Point Thomson: What are the issues?
Point Thomson, an undeveloped field 60 miles east of Prudhoe Bay, is unusual in that its reservoir pressure is very high - 10,200 pounds per square inch - and it is a gas condensate reservoir, also known as a retrograde condensate reservoir. This means that the underground formation contains gas as well as condensate, a natural gas liquid. There are technical issues with Point Thomson besides the high pressure. Here is how Cathy Foerster, a commissioner on the Alaska Oil and Gas Conservation Commission, described the problem in her presentation to the Legislature: "In a reservoir like Point Thomson, the hydrocarbons are in the gas phase (in the reservoir rock) until the pressure drops below a certain point, called the dew point. When the pressure drops below the dew point of some of the hydrocarbons, the condensates switch to the liquid phase and drop out of the gas. When this happens a substantial portion of those liquids can be trapped and can never be recovered."
"In many retrograde condensate reservoirs gas cycling is done, reinjecting gas (that is produced) over and over again (cycling) to maintain high reservoir pressure until the liquid condensate has been recovered (or produced). Looking simply at the reservoir mechanics, and not getting into financial concerns or politics, cycling the gas until most of the liquids have been recovered is the way to achieve greater ultimate recovery and prevent waste from a gas condensate reservoir such as Point Thomson," Foerster told the Legislature.
Estimates of liquids at Point Thomson range from 200 million to 800 million barrels
Publicly available estimates of the liquid hydrocarbons associated with the gas at Point Thomson vary from 200 million to 500 million barrels, depending on the method of development, Foerster said. "If we produce Point Thomson as a gas reservoir without cycling first, a significant portion of those liquids are at risk. Don't let me underestimate the value of the liquid resource; it's the sized of another Alpine field," she said. Another problem with the reservoir is that loss of the liquids could damage the ability to produce gas because the condensates will become liquid first at the points of the lowest pressure, which is around the well bores.