| The Ahe Formation of Jurassic in the eastern Kuqa depression is a set of typical low porosity and low permeability tight sand stone reservoir,with strong heterogeneity and complex oil and gas distribution.Make detail studies of the pore structure characteristics for the Ahe Formation has important reference value for the late exploration and development.On the basis of previous researches,this article take eleven wells in Dibei area as the research object,using the data of core observation,rock slice observation,cathodoluminescence analysis,scanning electron microscopy,mercury penetration analysis and physical property in Formation,finally completed the study of Ahe Formation,achieved the following points:(1)According to the sedimentary characteristics and logging response characteristics,braided-river delta is the main depositional systems developed in Dibei area,the sand body mainly includes distributary and channel bar deposit.The rock types mainly includes lithic sandstone and feldspathic lithic sandstone,withing high content of mixed base.Rock particles contact closely by linear-bump contact.(2)The reservoir space of the Ahe Formation sandstone in research area are: residual original intergranular pore,intergranular dissolved pore,intragranular dissolved pore,mold hole,large hole,micro pore and micro cracks;The throat types mainly include: lamellar throat,tubular throat,and tube-bundled throat.(3)The study on sandstone diagenesis shows that the destructive diagenesis of Ahe Formation mainly include compaction,cementation,quartz cementation and authigenic clay mineral filling,etc.The constructive diagenesis mainly include dissolution and fracture effect,etc.The most important factor is compaction.(4)The Ahe sandstone Formation was in acidic aqueous medium in the early diagenetic environment,the carbonate cemetation did not develop,mainly developed quartz cementation.In addition,somewhere in cracks developed the self-healing phenomenon.According to the above phenomenon speculate that when the compaction reaches to a certain intensity,with enough silica source,the quartz cementation tend to occur in the cracks of quartz with more fresh face.(5)Fracture is a typical diagenetic characteristic of Ahe Formation in Dibei area.The tectonization is the main control factors of the cracks.On the one hand,the cracks can connect isolated porosities of sandstone to enhance the connectivity of pore-throat.On the other hand,when rigid particles were ruptured,the original rock structure was damaged,then the particles would rearrangement to be more closely.Therefore,the influencing mechanism of fractures for sandstone reservoir needs further research.(6)According to the correlation analysis of physical properties and mercury injection parameters,the maximum connected pore-throat radius has the best correlation with porosity and permeability,so choose it as the standard parameter for the classification of pore-throat structure.Then combined it with Pd,SHgmax,porosity and permeability to classify reservoir types.(7)On the basis of pore-throat types,diagenesis and reservoir classification,synthesize the relevant data of sedimentary facies,sand body thickness,porosity and permeability,etc.Then divided the Ahe sandstone Formation into five categories: the type-? and type-? are high quality reservoirs,with high-mid pore-large throat and high-mid pore-mid throat structure.for big-hole in coarse throat and big-hole in the throat,these two types of reservoir usually developed in areas with a strong tectonic compression.The type-? is the second best reservoir,with high-pore-fine throat structure.This type usually has a lot of micro-pores,but the pore connectivity is poor.The type-? is the most widely distributed reservoir in Dibei area.The ?-type reservoir is the worst type,basically do not have gas deliverability.According to the above standard,the effective reservoir in Dibei area mainly distribute in the range of the channel sand body. |
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