Cold Lake Borehole Mining

Abstract

Abstract As part of an ongoing research and development effort, Imperial Oil has embarked on a program to develop new low cost in situ recovery technologies for oil sands as an alternative to cyclic steam stimulation. Oil such technology is borehole mining, which utilizes high pressure water jets to create a cavern in the formation and force the liberated bitumen to the surface through the annular space between the casing and the jetting string. This paper reviews the borehole mining concept and discusses the results of two field pilots conducted in 1990-and 1991 at Imperial Oil Resources' Cold Lake lease. It focusses on the behaviour of the oil sands matrix as the cavern is created and the performance of the hydraulic pumping system. It concludes that valuable knowledge has been gained with respect to design parameters for borehole mining, but that the process is unsuitable for producing the Cold Lake lease owing to poor mining efficiency. and instability of the shale roof of the cavern. Introduction The Cold Lake oil sands deposit in north-eastern Alberta contains over 40 billion cubic metres of bitumen (Figure 1). Imperial Oil currently operates several pilot and commercial oil sands production projects in this area. Bitumen is produced from a reservoir approximately 40 m in thickness at a depth of about 450 m. Total production from almost 1,800 experimental and commercial wells exceeds 14,000 m3 per day. Owing to the low energy state and high viscosity of bitumen at reservoir conditions, high pressure thermal methods are used at Cold Lake. The majority of Imperial's bitumen production is obtained using cyclic steam stimulation (CCS). However, to achieve higher recovery levels and profitability, Imperial Oil has embarked on an R&D program to develop lower cost alternatives to cyclic steam stimulation. While conducting a well repair program in early 1989, Imperial identified an alternate bitumen recovery process. A surface discharge of bitumen was discovered near an abandoned well at Cold Lake(1). The bitumen had been displaced up the abandoned hole by adjacent steaming operations. To plug the abandoned well, a relief well was drilled into the Clearwater Formation so that its bottom was within one metre of the existing well. A water jetting tool was lowered into the relief well to cut out a thin window in the casing and create a cavity to place cement. While jetting, large volumes of oil and sand accumulated in the return tank. The sand, bitumen and water were observed to separate as they flowed into the tank. Consequently, Imperial initiated a research program to explore FIGURE 1: Location of the four major cretaceous oil sands deposits in Alberta. Available In Full Paper. The potential of hydraulically mining oil sands as a more economical alternative to steam-based processes (Figure 2). Initially, physical model tests were conducted in the laboratory to visualize the mining process, followed by two small scale field pilots, conducted in 1990 and 1991. The purpose of this paper is to share the experience gained in executing those two field pilots.