One of the most common strategies to effectively produce from tight gas carbonate reservoir is by completing the wells with acid fracturing technique, where the etched fracture half length alters the flow pattern from formation in to the wellbore with its high conductive flow path.
The treatment success, apart from operational aspects, is also measured by addressing the issue of fractured geometry created, zonal coverage achieved and the actual well potential based on its petro-physical and rock mechanical properties and relate this to well’s production behavior. In the high pressure/high temperature tight rock formation with minimum number of natural fractures, it is very common to observe immediate production gain following an acid fracturing treatment.
The well in discussion was acid fractured 3 years earlier with almost 90% of cumulative production occurred during the last one year. It was observed that it is declining faster than expected. Review of the well performance led to two main possible causes, i.e. reservoir pressure decline and reduction in fracture length/conductivity. Acid re-fracturing strategy was considered and decided to restore the well’s productivity by further extending the fracture half length by enhancing the fracture conductivity.
The results showed that Productivity index (PI) increased by 2.5 folds during the post treatment production test. However, after 3 months of continuous production, the PI declined down to 1.2 folds despite the pressure build up performed indicated fracture conductive behavior. This paper discussed key lessons learned to further improve the outcome by integrating production analysis, reservoir quality evaluation as well as stabilized production expectation with stimulation approach during candidate evaluation process.