A hive of activityDrilling rig returning to Point Thomson as field development continues Alan Bailey Petroleum News
ExxonMobil is activating the powerful Nabors 27E drilling rig, for transportation by ice road in the coming winter to the company’s huge Point Thomson gas condensate field on the North Slope, company executives told Petroleum News Oct. 16. The rig will continue drilling operations that were started at the field several years ago.
With up to 1,200 people and 70 Alaska companies involved in activities ranging from gravel laying to pipeline installation, field development has been moving steadily ahead, said Nathan Sanborn, project manager for the Point Thomson Initial Production System. The company has spent the last couple of years developing infrastructure, including the gravel pads, gravel roads and the airstrip. And the pipeline that will deliver condensate from the field to the North Slope pipeline system has been completed, as has the permanent operations camp for the field, Sanborn said.
Pad and road construction at the field’s surface site has involved moving more than 2 million cubic yards of gravel over the past two winter construction seasons, said Christina Nordstrom, Point Thomson technical manager. And the construction of roads between the pads, and to the airstrip and the project’s water source, has involved building four bridges, she said.
Fuel tanks have been installed, capable of holding up to 2.1 million barrels of diesel fuel, both for power generation prior to field startup, and for use as an alternative to gas-fired generation once the field is in operation.
A challenging field The Point Thomson field is particularly challenging to develop. The field reservoir contains a mixture of natural gas and condensate, a very light form of oil, at a very high pressure. And, with the reservoir extending offshore, offset from the onshore surface well pads, field development involves drilling deviated wells into those high pressures, a technically difficult operation. Because reservoir pressure must be maintained, to prevent the condensate dropping out of solution inside the reservoir, gas at high pressure will need to be continuously cycled through the reservoir using an appropriate configuration of wells. Condensate will be extracted from the gas after the gas reaches the surface through a production well, before the gas is sent back underground through an injection well.
In the absence of a means of marketing gas from the field, initial field production will consist of just condensate, with the gas being continuously recycled. A small amount of gas will be used as fuel for the production facilities.
Initial drilling In 2009 and 2010 ExxonMobil used the Nabors 27E rig to drill two wells in the field from an existing exploration gravel pad, a pad that is now called “central pad.” The company has since expanded the pad, so that it can accommodate the field’s production facilities and support infrastructure.
Nordstrom said that tests using those initial wells indicated good pressure communication between the wells through the reservoir, an important factor in achieving success with the gas recycling production technique.
“All of the indications that we have from the two wells that were drilled in 2009 and 2010, and the subsequent reservoir modeling, support good communication,” Nordstrom said. ExxonMobil has a pretty good handle on how the production will work out, she said.
And Sanborn commented that, with ExxonMobil having had experience of drilling more challenging deviated wells elsewhere, the company is confident in its ability to successfully carry out the necessary drilling at Point Thomson.
Initial development plan In 2012, following a protracted legal dispute, ExxonMobil and the state of Alaska agreed on an initial development plan for Point Thomson. That plan envisages an initial production rate of 10,000 barrels of condensate per day from the field, with production starting at the end of the winter of 2015-16. Sanborn confirmed that the Point Thomson project is on target for achieving the plan objectives, with field startup anticipated prior to May 2016 and involving the cycling of 200 million cubic feet of gas per day for condensate production.
The pipeline that ExxonMobil has constructed for exporting condensate from the field has a maximum capacity of 70,000 barrels per day, presumably to accommodate potential future field expansion. As it stands, the pipeline could handle production above 10,000 barrels per day, should the hydrocarbons produced from the field contain more condensate than anticipated, Sanborn said. But initial gas compression facilities being installed in the field limit the gas recycling to a maximum of that 200 million cubic feet per day figure, he said.
However, the scale of the $4 billion development at Point Thomson, including an airstrip that can accommodate a DC-6 aircraft and a 200-person operations camp, would appear to signal expectations of further development to come. With natural gas reserves of 8 trillion cubic feet, a quarter of the total Prudhoe Bay gas reserves, there are definite future opportunities, Sanborn said.
“We’re laying the foundation for whatever comes in the future,” he said.
Pad configuration Although eventual Point Thomson development may involve the use of three surface gravel pads, the existing central pad plus a west pad and an east pad, the initial development will only require the central and west pads. The necessary extensions to the central pad and the construction of the west pad have both been completed, Nordstrom said. The central pad currently houses the field’s permanent operations camp and several temporary construction camps, Sanborn said. The well cellars for wells on both pads have also been completed, he said.
At field startup, one of the two previously drilled wells on central pad will act as a gas injector well, with production coming from the other central-pad well, Sanborn explained. Then, upon completion of facilities at west pad and completion of the pipeline tie-in between that pad and central pad in the first quarter of 2016, a well to be drilled from west pad will become the field’s production well, with both wells on the central pad then becoming gas injectors.
With a larger internal diameter than the central pad wells, the west pad well will have a higher production capacity than either of the other wells, Nordstrom said. In addition to being designed with smaller diameters, the two central pad wells will require corrosion resistant liners, following the discovery of hydrogen sulfide in the gas coming from the Point Thomson reservoir, she said.
Drilling activities This winter the Nabors 27E rig will drill a disposal well, complete the two central pad wells and install the liners in those wells, Sanborn said. The rig will then move to the west pad to drill the single well there. Drilling on west pad will start in the fourth quarter of 2015, in anticipation of field startup in 2016, Nordstrom said.
The Nabors rig was upgraded several years ago to enable it to handle the challenging drilling of the two initial Point Thomson wells. ExxonMobil has commissioned further rig upgrades, including the installation of a more powerful top drive, prior to mobilizing the rig for the coming phase of drilling, Sanborn said.
Module construction Meantime, fabrication of the major production modules for the Point Thomson field has been progressing in South Korea. Weighing a total of about 10,000 tons, the modules consist of a utilities module, a process separation module, a power generation module and a control building. Completion of the modules is anticipated in the next nine months or so, in preparation for shipment in June 2015, for barging to the Point Thomson site that summer, Sanborn said.
On-site work during the coming winter will include the building of the foundations for the processing facilities, Nordstrom said.
Meantime engineering company CH2M Hill is installing underground features such as some of the cabling in central pad, in preparation for the arrival of the modules. The company is also installing some of the on-pad flowlines that will connect wells to surface facilities, Sanborn said.
CH2M Hill has fabricated a large switchgear module, one of several modules being manufactured in Anchorage for transportation by truck to the North Slope. ASRC Energy Services is also involved in the fabrication of some of these modules, which include a methanol injection module, a grey-water module and a metering skid, Sanborn said. The various truckable modules will be completed by the end of this year, for shipment by winter ice road to the Point Thomson site, Sanborn said.
Focus on safety With programs like “drips and drops,” the inspection for oil leaks of any vehicles using the field’s ice road during the winter, and the immediate cleanup of any oil spilled on pads or roads, safety performance and environmental protection form significant components of the Point Thomson project, Sanborn said. ExxonMobil has established a “Point Thomson Academy,” a training school that operates two-day safety and environmental courses for all on-site supervisors, he said.
So far the Point Thomson project has only seen a few minor injuries, with no lost-time incidents, Sanborn said.
And given the need to inject gas at 10,000 pounds per square inch into the field reservoir, the Point Thomson project team is ensuring that all equipment has appropriate pressure ratings and can operate at those high pressures in the Arctic cold, Sanborn said.
“We fully test everything, 100 percent,” he said.
Moreover, field operators hired for Point Thomson are undergoing a two-year, on-the job training program, gaining experience in the operation of similar high-pressure fields elsewhere in the world, Nordstrom commented.
Did you find this article interesting?
Tweet it
 | Digg it
|
Print this story | Email it to an associate.
Click here to subscribe to Petroleum News for as low as $89 per year.
|
