Research On The Characteristics Of Low-permeability Reservoir And Its Influence On Productivity In NiuJuanHu Oil Field

The reservoir of Xishanyao has the feature of low-porosity,low-permeability,and low pressure in NiuJuanHu oil field.The article is aimed at the Xishanyao reservoir, with the technique of casting sections, scanning electron microscopy, X-diffraction, grain size analysis, image pore, mercury penetration, rate-controlled mercury penetration, nuclear magnetic resonance, oil-water relative permeability, experimental results of oil-water displacement in microscopic model of real sandstone, the features of microscopic pore strueture and percolation characteristics have been analysed completely about nothern area,eastern area,and southern area in NiuJuanHu oil field. With the mercury penetration, core electrical experiment and the analysis of sealed coring, the initial oil saturation of the three areas are evaluated.The evolutional model of the reservoir property has been established by analyzing sedimentation and diagenesis,at the same time, master control elements of the reservoir property have been analysed quantitatively. Combining the features of the reservoir and production performance, the factors of the deliverability are analysed. The conclusions are in following:(1)There are pores and pore-throats of various genetic types in Xishanyao reservoir,the main types of the pores include tuffaceous emposieu, intergranular pore and feldspar emposieu.The main types of the throat are point throat, lamellar throat.In eastern area and southern area, gross pore and throat have highly frequency distribution, widely distribution range, and better communication. In northern area,the pore and throat are tiny,the radius are more concentrated,the pore structure is worse.(2)The features of oil-water relative permeability curve, the range of homo-vadose region, the interstitial oil saturation,the movable oil saturation,and oil displacement efficiency are different among the three areas,the main factors of these parameters are pore structure.(3)The initial oil saturations stand for the quality of the reservoir.Because of different initial oil saturations in the three areas, the reservoir deliverabilities of the three areas are different. Useing the mercury penetration and core electrical experiment to evaluate the initial oil saturations,which showed that initial oil saturation is affected by pore structure. (4)The porosity evolution pathways of the three areas are different because of the sedimentation, diagenesis and tectogenesis.The compaction and cementation are stong in the nortern area, the compaction and denudation are strong in the eastern area, the early cementation and late cementation are strong in the southtern area,but the compaction is weak.By the quantitative analysis of the main controlling factors about reservoir property, denudation, standard deviation and cementation all affect porosity major; denudation, the content of interstitial material and cementation all affect permeability major.(5)The deliverability of the three areas are low, water content ratio rises faster,the difference of deliverability among the three reservoir are large.Combining the features of lithology, physical property, pore structure, oil-water relative permeability, and initial oil saturations with the deliverability in these areas,the microscopic pore structure greatly affect the deliverability.