Abstract

Having explored many methods to improve efficiencies in conventional drilling processes, operators in the traditional North American land market are ever more attracted to innovative and cost effective means to drill wells. These innovative operators have turned to coiled tubing directional drilling (CTDD), with its promising inherent efficiencies in tripping and connection times, and with its smaller, logistically simpler footprint to optimize the drilling process even further. New downhole drilling technologies found in the conventional drilling arena are being applied to this operation to overcome the intrinsic limitations associated with the non-traditional slide-only drilling method associated with coiled tubing drilling. Together with innovative modifications to traditional CT rigs to address the fit-for-purpose needs of drilling, this novel approach to cost reduction is being applied in a cost-sensitive land market in the Rocky Mountain region of the US.

This paper provides an overview of the drilling application faced by the operator, of the specialized hybrid Coil Tubing drilling rig and of the novel application utilizing the modern, non-rotating rib-steering downhole drilling tools. The paper will benchmark the performance of the built-for-purpose operation compared to previous wells drilled with conventional rigs and directional motors, as well as other CTD systems. Additionally, a well to well performance of the drilling operation over a multi-well period will be evaluated, together with a discussion on lessons learned and a presentation of potential future improvements. The application of automated drilling systems with coiled tubing drilling heralds in a new age in developmental drilling in low spread cost markets.

Overview

Traditional drilling in North America is increasingly focused on developing natural gas reservoirs, whether they are conventional sandstone formations or unconventional shale plays. One of the most popular basins in recent years for unconventional shale and tight sands gas has been the Piceance Basin. The Piceance Basin is a geologic structural depression trending northwest - southeast in northwestern Colorado, in the United States (see figure 1). The basin is more than 100 miles (161 km) long and has an average width of over 60 miles (96.5 km), encompassing an area of approximately 7,110 square miles (18,415 sq. km). It includes geologic formations from Cambrian to Holocene in age, but the thickest section is comprised of rocks from the Cretaceous Period. The basin contains reserves of coal, natural gas, and oil shale. The basin has come to increasing public attention in recent years because of widespread drilling to extract natural gas. The primary target of gas development has been the Williams Fork Formation of the Mesaverde Group, or Cretaceous age. The Williams Fork is a several-thousand-foot thick section of shale, sandstone and coal deposited in a coastal plain environment. The formation has long been known to contain natural gas (see figure 2). However, the sandstone reservoirs have low permeability and limited areal extent, which made gas wells uneconomic in the past. Advances in hydraulic fracturing technology within the past decade, along with higher natural gas prices, have made gas wells broadly economic in the area. (Wikipedia 2007), (Colorado Geologic Survey 2007)

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