Point Thomson: Alaska's big Arctic project: extending industry infrastructure on the North Slope.

• Author: Bradner, Mike
• Position: SPECIAL SECTION: Arctic Oil & Gas - Cover story

The Point Thomson project sixty miles east of Prudhoe Bay is one of the largest and most technically challenging oil and gas projects built in years on the North Slope. It is requiring $4 billion by its owners, mainly Exxon Mobil Corporation and BP Exploration (Alaska), Inc., and while it will produce condensates, a natural gas liquid, it can also be seen as the first part of the larger natural gas pipeline and liquefied natural gas (LNG) project that will commercialize Alaska's large North Slope gas resources,

This is no conventional oil and gas field. Point Thomson is mainly a natural gas deposit with about 8 trillion cubic feet of gas, but there is also an estimated 200 million barrels of liquid condensates in the reservoir along with the gas.

There are difficulties, however. The reservoir is at an extreme high pressure at over ten thousand pounds per square inch, which is about twice the original (reservoir pressure of the Prudhoe Bay field. It is one of the highest-pressure oil and gas reservoirs in the world, and safely drilling into, and producing from, such a high-pressure field is tricky, requiring advanced technologies and experienced companies.

High Pressure

Point Thomson was discovered in the 1970s by ExxonMobil but remained undeveloped because the field was remote and there was no way to market the natural gas. The liquid condensates, however, can be produced and, if transported to Prudhoe Bay, mixed (with the crude oil in the Trans Alaska (Pipeline System, or TAPS, and sent to market. But producing the condensates also involves producing gas, and since state law prohibits the flaring of gas it must be injected back underground, an expensive proposition with a high pressure reservoir.

Given the delays in building the gas pipeline the state Department of Natural Resources, which manages the state's North Slope's lands, pressed ExxonMobil and the other lease owners to pursue ways to develop and produce the condensates as a way to develop the leases.

The plan ExxonMobil ultimately developed was gas "recycling," or producing the gas and liquids, removing the liquids, injecting the gas back underground, and shipping the condensates on to Prudhoe Bay and TAPS through a new pipeline.

The principle of gas cycling is to drill wells and produce the gas, which contains the condensates, remove the condensate liquids at the surface (this is accomplished by lowering the pressure so the liquids "drop out" of the gas) injecting the gas back underground, and sending the liquids on to Prudhoe Bay.

This isn't easy with such a high-pressure field, however. The well casings and tubular piping for the wells have to...