低孔低渗致密砂岩气藏束缚水饱和度模型建立及应用——以苏里格气田某区块山西组致密砂岩储层为例

Irreducible Water Saturation Models of Tight Sandstone Gas Reservoirs with Low Porosity and Permeability and Its Application-Taking a Block of Shanxi Formation Tight Sandstone Reservoir in Sulige Gas Field as an Example

研究区的储层具有低孔隙度、低渗透率、低压力、低丰度和高含水饱和度等特点。束缚水饱和度与地层的孔隙结构、岩石性质及形成条件有关,所以对不同类型的储层,影响其束缚水饱和度的因素不同,求取方法也不同。针对研究区的实际情况,利用核磁共振资料、测井资料分别建立了3种计算束缚水饱和度模型:①孔隙度建立模型,该模型对低孔、低渗及孔隙结构复杂的储层适用性很差;②用多元线性回归求束缚水饱和度,该方法取得了较好的效果;③用孔隙结构指数建模,该模型与核磁分析吻合程度最高,效果最好。因此根据研究区储层特点,选择利用孔隙结构指数建立束缚水饱和度模型,大大提高模型准确度,为后期测井解释提供了可靠依据。

Reservoirs in the study area have characteristics of low porosity,low permeability, low pressure, low abundance, and high water saturation. Irreducible water saturation is related to the pore structure, rock properties,and formation condition. So for different types of reservoirs, there have different factors influ- encing the irreducible water saturation,and the way to calculate are also different. According to the actual situation of the study area, we establish three models to calculate irreducible water saturation on the basis of NMR and well-logging data： porosity model which is very bad for low porosity, low permeability, and pore structure complex reservoirs; multiple linear regression analysis for pore structure index and shale content to get irreducible water saturation,which achieved good results;Pore structure index model which has high degree of agreement with NMR analysis and good effect. Therefore, according to the reservoir characteristics of the study area, the model established by pore structure index improves the accuracy of in- terpretation model,and provides a reliable basis for the post-logging interpretation.