简介：Themeasurementofundergroundmediumvariationusingarepeatedartificialsourcehasgraduallybecomeanimportantgoaltopursue.Inrecentyears,wehavedevelopedandimprovedatechnologysystemwithlargecapacityairgunsexcitedinlandreservoirsbytransplantingmarineseismicexplorationtechnology.Theexcitationeffecthasacloserelationshiptoairguncapacity,waterenvironment,andexcitationconditions.Inviewthatlargecapacityairgunmustbeexcitedwithoutawaterenvironment,weexpandthesystemtouseindownhole.BasedontheBHS-2200LLdownholeairgunwithacapacityof250in3,thispapercarriesoutacomparativeanalysisonthecharacteristicsofanairgunsourceexcitedin0.2m-and5.0m-diameterwells,andtheresultsshowthat:(1)Thedominantfrequencyoftheairgunsignalexcitedina5.0mwellismainlyfrom10Hzto40Hz,lowerthanthatina0.2mwell,andthelargerbodyofwaterisgoodforbubbleoscillation.(2)Intermsofexcitingenergy,thesignalexcitedina5.0mwellhasstrongerenergythanina0.2mwell,withadifferenceof1orderinmagnitude,andthesignalcanbedetectedupto9kmexcitedina5.0mwellwithasingleshot.(3)Theairgunsignalhasgoodrepeatabilityinbothexcitationwells.Thedownholeairgunexcitationtechnologysystemhaspotentialapplicationindynamicmonitoringnearafaultzonewithasmallscalerange,explorationofoilandmineralresources,andmodernurbangeophysicalenvironment.

简介：Tomaintaingashydratestability,low-temperaturedrillingfluidsandhighdrillingspeedsshouldbeusedwhiledrillingingashydrate-bearingsediments.Theeffectofthedrillingfluidondownholerocksurfacesatlowtemperaturesisveryimportanttoincreasethedrillingrate.Thispaperanalyzedtheactionmechanismofthedrillingfluidondownholerocksurfacesandestablishedacorrespondingevaluationmethod.Thesofteningeffectofsixsimulateddrillingfluidswith0.1wt.%offourcommonsurfactantsandtwocommonorganicsaltsonthedownholerocksurfacestrengthwasevaluatedexperimentallyusingtheestablishedmethodatlowtemperature.Theexperimentalresultsshowedthatthesurfactantsandorganicsaltsusedinthedrillingfluidsaidedinthereductionofthestrengthofthedownholerocksurface,andtheestablishedevaluationmethodwasabletoquantitativelyrevealthedifferenceinthesofteningeffectofthedifferentdrillingfluidsthroughcomparisonwithwater.Inparticular,themostcommonsurfactantthatisusedindrillingfluids,sodiumdodecylsulfate(SDS),hadaverygoodsofteningeffectwhiledrillingunderlow-temperatureconditions,whichcanbewidelyappliedduringdrillinginlow-temperatureformations,suchasnaturalgashydrate-bearingsediments,thedeepseafloorandpermafrost.