SongkeWellNo.2,oneofthemainpartofthescientificdrillingprojectinSongliaoBasin,whichwasdrilled7018mandacquiredthepartofcorescontinuouslyfromtheLowCretaceoustotheCarboniferousandthePermianfromthe2843mdeep,canbeconsideredasthedeepestcontinentaldrillingprojectinAsia.Aimingatthefeaturesoflongerwellsections,largerdiametersandmultiplespud-insforcoringofSongkeWellNo.2,thisprojectbrokethroughthe"coringinsmalldiameterandreaminginlargediameter"spud-indrilling-completionprocedureswhicharealwaysusedinlarge-diameter-wellcoringforcontinentalscientificdrillingprojectsindomesticandoverseasandthedrillingmethodofshort-singlecylinderroundtripfootage.Atthesametime,"coringinthesamediameterandcompletingdrillingatonesinglediameter"wasachievedatallφ311mmandφ216mmcoringsectionsofmorethanonethousandmeterslong,high-efficientoperationwith"drillinglongfootagewithdrilltoolscombinedinmulticylinders"wasachievedatdeepcoringsection.Fourworlddrillingrecordswerecreatedwhichincludemorethanathousandmeterscontinuouscoringatφ311mm,andthefootageperroundtripfootageatφ311mm,φ216mmandφ152mmisallmorethan30m,allofthesebreakthroughsreducedatleast300daysforthisproject;moreover,consideringthecharacteristicsofformationsthatthegeothermalgradientishighinthedrilledsectionsandtheinside-welltemperatureisover240℃afterdrillingcompletion,aformate-polymerwater-basedmudsystemwasdevelopedbycompoundingattapulgiteandsodiumbentoniteandbyaddingindependentlydevelopedhigh-temperaturestabilizer,whichcanprovidecriticaltechnicalsupportforsuccessfulwellcompletionat7018minthesuper-high-temperatureenvironmentItisthefirsttimethatthewater-basedmudisoperatedattheworkingtemperaturehigherthan240℃inChina;Besides,consideringthehigh-qualityrequirementoncoresimposedbytheproject,themethod"mechanicalcor
