低渗特低渗致密砂岩储层油水分布规律及主控因素--以鄂尔多斯盆地合水地区为例

Distribution of oil and water in low permeability tight sandstone reservoirs andmain controlling factors--taking the heshui area of ordos basin as an example

为明确西峰油田长2油藏油水分布规律及主控因素,本文通过水质分析、压汞、核磁共振、物性测试、试气试采等可知,研究区地层水主体为CaCL2型,少量为Na2So4型,其中CaCl2型地层水为最原始的地层水水型,Na2So4型地层水可能是古大气水溶入地层中所致或者为水淹所致;地层水微观存在形式主要为自由水、毛管压力水;研究区油水分布规律较为复杂,平面上呈片状,空间上以透镜状为主,部分井存在"上油下水"现象。研究区油水分布主要受控于构造,其次是沉积相和储层分均质性,区域构造决定了东部以及北东部油气较为富集的基本格局,鼻状隆起控制油水接触关系;三角洲前缘亚相决定了水流优先从砂体轴向突进,导致储层非均质性较强,并在在水动力条件频繁变化的水下分流河道侧翼部位发育泥质夹层和钙质夹层,为油气的聚集和保存提供了非常好的遮盖条件。

In order to clarify the oil and water distribution rules and main controlling factors of chang2 reservoir in xifeng oilfield,this paper,through water quality analysis,mercury injection,nuclear magnetic resonance,physical property testing,and gas test and trial production,shows that the main formation water in the study area is CaCL2 type,and a small amount is Na2So4 type.Among them,CaCL2 type formation water is the most primitive formation water type,and Na2So4 type formation water may be caused by ancient atmospheric water dissolving into the formation or by water flooding.The microstructure of formation water is mainly free water and capillary pressure water.The distribution law of oil and water in the study area is relatively complex,which is flaky in plane and lenticular in space.Some Wells have the phenomenon of"oil loading and water launching".The distribution of oil and water in the study area is mainly controlled by the structure,followed by the sedimentary facies and reservoir heterogeneity.The regional structure determines the basic pattern of relatively rich oil and gas in the east and the north east,and the nose uplift controls the oil-water contact relationship.The subfacies of the delta front determines that the water flow is preferentially from the sand body to the axial thrust,leading to the strong heterogeneity of the reservoir and the development of shale interlayer and calcareous interlayer in the flanking part of the distributary channel with frequent changes in hydrodynamic conditions,which provides a very good covering condition for the accumulation and preservation of oil and gas.