大庆油田含钙薄互储层水淹层判别方法

Identification of Waterflood Interval in Laminated Calcium Reservoir of Daqing Oilfield

大庆长垣西部萨尔图、高台子油层含钙薄互储层具有岩性复杂、孔隙度和渗透率低、单层厚度小的固有特性,致使储层四性关系混乱,测井响应有效信号减弱,注水开发后地层水电阻率难于确定。从原始油藏入手,以多元回归分析为手段,建立起水淹前实测纯油层、纯水层电阻率与测量环境、储层岩性及物性参数的内在关系。通过水淹后当前地层电阻率与纯油、纯水电阻率对应比较,找出水淹与未淹情况下油、水层电阻率的差异,在未知地层水电阻率情况下实现水淹层识别。经5口生产井19个水淹层检验,水淹层解释符合率达到89.4%。

Enormous difficulties in identification of waterflood interval are caused by many features of laminated calcium reservoir of Western Changyuan, Daqing, such as complicated lithology, low porosity and permeability, small thickness of monolayer, as well as relations among reservoir properties being in confusion, weak effective logging signals, especially its formation water resistivity after water injection being difficult to be determined. Applying data sampled from the original reservoir, using multivariable regression analysis method, established are empirical relations between actually measured resistivities of net pay zones or net water zones and various parameters of logging environment, reservoir lithology and petrophysics before water injection, and then criterions of distinguishing oil- or water-bearing layers are constructed with differences of actually measured resistivities to resistivities calculated with the empirical relations in net oil- or water-bearing layers. It is believed that the electric character of oil-and-water-bearing layer is identical to that of waterflood layer, and the criterions of the two also are the same, so that the waterflood identification can be actualized in condition of unknown formation water resistivity. In tests of 19 water-out layers in 5 production wells, the interpretation accordant rate reaches to 89.4%.