Abstract
Petroleum Development Oman (PDO) is currently exploring and developming a number of on-shore unconventional deep gas fields for which hydraulic fracturing is playing a key role in proving the commerciality of such reserves. However, stimulating unconventional deep sandstone gas reservoirs with the conventional slick water or crosslinked polymer systems is associated with many challenges. While crosslinked systems frequently cause post-stimulation damage in tight formations (due to the high gel residues in the pores), slick water treatments are, in turn, associated with high surface treating pressures and low-carrying capacity for the high-strength proppants required to withstand the extreme stresses in the deep unconventional formations. In addition, the tightness and high capillary pressures characterizing unconventional reservoirs commonly lead to undesired post-fracturing results, including slow cleanout and poor productivity. The objective of this paper is to describe successful field trials using new fracturing strategy, which was deployed in deep unconventional sandstone gas wells in the Sultanate of Oman. Linear-gel fracturing systems combined with high-strength ceramic proppant were utilized to unlock the gas from deep, highly stressed formations with porosity of 3-7% and permeability of 0.1-0.001 mD. The paper describes the rationals behind the change of the existing frac strategy and the outcome of the new one.
