The Research Of Microscopic Pore Structure And Waterflood Development Feature In NiuJuanHu Oil Field

This article is aimed at the reservoir feature of low-porosity, low-permeability, low-pressure and the current exploitation status of high water cut in NiuJuanHu oil field. The advanced experiments have been utilized in this article, such as casting section, SEM, rule mercury penetration, water-oil displacement experiment, nuclear magnetic resonance, constant rate mercury penetration and microscopic water displacing oil experiment. The features of microscopic pore structure have been analysed completely, at the same time the microscopic water-oil filtration mechanism and the affecting factor have been researched in core yardstick. The main affecting factors of waterflood development have been analysed. Moreover, combining the development plans of advance water injection, fracture and sup-breakdown pressure injection, the orientation and feature of water breakthrough have been researched with a great quantity of production performance data, and the causes of high water cut have been found out from the aspects of geology and engineering. The article has acquired following conclusions:1.The main pore types of Xi ShanYao reservoir are tuffaceous emposieu, intergranular pore and feldspar emposieu. The types of pore combination are intercrystal pore-emposieu and intergranular pore-emposieu. The main throat types are point throat, lamellar throat and curved lamellar throat. Totally the connectedness of pore and throat is bad, the coordinate number is short, the reservoir is divided as sopore-fine throat.2.The most obvious feature of pore structure in NiuJuanHu oil field is great pore-throat radius ratio. The aeolotropism of pore and throat is obvious, and the capillary resistance is strong when fluid goes to throat, so the mobile fluid saturation of reservoir is low, and the oil is hard to be developed.3.The reservoir of NiuJuanHu oil field is drived by elastic energy, but the recovery ratio of elastic drive is only 1.6%. In order to keep appropriate displacing pressure difference in production process, the advance water injection must be implemented to raise the reservoir pressure.4.Tow obvious features have displayed in permeability ratio curve:a. When the Sw moves upward a bit, the oleic permeability drops rapidly. b. The distance of oil-water collective infiltrating fluid is narrow. The SWB and SOR are both upper. It has been reflected in permeability ratio curve that the time of oil-water simultaneous extraction is short. When water breaks through the commercial well, the crude output is dropping sharply and the water content is moving upward readily.5.The causes of high water cut in NiuJuanHu oil field include both geological and engineering factors. Geological causes include structure, split and aeolotropism, and engineering causes include the effect of advance water injection, adaptiveness of well patterns and the opportune moment of fracture.6.The main causes of high water cut is water breakthrough caused by splits. The splits are induced splits created by sup-breakdown pressure injection and hydraulic fracture. The orientation of spilts are obvious. The splits in northern area are distributed in north-east direction, and the splits in southern area are distributed in north-east and east-west direction. The northern splits are broader than southern splits.7.Many problems have arised in the implement process of dvance water injection, such as long injection time, high injection pressure, great water intake per unit thickness. When producible wells are breaked down, the water content moves upward speedily, waterflood efficiency is low, the production time with low water is short, and it is hard to stable yields.8.The orientation of fracturing splits is controlled by areal crustal stress, and the areal crustal stress can alter because of affection advance water injection, so it affects the validity of fracturing seriously.