About This Item
Share This Item
This report reviews the history of exploration on the Nesson anticline leading to the discoveries of the Beaver Lodge and Tioga fields. The point is made that the discoveries were the result of good geological and geophysical work combined with economics, geology, and good fortune.
The structure of these fields is thought to be due to faulting in the basement which has been intermittently active since Ordovician time. Indirect evidence also suggests cross faulting to the main Nesson anticline trend.
The producing reservoirs are now entirely in porous zones in the upper part of the Mission Canyon formation of the Madison group of Mississippian age. Productive reservoirs are known in the formations of Devonian and Silurian age although they are not producing at present. The Mission Canyon formation is light gray to brownish gray limestone with oolitic and fragmental to finely crystalline texture. The porosity is most marked in the upper 200 feet of the formation.
The reservoirs of the Beaver Lodge and Tioga Madison pools appear to be water-drive and possible gas-expansion types. The reservoirs are still above bubble point and no secondary gas cap is believed to be forming. Gas-oil ratio for both fields averages about 1,100:1, and reservoir pressures at present are 3,270 for Beaver Lodge and 3,188 pounds for Tioga. Reserves in the Mission Canyon pay for Beaver Lodge are estimated to be 155 million barrels; for Tioga 57 million barrels. API gravity of the oil in Beaver Lodge is 43.1°; in Tioga 42.5°. The MER of the fields is not known positively, but it has been suggested that the MER for Beaver Lodge is 15,000 barrels daily and a MER of 10,000 barrels per day for Tioga.
Conservation laws were in effect when these fields were discovered and the fields are being developed along sound lines of conservation. Production is limited to an amount which does not exceed the reasonable market demand.
End_of_Article - Last_Page 530------------