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根据气体在浓度梯度作用下进行自由扩散的原理,开展浓度梯度驱动下的天然气扩散运移物理模拟实验,对扩散在低孔渗致密砂岩气成藏中的作用和贡献、低孔渗致密储层天然气成藏机制进行探讨。结果表明:浓度梯度驱动下的天然气扩散运移模拟实验后低孔渗致密砂岩最大含气饱和度与物性总体呈负相关关系,渗透率≤0.1×10-3μm2时最大含气饱和度与孔隙度具有更好的负线性相关性,渗透率>0.1×10-3μm2时最大含气饱和度与渗透率具有更好的负线性相关性;当低孔渗致密砂岩的孔隙度小于0.6%、空气渗透率小于0.01×10-3μm2时,扩散可能对低孔渗致密砂岩含气饱和度的增加起主要作用和贡献;扩散是低孔渗致密储层天然气成藏的重要机制之一,是中低丰度低孔渗致密储层大面积含气的重要原因之一。
According to the principle of free diffusion of gas under the action of concentration gradient, physical simulation experiments of diffusion and transport of natural gas driven by concentration gradient are carried out. The effects and contributions of diffusion in tight sandstone gas reservoir with low porosity and permeability, Natural gas accumulation mechanism to explore. The results show that the maximum gas saturation of tight sandstone with low porosity and permeability is negatively correlated with the overall physical property after the simulation experiment of natural gas diffusion driven by the concentration gradient. When the permeability is less than or equal to 0.1 × 10-3μm2, the maximum gas saturation and porosity Has better negative linear correlation, the maximum gas saturation with permeability> 0.1 × 10-3μm2 has a better negative linear correlation with permeability. When the porosity of the tight sandstone with low porosity is less than 0.6%, the air permeability When the rate is less than 0.01 × 10-3μm2, diffusion may play a major role in the increase of gas saturation of low permeability sandstone. Diffusion is one of the important mechanisms of gas accumulation in tight reservoirs with low porosity and permeability. One of the important reasons for the low porosity and permeability of dense reservoirs over large area gas.