Reservoir Description On Chang 2 Reservoirs Of Yanchang Formation In Zhangjiawan Area Of Zhiluo Oilfield

Zhangjiawan area of Zhiluo oilfield located in the structural unit in middle of Northern Shaanxi Slope,Ordos Basin.Chang 2 reservoir of Yanchang Formation is the major reservoir in Zhangjiawan area of Zhiluo oilfield.It has the advantages of buried shallower and physical properties better.The chang 2 reservoir still has good reservoir exploration and development potential.In order to find favorable reservoir,the thesis is guided by sedimentary petrology,reservoir geology,petroleum geology,geophysical well logging and other related theory,combined with Multi-statistical analysis,relied on the current advanced experimental testing methods,used the information of geological outcrops,drilling,logging,adopted the macroscopic and microscopic research methods,we conducted a detailed study on the reservoir characteristics and classified evaluation of Chang 2 reservoir in Zhangjiawan area of Zhiluo Oilfield.The chang 2 formation has obvious depositional cycle characteristics,so chang 2 formation can be divided into chang 21 formation,chang 22 formation and chang 23 formation.Because of formation sedimentation stability in this area,stability of formation thickness changes.The structure of this area is relatively simple,overall performance as a western-leaning monoclinic.There are some low nose-shaped bulge on the western-leaning monoclinic.This is similar to the general tectonic setting of ordos basin.Provenance of North East region developed delta front deposition,genetic types are mainly underwater distributary channel sandstone deposited,distributary channel flank sedimentary and distributary bay take second place.Chang 2 reservoir sandstones are mainly feldspathic sandstone,the detrital compositions are mainly of feldspar in this area,quartz and debris take second place.Most of cements are calcite and chlorite.Reservoirs mostly develop intergranular pore and corrosion pore.The type of pore structure is mainly fine pore throat in chang 2 reservoir.According to the research of macroscopic and microscopic in this area,we think chang 2 reservoir has strong heterogeneity.Chang 2 reservoir average porosity is 12.5% and the average permeability is 1.31×10-3?m2 of the developed blocks in this area.The Chang2 reservoirs which are low porosity and low permeability.On the basis of the influence of diagenesis,which can be divided into constructive diagenesis,damage diagenesis and keep diagenesis.Diagenetic stage of chang 2 reservoir mainly in the middle diageneticstage of A period.According to the standard of this area,chang 2 reservoirs can be divided into four types,the chang 21 reservoir is mainly for class II reservoir and class IV reservoir,the class I reservoir has been widely distributed in different regions,the class III reservoir was only distributed in local region.The chang 22 reservoir is mainly for class II reservoir and class III reservoir,the class I reservoir has been distributed in northwest,central and southeastern of this area.Although the class IV reservoir has occupied a large area,the class IV reservoir has significantly reduced compared with chang 21 reservoir.