超低渗透砂岩平板模型应力敏感性实验

Experimental Study of Stress-dependent Sensitivity in Ultra-low Permeability Sandstone Planar Model

针对目前超低渗透储层应力敏感性测量存在的问题,本文采用超低渗透露头砂岩平板模型,以地层水为实验流体,在三轴应力相同的条件下,进行了平板模型的应力敏感性实验,并与小岩心的气测和水测应力敏感性实验结果进行对比,研究超低渗透储层的应力敏感性特点。形成了一种新的储层应力敏感性测试方法,研究表明,实验流体的物理性质会影响应力敏感性的评价结果,常规气测应力敏感性的结果偏大。实验岩心的尺寸会影响应力敏感性的评价结果,在本次实验条件下,平板模型的应力敏感性比小岩心的应力敏感性弱;平板模型渗透率变化规律与小岩心水测结果相近,与小岩心气测结果差别较大;平板模型在低有效应力区间的应力敏感性与小岩心水测结果相似,但由于受力不均匀,导致在高有效应力区间的应力敏感性比小岩心水测结果弱。平板模型不同位置的应力敏感性表现不同,应力敏感性在主流线和采出井附近的影响较大,且在低有效应力区间的影响程度大于高有效应力区间。

The permeability stress sensitivity of the ultra-low permeability sandstone rock is experimentally studied in this paper. Unlike the 1D rock plug sample in the classical method, the 2D fiat sandstone rock sample is used in this experiment and the synthetic formation water is used as the fluid medium. In addition, the permeability stress sensitivity of the 2D rock sample is compared with that of the conventional 1D rock plug sample. A novel research method for determining the rock permeability stress sensitivity is proposed. The experimental results indicate that the type of the fluid media and the size of the rock sample have a significant influence on the permeability stress sensitivity. The permeability stress sensitivity of the 2D flat rock sample is shown to be weaker than that of the conventional I D rock plug sample. The relationship between the permeability and the effective stress of the 2D sample is close to that of the 1D plug sample when the brine is used as the fluid media. But it is different from that of the 1D plug sample when the nitrogen is used as the fluid media. The permeability stress sensitivity of the 2D sample is almost similar to that of the 1D plug sample in the lower effective stress range. However, the former is weaker than the latter in the higher effective stress range because the effective stress in the 2D sample is not uniform. The local permeability stress sensitivity at different sites is different from each other in the 2D sample. The effective stress has a more significant influence on the permeability in the main flow lines and the near production well regions.