低渗油田可动油储集层流体性质评价方法——以鄂尔多斯盆地红河油田为例

Method for evaluating fluid properties of movable oil reservoirs in low permeability oil fields:A case study of Honghe Oilfield in Ordos Basin

鄂尔多斯盆地红河油田含油饱和度高的储集层测试往往为干层或水层,这是因为含油饱和度仅反映岩石空间中含油饱满程度,并不反映其可动流体的含油量。为提高储集层流体性质解释符合率,应用大量岩心核磁共振分析数据,开展了核磁共振谱图含油特征分析和可动油饱和度流体性质评价方法研究。首先,借鉴低渗储集层可动流体储集层物性评价方法,以可动流体中含油量为主要依据开展流体性质评价;其次,在物性评价基础上,开展有效储集层(Ⅲ类以上)含油饱和度和可动油饱和度与试油结论对比分析,建立可动油饱和度流体性质评价图板。结合物性评价将储集层流体划分为4类,解决了低渗储集层流体性质解释评价问题。研究认为,可动流体中的可动油对低渗储集层流体性质起关键性作用,如果原油在储集层内以束缚油形式存在,即使含油饱和度高也不产油,从而有效解决了红河油田含油饱和度高试油不出油问题。这种方法对类似低渗储集层流体性质评价亦有效。

The reservoir test with high oil saturation in Honghe Oilfield of Ordos Basin is often dry layer or water layer,which is because oil saturation only reflects the degree of oil fullness in rock space,and does not reflect the oil content of movable fluid.In order to improve the coincidence rate of reservoir fluid property interpretation,the analysis of oil-bearing characteristics of nuclear magnetic resonance spectrogram and study on movable oil saturation fluid property evaluation method are carried out by using a large number of core nuclear magnetic resonance analysis data.Firstly,by referring to the method of evaluating the physical properties of movable fluid reservoirs in low permeability reservoirs,the fluid properties are evaluated mainly on the basis of the oil content in the movable fluid.Secondly,on the basis of physical property evaluation,the comparative analysis of effective reservoir(above type Ⅲ)oil saturation and movable oil saturation with oil test conclusions was carried out,and the evaluation chart of fluid property of movable oil saturation was established.Combined with physical property evaluation,the reservoir fluids are divided into four types,which solve the problem of interpretation and evaluation of fluid properties in low permeability reservoir.It is concluded that the movable oil in the movable fluid plays a key role in the fluid properties of the low permeability reservoir.If crude oil exists in the form of irreducible oil in the reservoir,no oil can be produced even if the oil saturation is high,thus effectively solving the problem that no oil can be produced when the oil saturation is high with formation test in Honghe Oilfield.This method is also effective for evaluating the fluid properties of similar low permeability reservoirs.