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Room for expansion at Cosmopolitan field Johnson says further development Cook Inlet field facilities will depend on drilling results; natural gas development is on hold ALAN BAILEY Petroleum News
Since the initial production facilities are now in operation, with a capacity of up to 10,000 barrels per day of oil, any future expansion of the facilities at the Cosmopolitan oil field will depend on the results of development drilling, Benjamin Johnson, president of BlueCrest Energy, told the Alaska Oil and Gas Congress on Sept. 21. There is ample space on the Cosmopolitan pad for further facility expansion, should expansion prove worthwhile.
“So, we’re going to wait and see how our drilling turns out before deciding what, if any, expansion we need to make for the field,” Johnson said.
The field is in Cook Inlet offshore the southern Kenai Peninsula and is accessed by directional drilling from a surface pad near Anchor Point. Oil production started in April from a converted exploration well, with oil from the field being trucked to the Tesoro oil refinery at Nikiski. Johnson said that BlueCrest has no plans to build an oil pipeline, given the very high expense of building such a long line and the cost-effectiveness of trucking the oil. Building a pipeline would require a high level of oil production, he said.
Meanwhile, gas development in the field, which would require offshore production platforms, is on hold, he said.
Powerful rig For the drilling of development oil wells BlueCrest has brought in what Johnson characterized as Alaska’s most powerful drilling rig.
“This rig was specifically designed for drilling our wells,” Johnson said. “We are drilling some of the most extreme wells in Alaska in terms of the depth and the horizontal distance.”
The well bores at Cosmopolitan will extend three miles out from the onshore pad before extending another mile horizontally through the oil reservoir. This results in a measured well bore depth of 24,000 feet to reach targets at a vertical depth of 7,200 feet, Johnson said. The rig, which has a 750-ton top drive, has what Johnson thinks is the only 7,500-pounds-per-square-inch drilling mud system in Alaska, to ensure adequate control of the highly deviated wells. And the rig derrick can hold all 24,000 feet of drill pipe needed for a well, thus avoiding the need to suspend drilling operations for the loading of additional pipe, Johnson said.
The rig can move on rails between wellheads in minutes, Johnson added. He also commented that the field had been developed with a focus on environmental issues and neighbor protection. For example the LED lighting for the field facilities is focused inside the pad, to avoid disturbance to the field’s neighbors, he said.
The Cosmopolitan story Johnson reflected on the story behind the Cosmopolitan field and how BlueCrest had come to acquire and develop what it now recognizes as a significant oil and gas resource.
When Pennzoil drilled the field discovery well in 1967, the well just clipped some oil at the side of the field. And the company, not having good well logs, abandoned the prospect, having concluded that the oil column was very thin, Johnson said. Then 25 years later ARCO, thinking that Pennzoil may have missed a large discovery, shot some seismic over the prospect. The seismic revealed a large 15,000-acre dome-shaped structure in the subsurface. But, with no equipment available for offshore drilling, the company was faced with the need to drill a fairly risky directional well from onshore.
In 2001 ConocoPhillips did drill a well from onshore, confirming the presence of oil in the prospect and showing the potential for more oil than previously thought. A further well drilled in 2003 included a somewhat horizontal section through the Hemlock formation - a relatively short horizontal section of the well produced 1,000 barrels per day of oil, Johnson said.
Pioneer Natural Resources then acquired the prospect, shooting a 3-D seismic survey to better define the Cosmopolitan structure. Although this survey provided a clear delineation of the scale of the structure, gas at the top of the structure disrupted the seismic signals, thus blotting out any image of the structure inside the dome. In fact, the seismic image suggested that the dome had caved in at the top.
Pioneer drilled a well into the structure in 2007 but this long, undulating horizontal well missed many of the reservoir sands, Johnson said.
New offshore well Johnson said that BlueCrest’s geophysicists had attributed the collapsed appearance of the structure to the distortions to the seismic imaging caused by a gas cloud in the subsurface. A recalculation of the seismic results on the assumption of the presence of a gas cloud indicated the existence of a large geologic dome, he said. The drilling of a well in 2013 from an offshore rig after BlueCrest had acquired the rights to the Cosmopolitan prospect not only confirmed that this dome structure was present but also found a 5,000-foot thickness of gas-bearing sands. Apart from a couple of water sands, everything else was filled with gas. Below the gas lay about 1,200 feet of oil sands, separated by some shales, Johnson said.
Johnson showed cross sections of the subsurface geology and the various well trajectories, showing that the earlier wells had hit the edges of the hydrocarbon pools, thus failing to reveal the full extent of the subsurface hydrocarbon resources. However, the well that Pioneer drilled in 2007 has turned out to have continuing value - BlueCrest has converted this well into an oil production well, enabling the Cosmopolitan field to come on line before the main development drilling program got underway.
But the gas resource in the field, while large, is too shallow to be accessed from onshore drilling. Thus, with probably two offshore platforms required for development, BlueCrest has no immediate plans to bring the gas on line, Johnson said.
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