This　study　presents　surfactant　injection　as　a　replacement　technology　for　mechanical　pigging　to　reduce　liquid　accumulation　for　wet　gas　transmission.　The　hilly　terrain　gas/liquid　flow　development　characteris-tics　under　surfactant　injection　were　explored　in　pipelines,　and　a　comprehensive　experiment　was　per-formed　through　flow　observation　and　the　measurement　and　analysis　of　the　flow　characteristic　parameters.　The　250　ppm　sodium　dodecyl　sulfate　(SDS)　surfactant　was　employed　according　to　the　vari-ation　characteristics　of　the　flow　pattern　and　pressure　drop　at　different　concentrations.　Flow　observations　and　liquid　holdup　characteristics　indicate　that　owing　to　the　formation　of　aqueous　foam,　the　gas/liquid　interface　and　phase　characteristics　change　significantly,　and　the　liquid　holdup　decreases　by　several　or　even　more　than　ten　times　and　maintains　a　low　value　(0.004-0.070),　except　for　the　initial　gas-liquid　flow　at　low　gas　flow　and　high　liquid　flow　rates.　The　aqueous　foam　effectively　suppresses　the　slug　and　pseudo　slug　initiation,　the　gas/liquid　convection　of　the　slug　body,　and　the　large　wave　rolling　of　the　pseudo-slug　body,　which　induces　the　dissipation　of　intermittent　flow.　The　pressure　drop　under　the　influence　of　aque-ous　foam　decreases　drastically　(60%　ti　85%)　at　certain　gas　and　liquid　velocities　and　fluctuates　smoothly　near　zero　over　a　wide　experimental　range.　The　surfactant　suppression　on　partially　blocked　pseudo-slug　body　induces　a　significant　decrease　of　pseudo-slug　frequency　from　0.17　ti　0.42　Hz　to　0　ti　0.06　Hz　and　transitional　velocity　from　1.21　ti　1.90　m/s　to　0　ti　1.11　m/s.　This　research　is　highly　significant　for　surfactant　injection　schemes　and　efficient　and　sustainable　production.(c)　2023　Elsevier　Ltd.　All　rights　reserved.