It’s a given that geologist and AAPG member Michael Johnson has had a highly exciting, successful career in the oil and gas industry.
This is due for the most part to his finely honed geological expertise in combo with the tenacity to follow through on his convictions.
It’s a combination that has served him well – and has resulted with him being named this year’s AAPG Explorer of the Year.
This intrepid oil finder’s career kicked-off in 1949 when he joined Amerada Petroleum after graduating from Ohio State University, where he earned bachelor’s and master’s degrees in geology. Amerada assigned him to the Williston Basin office in Billings, Mont.
Johnson barely had time to get his desk organized before he was drafted into the U.S. Army where his initial assignment was to serve as an instructor in the interpretation of aerial photographs. He later did a tour of duty at the Armed Forces Special Weapons Project at the Nevada Test Site.
Upon concluding military service in 1953, Johnson returned to Amerada’s Williston Basin office for a brief stint before being assigned to Tulsa headquarters. While there, he assisted in the development of the basin’s Nesson Anticline fields.
The main pay zone of these fields is a low permeability reservoir known as the Rival sub-interval of the Mississippian Madison limestone. Johnson noted the reservoir was unusually productive, educating him early on in the importance of fracture porosity as a major contributor to reservoir quality.
After leaving Amerada in 1958, the young geologist joined Apache Oil as Rocky Mountain exploration manager. Apache was focused on the Piceance Basin, but a lack of pipeline and low gas prices took their toll, and the company soon closed the Denver office, placing Johnson on part-time retainer.
The next phase of his career entailed a full-time retainer affiliation with Wessely Energy and Headington Oil Co. – as well as work for clients in Central America, the eastern Mediterranean and the North Sea.
Call of the (Williston) Wild
No matter where this talented explorer searched for hydrocarbons, however, the lure of the Williston Basin was omnipresent. In fact, Johnson enjoyed remuneration from 12 fields in North Dakota, alone, during the latter phase of his career.
Johnson’s ultimate grand slam in the Williston occurred at the now-significant Parshall Field in North Dakota’s Mountrail County, where EOG drilled the discovery well in 2006 based on an idea that originated with Johnson.
Parshall was the defining point where all of the talented oil finder’s diverse experience in the geology of the Williston Basin and in aerial photo interpretation coalesced.
The giant Elm Coulee Field, which had been discovered in the mid-1990s in Montana, played a role in the Parshall find. (AAPG member Dick Findley received the 2006 AAPG Explorer of the Year honor for the Elm Coulee discovery.)
“I came up with the idea that eastern Mountrail County would be a good place to try to find another big Bakken oil field,” Johnson said. “When I started looking in that area, I found it had some resemblance to Elm Coulee.
“I had just finished doing a study of Elm Coulee, so I had a pretty good idea of what caused it to trap and what the characteristics were, what the geologic setting was,” Johnson said. “So I tried to use that as an analog in looking for another one like it.
“I saw there was a similarity in the electric logs at Elm Coulee Field with several wells in eastern Mountrail County,” Johnson said. “Then I noticed also by looking at additional data there had been some wells there, which I call the Parshall area, that had free oil recoveries on drillstem tests and also some wells that had actually produced oil, but not in great amounts.
“That showed the area was mature, because there wouldn’t be any oil if it wasn’t,” Johnson said. “The drawback was, the oil wasn’t in large volumes.”
Another drawback was the low vitrinite reflectance and the low Tmax, indicating immaturity. Yet this was contrary to what the free oil was showing.
Another downside to the prospect area was the earlier failure of a couple of horizontal wells due to mechanical problems. Johnson noted that’s hard to explain to someone if you’re trying to sell acreage.
Logs Don’t Lie
Undeterred, Johnson and partner Henry Gordon, president of Strata Resources, purchased 5,500 acres around the Gulf Oil Nelson Farms well, which was a seeming look-alike to Elm Coulee Field.
The two partners sold their acreage to a couple of independents who pooled their holdings with EOG, which had some offsetting acreage.
In turn, EOG drilled the discovery well for the Bakken reservoir in eastern Mountrail County. The horizontal well, which was a twin to the Gulf Nelson Farms well, marked the discovery of Ross Field in late 2005 prior to Parshall.
While that action was ongoing, Johnson and Gordon decided to head south about 25 miles to another well – the Lear #1 Parshall – where the logs again looked like logs from Elm Coulee.
The goal was to try to also buy acreage in that vicinity.
“Bob Berry, a Tulsa geologist, financed the purchase of that block, buying about 38,000 acres there,” Johnson said, “based on just one well in the middle of the block – I was amazed this acreage was not already leased.”
Selling the purchased block was no slam-dunk, as operators were familiar with the questionable maturity of the Bakken oil in this general locale and the earlier horizontal well failures.
EOG ultimately acquired the block from Berry and drilled the #1-36H Parshall discovery well, which was a twin to the Lear well drilled in 1981. Pressures were so high in this initial well that it blew out once the lateral leg reached 1,200 feet into the middle member of the Bakken. Upon completion, the well was kicking out 463 bopd.
“Both discoveries were twins to old wells drilled 20 years ago, and that’s how we relied on petrophysics to pick up the acreage,” Johnnson said. “EOG also felt the logs were telling us something, and that’s why they twinned those wells.”
The American Dream
Johnson emphasized that Parshall, which covers 225,000 acres and could extend to over 400,000 acres, has exceeded expectations.
He noted that reserve estimates, based on 500 Mbo per well – which is less than reserve figures made public by operators – are estimated at 175 MMbo for the existing field size and 350 MMbo if the field extends to 400,000 acres. In fact, ultimate attainable field size for Parshall and its extensions could bump that number up to 500 MMbo.
Parshall is of particular importance in that it is a new type of unconventional stratigraphic trap that is productive from the Middle Bakken member. The boundary between thermally mature and immature Bakken forms part of the updip trap, making it different from any Bakken field in North Dakota.
Parshall’s discovery had a decided impact on the U.S. Geological Survey’s recent assessment of the Bakken formation in the Williston Basin in Montana and North Dakota.
“This was a surprise discovery in Parshall in that this success was outside the Bakken oil window that was preciously understood – it was to the east of that,” said AAPG member Rick Pollastro, USGS geologist and Bakken formation task leader. “It was outside the area of what was thought to be the continuous accumulation.
“We had to re-establish the area where the oil generation window for the Bakken was to do our assessment,” he noted. “From the oil taken from those wells, we think it was generated in place. That’s the model I developed – some agree and some have a different story.”
Like most success stories in this business, getting the deal done at Parshall took not only a heap of geologic smarts but unwavering perseverance as well.