Blockage mechanisms and de-blockage technologies for the Lower Paleozoic carbonate gas reservoirs in the Ordos BasinOA

The Lower Paleozoic carbonate gas reservoirs in the Ordos Basin are widely distributed and possess significant resource potential.However,these reservoirs commonly exhibit ultra-tight pore throat systems,strong heterogeneity,and pronounced waterwet characteristics.During the long-term production,wellbores and near-wellbore zones are prone to blockage and liquid accumulation,manifesting as production decline and frequent shutdowns,which severely constrain later development efficiency.Therefore,the mechanism identification for blockage and optimization of de-blockage processes are therefore critical steps for maintaining deliverability in tight carbonate gas wells.Based on field diagnoses in blocks such as Jingbian and Surig,this study systematically summarizes the composition characteristics of blockage materials and their coupled evolution mechanisms through integrated core and cuttings analysis,physical property and wettability tests.Existing research generally agrees that blockage often exhibits composite characteristics,with inorganic scaling as the dominant factor,while organic deposition plays a secondary role.Water blocking frequently occurs in tight strongly water-wet pore-throat systems and often enhances and stabilizes blockage.Focusing on the composite blockage remediation,this article reviews the chemical de-blockage technologies such as staged slow-rate acid systems,acid-base composite systems,and foam-assisted rehydration,combined with physical de-blockage methods like coiled tubing jetting.Novel techniques such as nanowettability regulation and CO_(2) foam rehydration demonstrate good adaptability in deep water blocking and micropore coalescence sections.Finally,the future research directions for de-blockage technology are proposed to enhance the engineering guidance value for mature gas field remediation.