The American Association of Petroleum Geologists (AAPG) played to a standing-room-only crowd during its Discovery Thinking session Monday at the annual convention in Denver, Colo.

The man at the top of the pack was Michael S. Johnson, named explorer of the year by the organization when it presented him with the Outstanding Explorer Award the previous day for his discovery of Parshall field, the best producing field in the Bakken Shale oil play in North Dakota.

Delegates lined the walls and stood outside the doors waiting to hear how he did it.

Horizontal drilling and new fracture techniques have revolutionized oil and gas production, Johnson said, and the Bakken play is a prime example of that technology.

The Bakken play started in Montana where Elm Coulee field was the flagship operation. Johnson followed the trends and looked for an Elm Coulee look-alike to the east in North Dakota. He found it on the eastern side of the Nesson Anticline in Mountrail County at Parshall field.

EOG Resources Inc. drilled its first horizontal well into Ross field in 2005 and followed up with a horizontal well in Parshall the following year. It continued the work with 35 extensions in the two fields with no dry holes and delineated a trend some 75 miles (120 km) long and 25 miles (40 km) wide covering 58 townships, or 1.24 million acres.

The operators could drill 1,950 wells on 640-acre spacing with an average production of 350,000 bbl of oil per well. Eventually, Johnson expects the Bakken play to produce a billion barrels of oil.

The play doesn't start in Montana, move to North Dakota and stop. It has prolific potential in Canada, as well. There, the Viewfield area alone should produce some 1.1 Bbbl of oil from a projected 800 wells. That area is about 120 miles (193 km) north of Parshall field.

North Dakota projected its share of the Bakken play at between 2.1 Bbbl and 2.6 Bbbl of recoverable oil.

Overall, Johnson said, the Bakken has added some 4 Bbbl of oil discoveries in the past three years.

That figure applies not only to the Bakken, but also to the area. Before the Bakken discoveries at Ross and Parshall, the area had only one small shallower Madison field in production.

In his analysis, Johnson looked at an old Gulf Oil well where Ross field now stands. It had promising potential in the Middle Bakken Dolomite between upper and lower shale areas.

He also looked at a Lear Oil well at the site of Parshall ffield. On the strength of information from those two wells, he and a partner bought 40,000 acres in the area. In 2005, he was the only bidder for the area in the state land sale, and he picked up properties for about US $3 an acre.

He urged AAPG members at he meeting to find a good geologic idea and follow it.

Now, the play has some 200 single-lateral horizontal wells. Costs have dropped from around $6 million a well to between $4 million and $4.5 million. When oil prices were higher, an operator could expect payout in six months. One well paid out in only four months.

One reason the play was overlooked, aside from the evolution of horizontal drilling and better fracturing, was the unique trap.

Carbon dioxide and water converted kerogen to hydrocarbons. That increased the fluid volume, which created natural fractures. To the east, the mature-immature boundary formed a barrier to migration as the shale permeability got tighter.

Initial production from wells is flush with some wells averaging 4,000 b/d. Within a few months, that production drops to 200 to 300 b/d and lasts for a long time.

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