Fracturing Very High Permeability Gas Wells in Offshore Brazil: It Works!

Abstract

This paper presents the results of a fracpack campaign in a series of very high permeability gas wells in Espirito Santos Basin, off-shore Brazil. This first fracpack campaign in four wells was conducted from March 2007 to June 2008. Permeability ranges from high 50 mD to very high 200 mD. The main debate was internal: why does someone need to fracturing very high permeability gas wells? In fact, this question is associated to two issues: overcome formation damage and assure very reliable sand control. The answer is obvious: fracpack. Several injection tests and minifrac prior to the main treatment were performed in order to address mainly closure stress and fluid leakoff although perforation friction, near-wellbore tortuosity were minor concerns. The main drive was the amount of fluid required to effectively propagate a fracture in such very high permeability gas wells. Again, someone claimed the volumes would be enormous! However, it was observed that this volume was almost the same ordinary volume used in Campos Basin´s regular oil fracpacks. The results were outstanding. The production tests showed some of the greatest absolute open flows in Brazilian gas wells. All the wells are current in production and sustaining the very high productivity levels. Introduction The Peroá gas field, discovered in September, 1996 from 1-ESS-77 well, lies in 70 m water depth and is located around 52 km offshore near the mouth of Doce river - Fig. 1. The main Peroá reservoir is channelized Oligocene turbidites sandstones deposited in the base of escarpment toward diapirism salt channels. Petrophysics and log data point out good to very good porosity (17% to 24%) and gas permeability (50 mD to 200 mD), Sw from 15% to 36%. Original reservoir pressure is from 209 and 290 kgf/cm2, 2460 to 2700 m TVD.