- St. Croix Seismic reps seek permits to continue searching for oil and gas in Juab
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By Myrna Trauntvein
Times-News Correspondent
Work will continue in Juab County this summer as geologists continue to search for oil and natural gas in the area near Levan.
Russ Nielsen and Clark Gentry, representing St. Croix Seismic, met with county commissioners seeking a general use permit to allow the work to go forward in the south range, by Yuba and at Chicken Creek.
“We have the permission of the landowners and the state trust lands,” said Nielsen.
Stakers and flaggers will be the first on scene.
The reflection seismic method is used at the Earth’s surface to image rock structures and estimate rock types that might form underground oil and gas reservoirs.
The reflection seismic method is based on measuring the time that it takes for sound waves to travel from a seismic source (for example a man-made explosion) through the earth to a rock layer that reflects the sound back to a recording device.
It is similar, in principle, to medical imaging methods that image the inside of a human body, such as NMR and Ultrasound scanning.
“We will use some dynamite,” said Nielsen.
The small underground explosions will consists of 10-pound charges but most the work will be done by a seismic vibration truck.
Seismic signals are induced by a vibration truck that delivers three 10-second sweeps that cover the 25 to 250 Hz range. Geophones are spaced every 8 feet; two geophones are used at each location for redundancy and signal strength. The vibration truck conducts sweeps along the geophone line at 16-foot intervals, making this a time-consuming process.
With this setup, the geophysicists can interpret seismic reflections from beds 1000 feet below the surface. Background noise is always a chief concern when conducting seismic surveys. The usual difficulties are noise from power lines, livestock near the geophones, first arrival waves.
The work is being done for Pioneer Natural Resources, he said. Much of the work was taking place because of the Wolverine Mine.
“We have already eliminated one line,” said Nielsen.
A helicopter will be used to help move and drop bags, he said.
“We should be able to shoot four to five miles per day,” Nielsen said.
The crews plan to be on-hand for work in June and will need to be out by winter.
Seismic data does not directly identify the age of or type of rock. For this, it is necessary to match the seismic reflections with data from drilled wells and knowledge of rocks that can be seen at the surface. The process of labeling seismic reflections with specific rocks is “Interpretation.” It is usually done on a computer screen or with a 3D visualization system.
“It is because of Wolverine Gas and Oil’s great discovery in Utah’s Sevier County that we are doing this work,” he said.
Wolverine’s discovery well, the 17-1 Kings Meadow Ranch, hit nearly 500 feet of Navajo Sandstone pay in Utah’s Sevier County in late 2003.This well was completed and began producing in May 2004. A second well was completed in September 2004. These two wells are currently producing 1,600 BOPD and 160 BWPD. At that time, they had produced over 376,665 barrels of good quality, 40 degree gravity crude. The discovery well had produced 273,666 barrels.
“We have drafted a general use permit,” said Nielsen.
However, said Pat Ingram, county clerk/auditor, the county had a conditional use permit and a digging permit which the company would need to purchase rather than the general use permit.
The company will be crossing some county roads but will mark those roads while they are in use, for safety reasons.
“We are under bond,” said Nielsen.
The Wolverine seal is the middle Jurassic Arapian, a 5,500-foot mudstone with halite, gypsum and anhydrite layers. These layers are good reflectors, making seismic interpretation more difficult. The reservoir is the lower Jurassic Navaho, a 1,200-foot aeolian sandstone. They consider the source rock to be of Mississippian age whereas the previous paradigm was that it was the Permian Phosphoria. The trap is described as large scale fault-bend fold.
It is hoped that the work to be done in Juab County will show that the area has as much potential as does Sevier County.
The Juab County Planning Commission may need to be the ones to sign the permits.
“In the 1980s,” said LuWayne Walker, commissioner, “a sesimic crew left some dynamite behind. We had to go out and carry all of that out. There was 60 to 70 pounds.”
“We want you to be responsible with the dynamite and make certain that none is left lying around,” he said.
On December 22, 2003 the operators hit the Navaho Sandstone at 5,800 foot instead of the anticipated 7,200 foot. By December 24, they had 500 foot. of oil shows and had established the NAV1 reservoir with flow and correlation to the Rangely Weber Oil. The petrophysics of the discovery well are gross pay 487 foot, net pay 424 foot, aver-age porosity 12 percent and water saturation 38 percent. The permeability was reported as 100 mD, but they were unable to comment on how much natural fractures contribute to this permeability. Potential reserves are estimated at 75-200 million barrels for this 1,600 acre field, and they are hoping for 50 percent oil recovery. The finding costs were $5.5 million split among 10 partners. Estimated development costs for the field are $56 million.
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