超低温液氮辅助CO<sub>2</sub>吞吐提高页岩渗流能力试验研究

万涛; 王波; 王伟; 康振; 刁广智; 王斌

超低温液氮辅助CO₂吞吐提高页岩渗流能力试验研究

万涛^1,,
王波¹,
王伟¹,
康振²,
刁广智¹,
王斌^{1, 2, ,}

1.
中国石油长庆油田分公司第五采油厂，陕西定边 710200
2.
中国石油长庆油田分公司勘探开发研究院，陕西西安 710016

基金项目: 国家科技重大专项（2016ZX05050）“鄂尔多斯盆地大型低渗透岩性地层油气藏开发示范工程”资助。

详细信息

作者简介:
万涛（1987—），男，重庆忠县人，2011年毕业于重庆科技大学石油工程专业，2011年获重庆科技大学石油工程专业学士学位，工程师，主要从事油田开发方面的研究工作。E-mail：2326169049@qq.com

通讯作者:
王斌（1973—），男，E-mail：wangbingktkf@163.com

中图分类号: TE348
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- 文章访问数: 25
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出版历程
- 录用日期: 2025-02-03
- 网络出版日期: 2025-02-09

Experimental study on improving permeability of shale by CO2 flooding assisted by ultra-low temperature liquid nitrogen

WAN Tao^1,,
WANG Bo¹,
WANG Wei¹,
KANG Zhen²,
DIAO Guangzhi¹,
WANG Bin^{1, 2, ,}

1.
No.6 Oil Production Plant of PetroChina Changqing Oilfield Company, Shaanxi Dingbian 710200
2.
Exploration and Development research institute, PetroChina Changqing oilfield Company, Shaanxi, Xi’ an 710016

摘要

摘要:
页岩储集层岩石致密、孔喉细小、渗透率极低，了解页岩渗流机理是提高页岩油气采收率的关键。为此，开展页岩岩心液氮（LN₂）低温处理试验和循环注CO₂吞吐试验，分析液氮低温处理后不同注气压力循环注气吞吐对页岩油采收率、岩心物性和油气两相相对渗透率的影响，明确处理前后微观孔隙结构的变化特征。试验结果表明，LN₂注入后页岩可产生313.5 MPa热应力，诱导微裂缝形成。LN₂汽化体积膨胀作用和循环注CO₂吞吐能够在微裂缝形成后在岩心中形成再加压机制，扩展诱导裂缝，提高渗流能力。CO₂吞吐采收率与注入压力成正比，超临界态CO₂首轮和3轮累计吞吐采收率比亚临界态CO₂高32.4%和34.9%，提高幅度达154.6%和101.7%。高压注CO₂所需的吞吐次数减少，产出油量主要来源于前2轮吞吐。与初始页岩岩心相比，超临界态CO₂循环吞吐后平均孔径增大幅度为176%，最大油、气相对渗透率分别提高了1.8倍和2.3倍。研究成果对页岩油气增产具有一定参考意义。
- 页岩 /
- CO₂吞吐 /
- 液氮 /
- 孔隙结构 /
- 微裂缝
Abstract:
Shale reservoir has tight rock, small pore throat and very low permeability. How to enhance the permeability of shale is the key to improving the recovery rate of shale oil and gas. Through conducting liquid nitrogen (LN₂) low-temperature treatment experiments on shale cores and cyclic injection of CO₂ flooding experiments, the effects of cyclic gas injection at different injection pressures after LN₂ low-temperature treatment on the recovery rate of shale oil, core physical properties, and relative permeability of oil and gas phases were studied, and the changes in the microscopic pore structure before and after the treatment were clarified. The experimental results show that after LN₂ injection, the shale can generate a thermal stress of 313.5 MPa, inducing the formation of micro-fractures. The volume expansion effect of LN₂ vaporization and cyclic CO₂ flooding can form a re-pressurization mechanism in the core after the formation of micro-fractures, expanding the induced fractures and improving the permeability. The recovery rate of CO₂ flooding is proportional to the injection pressure. The cumulative recovery rates of the first and third rounds of supercritical CO₂ flooding are 32.4% and 34.9% higher than those of subcritical CO₂, with an increase of 154.6% and 101.7%, respectively. The number of required flooding cycles for high-pressure CO₂ injection is reduced, and the produced oil mainly comes from the first two rounds of flooding. Compared with the initial shale core, the porosity after supercritical CO₂ cyclic flooding increases by 78.6%, the permeability increases by 27,204%, the average pore diameter increases by 176%, and the maximum relative permeability of oil and gas increases by 1.8 times and 2.3 times, respectively. The research results provide a reference for the production increase of shale oil and gas.
- shale /
- CO₂ huff-puff /
- liquid nitrogen /
- pore structure /
- microcracks

HTML全文

图 1 岩心试验仪器

Figure 1. Flow chart of core experimental instruments

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图 2 试验页岩样品矿物组成及含量

Figure 2. Mineral composition and content of experimental shale samples

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图 3 LN₂低温处理过程中岩心温度随时间的变化

Figure 3. Changes in core temperature over time during LN₂ low-temperature treatment

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图 4 未处理岩心和LN₂低温处理后CO₂吞吐采收率对比

Figure 4. Comparison of CO₂ huff and puff recovery after untreated core and LN₂ low-temperature treatment

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图 5 LN₂低温处理后岩心在不同注气压力下吞吐采收率对比

Figure 5. Comparison of recovery efficiency of LN₂ low-temperature treated core under different gas injection pressures through huff and puff

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图 6 初始岩心与LN₂低温处理和CO₂吞吐后的岩心孔隙度和渗透率变化

Figure 6. Changes in porosity and permeability of initial core after LN₂ low-temperature treatment and CO₂ huff and puff

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图 7 3种不同注入压力吞吐后页岩渗透率随上覆压力的变化

Figure 7. Changes in shale permeability with overlying pressure after three different injection pressures of huff and puff

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图 8 初始页岩与LN₂低温处理和循环注气后T₂谱分布

Figure 8. T₂ spectrum distribution after initial shale and LN₂ low-temperature treatment and cyclic gas injection

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图 9 初始岩心和LN₂低温处理和循环注气后岩心3端面CT扫描图像

Figure 9. Initial core and LN₂ low-temperature treatment and CT scan images of core 3 end face after cyclic gas injection

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图 10 处理前后页岩油气两相相对渗透率曲线的变化

Figure 10. Change of Relative permeability curve of Shale oil and gas phases before and after treatment

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表 1 试验页岩岩心基本参数

Table 1 Basic parameters of experimental shale core

岩心编号	直径/mm	长度/mm	孔隙度，%	渗透率/10⁻³ mD	TOC，%	镜质体反射率，%	试验设计
1	38.25	51.75	7.32	0.45	2.11	1.15	LN₂低温处理+4 MPa循环注CO₂吞吐
2	38.14	54.21	7.47	0.37	2.83	1.21	LN₂低温处理+7 MPa循环注CO₂吞吐
3	38.16	52.42	6.74	0.24	3.03	1.18	LN₂低温处理+10 MPa循环注CO₂吞吐
4	38.11	51.56	7.21	0.33	2.81	1.07	10 MPa循环注CO₂吞吐（对比试验）

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表 2 低温处理中形成的热应力及计算参数

Table 2 Thermal stress and calculation parameters formed during low-temperature treatment

岩心编号	E/10³ MPa	ν	α/10⁻⁶ ℃⁻¹	T_i/℃	T_s/℃	σ_thermal/MPa
1	61.0	0.296	15	78.5	−177.3	303.3
2	56.4	0.284	15	78.5	−181.1	281.9
3	70.3	0.311	15	78.5	−178.6	355.5

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表 3 不同注气压力下页岩处理前后孔径参数变化

Table 3 Changes in pore size parameters before and after shale treatment under different gas injection pressures

孔隙结构参数	平均弛豫时间/ms	平均孔径/nm	最大弛豫时间/ms	最大孔径/nm
岩心1处理前	0.63	2.7	76	326
岩心1处理后	0.96	4.1	564	2425
岩心3处理前	0.48	2.1	151	649
岩心3处理后	1.36	5.8	982	4222

下载: 导出CSV

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