A Unique Stimulation Approach to Enhance Production Efficiency of Horizontal Wells in Heterogeneous Carbonate Reservoirs
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.