致密岩心带压渗吸规律实验研究

江昀; 许国庆; 石阳; 余玥; 王天一; 曾星航; 郑伟

doi:10.11781/sysydz202101144

致密岩心带压渗吸规律实验研究

doi: 10.11781/sysydz202101144

江昀^1,,
许国庆²,
石阳^1, ,,
余玥³,
王天一¹,
曾星航²,
郑伟¹

1.
中国石油勘探开发研究院, 北京 100083
2.
中国石化石油工程技术研究院, 北京 100101
3.
中国石油西南油气田分公司, 成都 610056

基金项目:

国家科技重大专项“致密油储层高效体积改造技术” 2016ZX05046-004

详细信息

作者简介:
江昀(1990-), 男, 博士, 工程师, 从事非常规储层改造基础理论研究。E-mail: jiangyun119@petrochina.com.cn

通讯作者:
石阳(1983-), 男, 高级工程师, 从事油气藏改造与保护。E-mail: shy312@petrochina.com.cn

中图分类号: TE311
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出版历程
- 收稿日期: 2020-06-19
- 修回日期: 2020-10-10
- 刊出日期: 2021-01-28

Forced imbibition in tight sandstone cores

1.
PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China
2.
SINOPEC Research Institute of Petroleum Engineering, Beijing 100101, China
3.
PetroChina Southwest Oil & Gas Field Company, Chengdu, Sichuan 610056, China

摘要

摘要: 致密油藏体积改造压后闷井过程中发生的渗吸置换，通常在压差（基质外部流体压力与孔隙压力之差）作用下进行，但渗吸置换物理模拟却通常在常压下进行（即自发渗吸），带压条件下的渗吸置换特征尚未提及。为研究压差作用下的渗吸置换（即带压渗吸）规律，首先，建立基于低场核磁共振测试技术的带压渗吸实验方法；其次，分析自发/带压渗吸的异同；最后，建立带压渗吸无因次时间模型。结果表明，质量分数为96.76%~97.25%的油相集中分布于纳米孔（1 ms ≤ T₂ ≤ 100 ms）内，纳米孔是主要储集空间；相比于自发渗吸，带压渗吸置换效率大幅提升是由强化的渗吸作用和压实作用共同造成的；岩心尺度建立的带压渗吸无因次时间模型可行，为确定油藏尺度压后闷井时间提供了新思路。
- 致密砂岩 /
- 带压渗吸 /
- 低场核磁共振测试 /
- 无因次时间模型 /
- 闷井时间
Abstract: Spontaneous imbibition (SI) generally occurs under forced pressure (pressure difference between hydraulic fluid pressure and original pore pressure) during a shut-in period. However, the experimental study of SI is commonly performed at atmospheric pressure and the effect of forced pressure is often neglected. In this study, the mechanism of SI in tight sandstone samples under forced pressure (forced imbibition, FI) was studied. A new experimental method for forced imbibition was firstly constructed based on low-field nuclear magnetic resonance(LF-NMR) measurements. After that, a correlation between SI and FI was discussed. Finally, a new dimensionless time model considering the effect of forced pressure for FI was constructed. The results showed that 96.76%-97.25% wt% of the oil was distributed in nano-pores (0.1 ms ≤ T₂ ≤ 100 ms) of core samples, occupying the major pore space. The ultimate oil recovery for FI was significantly improved relative to that of SI, which was associated with the synergetic effect of enhanced SI and compaction. The new dimensionless time model for FI was proved to be effective and it provides a new method to calculate shut-in time at field scale.
- tight sandstone /
- forced imbibition /
- LF-NMR /
- dimensionless time model /
- shut-in time

HTML全文

图 1 压后闷井过程中两相渗流区域示意

Figure 1. Schematic diagram for two-phase flow regions during shut-in period

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图 2 渗吸作用主导的两相渗流区内压差作用下逆向渗吸示意

Figure 2. Counter-current imbibition under forced pressure in two-phase seepage zone dominated by imbibition

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图 3 自发/带压渗吸实验装置示意

Figure 3. Schematic diagram of experimental devices for spontaneous imbition/forced imbition

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图 4 高压压汞测试中孔隙直径分布结果(a) 和低场核磁共振T₂谱(b)

Figure 4. Pore size distribution of core samples (a) and T₂ by Low-field nuclear magnetic resonance (b) in high pressure mercury injection

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图 5 自发/带压渗吸置换效率随时间(a)和时间平方根(b)变化关系曲线

Figure 5. Oil recovery for SI/FI vs. imbibition time (a) and its square root (b)

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图 6 有效孔隙半径随有效应力变化关系曲线

Figure 6. Effective pore radius vs. net confining stress

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图 7 自发渗吸T₂谱及孔隙油相分布(a) 和选定时间节点测定的T₂谱渗吸实验前后纳米孔隙内油相分布(b)

Figure 7. T₂ distribution during SI and corresponding frequency of oil distribution in pores at selected time intervals (a) and frequency of oil distribution in nanopores before and after SI (b)

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图 8 带压渗吸T₂谱及孔隙油相分布(a-d) 和选定时间节点测定的T₂谱渗吸实验前后纳米孔隙内油相分布(e-h)

Figure 8. T₂ distribution during FI and corresponding frequency of oil distribution in pores at selected time intervals (a-d) and frequency of oil distribution in nanopores before and after FI (e-h)

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图 9 渗吸置换效率随无因次时间变化关系曲线

Figure 9. Oil recovery as a function of dimensionless time

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表 1 带压渗吸实验岩心样品物性参数

Table 1. Petrophysical properties of tight core samples for forced imbibition experiment

类别	编号	深度/m	直径/cm	长度/cm	渗透率/(10^-3 μm²)	孔隙度/%
高压压汞	A11	2 179.7	2.51	1.76	0.034	10.54
	A12	2 179.9	2.53	1.71	0.030	9.71
	A13	2 180.4	2.53	1.70	0.048	12.53
	A14	2 180.6	2.53	1.72	0.031	8.79
	A15	2 180.6	2.53	1.71	0.049	11.32
自发/带压渗吸	A21	2 179.7	2.51	5.21	0.034	10.54
	A22	2 179.9	2.53	5.26	0.030	9.71
	A23	2 180.4	2.53	4.96	0.048	12.53
	A24	2 180.6	2.53	5.23	0.031	8.79
	A25	2 180.6	2.53	4.60	0.049	11.32
接触角	B11	2 176.6	2.53	1.35	0.048	12.37
	B12	2 177.6	2.53	1.28	0.057	10.69
	B13	2 178.4	2.53	1.32	0.023	8.42
含油量标定	B21	2 176.6	2.53	3.62	0.048	12.37
	B22	2 177.6	2.53	3.66	0.057	10.69
	B23	2 178.4	2.53	3.61	0.023	8.42
脉冲衰减	C1	2 179.2	2.51	3.24	0.026	10.25
	C2	2 180.5	2.52	3.21	0.015	7.57
	C3	2 180.8	2.52	3.27	0.037	10.67
	C4	2 180.7	2.53	3.51	0.014	7.36

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表 2 带压渗吸实验流体样品物性参数(20 ℃, 1 atm)

Table 2. Physical properties of fluid samples for forced imbibition experiment

流体类型	密度/(g·cm^-3)	黏度/(mPa·s)	界面张力/(mN·m^-1)
煤油	0.83	2.53	26.82
氘水	1.09	1.25	72.75

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表 3 平均值法表面弛豫率计算结果

Table 3. Calculation results of surface relaxation by average method

岩心编号	T_2LM/ms	R_p/nm	ρ/(μm·s^-1)
A21	3.11	34.2	2.75
A22	5.49	78.2	3.56
A23	2.08	58.5	7.02
A24	1.29	55.3	10.68
A25	3.20	81.4	6.37

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表 4 基于低场核磁T₂值的孔隙类型分类

Table 4. Pore size classification based on T₂ value by low-field nuclear magnetic resonance

T₂/ms	孔隙直径/nm	孔隙类型
0.1~100	1~1 000	纳米孔
≥100	≥1 000	微孔/中孔

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表 5 气体滑脱因子与平均孔隙半径计算结果

Table 5. Gas slippage factor and average pore radius

岩心编号	有效应力/MPa	克氏渗透率/(10^-3μm²)	气体滑脱因子/MPa	有效孔隙半径/μm
C1	2.5	0.016 0	0.34	0.53
	5.0	0.007 8	0.59	0.31
	10.0	0.002 0	1.42	0.13
	15.0	0.001 0	3.22	0.06
C2	2.5	0.009 5	0.60	0.30
	5.0	0.008 1	0.80	0.23
	10.0	0.001 6	1.45	0.13
	15.0	0.000 6	1.81	0.10
C3	2.5	0.018 0	0.38	0.48
	5.0	0.004 1	1.29	0.14
	10.0	0.002 1	1.90	0.10
	15.0	0.001 1	2.02	0.09
C4	2.5	0.009 2	0.56	0.33
	5.0	0.004 2	1.23	0.15
	10.0	0.003 6	1.99	0.09
	15.0	0.001 1	4.35	0.05

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