苏北盆地页岩油基质与裂缝流动能力实验研究

doi:10.13809/j.cnki.cn32-1825/te.2024.03.003

摘要/Abstract

摘要：

页岩油藏具有复杂的孔隙结构和超低渗透能力，合理评价储层基质和压后不同类型裂缝流动能力对制定合理工作制度和有效开发页岩油藏具有重要指导作用。采用巴西劈裂方法模拟不同裂缝形态，基于核磁共振技术构建了一套评价基质和裂缝流动能力方法，并以苏北盆地高邮凹陷阜宁组二段（以下简称阜二段）页岩岩心为基础开展了基质和裂缝导流能力评价研究。实验结果表明：页岩储层最小流动孔隙尺度为10 nm，应力条件下流动规律表现为非线性、线性两段式；影响裂缝系统导流能力因素包括裂缝类型、开度、应力大小和驱动压差等；应力越大渗透率损失越大，最高可达95%，缝网越复杂开度越大，渗透率损失越大；生产过程中需要依据裂缝发育情况、上覆岩层有效应力特征来合理控制地层流体压力与井底流压的差值，保障油井能稳定生产，压力均匀向外传播；高邮凹陷阜二段页岩油井有效应力介于7~10 MPa、流动压差介于10~15 MPa为合理下泵时机或进行地层补能时机。研究成果对完善页岩渗流机理理论和现场应用具有重要意义。

关键词: 页岩油, 裂缝类型, 流动能力, 有效应力, 核磁共振

Abstract:

Shale oil reservoirs present complex pore structures and ultra-low permeability, making the evaluation of flow capacity in both the reservoir matrix and various fracture types after fracturing crucial for developing effective work systems. In this study, the Brazilian splitting method was utilized to simulate different fracture morphologies. We constructed a set of methods for evaluating matrix and fracture flow capacity based on nuclear magnetic resonance（NMR）technology. This evaluation was conducted on shale cores from the second member of Funing Formation of Gaoyou Sag in Subei Basin（referred to as the Fu-2 member）. Techniques including NMR, Brazilian fracturing, and high-pressure saturation were applied to develop these evaluation methods. The experimental results indicate that the minimum flow pore size of the shale reservoirs is 10 nm. Under stress conditions, the flow pattern exhibits a two-stage equation: nonlinear and linear. Factors affecting the fracture system’s conductivity include crack type, opening degree, stress magnitude, and driving pressure difference. Higher stress levels result in greater permeability loss, reaching up to 95%. The more complex the fracture network and the larger the opening, the greater the permeability loss. During production, it is essential to manage the pressure difference between the formation fluid and the bottomhole flow based on the crack development and effective stress characteristics of the overlying strata to ensure stable oil well production and uniform pressure propagation. For the shale oil in Fu-2 member of Gaoyou Sag, it is recommended to maintain an effective stress range of 7 MPa to 10 MPa and a flow pressure difference range of 10 MPa to 15 MPa as optimal for pumping or reservoir energy replenishment. These research findings significantly contribute to the theoretical understanding and practical application of the shale seepage mechanism.

Key words: shale oil, fracture type, flow capacity, effective stress, nuclear magnetic resonance

中图分类号:

TE357

段宏亮,谌廷姗,孙敬, 等. 苏北盆地页岩油基质与裂缝流动能力实验研究[J]. 油气藏评价与开发, 2024, 14(3): 333-342.

DUAN Hongliang,SHEN Tingshan,SUN Jing, et al. Experimental study of oil matrix and fracture flow capacity of shale oil in Subei Basin[J]. Petroleum Reservoir Evaluation and Development, 2024, 14(3): 333-342.

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岩心编号	井号	层位	层理缝密度/ （条/cm）	孔隙度/ %	渗透率/ 10^-3μm²
J1	H101	Ⅴ-1	2	3.90	0.079 0
J2	H101	Ⅴ-2	10	4.79	0.099 1
J3	TY1	Ⅲ-1	10	5.38	0.010 5
J4	HY1	Ⅳ-5	4	4.14	0.002 5

岩心实验次数	最大饱和压力/MPa	饱和时长/h	累计饱和油量/mL	累计含油饱和度/%
J1第一次饱和	15.7	23	0.014 6	2.36
J1第二次饱和	21.6	31	0.036 3	2.88
J1第三次饱和	26.2	37	0.057 2	9.26
J1第四次饱和	31.4	35	0.059 7	9.66
J1第五次饱和	36.2	38	0.060 9	9.86
J2第一次饱和	15.7	28	0.236 0	25.64
J2第二次饱和	21.1	48	0.248 2	26.97
J2第三次饱和	26.2	50	0.268 9	29.22
J2第四次饱和	31.2	39	0.277 5	30.15
J2第五次饱和	36.1	42	0.282 1	30.65

岩心	井号、层位	裂缝形态
L1	H101、Ⅳ-8	单缝
L2	H2C、Ⅳ-5	双缝
L3	HY1、Ⅳ-5	分支缝