In a shallow Australian oil field, TSO designs with 20/40 LWC increased fracture conductivity between 500 and 4000% compared to earlier low-concentration sand and HSP designs. Although the fractures were designed to be high conductivity but short, they provided a sufficiently large effective wellbore radius to reduce the matrix velocities and eliminate the severe production declines previously attributed to fines plugging.
The Mereenie field, located about 185 miles west of Alice Springs in the Northern Territory of Australia, consists of a large gas cap surrounded by a narrow oil rim. The oil rim has been the predominant target, with the majority of oil produced from the Pacoota P3-120/130 sandstone reservoir. At approximately 4,500 to 5,000 ft, the reservoir exhibits permeabilities of 5 to 100 md. Pressure-transient analysis and production characteristics of early wells indicated increasingly high levels of near-wellbore damage, discovered later to be associated with fines migration and an extensive illite clay network. In an attempt to overcome this impairment, seven hydraulic fracturing treatments were performed between 1983 and 1987; however, postfracture results were disappointing. Extensive well testing, laboratory work, and reservoir/fracture modeling identified major problem areas associated with both the reservoir and the fracture treatments. During 1991-92, seven additional treatments were performed to achieve a tip screenout (TSO) to form a short, highly conductive flow path to bypass the damage. These resulted in a significant increase in production, an upgrade in the field's recoverable reserves, and additional development drilling.
Author(s): Anthony Papinczak, SPE, SPE, Santos Ltd., and W.K. Miller II, NSI Technologies Inc.
Paper Number: SPE 25379