Abstract
Economical hydrocarbons production from unconventional resources is intrinsically related to stimulation effectiveness and capacity of the created hydraulic fractures to drain the target resource in an efficient manner, this is certainly without overlooking the significance of other resource geological, petrophysical, geomechanical, and other rock quality aspects. Considering the unique characteristics of each unconventional resource and the varying rock qualities and geological features, each resource should be considered separately when attempting to define the most optimum stimulation design approach that yields the best well productivity results and best EUR's, this means that a stimulation design approach that was successful in a specific play might not yield the same success if applied in a different play. In general, the overall stimulation effectiveness in unconventional horizontal multi-stage completions requires a good understanding of the geological, petrophysical, and geomechanical characteristics of the asset in hand as well as an understanding of the natural fracture's distribution, rock heterogeneity, and other aspects, eventually integrating those understandings to design an effective stimulation approach that similarly considers cost and operational efficiency parameters. Efficiency of the stimulation treatments requires an optimal placement of perforation clusters, with reasonable spacing that allows for creating the target fracture geometry/complex fracture network while considering fracture interferences, and other geometry controlling aspects. One of the most important considerations when designing a fracture treatment is fracture conductivity which is the ability of fractures to convey produced fluids into the wellbore (fracture permeability multiplied by fracture width (md-ft). In general, fracture conductivity along the created fracture network as well as in the near-wellbore area defines how effective is the fracture in delivering hydrocarbons into the wellbore, the target fracture conductivity values however vary with respect to formation rock permeability ranges and nature of produced fluids.
This paper presents a comparative study of fracturing design and operational execution approaches for two exploration wells drilled in the oil-bearing Shilaif unconventional formation in the UAE, both wells are drilled targeting the same rock sequence and both possess very similar rock qualities. The paper covers aspects studied to analyze the suboptimal performance of the first well and the adjustments made to the fracturing design and fracture conductivity improvement of the second well, and how it entirely changed the productivity profiles and significantly improved the EUR for the target resource, which in turn had made this asset much more attractive for future full development plans.
