Matrix stimulation treatments are applied to improve well productivity and enhance hydrocarbon recovery from the formation. However, in some wells optimum results cannot be achieved using conventional stimulation techniques since it is difficult to ensure efficient placement of the stimulation fluid across the entire stimulation interval, which is a prerequisite for a successful result. The situation becomes even more challenging in heterogeneous reservoirs with large permeability variations or possible presence of natural fractures in a complex geological environment.
Other complications may occur when conventional stimulation treatments keep creating undesired wormholes over the same spot in the borehole. These complications can make future treatments even more challenging, and sometimes enlarge the hole to an extent that makes further intervention difficult.
A novel approach has been successfully executed in a supergiant onshore field in Abu Dhabi, after an extensive study of different types of heterogeneous reservoirs. The objective was to develop an economically justified stimulation strategy using different treatment fluids and a unique placement approach for proper reservoir drainage. In this field, the production comes from various carbonate reservoirs, where the different layers require different methodologies to support the reservoir pressure. This approach consists of chemical diversion, dual injection for acid placement, and optimized jetting .
The paper presents data from a group of wells that were also restimulated as part of the field pilot. The methodology of candidate selection, treatment design and execution, and production logging before and after stimulation is described.
Production improvements have been highlighted for the treated wells. Chemical diversion enhanced the acid stimulation and previously underexposed subunits began contributing to flow. The pilot wells have validated the engineered methodology adopted for the scope of work.