High non-Darcy skins were observed on wells in the 'Unayzah reservoir. Reduced pads and aggressive fracpacks with 16/30 CarboProp improved conductivity, providing 36 mmcfd against 4000 psi surface pressure, with good sand control.
This paper presents a methodology for an integrated reservoir study to identify different facies in the reservoir, select perforations interval and type of hydraulic fracture, understand pre- and post-fracture reservoir performance, and optimize fracturing treatments and reservoir development. The target formation is mainly from a Permian eolian ‘Unayzah-A gas bearing sandstone reservoir which is highly heterogeneous and poorly consolidated that requires a systematic and integrated assessment prior to its development.
Integrated reservoir studies utilizing engineering and petrophysical data showed the complexity and heterogeneity of the ‘Unayzah-A reservoir. The reservoir constitutes of clay mineral (illite) and hence it is highly susceptible to formation damage associated with drilling fluids. In order to remove damage, control sand production, and improve productivity, all gas wells are routinely fracture stimulated employing screen or screenless completion.
This paper provides a summary of the reservoir and fracture treatments focusing particularly on the fracture design, execution, fracture modeling, and post-treatment production analysis from the recently completed wells. A comprehensive data set of logs, pre- and post-fracture pressure buildup tests (PBU's), drill stem tests (barefoot and cased hole DST), and detailed fracture modeling are presented to demonstrate the fracture performance in this complex eolian dune reservoir environment.
Estimation and interpretation of reservoir pressures, fracture geometry, and transient tests from these wells indicate possible water-zones compartmentalization, reservoir continuity, and depletion as primary drive mechanisms.
This paper shows that understanding reservoir quality and characteristics, using focused reservoir studies, leads to successful completion results and optimum development. The study identifies the dominant flow unit, eliminates unnecessary perforation intervals, determines stimulation treatment type and size and optimizes cost for overall field development.
Author(s): Saudi Aramco, A.S. Raba’a and Z. Rahim
Paper Number: SPE 93479