Research On Reservoir Heterogeneity And Their Controlling For Remaining Oil Of Pu-I Oil Group In Putaohua Oilfield

Taking the narrow and thin sandstone reservoirs of Pu-I oil group in Putaohua oilfield as a case,in view of the special geologic condition,a study on the reservoir heterogeneity research was carried out in this paper based on the data of geology,welllogging,and production performance.For the purpose of improving recovery ratio,this paper giving a detailed description in planar,interlayer,in-layer and microscopic heterogeneity,in order to reveal the relationship between reservoir heterogeneity and remaining oil formation.Controlled by sedimentation,the main reservoir sand of Pu-I oil group shows a narrow banded or branched distribution laterally.Reservoir properties are preferable along the main line of underwater distributary channel and the extension direction of the main body of sheet sand,but become worse along the vertical sides. The remaining oil distributes on lateral edge of underwater distributary channel and the main body of sheet sand,or distributes on the narrow thin sand bodies with poor injection.The interlayer heterogeneity of Pu-I oil group is extraordinary serious caused by difference of vertical sandstone thickness and interlayer interference. The absorbent capacity of thick reservoirs composed of underwater distributary channel sand and the main body of sheet sand is large with serious waterflooding. The non-dominated sand bodies with small thickness,such as non-main body of sheet sand and the sand between underwater distributary channels,have poor physical properties. This kinds of reservoirs have a weak capacity on water absorption or even non-absorbent,resulting poor or no-used oil reservoirs.A five-order classification scheme was proposed to analyze the architecture elements of Putaohua reservoir and describe the in-layer heterogeneity. Research results indicate that parts of the thick sandbodies thought to be flaky distribution are vertically superimposed and laterally connected by single sandbodies,which can be divided by erosional surface, argillaceous or calcic constructional surfaces. Interbeds in the single sandbodies have a obvious effect on the water-oil motion and easy to form remaining oil at the upper of them. At the bottom of positive rhythm channel sands,large pores are easy to form,and the water cycling is inefficient,this results low oil recovery in thick sands of P-I oil group. A method by using "dynamic screening well,monitoring to determine layer,detailed geological data verification " was put forward to identify large pores.The study on microscopic heterogeneity was carried out by structure analysis of pore and throat. According to the identification of typical samples in different sedimentary facies,a further understanding of the remaining oil distribution law in narrow and thin sandstone reservoirs using commingled injection and production have been formed through micro-displacement experiments.