Reservoir stimulation techniques to minimize skin factor of Longwangmiao Fm gas reservoirs in the Sichuan Basin

The Lower Cambrian Longwangmiao Fm carbonatite gas reservoirs in the Leshan-Longnüsi Paleouplift in the Sichuan Basin feature strong heterogeneity, well-developed fractures and caverns, and a high content of H2S, so these reservoirs are prone to reservoir damages caused by the invasion of drilling fluid or the improper well completion, so to minimize the reservoir skin factor is key to achieving high yield of oil and gas in this study area. Therefore, based on the geological characteristics of the Longwangmiao reservoirs, the binomial productivity equation was applied to demonstrate the possibility and scientificity of minimizing the skin factor. According to the current status of reservoir stimulation, the overall skin factors of reservoir damage caused by drilling fluid invasion, improper drilling and completion modes etc were analyzed, which shows there is still potential for skin factor reduction. Analysis of reservoir damage factors indicates that the main skin factor of Longwangmiao Fm reservoirs consists of that caused by drilling fluid and by improper completion modes. Along with the minimization of skin factor caused by drilling and improper completion, a fracture-network acidizing process to achieve “non-radial & network-fracture” plug-removal by making good use of natural fractures was proposed according to the characteristics of Longwangmiao Fm carbonatite reservoirs.