膨润土/ g·L⁻¹	CO₃²⁻/ mg·L⁻¹	HCO₃⁻/ mg·L⁻¹	层位
23-8	2300	1.60	48	4.2	14.0	3/2	22.0			飞仙关
	2741	2.06	57	5.2	16.5	8/9	21.0	2520	3340	龙潭
	2835	2.01	98	6.8	21.1	39/37	21.0	3760	11 340	龙潭
23-6	2244	1.58	51	3.8	11.0	4/3	19.0			飞仙关
	2915	1.79	82	4.8	16.8	18/19	19.5	4380	5734	茅口
	3148	2.00	93	5.4	19.2	29/27	19.0	3910	8920	龙马溪
21-2	2600	1.70	62	4.6	13.0	3/4	21.0			飞仙关
	2813	1.84	93	5.0	18.5	10/12	20.0	880	3780	龙潭
	3092	1.85	81	4.0	20.0	22/20	19.0	2560	9394	茅口

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表 2 威204H14-X井钻井液受地层煤/地层水中CO₃²⁻和HCO₃⁻污染后的基本性能

井深/ m	ρ/ g·cm⁻³	FV/ s	φ₆/φ₃	Gel/ Pa/Pa	Ca²⁺/ mg·L⁻¹	OH⁻/ mg·L⁻¹	CO₃²⁻/ mg·L⁻¹	HCO₃⁻/ mg·L⁻¹	层位	CaO/ kg
2665	1.73	50	3/2	2.5/4.5	1400	540	25	0	飞仙关	0
2740	1.80	65	9/8	2.5/16.0	0	0	1150	3140	长兴	300
2780	1.81	71	12/10	5.0/22.5	800	0	300	3355	龙潭	150
2824	1.85	75	13/12	5.0/24.0	600	0	260	3416	茅口	0

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表 3 主要材料水溶液滤液中CO₃²⁻/HCO₃⁻的检测

材料	OH⁻/（mg·L⁻¹）	CO₃²⁻/（mg·L⁻¹）	HCO₃⁻/（mg·L⁻¹）
A	0	1272	1171
B	0	0	7930
C	0	1200	10 980
注：采用高速搅拌20 min配制5%水溶液，C在高速搅拌后起泡严重，膨胀体积约为150%～200%

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表 4 威204H23-5井受CO₂污染处理前后钻井液的基本性能

时间点	ρ/ g·cm⁻³	FV/ s	φ₆₀₀	φ₃₀₀	φ₆	φ₃	PV/ mPa·s	YP/ Pa	Gel/ Pa/Pa	Ca²⁺/ mg·L⁻¹	CaCl₂/ t
受污染前	1.88	54	118	73	7	5	45	14.0	3.0/12	350	0
第1次污染处理前	1.85	150	217	162	46	46	55	53.5		0	0
第2次污染处理前	1.85	＞300					0	0
处理1个循环周	1.90	95	156	103	21	19	53	25.0	7.5/38	0	1.0
处理2个循环周	1.93	75	142	90	10	9	52	19.0	5.0/21	0	2.0
48 h	1.95	54	124	76	8	6	48	14.0	3.5/16	600	3.5

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