Study On Chemical Selective Plugging Agent In Tianwaitian Gas Field

Aiming at the development contradiction of severe water breakthrough in East China Sea Gas Field,a series of laboratory experiments are conducted.A preferred method for chemical selective plugging agent is estabilished and a selective plugging agent of gelled foam is developed under the gas reservoir conditions.In addition,the gelled foam stability,injection performance and plugging performance are evaluated.Plugging mechanism is analyzed and the field test is carried out.By screening gel system,foam system,gel foam system and polymer system,the gel foam system as the selective plugging agent is finalized.Based on the foam property for determining,the gelled foam is optimized by improved airflow method and the GSC method,and the appropriate ingredient of gelled foam is that the mass fraction of CAB-35 foaming agent 0.3%~0.4%,the LF polymers is 0.3%~0.4%,and the REL&MNE crosslinker is 0.3%~0.4%.The foaming volume of gel foam is 160 mL~165 m L,the half-life period is 887 s~964 s,and the foam comprehensive value increased largely to 141920 mL·s~159060 mL·s.It is found that the best injection mode of gel foam is gas-liquid mix injection,the best gas/liquid ratio is 1:1,the approviate gas injection rate is 0.5 m L/min by the core flow experiment.The displacement experiment shows that the strata with the same conditions,the amount of water plugged by gel foam system is greater than that of the seal gas,and the plugging agent for water plugging rate increases with the increase of formation permeability enhancement.When layer permeability is different,the plugging agent has good formation heterogeneity selectivity,plugging agent priority to block high seepage water flow pathways,and low permeability gas channel has not been closed.Thus,the gel foam system has good selective plugging performance.It is found that the gel foam has the strong ability of water plugging and weak ability of gas plugging by the visualization physical simulation device.Thus,it has good selective plugging performance.Based on the laboratory research achievement and combined with the Tianwitian gas field production characteristics,construction scheme is optimized,including water plugging way,water plugging agent,slug composition,dosage calculations,construction procedures and construction process design.