﻿ 通道压裂裂缝导流能力数值模拟研究

Numerical Simulation for Flow Conductivity in Channeling Fractures
YANG Yingtao, WEN Qingzhi, DUAN Xiaofei, WANG Shuting, WANG Feng
School of Petroleum Engineering, China University of Petroleum (Huadong), Qingdao, Shandong, 266580, China
Abstract: To determine the conductivity of channeling fractures under field conditions and to identify factors that may affect such conductivity, a fluid flow model has been established in accordance with distribution of fractured sand bars. In addition, a numerical simulation has been performed to determine flow patterns of fluids in certain fracture and to calculate conductivity of such fractures. Research results showed that structures and distribution of pore channels in channeling fractures were key factors that might affect the conductivity of fractures. In the case that no continuous large channels were generated, or such major channels collapsed to generate dispersedly distributed pore structures, fluids in the fracture might encounter significant flow resistance. Under such circumstances, conductivities of channeling fractures might be reduced significantly. Relevant research results might provide a solid foundation to enhance conductivity of channeling fractures.
Key words: channel fracturing     flow conductivity     mathematical model     numerical simulation

1 通道压裂裂缝模型

1.1 通道压裂砂堤分布规律

 图 1 可视裂缝模拟系统组成 Fig.1 Composition of visible fractures simulation system

 序号 泵注液体 排量/ (L·min-1) 砂比，% 纤维/g 时间/s 1 前置液 428.6 2.1 2 携砂液 428.6 5 1.1 3 携砂液 428.6 7 1.2 4 中顶液 428.6 1.0 5 携砂液 428.6 7 54.0 1.1 6 中顶液 428.6 1.0 7 携砂液 428.6 10 77.1 1.1 8 中顶液 428.6 1.0 9 携砂液 428.6 13 100.3 1.1
 图 2 通道压裂砂堤分布 Fig.2 Distribution of channel fracturing sandbars

1.2 充填层二维结构模型

 图 3 通道压裂充填层模型平面截取部分 Fig.3 Fracture Horizontal section of filling model in channel fracturing
 图 4 通道压裂充填层平面结构简图 Fig.4 Horizontal structure of filled layer in channel fracturing
1.3 充填层内流体流动模型

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2 充填层内流体流动规律模拟及分析 2.1 数值模拟 2.1.1 模拟方法及过程

2.1.2 流体性质及流动状态

 生产时间/d 井底流压/MPa 气体密度/(g·cm-3) 气体黏度/(mPa·s) 体积系数 地下流量/(kg·s-1) Re 0 48.92 283.47 0.031 1 0.003 410 2.02 0.000 51 19 38.12 242.15 0.027 6 0.003 992 2.05 0.000 68 37 32.56 217.23 0.025 5 0.004 450 2.25 0.000 90 52 30.32 208.63 0.024 2 0.004 633 1.60 0.000 71 70 27.33 190.02 0.023 0 0.005 087 1.46 0.000 75 85 25.30 179.73 0.022 1 0.005 378 1.33 0.000 82 100 23.95 173.88 0.021 7 0.005 559 1.25 0.000 74 115 23.45 170.21 0.021 0 0.005 679 1.22 0.000 76 133 22.27 163.43 0.020 7 0.005 914 1.16 0.000 77 148 20.41 149.81 0.020 4 0.006 452 1.03 0.000 75 164 19.57 145.24 0.019 6 0.006 655 0.97 0.000 76 180 19.40 143.98 0.019 5 0.006 713 0.57 0.000 40
2.1.3 模拟结果及分析

 图 5 井底流压48.92 MPa条件下模拟数据 Fig.5 Simulation results performed at BHFP of 48.92 MPa

2.2 导流能力的计算

 图 6 不同生产时间下的裂缝导流能力 Fig.6 Fracture conductivity at different times

 图 7 M.R.Gillard等人试验中使用的简化不连续充填层结构 Fig.7 Structure of a simplified discontinuous filling layer used in tests of M. R. Gillard and others

 图 8 A井实际产量与计算产量的对比 Fig.8 Actual and calculated productivities of Well A

3 结论及建议

1)影响通道压裂裂缝导流能力的主要影响因素是空隙通道的结构和分布。

2)通道压裂井产量较预期产量大幅降低的原因是通道压裂裂缝内没有形成连续的大通道或大通道坍缩形成离散分布的空隙结构，导致导流能力降低。

3)要保证通道压裂的效果，就要确保通道压裂时形成连续性强的大通道。

4)数值模拟时仅考虑了充填层内流体为单相气体的情况，未考虑地层流体为气液两相流，建议考虑气液两相流进行进一步分析。

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#### 文章信息

YANG Yingtao, WEN Qingzhi, DUAN Xiaofei, WANG Shuting, WANG Feng

Numerical Simulation for Flow Conductivity in Channeling Fractures

Petroleum Drilling Techniques, 2016, 44(06): 104-110.
http://dx.doi.org/10.11911/syztjs.201606018