The Anatomy Of The Volcanic Edifices And It' Control To The Reservoir Of Yingcheng Formation In Songnan Gas Field

Gas field in the south of songliao basin is located in changling fault depression Central uplift high position of songliao basin southern part . Oil and gas migration favorable long-term point to areas. With exploration success in the south of songliao basin gas field,(By the end of 2007 submitted to the State Reserve Committee of proved reserves of natural gas as 433.60×108m3, composite gas area 16.83km2. Deep reservoir has become a deeper China PetroChemical Corporation upstream industry the importance of the set target of natural gas. The research aimed at accuracy to dissect volcanic edifice in the south of songliao basin gas field, and based on lithology,lithofacies and single-well divided. Divided Volcanic edifice cycles-subcycle-stage in the south of songliao basin gas field by means of geology geophysics and other methods.Taking cycle as time frame divide volcanic edifice,Regard stage as the smallest units which control lithology lithofacies space distribution characteristics ,Through the adjoining drilling controlling, combining with the seism features,Do research on volcanic internal lithology lithofacies reservoir distribution characteristics and analyze control function about the volcanic edifice affect on reservoir.1.Volcanic lithology, lithofacies characteristics in the south of songliao basin gas fieldLithology characteristics :Volcanic lithology are mainly acidic lava in the south of songliao basin gas field,with minor dacite, overall alkaline.There are five classes tekinds of lithology.Including rhyolite(stomatal almond rhyolite, pyromeride, rhyolite tectonic rhyolite, felsitic rhyolite, massive rhyolite, breccia rhyolite),volcanic pyroclastic(Rhyolitic crystal tuff, Rhyolitic rock debris vitric tuff),volcanic breccia (rhyolitic-explosivebreccia), volcanic pyroclastic lavas(rhyolitic tuff lava,rhyolitic welded tuff lava).Lithofacies characteristics:According to division principle of volcanic facies(PJ Wang et al.,2003),four volcanic facies and nine subfacies are recognized.There are volcanic conduit facies(volcanic neck subfacies and hydrothermal berccias subfacies), effusive facies(upper effusive subfacies,middle effusive subfacies,lower effusive subfacies), explosive facies(pyroclastic flow deposit,Air-fall), volcanogenic sedimentary facies(epiclasts-bearing volcanogenic sediments,reworked volcanogenic sediments).2.Volcanic stages and cycles divide in the south of songliao basin gas fieldIn this paper ,we adpot cycles-subcycles-stages three grade dividing plan about volcanic in the south of songliao basin gas field,cycles,subcycles,stages are divided by different levels of geological surfaces.according to seism,logging and so on, discern different levels of geological sufaces.In combination with lithology,lithofacies analysis, Geofence and contrasting the logging with seism,divided volcanical into four cycles,six subcycles,twenty-four stages in the south of songliao basin gas field.drilling only revealed cycle IV,cycle III,cycle II ,three cycles volcanical.cycles IV volcanic lithofacies are mainly explosive facies(68%), effusive facies second(25%),cycles III are mainly effusive facies(88%),explosive facies second(10%). cycle II only had a few drilling results,as for YS101,CS1-2,so we don't make the discussion on its.3.volcanic edifice divided and type in the south of songliao basin gas fieldVolcanic edifice division in the south of songliao basin gas field take cycle as stage time frame of a different tectonic evolution,take subcycle as synchronizing the interface of adjacent volcanic edificie.hence,We divided the volcanic in the south of songliao basin gas field into seven volcanic edifice. VE-4 of cycle III and VE-7 of cycle IV are the largest volcanic edifice.type of volcanic edifice can be divided into single cone composite volcanic edifice(VE-2,VE-3),single cone lava volcanic edifice(VE-6),multi-cone composite volcanic edifice(VE-1),multi-cone lava volcanic edifice(VE-4),no-cone clastic volcanic edifice(VE-5,VE-7).4.Volcanic edifice intermal character in the south of songliao basin gas fieldAccording to lithology lithofacies by core,detritus,logging divided,combined with stage distribution characteristics which discorned by seismic profiles.We carry on an investigation into four volcanic edifices of lithology and subfacies characteristics of the spatial distribution which the drilling control VE-4, VE-5, VE-6, VE-7 and so on. For the three volcanic edifice (VE1,VE2,VE3) under the control of no drilling or drilling only a small number of institutions,we based on seismic facies rough division of their lithology and lithofacies. Favorable reservoir bed in the south of songliao basin gas field were upper effusive subfacies of effusive facies and pyroclastic flow deposit, In VE-4 upper effusive subfacies of effusive facies was the lagest of average thickness(33.21m),extends as far as the greatest distance 5km .In VE-7 pyroclastic flow deposit was the lagest of average thickness(36.91m), extends as far as the greatest distance 9km. 5.Reservoir character of volcanic edifice in the south of songliao basin gas fieldThe reservoir space in the south of songliao basin gas field divided into original pore (original hole,hole in almonds,matrix contraction joints,mineral bombing crack etc). Induced porosity(crystal-dissolved in the solution,matrix hole etc). Cracks(structural fractures,filling-remnants structural fractures).In VE-4 volcanic edifice reservoir space is main of original hole,hole in almonds,matrix hole.In VE-7 volcanic edifice reservoir space is main of detritus hole,crystal-dissolved in the solution,matrix hole.VE-4 is the best reservoir,VE-7 is second,VE-5,VE-6 are worse.The area of the reservoir will be categorized into four categories, first and second class to the advantage of the reservoir. First class reservoir distributed 3, 5, 6 and 7 four stages of VE-4 volcanic edifice, to 7 stage of the largest percentage,extend farthest,which is the main producing pay in the south of songliao basin gas field. 5,6 stages extend the range of secondary which are second producing pay ,second class reservoir mainly located in2, 3, 5 and 6 four stages of VE-4 volcanic edifice and 2stage of VE-7 volcanic edifice.