Arshad Waheed

A Novel Approach to Acidizing of Carbonates: Case History From the Gulf of Suez in Egypt

This case history develops through the drilling of a relatively underexplored and less promising limestone formation in the Gulf of Suez area of Egypt. The target formation, known as Thebes of Eocene Age, was faulted and the two separated pay sections presented differentrock compositional scenarios. Even though the geological description broadly classified these zones as carbonates, the stimulation treatments designed for the two zones were totally different. The process that was undertaken in determining the best solution was based on the introduction of some novel analytical techniques and a comprehensive approach to acidizing-treatment design. This paper details some of the new approaches that were used, including a composite log developed for carbonate-stimulation design. The emphasis on reservoir characterization in terms of its petrophysical properties and production capability is paramount in carbonates because of the extreme reservoir heterogeneity and a general noncorrelation between rock porosity and permeability. Furthermore, a new matrix acidizing simulator was run with input data from the composite log for modeling fluid distribution and skin evolution from the treatment. On the basis of these simulation runs, a couple of pre-emptive measures were taken to improve the treatment(laid distribution profile. Bottomhole pressure gauges in conjunction with real-time monitoring of skin evolution during the treatment were analyzed for determining the effectiveness and applicability of foamed treatments, in-situ crosslinked acid systems, and maximum pressure differential and injection rate (MAPDIR) techniques. The post-stimulation production results and pressure-buildup surveys confirmed the success and effectiveness ofthe stimulation treatments.