Enhancing Increased Production in an Open Hole Well by the Acid Stimulation Design Optimization using Self-Aligning-Jetting-Tool in Mexico Offshore

Abstract

An operator in Mexico was seeking a solution for improving methods for acid stimulation treatment in open-hole wells. Previous bullheading acid treatment in the same field was less efficient compared with selective treatment according to production conditions. In the shallow waters (offshore, Mexico), the acid stimulations are normally performed with bullheading technique; however, there are some cases where it is complicated to stimulate the production zone uniformly, especially in large openhole sections that presents fractures. Selective acid treatment technique is an alternative solution that represents an opportunity for the optimization of stimulations in Mexico and globally. The selected well has a 234 m open-hole section in a naturally fractured carbonate formation. Breaking usual paradigms, an unconventional treatment based on hydro-mechanical method for selective stimulation along the open hole was applied and completed with successful results. The operation was completed using coiled tubing (CT) deploying the Self-Aligning Jetting (SAJ) tool to stimulate 15 specific zones along the open hole section, each one selected for having the best petrophysical parameters. A 65% decrease in the acid treatment volume was obtained, which translates into savings in well flow back time, thus less Nitrogen to kick off the well, and removal time to the floating Storage/Production vessel (FSPV), in conclusion, oil production was incorporated more quickly after the well stimulation in comparison to the bullheading treatment. Comparing the two last open-hole stimulations in the same field, the productivity index obtained from conventional stimulation (bullheading) was in the order of 82 bpd/(kg/cm2), while selective stimulation was in the order of 160 bpd/(kg/cm), which is equivalent to an increase 95%. This paper presents the innovative technique of the stimulation with mechanical diversion using SAJ as the best option for injecting high-pressure fluids into specific targets through the open hole, and the advantages of the zones with the greatest oil production potential being stimulated, preventing the treatment from focusing only on a fractured zone or on areas with water or gas production potential.