Analysis Of Reservoir Micro-characteristics Of Chang 10 Oil-bearing Layers In The G Area Of Ansai Oilfield

Currently, Little research around micro-characteristics of Chang10 oil-bearing in Ansai Oilfield has been carried out because of it being a new exploration series, restricting its further exploration and development. With the guidance of multidisciplinary theories such as petroleum geology, reservoir geology,petroleum development geology and petrophysics, and based on the description of cores and a large amount of data of conventional and casting thin section, SEM, X-ray analysis of clay minerals, cathodoluminescence, electron microprobe, granularity analysis, pattern analysis of pore structure and high-pressure Hg injection, this paper provides a systematic and in-depth analysis and research of reservoir microcharacteristics including petrological chacharacteristics, diagenisis, pore evolution, pore structure, microheterogeneity, physical properties, of Chang 101, which is the main oil-bearing strata of Chang 10 in the G area of Ansai Oilfield.The study shows that, Chang 101 reservoirs in this area are chiefly composed of medium-fine grainded feldspar and feldspar-lithic sandstones, the content of matrix is low, and the cement content, which is mainly made up of laumontite, calcite, chlorite, is high. All sandstones have entered B and C period of late diagenetic stage. The dominant diagenesis types are compaction, cementation and dissolution, of which compaction and cementation cause Chang 101 reservoirs lost almost all their initial porosity, and dissolution effectively improved its physical property. Pore types of Chang 101 reservoir are mainly remnant intergranular porosity, feldspar dissolved porosity, laumontite dissolved porosity and lithic dissolved porosity. The reservoir throats chiefly consist of sheet throat, curved sheet throat and bundle throat. Pore-throat association mainly includes medium pore and fine throat type and small pore and micro-fine throat type. The permeability is largely controled by the pore and throat of reservoir, which turns out the more volume of the pore and throat, the higher permeability. Chang 101 reservoir is mainly low to ultra low porosity and ultra low to extreme low permeability reservoir. During the process of development of Chang 101 reservoir, it generally appears many problems such as high water injection pressure, poor water absorbing capacity, rapid decline of production, and the root causes of these problems are ascribed to the thin pore throats. In this area, strong tuff fillings and diagenesis heterogeneity cause strong pore structural heterogeneity, and from macroscopic view, this represents as strong intra-layer permeability heterogeneity, which is easy to arise fingering of the water. The reservoirs are divided into four categories through comprehensive evaluation of parameters, and the reservoirs of Chang 101 mainly belong to classâ…¡andâ…¢.This paper not only provides basis for the following effectively and properly development of Chang 101 in this area, but also has significance to the further study of Chang 10 in the northern part of Shaanxi province in Osdos basin.