地层含水条件下砂岩储层气相渗流通道大小量化评价方法--以鄂尔多斯盆地苏里格气田储层为例

Quantitative evaluation on the size of gas-phase flowing channel in water-bearing sandstone reservoirs:An example from Sulige gasfield,Ordos Basin

孔隙型砂岩在地层含水条件下的真实气相渗流通道大小,与室内干燥岩心实验测试结果往往存在较大差异,难以实现量化评价,气藏开发评价时难以获得可靠的参数。针对这一难题,利用地层含水条件气相渗透率与地面干燥岩心气测渗透率比值,定义了“气相渗流通道指数”这一指标,建立了一套地层条件下砂岩储层气相渗流通道大小的量化评价方法和数学模型。以鄂尔多斯盆地苏里格气田储层为例,选用不同渗透率的砂岩岩心,在不同含水饱和度条件下开展了实验测试和评价工作,揭示了地层含水条件下砂岩储层气相渗流通道大小的变化特征,即总体上随含水饱和度增加而减小,但不同渗透率砂岩减小幅度有所差异,分析认为孔喉空间赋存水对低渗—致密砂岩气相渗流能力的影响十分显著,开发过程中需要高度重视和防治水对储层的伤害。

In the gas-phase flowing channel in porous water-bearing sandstone reservoirs,there is usually great discrepancy in its size individually measured from in-situ condition and lab test on dry cores.It is hard to obtain a reliable parameter for quantitative reservoir evaluation.So,an indicator of gas-phase flowing channel index was defined by the ratio of the gas-phase permeability under in-situ water-bearing condition to the gas permeability of dry cores.And then,some quantitative evaluation methods and mathematical models were developed for in-situ gas-phase flowing channel in sandstone reservoirs.Several cores with different permeability were sampled from sandstone gas reservoirs in Sulige gasfield,Ordos Basin,and many experiments and evaluations were carried out at different water saturation to investigate the change of channel size.In general,the size may decrease with an increase of water saturation,but the decreasing magnitude varies with permeability.In conclusion,whether or not water in pore and throat has an obvious impact on gas-phase seepage in low-permeability or tight sandstone reservoirs.Water damage to these reservoirs should be highly valued and prevented in the process of development.