The Descriptionon Reservoir Of Chang6 In Yong554 Well Area Of Yongning Oilfield

Chuankou oilfield belongs to one of seven oilfield affiliated withYanchangOil administration bureau. And C33 area is as the main exploitation of southern Chuankou oilfield, in which uppermost oil layer is Chang-6 reservoir of Yanchang Formation. Oil-bearing area can reach to 12.2km2 and reported proven reserves have numbers of 559.4573 tons. However, with the the ever growing needs of energy by domestic industries, petroleum industry is faced with a serious situation.For solving these issues, improving the oilfield productivity and adapting to the development demands of efficiency development of water injection. Based on analysis of the previous achievement and basic data and combining with geology, logging, production test data and productive dynamic characteristics, this study aims to solving the problems in C33 area of Chuankou oilfeild, including strong horizontal heterogeneity in planes, inter layers and interior layers, water driving wave and limited volume during waterflooding and low degree of producing reserves. And this article has a detailed research on depositional and reservoir characteristics, especially on petrology, diagenesis, physical property, pore structure, anisotropy and percolation. Then this research could establish the reservoir classification standard and further reservoir evaluation for comprehensive adjustment, measures of excavating remaining oil potential and efficient and rational development of reservoirs. The researching contents conclude the following three parts:1) reservoirpetrology and diagenesis. 2) pore structure and physical property.3)detailed characterization on anisotropy.Finally, this study gets the following conclusions:1) The Hthology of Chang 6 reservoir is mainly gray fine-grained feldspar sandstone with lower mineral maturity, high structural maturity, which could indicate a low-energy and stable sedimentary environment.2) Chang 6 reservoir has strong diagenesis which is between late A phase and early late B phase. The main reasons of destroying reservoir porosity and decreasing permeability are compaction and cementation of carbonate, clay minerals and laumonite. But the development of clay film formation and dissolution protect primary pores and the secondary pores and improve the reservoir physical properties.3) The max porosity of Chang 6 reservoir is 18.06%. Minimumporosityis 1.28%. Average porosity is 9.21%. The max permeability of Chang 6 reservoir is 14.10×10-3μm2. Minimumpermeabilityis less than 0.16×10-3μm2. Average permeability is 1.44×10-3μm2. Chang 6 reservoir could be defined as low pore and low permeability reservoir.4) The pore types of Chang 6 are residual intergranular pore, chemical erosion intergranular pores, chemical erosion intragranular pore, pore in the filler content, pore in the filler content in chemical erosion, moldic pore, authigenic mineral intercrystal pore and fracture pore. The pore assembly types are mainly Residual intergranular pore type, intergranular pores-micropore type, corrosion holes-micropore type, micropore type and compound type, which belongs to orifice-thin throats type and orifice-micro-thin throats type. According to rate-controlled test, distribution interval of Chang 6 throat radius is between 0.2 and 0.7μm. The distribution interval of Chang 6 pore radius is between 100 and 200μm.Throat distribution curve is fine. The pore is coarse. It is nearly normal unimodality. According to pore-throat classification standards of clastic rock, reservoir pore of Chang 6 is bigger pores and thin throats. The connectivity and tortuosity of the throat have a significant influence on permeability.6) Statistic analysis of data shows Chang 6 reservoir in researching area appears medium to strong heterogeneity. But due to existence of micro-fracture, the heterogeneity of Chang 6 reservoir is more serious. And with constantprogradation of sand in delta front, the heterogeneity of reservoir shows stronger trend.6) Chang 6 reservoir belongs to the extremely low permeability reservoir which shows different seepage characteristics with normal reservoir. 7) Based on the comprehensive analysis on reservoir physical property, microscopic reservoir pore structure characteristics, capillary pressure curves characteristics and reservoir heterogeneitycharacteristics, meanwhile combining with lithology and oil-bearing strata, Chang 6 reservoir in researching area could be divided into four types which are good(I type), medium(IItype), bad(IIItype) and non(IVtype) reservoir. And Chang 611 is mainly I+II type reservoir. I+II type reservoir of Chang 612 is accounting for 57%. I+II type reservoir of Chang 613 is accounting for 37%.