A Journey Unlocking Additional Unconventional Resources: Extensive Integration of Subsurface & Completion. A Case Study from UAE Unconventional Oil Play

Abstract

Unconventional play is associated with several challenges due to the complex nature of the reservoir. Identifying potential zones to target wells, stimulating, and planning field development to recover the hydrocarbon remains bleak without proper evaluation. This paper illustrates successful implementation of reservoir characterization, stimulation, and field development of the Shilaif formation Onshore UAE. The Shilaif formation is argillaceous limestone, fine-grained packstones and shaly lime mudstone-wackestones. This complex lithology was deposited under intra-shelf basinal conditions during the Cretaceous period. Previous studies spe-211005-ms published elaborated on data integration approach adopted to characterize the Shilaif member, enabling identification of the potential zones for horizontal well placements and successful development of this organic-rich rock. Based on this study, extensive evaluation of geomechanical properties of the reservoir was done to guide stimulation. The hydrocarbon resource quantified was confirmed producible and pad drilling planned to fully extract the hydrocarbons. Geomechanical modelling was done to guide hydraulic fracturing using elastic properties, unconfined compressive strength and tensile strength derived from acoustic data acquired. Overburden stress, stress profiles and pore pressure from the mechanical earth model built resulted in efficient fracturing of the reservoir to release the hydrocarbon. Successful stimulation increased permeability profile post-frac as evident from the production data. Stress profiles and orientation determination from this study also guided subsequent well planning as pad drilling was initiated with horizontal wells targeting two different benches within Shiliaf formation first time. This study well is a success as part of wells drilled with similar extensive integration of elemental spectroscopy to reduce the uncertainty in total organic carbon (TOC), nuclear magnetic resonance (NMR) to provide lithology independent porosity and distinguish producible and non-producible fluids, acoustic log for stress determination and mechanical earth modeling which guided reservoir stimulation. A pre-frac injection test carried out revealed reservoir pressure and permeability in the different frac-zones and helped stage the hydraulic fracturing exercise. The mechanical properties estimation of reservoir rock with inputs from acoustic log, guided the staging of hydraulic fracturing and improving zone selections and optimizing hydraulic fracturing process. This has proved efficient in successful development of the organic rich rocks of the Shilaif formation.