Innovative Completion Technology Enhances Production Assurance in Alaskan North Slope Viscous-Oil Developments

Abstract

In the challenging North Slope operating environment, use of innovative production equipment has provided solutions to zonal isolation and packer integrity problems in viscous oil reservoirs. Operators have employed new tools and technology utilizing expandable rubber materials to manage annular fluid flow, control solids/shale production, and achieve zonal isolation in wells where high costs, shallow depths, and long step-outs create unique completion challenges. The new technology is allowing once bypassed zones to be added to existing developments, and making future developments more economically viable. The new design approach involves installing swelling rubber packer (SRP) technology as part of the completion. This technology is based on specially designed swelling properties of rubber in crude or mineral oil based mud (MOBM) to expand and seal the annulus. The paper describes one operator's use of as many as 17 devices in a tri-lateral horizontal undulating well to manage annular flow and minimize shale/solids production. The successful application of this technology has allowed shale interbedding to be effectively isolated behind blank pipe, thus allowing an additional zone to be added to the existing development. To date the technology has been applied to eleven wells, improving production assurance. Another major operator on the North Slope has used the technology to isolate potentially conductive fault crossings along the lateral and inadvertent zonal crossings while kicking off from the parent bore. Multiple packers have been run in single laterals to achieve the desired isolation without noticeable effects on liner running drag. Recent density caliper data shows significantly more washout than previously envisioned, increasing the desire to manage annular flow. Development and application of this SRP technology is detailed in the paper, including documentation of improved efficiencies as a result of its use. The paper will also discuss field operations, installation, and unique considerations associated with design and installation in viscous oil environments. Introduction On the North Slope of Alaska, it has been estimated that between 20–25 billion barrels OOIP of viscous oil are contained within shallow, regionally extensive sands. [1,2,3,4,5,6](Figure 1) To date, development of these viscous oil sands has been deferred in favor ofthe warmer, less viscous oil that lies below. The presence of the highly viscous oil in the shallow sands results from oil biodegradation and low reservoir temperatures due to the extreme northern latitude, the presence of 1,800 feet of permafrost, and its relatively shallow burial depth.

Viscosity of Alaska Heavy Oil Saturated with Methane

“…Estimates of more than 80% of the total world oil reserves are heavy oil, extra-heavy oil, and bitumen (5.5 trillion barrels vs 1.02 trillion barrels of conventional crude oil). − One heavy oil reserve is located on the North Slope of Alaska (United States) . Although the Alaskan heavy oil reserves are enormous (approximately 20–25 billion barrels of original oil in place), difficult technical and economic aspects are involved in producing the oil. Challenges include high viscosity and asphlatene content from biodegradation, low reservoir temperatures due to the high northern latitude, the presence of 1800 ft (550 m) of permafrost, and relatively shallow burial depth.…”

Application of Innovative Reaming and Completion Technology in Williston Basin Wells

“…(3) Since hole gauge and quality can affect packer sealing performance, the focus with use of the PDC reamers is to drill a smooth wellbore that is as close to 6-inch gauge as possible. Some eccentric or bi-center tools can drill an overgauge hole (for example, 6 1/8-inch or 6 ¼-inch in a 6-inch hole) which actually reduces the efficiencies and sealing effectiveness of the swellable packers.…”