Study On The Characteristics Of Chang 4 + 5 Reservoir In The Southeast Of Luopang Plateau In Dingbian Oilfield

Although the chang 8,chang 61,chang 4+5,chang 2 of yanchnag formation and the yan 9 yan 6 of yanan formation and the zhiluo formation of Jurassic are oil producing formation in southeast of luopangyuan of dingbian oilfield,but the chang 4+5 is tne main.It is necessary to research the reservoir characteristics of chang 4+5,provide geological basis for improve the efficiency of the oil field exploration and development.The paper based on the predecessors’research and the theory of petroleum geology,reservoir sedimentology, starting from the data of core observation, using logging and well logging data to district the chang 4+5 formation and to analysis the structure,sedimentary facies, effective sand body distribution,etc of chang 4+5 formation. Studied the mineral composition, pore characteristics, diagenesis of sandstone reservoir by using the data of core, cast thin section, scanning electron microscopy and X ray experiment. Studied the pore throat structure and the seepage characteristics of the reservoir by using the results of mercury porosimetry and phase permeability. Reserarched the "four" relationship and establish the interpretation chart of reservoir by combining with the oil testing and logging. Mainly achieved the following results and understanding:The structure of the study area is simple, developed small nose structure on the background of the western anticline, the top of the chang 4+5 formation developed four nose structure and one is throughout the entire districtThe underwater distributary channel sand body are the main development in the study area, the sand body are distributied to the North East,the chang 4+52 developed four main sand body and the chang 4+51 is five, the sand body’s width and thicjness of chang 4+52 is longer than chang 4+51, it’s length 5-10km,width 700-1.2km,thickness 14-18m.The chang 4+5 reservoir is mainly fine grained feldspar sandstone,29.8% of the average content of quartz,46% of the average content of feldspar; fillings are mainly developed clay minerals and carbonate cementation, clay minerals are kaolinite, green mudstone and illite, carbonate cements are mainly iron calcite; the reservoir pore types are mainly residual intergranular pore,feldspar dissolved pore and micro cracks. Chlorite film has protective effect on reservoir primary pores, iron calcite cements,authigenic kaolinite and illite are damage to the pore and permeability of reservoie. The chang 4+5 reservoir belongs to low permeability-extra low permeability reservoir, average porosity is 10.6%, average permeability is 1.12μm2, the average throat radius is 0.56μm. The reservoir heterogeneity of chang 4+52 is stronger than chang 4+51.The water type of the oil pool is mainly CaCl2,occasionally NaHCO3; The sand body distribute range on the plane and large thickness in the vertical of chang 4+5 reservoir, the geological reserves of chang 4+52 is 3.4 time as long as chang 4+51; on the plane, the oil pool is mainly concentrated in the underwater distributary channel sand body; The oil pool of chang 4+5 has the advantage of nearing the source, the sedimentary facies and diagenesis have controlled the distribution of the reservoirs,the good gap is the interdistributary bay mudstone. Based on the second logging interpretation and reservoir characteristics, puts forward 8 wells of unused reservoir as perforating suggestuons.