Prediction Of Favorable Reservoir Facies Belt Of Devonian In Northwestern Sichuan

In this paper,on the basis of sedimentary petrology,reservoir geology,logging geology,petroleum geology,and with detailed field observation,tracking and lateral stratigraphic contrast,a typical deposition profile found,systematic sampling and laboratory experiments,Northern western Sichuan Devonian stratigraphy and depositional system have been fine researched.And we preliminarily study on the characteristics of the key layers.we make reservoir facies prediction.We achieve the following findings:For stratigraphic division and correlation studies,Silurian and Devonian boundary should be constructed on unconformity surface.Concretely it is placed at the end of Devonian.Based on regional geological background and petrological characteristics,the Devonian includes Pingyipu group,Ganxi group,Yangmaba group,Jinbaoshi group,Guanwushan group,Shawozi group,Maoba group.The fine-grained clastic sedimentary rocks is in the lower part of Devonian.The carbonate is in the upper part of Devonian.Pingyipu and Ganxi group are conformable contact.Based on lithological boundaries,quartz sandstone became muddy silt,silty mudstone;Ganxi and Yangmaba group are conformable contact.Biology and bioclastic emergence of a large number is bounded;Yangmaba and Jinbaoshi group are conformable contact.The boundary is that Jinbaoshi group thick-middle quartz sandstones appear;Jinbaoshi group and Guanwushan group are conformable contact.The boundary is that quartz sandstone in upper Jinbaoshi group and carbonate rocks in the bottom of Gunwushan group;Guanwushan group and Shawozi group are conformable contact.It is difficult to distinguish the boundaries.Mutation dolomite and limestone are the boundaries between the two groups;Shawzi group with Maoba group are conformable contact.The boundary is that Maoba group bioclastic limestone appears.For the depositional system,We believe that the southwestern part of Sichuan Devonian mainly is mixed deposition platform system.The mixed deposition platform system is developed in the early weathering interface.From the early to late,it constitutes a major transgressive cycle.From west to east,Lower Devonian system includes clear water platform,muddy water platform,sandy shore zone.From west to east,Middle Devonian systems includes basin-slope,platform margin beach,clear water platform-mixing platform,tidal flat-sandy shore zone.From west to east,Upper Devonian system includes basin-slope,platform margin beach-clear water platform facies.Entire Devonian is constantly advancing landward.Preliminary research on reservoir characteristics,Jinbaoshi group fine-grained quartz sandstone,Guanwushan group and Shawozi group dolomite are the main reservoir rock;Fine-grained quartz sandstone intergranular dissolved pore were more developed.Its reservoir performance is good.And it is generally I class reservoir;Dolomite intergranular pore,intergranular solution pores and small caves were well developed.Its reservoir performance is medium.And it is generally ? class reservoir.Finally,we made favorable reservoir facies prediction.We believe that the area of Yanmenba-Tianjinshan-Bantongya developed Jinbaoshi group quartz sandstone and Guanwushan group dolomite.The area of southwestern Tongko,Cizhuya in Mianzhu to Jiangyou developed Jinbaoshi group quartz sandstone and Guanwushan group dolomite.These areas are the most advantageous reservoir facies belts.