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The natural gas industry in Indonesia plays a crucial role in meeting the country's increasing energy demand. However, mature gas fields face challenges such as liquid loading, which hinders production. One way to improve gas well production when facing liquid loading issues is by injecting surfactants through a capillary string to lower the density and surface tension of the produced fluids. This paper proposes a well candidate selection method for capillary string surfactant injection (CSSI) to enhance gas production in the "N" field located in East Kalimantan. The methodology involves several steps, including production history analysis, critical velocity and rate calculation, ratio of success analysis, bottom hole pressure survey, nodal analysis, and gain prediction. The proposed method was applied to 43 gas wells in the field, and potential CSSI candidates were identified. The results show that 29 wells exhibited indications of liquid loading, while 5 wells were identified as potential candidates for successful CSSI implementation. The findings emphasize the importance of historical data and establish a specific cutoff to assess the feasibility of CSSI. This study provides insights into improving gas production in mature gas wells using CSSI and contributes to the optimization of Indonesia's natural gas industry.