致密砂岩气藏渗流机理及开发技术

致密砂岩气藏具有相对复杂的渗流规律,明确其储层条件下的渗流机理有利于制订合理、有效的开发方案。通过总结国内外相关的研究成果,并有针对性地进行了补充实验研究,取得了致密砂岩气藏渗流机理的一些新认识:1实际生产过程中,由于受到孔喉半径较小、废弃地层压力较高的限制,无需考虑其滑脱效应和高速非达西渗流对渗流特征及开发效果的影响;2其阈压梯度和应力敏感程度随着储层渗透率的降低而增大,随着储层含水饱和度的升高而增大;3压力梯度可以显著的影响气水两相的渗流能力,随着压力梯度的增大,气相相对渗透率逐渐降低,水相相对渗透率逐渐升高。基于渗流机理的认识和美国致密砂岩气藏的开发情况,总结了有效的开发技术对策:大型水力压裂技术、井网加密技术、小井眼钻井及欠平衡钻井技术、控压开采技术。

The research of percolation mechanism and technical countermeasures of tight sandstone gas reservoirs

Tight sandstone gas reservoirs has relatively complex seepage law so that it is useful to develop reasonable and effective development programs by understanding seepage law under reservoir conditions. According to the research of percolation mechanism of tight sandstone gas reservoirs from domestic and abroad and also experiments which is target to the research. We make some new understanding: (1)There is no need to consider the slippage effect and high-speed non-Darcy flow when in the actual production process because of the limit of high pressure of abandoned formation pressure and small pore throat radius in actual production. (2)The lower of the reservoir permeability or the higher of the water saturation will make threshold pressure gradient higher. (3)Pressure gradient influence the seepage law of gas and water significantly. The higher of the pressure gradient, the lower of the gas permeability and in contrast the higher of the water permeability. This article conclude effective technical countermeasures base on the understanding of the mechanism for seepage and development situation about tight sandstone gas reservoirs in the United States. Those are large hydraulic fracturing, well infilling, slim hole drilling, under-balanced drilling and pressure control mining.