In 1989, the first horizontal well in a vertical hydrocarbon miscible flood reservoir in Canada was completed in the Rainbow Keg River G Pool. The performance of this well exceeded original expectations. Despite the high drilling cost, the well paid out in less than one year.
Since then Husky Oil has launched an extensive horizontal well drilling program in the Rainbow carbonate reservoirs. By the third quarter of 1991 six wells had been drilled and completed as Keg River oil producers. Although these wells were all drilled in miscible flooded Keg River reefs, the geological variation, the well location and the past reservoir history have made the drilling of each well unique.
This paper will discuss the factors which have been keys to the successful application of horizontal well technology in the planning, execution and production optimization phases. Key factors such as management commitment, integration of multi disciplinary technical expertise and an effective team approach have all contributed to Husky's horizontal well success in the Rainbow Area.
As of January 1, 1992 Husky had six horizontal wells on production in five Rainbow vertical hydrocarbon miscible floods (Figure 1). The horizontal wells have the advantages over vertical wells of low drawdowns to minimize coning/channelling of gas and water, and larger drainage area resulting in incremental oil sandwich recovery1–2. To date these wells have been very successful in reducing gas coning (Figure 2) and in improving oil productivity (Figure 3). Payout of capital investment costs is typically less than one year. These horizontal wells have produced a total of 18O 000 m3 of oil, much of which is incremental over what the existing vertical wells would have recovered.
An earlier study determined that a medium radius technique will offer the most advantage. It would avoid the overly-long wellbores and drilling time associated with long-radius holes, and the uncaseable hole that would result with the short-radius technique1,3.
The lengths of the horizontal sections have increased from 178 m in the very first well to as long as 720 m (Table 1). Each well was drilled into a progressively riskier target in terms of potential for:
applying horizontal technology to the wrong
reservoir type, and not achieving payout;
improper well placement because of lack of accurate definiton of gas-oil and oil-water contacts, heterogeneous rocks (probability of drilling into tight rocks) and uncertainty about the effective drainage areas of the vertical wells; and
unsafe conditions and cost overruns during the drilling and completion operations.
The approach to planning for and solving each of these potential and actual problems is what made this horizontal well program a success, and is the topic of this paper.
Realizing the potential benefits of horizontal well technology, but also its high risk and cost, management set up a multi-disciplinary task force to evaluate the application of this technology to Husky operated properties. The team consists of staff from reservoir engineering, geology, geophysics, production engineering, drilling and completions, research and development, business support, and field operations.