深层致密砂岩储层脆性指数评价新方法

刘惠民; 郑金凯; 赵文山; 杜振京; 李静; 王昊

doi:10.12090/j.issn.1006-6616.2019.25.04.047

深层致密砂岩储层脆性指数评价新方法

doi: 10.12090/j.issn.1006-6616.2019.25.04.047

1.
中国石化胜利油田分公司油气勘探管理中心, 山东东营 257017
2.
中国石油大学(华东)地质力学与工程研究所, 山东青岛 266580

基金项目:

国家科技重大专项 2016ZX05002-002

国家自然科学基金 41272141

详细信息

作者简介:
刘惠民(1969-), 男, 教授级高级工程师, 从事油气勘探研究与管理工作。E-mail:hmliu@vip.163.com

通讯作者:
李静(1967-), 女, 教授、博士生导师, 地质力学及油气储层预测。E-mail:lijing0681@163.com

中图分类号: TE311;TU45
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出版历程
- 收稿日期: 2018-09-22
- 修回日期: 2018-12-07
- 刊出日期: 2019-08-01

A NEW METHOD FOR EVALUATING BRITTLENESS INDEX OF DEEP TIGHT SANDSTONE RESERVOIR

1.
Manage center of Oil and Gas Exploration, Shengli Oilfield Company, SINOPEC, Dongying 257017, Shandong, China
2.
Research Institute of Geological Mechanics and Engineering, China University of Petroleum, Qingdao 266580, Shandong, China

摘要

摘要: 储层岩石脆性评价是储层压裂改造方案设计的重要基础工作，对储层压裂改造效果有着重要影响。以准中地区深层致密砂岩储层为研究对象，开展了0~90 MPa多级围压下的岩石三轴试验，分析了围压变化对于岩石脆性的影响。针对现有脆性指数对目标储层岩石脆性评价效果不理想的情况，基于应力-应变曲线中的能量转化关系建立了新的脆性指数模型，包括岩石峰前峰后脆性指数和综合脆性指数。研究结果表明：试验围压对岩石脆性评价有着显著影响；岩石峰前脆性随围压增大先增加后减小，峰后脆性和综合脆性随围压增大而递减；研究区储层含砾细砂岩的脆性较细砂岩的脆性小，脆性差异主要表现在峰后脆性。
- 岩石力学 /
- 脆性指数 /
- 应力-应变曲线 /
- 能量转化 /
- 峰前脆性 /
- 峰后脆性
Abstract: Reservoir rock brittleness evaluation is important foundation work for the design of reservoir fracturing reconstruction scheme, which has great influence on reservoir fracturing reconstruction effect. Taking the deep tight sandstone reservoir in the central part of the Junggar Basin as the research object, the rock triaxial test under 0~90 MPa multilevel confining pressure was carried out and the influence of confining pressure variation on brittleness rock was analyzed. In view of the unsatisfactory effect of the existing brittleness index on the evaluation of rock brittleness in target reservoirs, based on the energy conversion relationship in the stress-strain curve, a new brittleness index model, which includes the pre-peak brittleness index, post-peak brittleness index and the comprehensive brittleness index, is established. The results show that the confining pressure has a significant influence on the evaluation of rock brittleness; the pre-peak brittleness increases first and then decreases with the increase of confining pressure, while the post-peak brittleness and comprehensive brittleness decrease monotonously with the increase of confining pressure. The study shows that the brittleness of the reservoir gravel fine sandstone is poorer than that of the fine sandstone, and the brittleness difference is mainly manifested in post-peak brittleness.
- rock mechanics /
- brittleness index /
- stress-strain curve /
- energy conversion /
- pre-peak brittleness /
- post-peak brittleness
注释:

责任编辑：范二平

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图 1 细砂岩压后破坏情况

Figure 1. Failure of fine sandstone after compressure

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图 2 含砾细砂岩压后破坏情况

Figure 2. Failure of gravel bearing fine sandstone after compression

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图 3 细砂岩莫尔包络线

Figure 3. Moire envelope of fine sandstone

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图 4 含砾细砂岩莫尔包络线

Figure 4. Moire envelope of boulder fine sandstone

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图 5 峰值应力与围压关系曲线

Figure 5. The relationship between peak stress and confining pressure

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图 6 细砂岩应力-应变曲线

Figure 6. Stress-strain curves of fine sandstone

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图 7 含砾细砂岩应力-应变曲线

Figure 7. Stress-strain curves of gravel bearing fine sandstone

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图 8 岩石脆塑性模型

Figure 8. Rock brittle plastic model

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图 9 脆性指数与围压关系分布图

Figure 9. The distribution diagram of brittleness index and confining pressure

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图 10 脆性指数B₄不能考虑的情况

Figure 10. The situation where the brittleness index B₄ can not be considered

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图 11 脆性指数B_Ⅰ参数示意图

Figure 11. B_Ⅰ parameter diagram of brittleness index

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图 12 脆性指数B_Ⅱ参数示意图

Figure 12. B_Ⅱ parameter diagram of brittleness index

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图 13 脆性指数B_Ⅰ、B_Ⅱ和B₀与围压关系

Figure 13. The relationship between the brittleness index B_Ⅰ, B_Ⅱ and B₀ and the confining pressure

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表 1 岩石物理参数及三轴试验结果统计

Table 1. Rock physical parameters and statistics of triaxial axis test results

岩样编号	深度/ m	密度/ (g/cm³)	取心描述	围压/ MPa	泊松比 μ	弹性模量/ GPa	峰值偏应力/ MPa	峰值应力/ MPa
1#	4254.42	2.55	细砂岩	0	0.10	13.20	57.13	57.13
2#	4256.80	2.39	含砾细砂岩	80	0.19	25.05	273.20	353.20
3#	4258.05	2.50	细砂岩	70	0.14	26.13	278.98	348.98
4#	4259.85	2.39	含砾细砂岩	20	0.19	16.35	144.27	164.27
5#	4261.40	2.27	含砾细砂岩	80	0.16	20.41	235.40	315.40
6#	4262.70	2.37	含砾细砂岩	60	0.18	24.09	234.40	294.40
7#	4268.30	2.55	细砂岩	60	0.17	23.04	269.85	329.85
8#	4269.95	2.44	细砂岩	40	0.13	21.80	237.24	277.24
9#	4291.70	2.44	细砂岩	90	0.15	28.55	323.33	413.33
10#	4292.30	2.44	细砂岩	80	0.15	26.73	296.14	376.14
11#	4293.98	2.29	含砾细砂岩	80	0.17	23.10	252.80	332.80
13#	4296.15	2.25	含砾细砂岩	90	0.14	22.85	253.39	343.39

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表 2 内摩擦角ϕ与粘聚力C计算

Table 2. Calculation of internal friction angle ϕ and cohesive force C

岩样分组	低围压 ϕ/(°)	低围压 C/MPa	全局围压 ϕ/(°)	全局围压 C/MPa
细砂岩	43.82	12.20	35.89	21.24
含砾细砂岩	32.06	27.50	26.96	36.45

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表 3 基于应力-应变曲线的脆性指数

Table 3. Brittleness index based on stress-strain curve

公式	变量说明	文献
B₁=(ε_t－ε_r)/ε_t	(ε_t－ε_r)为可恢复应变，无量纲，ε_t为总应变，无量纲	^[16]
B₂=W_rW_t	W_r为可恢复应变能，J；W_t为总应变能，J	^[16]
B₃=(ε_p－ε_c)/ε_p	ε_p为峰值应变，无量纲；ε_c为残余应变，无量纲	^[17]
B₄=(τ_p－τ_c)/τ_p	τ_p为强度峰值，MPa；τ_c为残余强度，MPa	^[6]

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表 4 脆性指数计算结果

Table 4. Calculation results of brittleness index

岩心编号	围压/ MPa	B₁	B₂	B₃	B₄	岩心描述
1#	0	0.291	0.664	0.646	0.519	细砂岩
8#	40	0.378	0.582	0.701	0.364	细砂岩
7#	60	0.382	0.646	0.766	0.401	细砂岩
3#	70	0.323	0.447	0.594	0.320	细砂岩
10#	80	0.262	0.398	0.531	0.378	细砂岩
9#	90	0.297	0.365	0.497	0.300	细砂岩
4#	20	0.362	0.650	0.705	0.373	含砾细砂岩
6#	60	0.365	0.539	0.662	0.221	含砾细砂岩
2#	80	0.350	0.417	0.553	0.073	含砾细砂岩
5#	80	0.227	0.426	0.576	0.115	含砾细砂岩
11#	80	0.284	0.485	0.620	0.115	含砾细砂岩
13#	90	0.275	0.379	0.518	0.087	含砾细砂岩

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表 5 脆性指数B₀计算结果

Table 5. Calculation results of brittleness index B₀

岩心编号	围压/ MPa	E/ GPa	(-M)/ GPa	ε_p	τ_p/ MPa	τ_e/ MPa	τ_c/ MPa	B_Ⅰ	B_Ⅱ	B₀	岩心描述
1	0	13.68	66.01	0.65	57.13	44.59	27.49	0.400	4.825	1.932	细砂岩
8	40	22.05	31.24	1.53	237.24	122.18	150.83	1.137	1.417	1.611	细砂岩
7	60	23.02	24.90	1.58	269.85	135.13	156.63	1.239	1.082	1.330	细砂岩
3	70	26.33	20.00	1.78	278.98	101.85	189.64	0.930	0.760	0.707	细砂岩
10	80	26.80	20.56	2.08	296.14	82.13	184.13	0.818	0.767	0.628	细砂岩
9	90	29.55	25.91	2.20	323.33	72.16	226.26	0.766	0.877	0.672	细砂岩
4	20	16.54	19.82	1.24	144.27	99.35	90.41	0.744	1.198	0.892	含砾细砂岩
6	60	24.08	8.57	1.47	234.40	102.22	182.59	1.102	0.356	0.392	含砾细砂岩
2	80	26.00	2.24	1.90	273.20	58.17	253.33	0.973	0.086	0.084	含砾细砂岩
5	80	21.32	1.14	1.92	235.40	79.28	208.24	0.900	0.053	0.048	含砾细砂岩
11	80	23.15	1.78	1.76	252.80	98.08	223.68	0.998	0.077	0.077	含砾细砂岩
13	90	23.08	1.44	2.12	253.39	83.79	231.46	0.718	0.062	0.045	含砾细砂岩

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