Hard on the heels of an agreement between the State of Alaska and the leaseholders over the much-disputed Point Thomson unit on Alaska’s North Slope, unit operator ExxonMobil Corp. has filed a plan of operations for the unit with Alaska’s Division of Oil and Gas. The division wants public comments on the proposed plan by June 22.
Although the Point Thomson field is very large — it contains 300 million barrels of liquid oil and natural gas condensate and 8 trillion to 9 trillion cubic feet of natural gas according to the Alaska Department of Natural Resources — the field has yet to produce any oil or gas, despite the fact that Exxon discovered the field as long ago as 1977.
While being accused by some of “warehousing” the huge resource that the field contains and being challenged by the state for holding onto but not developing Point Thomson leases, Exxon has over the years put forward several plans for development in the unit, none of which have previously come to fruition.
Gas condensate
The Point Thompson field presents some particular development challenges.
Although there are known oil pools within the Point Thomson unit, the field consists mainly of a high-pressure gas condensate reservoir. The field could be operated as a conventional gas field, but the production of condensate from the field requires a procedure known as gas cycling. In gas cycling, the reservoir pressure is maintained by injecting produced gas back into the reservoir, thus flushing condensate in vapor form to the surface.
Because of the temperature and pressure conditions in the reservoir, much of the condensate would liquefy underground and remain trapped unless the reservoir pressure is maintained through the cycling process.
The production of condensate is desirable because it has a higher economic value than natural gas and, in liquid form, it could be mixed with crude oil for export through the trans-Alaska oil pipeline. Blowing down the reservoir as a gas field, although much less costly than building and operating a cycling system, would likely result in less gas recovery than would otherwise be possible. In addition there is as yet no means of marketing gas from the North Slope.
Plan proposed
In 2008 in the course of the recently ended dispute with the state over the state’s termination of the Point Thomson unit, Exxon proposed a modest-scale gas-cycling development that would enable some condensate production while also providing a means of verifying the feasibility of gas-cycling in the Point Thomson reservoir. In justifying the relatively small scale of its proposal, the company cited significant unknowns and associated risks in a Point Thomson development, including the possibility of poor pressure communication between gas injection and oil production wells; the possibility of discontinuities in the reservoir; the difficulty of injecting gas into an exceptionally high pressure reservoir; and the difficulty of drilling long reach directional wells into that high subsurface pressure (much of the reservoir is offshore and will need to be directionally drilled from onshore).
In 2009, with the dispute between Exxon and the state still raging, Exxon moved ahead with the drilling of two initial wells, an injection well and a production well, at an existing gravel pad at Point Thomson. In October 2010 the company announced that the drilling had been successful but did not elaborate on what it had found from the drilling.
Up to five wells
The plan of operations that Exxon has now submitted looks essentially to be a rerun of the plan that it proposed in 2008. The plan entails the drilling of a disposal well and up to five wells, including the two wells already drilled, from three gravel pads: a west pad, a central pad and an east pad. Using long reach drilling, the three pads would enable well access to the west, central and eastern sections of the field reservoir.
“Wells drilled from the proposed pad locations will be at or very near the technical limits of drilling reach,” the operations plan says.
The two existing wells were drilled from the central pad. Exxon plans one new well on the west pad and one on the east pad, with the location of the fifth well depending on the results of the drilling, the operations plan says. Produced hydrocarbons will be delivered to a central processing facility on the central pad.
Oil possibility
If one of the wells penetrates an oil pool, either in what is referred to as the “Brookian,” above the main reservoir, or in an oil rim around the perimeter of the reservoir, Exxon will evaluate the oil-bearing zone as appropriate, the plan says.
Wellheads on a single pad will be positioned unusually far apart, at a spacing of 40 feet, in recognition of the high pressures and flow rates likely to be involved in field operation, and the need to be able to bring in heavy tools and equipment.
“The production well flowing wellhead pressure is estimated to be over 3,000 psig (pounds per square inch),” the operations plan says.
Five-mile-long gathering lines will connect the east and west pads to the processing facility on the central pad.
Processing facility
At the processing facility, hydrocarbon liquids will be recovered and stabilized for delivery by pipeline to the trans-Alaska oil pipeline. Produced water will be injected into a disposal well, while produced gas will be compressed to 10,000 pounds per square inch for re-injection into the reservoir as part of the gas cycling process. The processing facility will be able to handle 200 million cubic feet of gas per day for the recovery of 10,000 barrels per day of condensate, the operations plan says.
The complete system will “provide essential information about the degree of reservoir connectivity and the producibility from key locations in the field,” the operations plan says.
Other facilities
Other components of what Exxon refers to as the “initial production system” include a gravel airstrip; a service pier, a boat launch; an in-field gravel road network; and a staging pad. Barges will transport facility modules, equipment, material and supplies to the central pad using an offloading structure adjacent the pad, which is on the coast.
And to accommodate the necessary infrastructure and facilities, Exxon will expand the central pad from its existing area of 13 acres to 56 acres.
Although Exxon plans an operations camp able to house 200 people during field construction, the operations plan says that the camp will be reconfigured to accommodate fewer people once construction has been completed.
Four gas-fired generators will supply electrical power for the field.
To transport Point Thomson production to the trans-Alaska oil pipeline Exxon plans to construct a 22-mile pipeline that will connect with the existing oil export pipeline from the Badami field. The Point Thomson export pipeline will have an outside diameter of 18.75 inches and will be held at least seven feet above the tundra on approximately 2,200 vertical support members. A pig launcher at the central process facility will enable the use of maintenance and inspection pigs, the torpedo-shaped devices that are sent down the insides of pipelines.
Pipeline construction will take place in the winter from ice roads, the operations plan says.
The Point Thomson field will not be connected by permanent road to the central North Slope. Instead, access to the field will be accomplished by sea during the summer open water season and by ice road during the winter. Access will also be possible by tundra travel using vehicles such as Rolligons. And the field’s airstrip will be available for year-round access by aircraft.
Schedule
A project schedule included in the operations plan indicates that detailed engineering design for the project is already in progress and that permitting and an environmental impact statement for the project will be completed this year. Infrastructure construction will start in 2013, with both the infrastructure and gathering lines being completed in mid-2015. Drilling will take place between early 2015 and early 2017, with the main sealift and module installation happening in 2015 and early 2016.
The operations plan also includes information about Exxon’s oil spill prevention and response plan; environmental protection measures; workforce development; and the company’s involvement with North Slope communities.
