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• 专家论坛 •

### 对启动压力梯度和压敏效应的反思、推导与评论

1. 1.中国石油勘探开发研究院,北京 100083
2.中国地质大学（北京）能源学院,北京 100083
• 收稿日期:2020-12-10 出版日期:2021-02-26 发布日期:2021-02-04
• 作者简介:陈元千（1933—）,男,教授级高级工程师,1952年考入清华大学石油工程系,1956年毕业于原北京石油学院钻采系,从事油气藏工程,油气田开发和油气储量评价工作,发表论文近400篇。

### Rethink, derivation and review on the starting pressure gradient and pressure sensitivity effect

Chen Yuanqian1,Liu Pan1,2,Lei Danfeng1

1. 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083
2. China University of Geosciences（Beijing）, Energy College, Beijing 100083
• Received:2020-12-10 Online:2021-02-26 Published:2021-02-04

Bear（1972）和Fatt（1952）分别提出的启动压力梯度和压敏效应,对于低渗透油气藏的开发具有一定的实际意义。所谓启动压力梯度,是指促使油气在地层中开始流动的临界压力梯度。所谓压敏效应是指地层渗透率随地层压降而降低的现象。尽管由于致密低渗的鄂尔多斯盆地油气藏开发分析的需要,我国的有关专家学者对启动压力梯度和压敏效应关注了近二十年,但对两者的认识至今仍处在初期的感性阶段,究原因是缺少基础理论上的研究。通过推导表明,达西线性流动的压力梯度和启动压力梯度均为常数,而达西平面径向流的压力梯度和启动压力梯度则为径向半径的函数。我国的专家学者将线性流的启动压力梯度这一常数直接用于平面径向流方程是不正确的。大量的实验数据表明,渗透率的压敏效应是存在的,但绝对不可以用于达西定律的流动方程。因为“达西定律是建立在常数渗透率基础上的”,否则,就会动摇地下流体力学、油气藏工程和油藏数值模拟的理论基础。

Abstract:

The starting pressure gradient and pressure sensitivity effect proposed by Bear（1972） and Fatt（1952） respectively have practical significance for the development of low permeability oil and gas reservoirs. The so-called starting pressure gradient refers to the critical pressure gradient that causes the oil and gas formations to start flowing. The so-called pressure-sensitive effect includes the phenomenon that the formation permeability decreases as the formation pressure drops. Due to the theoretical needs of tight and low-permeability reservoir development analysis in the Ordos Basin, relevant experts and scholars in China have paid attention to the starting pressure gradient and pressure sensitivity effect for nearly 20 years, but their understanding is still in the initial perceptual stage. The reason is the lack of basic derivation. The derivation in this paper shows that the pressure gradient and starting pressure gradient of Darcy linear flow are constant, but the pressure gradient and starting pressure gradient of Darcy plane radial flow both are functions of radial radius. It is incorrect to directly apply the constant starting pressure gradient of linear flow to the plane radial flow equation. Although the pressure sensitivity effect of permeability exists, it can never be used in the flow equation of Darcy’s law. Because constant permeability is the basis for the establishment of Darcy’s law. Otherwise, it will shake the theoretical foundations of Ground Fluid Dynamics, Petroleum Reservoir Engineering and Reservoir Numerical Simulation.

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