Modifiers matching hydrocarbon:

• linear,
• organic,
• aromatic,
• light,
• natural,
• minor,
• bound,
• molecular,
• dissolved,
• saturated,
• volatile,
• cyclic,
• complicated,
• flammable,
• liquid,
• airborne,
• conventional,
• clean,
• intermediate,
• unsaturated,
• toxic,
• simple,
• heavy,
• aliphatic,
• useful,
• dark,
• commercial,
• dangerous,
• carcinogenic,
• nitrogenous,
• heavier,
• desirable,
• vaporizable,
• fluid,
• typical,
• available,
• cheap,
• planar,
• familiar,
• combustible,
• inert,
• individual,
• neutral,
• viscous,
• floating,
• liquefied,
• residual,
• hard,
• supercritical,
• underground,
• liquifiable,
• conjugated,
• common,
• lighter,
• refined,
• complex,
• valuable,
• small,
• frozen,
• polygonal,
• synthetic,
• single,
• stable,
• basic,
• dilute,
• lower,
• hazardous,
• industrial,
• model,
• solid,
• greasy,
• particular,
• essential,
• important,
• acyclic,
• acetylenic,
• ordinary,
• regulated,
• main,
• reactive,
• pure,
• alternative,
• hydrophobic,
• soluble,
• base,
• nonpolar,
• gaseous,

Simple categories matching underground:

• structure,
• hydrocarbon,
• space,
• area,
• pipeline,
• housing,
• vegetable,
• facility,
• music,
• building,
• material,
• cable,
• place,
• cavity,
• installation,
• world,
• bunker,
• works,
• room,
• liquid,
• construction,
• topic,
• cave,
• duct,
• formation,
• tank,
• obstacle,
• property,
• utility,
• container,
• line,
• object,
• location,
• harvester,
• item,
• life,
• activity,
• service,
• reservoir,
• tunnel,
• conductor,
• aquifer,
• system,
• pest,
• relic,
• excavation,
• plant,
• stem,
• storage,
• void,
• fluid,
• opening,
• equipment,
• fixture,
• enclosure,
• obstruction,
• passage,
• development,
• supply,
• part,
• improvement,
• fortification,
• resource,
• wealth,
• treasure,
• cistern,
• cavern,
• pipe,
• work,
• feature,
• organ,
• shelter,
• band,
• group,
• expanse,
• conduit,