Ineffectiveness of Acid Fracturing for Stimulating a Tight Fractured Reservoir Rock, A Case Study

Abstract

Abstract Stimulating source rocks using hydraulic fracturing in unconventional source rocks is a common process. But such practice has not been followed when dealing with tight reservoir rocks. Tight carbonate reservoir rocks have in general been subjected to multistage acid fracturing. This paper describes the analysis of actual performance data to acid fracturing in a tight carbonate formation and the ineffectiveness of the process as measured by the performance responses of the producing wells. The case study relates to a tight formation that is considered a reservoir rather than a source rock. The formation permeability is in the range of 0.1-5 millidarcies. Development has been through numerous horizontal wells with limited multistage acid stimulation. Analysis of performance data for more than 30 wells Indicates no fracture flow and very limited stimulated production. Different diagnostic methods were used to determine the nature of the flow regime and to examine the true benefit of multistage acid fracturing. Most of the wells studied show primarily a radial flow condition after limited acid fracturing. The main observation is that the process of acid fracturing at best has resulted in local near wellbore stimulation on all these wells, and there are no significant indications of fracture-dominated flow. Many of the wells also show early signs of the boundary effect that explains the ineffectiveness of the recovery process.