Jack S. Moody
Mississippi Bureau of Geology
Jackson, Miss.
How would you like to find a new trend where gas wells can have more than 5 bcf/well of reserves and oil wells yield more than 100,000 bbl from easy drilling to no deeper than 4,000 ft?
Such is the circumstance for the long overlooked Oligocene Frio of southern Mississippi.
The term Frio has long brought dollar signs to the imaginations of Louisianans and Texans, but it is only beginning to register such in the Magnolia state.
The term "Frio" is used to represent the Upper Oligocene sediments that lie between the underlying Vicksburg group and overlying Heterostegina zone.
Current thesis work by Don Marlin at Louisiana State University, Baton Rouge, presents Frio stratigraphy in Louisiana's Florida Parishes, those just south of Mississippi.
Mississippi began romancing these stones in 1969 with the discovery of Frio gas in White Castle field, Wilkinson County. In 1982 commercial Frio oil began producing in Stamps field, also in Wilkinson County. By 1988 eight small Frio fields were producing in southern Mississippi.
In retrospect this time presented an interesting opportunity for the imaginative explorationist. Here was an area or trend with scattered production (the hydrocarbons were in the system), excellent rocks (the plumbing was good), shallow drilling, and available acreage.
About the only thing lacking was aggressive exploration that yielded significant results.
ARKLA ADDS IMPETUS
Aggressive exploration and significant results have now been furnished by Arkla Exploration Co.
Arkla was in the area playing the Tuscaloosa when something in Frio caught its attention. That something is believed to be a seismic bright spot similar to those visible in Fig. 1.
The right company in the right area with the right technology has elevated the Frio play to prominence.
To date it appears that Arkla has been able to pursue its Frio drilling with a 60% success ratio. Within these successes are individual wells with reserves of 5-6 bcf/well.
There are multiple producing sands with porosities of 30-32% and permeabilities in the darcies. Individual sands have had as much as 30 ft of gas pay.
What would arm-waving economics reveal about the merits of this play?
Consider the case for one of the 5 + bcf wells using costs of $70,000 for a dry hole and $120,000 for a completed well. Assume 80% net revenue interest, 7% severance tax, 10% operating expense, and $1.50/Mcf gas.
The 5 bcf yields a gross revenue of $7.5 million. Subtracting the severance tax ($525,000), royalty ($1.5 million), drilling and completion cost ($190,000), and operating cost ($750,000) leaves a net profit of $4,535,000.
Using a prospect cost of $200,000, which includes seismic, land, drilling, and so on, one could drill 22 prospects with the net profit of one of these good wells.
THREE SUBTRENDS
The overall Frio trend can be divided into three subtrends based on the type of production.
The southernmost Frio production in Louisiana is found along the northernmost growth faults and yields gas and condensate. This is the only area of this trend that is structurally controlled.
The next subtrend produces dry gas and is the area where Arkla has had so much success.
The gas play is in southernmost Wilkinson and Amite counties, Miss., and the adjacent portion of the Florida Parishes.
An important point for consideration is the shallow gas blowouts that occurred in Waveland field, Hancock County, Miss. What if that gas came from Frio?
The oil subtrend is just north and west of the gas play. There may be a number of opportunities for subsurface prospects in this part of the trend.
Many wells were drilled in the Wilcox trend in which the operators never considered Frio as a potential reservoir. The commercial production at Stamps field, Wilkinson County, was behind pipe for more than 10 years.
The Frio play is on, and the early results are impressive. Arkla has a number of field discoveries, and Independence field has 13 wells and is still being developed.
Some individual wells are projected to produce more than 5 bcf of gas from shallower than 4,000 ft. The oil trend has individual wells that have produced more than 150,000 bbl of oil from less than 3,000 ft.
Copyright 1990 Oil & Gas Journal. All Rights Reserved.
