基于<i>T</i><sub>2</sub>截止值确定致密岩心表面弛豫率

余玥; 孙一迪; 高睿; 达丽娜; 侯竞薇; 杨密

doi:10.11781/sysydz202202342

基于T₂截止值确定致密岩心表面弛豫率

doi: 10.11781/sysydz202202342

余玥^1,,
孙一迪²,
高睿^3, ,,
达丽娜⁴,
侯竞薇¹,
杨密⁵

1.
中国石油西南油气田公司, 成都 610000
2.
北京石油机械有限公司, 北京 102206
3.
中国石油勘探开发研究院, 北京 100083
4.
中国海洋石油国际有限公司, 北京 100028
5.
四川吉赛特科技有限公司, 成都 610213

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:
余玥(1991—)，女，硕士，工程师，从事非常规储层改造研究。E-mail: yuyue2@petrochina.com.cn

通讯作者:
高睿(1989—)，女，硕士，工程师，从事非常规储层改造研究。E-mail: gaorui69@petrochina.com.cn

中图分类号: TE311
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出版历程
- 收稿日期: 2021-03-10
- 修回日期: 2022-02-24
- 刊出日期: 2022-03-28

Determination of surface relaxivity for tight sandstone cores based on T₂ cut-off value

YU Yue^1
,,
SUN Yidi²,
GAO Rui^{3
, ,},
DA Lina⁴,
HOU Jingwei¹,
YANG Mi⁵

1.
PetroChina Southwest Oil & Gas Field Company, Chengdu, Sichuan 610000, China
2.
Beijing Petroleum Machinery Company Limited, Beijing 102206, China
3.
Research Institute of Petroleum Exploration & Development, PetroChina, Beijing 100083, China
4.
CNOOC International Company Limited, Beijing 100028, China
5.
Sichuan Geophysical Science & Technology Company Limited, Chengdu, Sichuan 610213, China

摘要

摘要: 确定致密岩心样品表面弛豫率的最常用方法是平均值法和比表面积法，但平均值法结合了压汞测试，会对岩心造成永久伤害。提出了一种基于T₂截止值确定致密岩心表面弛豫率的无损新方法。首先，使用该方法确定岩心样品表面弛豫率；之后，将计算结果与平均值法和比表面积法进行对比，并通过选择合适的表面弛豫率将核磁共振T₂谱转化为孔隙直径分布；最后，获取样品残余油分布。结果表明，四块岩心样品最终表面弛豫率分别为5.85，2.98，4.66，2.17 μm/s；结合三种方法计算结果可获取中孔和大孔的孔隙直径分布；残余油主要分布在微孔和中孔。该方法是一种无损测试方法，有助于快速有效确定致密岩心表面弛豫率。
- T₂截止值 /
- 核磁共振 /
- 孔隙直径分布 /
- 表面弛豫率 /
- 致密岩心
Abstract: The surface relaxivity for tight cores is commonly determined by the methods of average pore radius (ARS) or surface-to-volume ratio (SVR). The ARS method is time-consuming, and permanent damage to core samples will occur due to the injection of mercury. In this study, a non-destructive method is proposed, instead of the ARS method, to calculate the surface relaxivity of tight core samples based on T₂ cut-off value. Firstly, surface relaxivity is calculated using the new method (pseudo T₂ cut-off, PTC). Secondly, the calculated surface relaxivity of ARS and SVR methods are compared. Thirdly, the T₂ spectrum is converted into pore diameter distribution by choosing appropriate surface relaxivity. Finally, residual oil distribution can be obtained. The ultimate surface relaxivity values for tight sandstone core samples are 5.85, 2.98, 4.66, and 2.17 μm/s. Moreover, we obtained the pore diameter distribution in mesopores and macropores by jointly using these three methods. Residual oil is mainly distributed in micropores and mesopores. The new method proposed in this study is nondestructive and is helpful to quickly and efficiently determine the surface relaxivity of tight cores.
- T₂ cut-off value /
- Nuclear Magnetic Resonance (NMR) /
- pore diameter distribution /
- surface relaxivity /
- tight cores

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图 1 岩心样品示意

Figure 1. Schematic diagram of a core sample

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图 2 拟T₂截止值求解示意

Figure 2. Schematic diagram of pseudo T₂ cut-off values

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图 3 饱和油样品T₂谱

Figure 3. T₂ spectrum for fully oil-saturated core samples

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图 4 离心前后T₂谱(a)和T₂谱累积积分曲线(b)

Figure 4. T₂ spectrum (a) and cumulative T₂ distribution (b) before and after centrifugation

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图 5 拟T₂截止值与表面弛豫率关系

Figure 5. Correlations between surface relaxivity and pseudo T₂ cut-off values

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图 6 毛管力、孔隙半径分布以及渗透率贡献

Figure 6. Contributions of capillary pressure, pore radius distribution and permeability

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图 7 吸附/解吸等温曲线以及孔隙直径分布

Figure 7. Adsorption/desorption isotherms and pore diameter distribution

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图 8 表面弛豫率计算结果与伊利石含量关系

Figure 8. Calculated surface relaxivity as a function of illite content

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图 9 不同方法的孔隙直径分布换算

Figure 9. Pore diameter distribution calculated with different methods

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图 10 离心前后油相分布

Figure 10. Oil distribution before and after centrifugation

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表 1 岩心样品物性参数

Table 1. Petrophysical properties of core samples

测试方法	样品号	直径/cm	长度/cm	渗透率/10^-3μm²	孔隙度/%
接触角	A11	2.54	1.12	0.068	12.37
	A12	2.54	1.08	0.057	10.69
	A13	2.54	1.15	0.023	14.42
	A14	2.54	1.18	0.042	9.56
高速离心/低场核磁共振	A21	2.54	3.62	0.068	12.37
	A22	2.54	3.66	0.057	10.69
	A23	2.54	3.64	0.023	14.42
	A24	2.54	3.64	0.042	9.56
高压压汞	A31	2.54	1.76	0.068	12.37
	A32	2.54	1.71	0.057	10.69
	A33	2.54	1.72	0.023	14.42
	A34	2.54	1.72	0.042	9.56
氮气吸附/矿物组分	A41	2.54	0.13	0.068	12.37
	A41	2.54	0.14	0.057	10.69
	A43	2.54	0.14	0.023	14.42
	A44	2.54	0.15	0.042	9.56

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表 2 拟T₂截止值法表面弛豫率计算结果

Table 2. Calculation results of surface relaxivity using PTC method

样品号	转速/rpm	毛管力/MPa	拟T₂截止值/ms	表面弛豫率/(μm·s^-1)
A21	1 000	0.027	21.05	45.77
	3 000	0.240	12.92	8.29
	5 000	0.670	6.73	5.72
	6 000	0.960	4.13	6.48
	7 000	1.310	3.51	5.59
	8 000	1.710	2.53	5.93
	9 000	2.160	2.15	5.52
A22	1 000	0.027	65.79	14.79
	3 000	0.240	29.15	3.71
	5 000	0.670	21.05	2.85
	6 000	0.960	12.92	2.92
	7 000	1.310	7.32	2.71
	8 000	1.710	4.13	3.28
	9 000	2.160	3.51	3.12
A23	1 000	0.027	4.86	199.23
	3 000	0.240	2.98	34.72
	5 000	0.670	2.15	16.85
	6 000	0.960	1.75	11.98
	7 000	1.310	1.65	9.46
	8 000	1.710	1.56	7.62
	9 000	2.160	1.48	7.21
A24	1 000	0.027	29.15	33.21
	3 000	0.240	17.89	6.01
	5 000	0.670	15.20	2.55
	6 000	0.960	1 097.00	2.45
	7 000	1.310	9.33	2.12
	8 000	1.710	7.92	1.51
	9 000	2.160	5.72	2.64

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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 relaxivity using ARS method

样品号	T_2LM/ms	R_p/μm	ρ/(μm·s^-1)
A31	2.29	23.4	5.11
A32	2.53	18.8	3.72
A33	1.84	14.4	3.91
A34	2.60	22.9	2.49

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表 4 比表面积法表面弛豫率计算结果

Table 4. Calculation results of surface relaxivity using SVR method

样品号	S/(m²·g^-1)	V/10^-3(cm³·g^-1)	ρ/(μm·s^-1)
A41	1.11	4.47	1.76
A42	1.86	7.80	1.66
A43	2.60	10.40	1.54
A44	1.04	6.08	3.18

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表 5 岩心样品黏土矿物含量

Table 5. Clay mineral contents in core samples

样品号	伊利石/%	绿泥石/%	伊蒙混层/%
A21	4.23	6.88	5.95
A22	5.95	5.42	4.23
A23	6.05	7.30	6.05
A24	3.60	5.54	3.60

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