THE LINK: JULY 2023 37 The university and Hilcorp are already using polymers with another challenged oil deposit, viscous oil in the Schrader Bluff formation also at Milne Point. In production now underway and Hilcorp has seen a gain of 700 b/d in two wells where polymers are being injected at J Pad in the field, Prof. Dandekar said. The viscous oil has an API gravity of about 19 degrees compared with the larger Ugnu, where the API gravity ranges from 16 down to 10 degrees. There are about 12 billion barrels of oil-in-place at Schrader Bluff. Prof. Dandekar said, “About 20 percent of this oil can be recovered when only water is injected to move the oil. But this is expected to double over time to 40 percent as polymers are injected.” In comparison, oil recovery in conventional oil reservoirs like the neighboring Prudhoe Bay field typically see 40 percent recovery at the start and then improvement over time as waterflood and enhanced oil recovery projects are added. Prudhoe is now expected to see about 60 percent recovery of its 26 billion barrels of original oil-in-place. The viscous oil in Schrader Bluff and the heavy Ugnu oil are cold because they are shallow and near the frozen permafrost that underlies the North Slope. The best of the Ugnu oil has the consistency of molasses, Prof. Dandekar said. The key to unlocking these huge resources is to reduce the viscosity, or thickness, of the oil so that it will flow out of the reservoir rock and up producing wells. The polymer/water injection in the Schader Bluff J Pad project is accomplishing this. In the Ugnu, where most of the oil is basically immobile, the injection of the CO2 improves the viscosity to the point that the polymer and water injection does the rest, Prof. Dandekar said. Even then, getting this oil to flow through pipelines is challenging but it can be done when blended with the large volumes of conventional oil being produced in the North Slope field. Prospects are that production of viscous oil can be increased and someday the heavy oil produced but the availability of conventional oil will be important. The large heavy and viscous oil deposits on the slope have long been known because they overlie the large conventional oil reservoirs and companies drilled through the viscous and heavy oil on the way to the deeper targets that are easier to produce. ARCO Alaska first began experimenting with production techniques for viscous oil in the 1980s in the West Sak formation in the Kuparuk River field, which is now owned and operated by ConocoPhillips. Through trial and error ARCO found ways of economically producing the West Sak, which is a similar formation to Schrader Bluff, with a combination of waterflood and horizontal production wells. Similar techniques were adopted at Milne Point and Prudhoe Bay by BP when it owned those fields and now Hilcorp, the current owner. The difficult Ugnu deposit with its huge resource has always been enticing, however. When it owned Milne Point and Prudhoe BP tackled the Ugnu with an auger production device adapted from oil sands projects in Alberta, but costs and mechanical problems interceded. A more exotic approach explored by some BP engineers envisioned mining the heavy oil, much of its frozen or semi-frozen, from underground through a system or tunnels and small specialty rigs drilling up into the oil. The more conventional carbon dioxide and polymer injection seems more feasible, and now promising. Hilcorp is watching the university’s heavy oil research closely but is not yet formally engaged. So far, the project is being funded by the U.S. Department of Energy and the State of Alaska. The Ugnu is difficult, “but it’s a resource that is too big to ignore,” Prof. Dandekar said. — Tim Bradner
RkJQdWJsaXNoZXIy MTcxMjMwNg==