Abstract

Texaco Canada Petroleum Inc., (TCPI) has successfully conducted a 10-horizontal well primary production pilot project at Frog Lake, Alberta, Canada, where the heavy oil gravity ranges from 10 to 14 API, and the oil viscosity ranges from 20,000 to 50,000 cp. These 10 wells were completed in the Lower Waseca formation (one of five prospective formations in the field) and produced using the primary production technique of "cold production", which is the coproduction of sand and oil from the reservoir at ambient temperatures. These wells were very successful with most wells displaying productive capabilities in excess of 100 barrels of oil per day. Based on the success of the 10-well pilot, a long term staged development plan was established that will allow resolution of some technical challenges also identified by the 10-well project.

This paper summarizes "cold production" technology, the history of the Frog Lake field, completion and production techniques, and some of the operational and technical challenges encountered. A field wide development strategy and enhanced oil recovery potential are also discussed.

Cold Production Technology

A number of heavy oil and oil sand reservoirs in Alberta, Canada have been successfully produced under primary production at rates far in excess of the predictions based on radial Darcy flow. The primary heavy oil production is possible by allowing formation sand to be produced along with reservoir fluids using a progressive cavity (PC) pump. This process is called "cold" production because heat, such as steam, is not introduced into the reservoir to effect production of the heavy oil. Figure 1 shows a PC pump which can carry reservoir fluids and sand to surface through the rotational action of a rotor housed in a flexible rubber stator.

Typically, a cold production well will produce oil and water at sand cuts as high as 30 to 40% initially, which gradually decrease over time to stabilize at between 1 to 5% after one year of production. Cold production technology has been applied to many heavy oil and oil sand reservoirs in the Cold Lake region of Alberta, Canada with economic success. Figure 2 shows a representative cold production project with a six year production history. The range of reservoir characteristics and fluid properties amenable to cold production are shown in Table 1.

Currently, the two generally accepted theories on the dynamics of cold production are:

  1. sand production creates "wormholes" in the reservoir thereby increasing both the effective permeability and well bore radius, and;

  2. the oil flows due to the "foamy oil" phenomena, a type of reservoir drive mechanism involving the retention of solution gas by the viscous oil.

Other factors contributing to cold production may include increased drainage radius, gas expansion, and continuous pore de-blocking. Higher quality PC pumps allow co-production of the sand with the heavy oil. Sand production is encouraged through large diameter perforations in vertical wells and wide slots in horizontal well liners. Anticipated recoveries are increased to 8 to 12% of the original oil in place from negligible levels if the wells were produced without the co-production of the sand. As horizontal well technology developed, demonstrated increases in oil production from three to four times that of conventional vertical wells were common. Although the cold production mechanism is not fully understood, a combination of horizontal wells and cold production does have the potential to economically produce many heavy oil fields.

History of Frog Lake Property

Texaco Canada Petroleum Inc. (TCPI) is a 100% working interest owner of a 34,000 acre 53 section oil sand lease located at Frog Lake, Alberta.

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