Many operators in Kazakhstan are producing from carbonate reservoirs with fairly low permeability and porosity with the presence of dominant natural fractures. The completion and perforation of the reservoir are critical phases during which special attention must be placed on the well cleanup to obtain the maximum hydrocarbon productivity. Wells in the tight carbonate formation of certain fields in western Kazakhstan have historically been perforated in overbalance conditions or in static underbalance conditions that require killing the well immediately after the perforation for installing the permanent completion. After the permanent completion has been put in place, an acid wash must be performed to remove all the damage induced by the killing operation and the perforating debris. Both ways of perforating the wells expose the reservoir to potentially damaging fluids during and after the perforation. The exposure time of these fluids can be prolonged if adverse meteorological conditions are encountered. The damaging fluids can significantly impair the productivity by blocking the newly perforated tunnel, as well as by filtering through the natural fractures, which in turn makes it very difficult to remove even after as acid wash. As a result, the wells do not produce to their full potential.

A new perforating approach utilizing a dynamic underbalanced technique, in conjunction with a solids-free, viscoelastic-based, fluid loss pill, was introduced in several new wells in western Kazakhstan for a major operator. The fluid loss pill was designed to be solids-free and to be easily broken, leaving no residue downhole. There were four main requirements for the fluid pill:

The carbonate reservoir where this new approach was utilized has permeabilities varying from 6 to 38 mD, while the present reservoir pressure is approximately 4,200 psi at the reference depth of 3,550 m. The new perforation approach allowed obtaining a cleaner perforation tunnel, increasing the average production compared with wells draining from the same reservoir that were completed with the traditional technique. The average production obtained with the new approach is approximately double that of the conventional technique. This has been verified on a campaign carried out on 11 wells, all located in the same area of the field, four of which were completed with the new perforation approach. Several other treatments have been performed and have indicated similar trends in production.