The largest naturally occurring CO2 accumulation east of the Mississippi River is currently under exploitation northeast of Jackson, Miss.
Jurassic age sandstones (Norphlet and Haynesville) at depths of 14,000 to 18,000 feet produce food grade CO2 for tertiary operations in Mississippi, Louisiana and southeast Texas. Three trillion cubic feet (TCF) of sweet CO2 has been produced northeast of the Jackson Dome area with an additional 4 TCF proved.
Smackover carbonates and sandstones in the equivalent depth range could also contribute an additional 5-7 TCF; however, H2S concentrations of 2,000 to 7,000 ppm are common in Smackover reservoirs.
These Jurassic reservoirs were sourced during Late Cretaceous time with the piercement of an igneous intrusion referred to as the Jackson Dome.
Early Exploration History
The interior salt basins of east Texas, north Louisiana, and south-central Mississippi proved prolific for hydrocarbon generation and entrapment of large Jurassic age oil and gas pools (figure 1).
Significant Smackover and Buckner age oil discoveries in southern Arkansas and northern Louisiana during the late 1930s to the early 1950s helped push the Jurassic wildcat activity into central Mississippi in the early 1950s.
This area, with down-to-the-basin faults and salt-supported, four-way closures served as obvious areas to continue the Jurassic exploration trend. The Lower Smackover formation is one of the Gulf Coast Interior Basin’s major source rocks. The Upper Smackover carbonate play continues to be the most prolific carbonate reservoir play in the interior salt basins.
Before the 1950s, the oil industry was limited by the quality of seismic data that could be imaged due to poor reflectivity when recording below 13,000 feet.
Additionally, the thick fluvial deposits of the Cotton Valley sands above the Smackover section also hampered seismic data quality in this area. As low-fold common depth point (CDP) seismic data became available in the late 1950s, large deep Smackover structures were identified on 2-D seismic lines in Madison, Rankin, Scott and Yazoo counties in central Mississippi.
Early drilling of these structures identified an area in Rankin and Madison Counties as having highly pure CO2 in Jurassic sandstones and carbonate reservoirs. This CO2 sweet spot is specific to the northeast flank of the large volcanic feature known as the Jackson Dome.
Four wells drilled in the early 1950s helped to define this CO2 play. In 1950 and 1952 Conoco drilled the Cameron No.1 and Lee No.1, respectively, on the Virlilia anticline along the Madison/Yazoo county line. These more than 14,000-foot tests found the Smackover carbonates with porosity and permeability, but the drill stem test produced H2S and “non-burnable CO2 gas.”
In 1951, Lion Oil drilled the Denkmann No.2 on the Pisgah anticline in Rankin County. This more than 16,000-foot test discovered a 260-foot section of Norphlet sand with a 220-foot productive section that tested sweet CO2.
Shell would later use this test as the show well for their 1977 South Pisgah sweet CO2 discovery. In 1953 Loring Field was discovered by Carter Oil Company in northern Madison County. Carter Oil found Smackover Sandstones productive with 48-degree gravity condensate and a gas stream composed of 75-percent CO2. This two-well field ultimately produced 1 mmbo and 50 bcfg, according to state records.
Standard Oil acquired Carter Oil in 1960. The southern limits were defined in the late ‘60s by Shell’s exploration efforts on the Pelahatchie anticline, finding CO2 concentrations as high as 65 percent (figure 2).
Approximately 15 wells were drilled in these four counties during the 1960’s with most drill stem tests producing varying quantities of CO2, H2S and minor amounts of hydrocarbons.
With improved seismic resolution came increased interest in the area, with Chevron and Texas Pacific prospecting north of the Lion Oil test along the 20,000-acre closure now known as the Goshen Springs anticline.
Chevron’s 1963 attempt, whose surface location is now located under the Ross Barnett Reservoir, a recreational lake on the Madison-Rankin county line, blew out upon entering the abnormally pressured section just below the top of the Buckner carbonates and was junked and abandoned. This test would later serve as the seismic tie that would confirm an additional undrilled Norphlet structure now known as Dri Ice Field.
In 1967, Chevron’s second test, the Cox No.1 discovery well for Goshen Springs Field, logged more than 400 feet of productive Norphlet sand containing 99 percent sweet (food grade) CO2 (figure 3). Additional formations logged with significant CO2 volumes were the Smackover, Main Buckner and Haynesville sandstones.
During the same year, Texas Pacific Oil (acquired by Sun Oil Company in 1980) drilled the Yandell No.1 on a southwest satellite structure off the Goshen Springs anticline and was given the field name “Gluckstadt” after finding food grade CO2.
The Gluckstadt name came from the nearby community settled by German Catholic families in Madison, Miss. in 1905. (This German name translates to “Lucky Town” in English.)
This discovery logged hundreds of feet of CO2 in the abnormally pressured Norphlet Sands. These three wells, Denkmann No.2, Cox No.1, and Yandell No.1 identified a very large Norphlet sand pile or erg rich in sweet CO2 (denoted by red arrows in figure 3).
These drilling results also showed the Smackover formation to be heavily dominated by quartz-rich clastics and isolated carbonates.
By the late 1960s, with the area’s poor hydrocarbon exploration success and limited CO2 market, exploration moved southeast along the Smackover trend into Clarke, Jasper and Wayne counties where the carbonate ramps redeveloped and Smackover hydrocarbons were found and produced.
Beginnings of EOR: Shell Oil’s Operations
West Texas Permian Basin CO2 enhanced oil recovery (EOR) began in Scurry County, Texas in 1972. Shell Oil’s knowledge of the Jackson Dome area and the company’s asset base in southwest Mississippi were catalysts for EOR development on Mesozoic sandstones of Tuscaloosa age at Little Creek Field in Lincoln and Pike counties.
If EOR proved economic, Shell’s operated Mallalieu and Olive Tuscaloosa fields would follow Little Creek development. In addition, Shell’s operated fields of Weeks Island and East Bay Fields in south Louisiana would also be tested as EOR candidates.
Chevron had leased most of the crestal Goshen Springs acreage and had more than 20 possible well locations (figure 3).
In the mid-1970s, Shell’s leasing concentrated south and north of Chevron’s leasehold acquiring over 50,000 acres over nine proposed CO2 prospects.
Average terms of these CO2 leases were 10 years at $35 per acre and burdened with a one-eighth royalty. Shell drilled five structures finding CO2 in all and delineated South Pisgah and Hollybush Creek Fields’ sweet CO2 reservoirs with 10 wells during the late 1970s.
Estimated sweet CO2 reserves of 1 TCF were booked with 80 percent of the reserves in the normal pressure Haynesville sands at 15,000 feet. Cumulative deliverability rates of 250 million cubic feet of gas per day (MMcfpd) of CO2 were banked for Little Creek and Weeks Island testing.
Shell’s internal estimates for additional company-operated Gulf Coast CO2 EOR properties would require an added deliverability of 500 MMcfpd of CO2.
These volumes would be supplied from the development of Lone Pine, Central Fannegusha and the Leesburg discoveries (figure 3).
Pipeline construction to deliver the CO2 from the Jackson Dome source area to southwest Mississippi and continuing into south Louisiana’s Weeks Island Field was completed in the early ‘80s. A total of 188 miles of 20-inch pipeline was laid through Mississippi to Donaldsonville, La., followed by a 44-mile, 10-inch line to Weeks Island.
Completion of Little Creek unitization in 1981 was followed by Little Creek EOR in 1982. In conjunction with Shell’s EOR efforts in Mississippi, Pennzoil had drilled a Section 16 well in Goshen Springs Field in 1982 and laid a 42-mile, 8-inch pipeline to Tinsley Field, the second largest oil field in the state.
Chevron’s Cox well, drilled in 1967, finally went online in 1983 and also supplied CO2 to Tinsley Field (figure 4).
Generally low oil prices in the late 1980s and ‘90s limited EOR profitability. With the continued divestment of domestic oil properties by the major U.S. oil companies during this era, EOR from CO2 in the southeast and specifically Mississippi was reduced to less than 3,000 BOPD.
Lost Decade of the ’90s
Charles H. “Chuck” Simpson arrived on the scene in 1990 from Baton Rouge, La., and aggressively promoted a new pipeline from Goshen Springs field that would serve as a CO2 source for the prolific fields located in southeast Mississippi.
Fields targeted were Chevron’s Heidelberg, Exxon’s West Yellow Creek, Shell-Texaco’s Pachuta Creek, and Amerada Hess’s Eucutta Field. Both Chevron and Amerada Hess had internal studies transporting CO2 to southeast Mississippi. Amerada Hess had outlined their proposed CO2 pipeline into southeast Mississippi per 1989 correspondence (figure 4).
Simpson acquired new leases (10-year) under the entity of Cherokee Associates and took assignment of some Texaco leases in the two-well field of Goshen Springs. Goshen Springs at the time was estimated to contain more than 8,000 acres of productive area with recoverable reserves of food grade CO2 of 1.2 TCF.
Simpson’s group, Pisgah Partners, through Magna Carta LLC, controlled more than 4,000 acres over the productive limits of the field. In 1991, Simpson purchased the shut-in Cox No.1 from Chevron and by 1993 sold CO2 to Pennzoil at their Tinsley field. In 1996, Simpson sold the Cox and operations to Pennzoil and retained a working interest of 50 percent.
Low oil prices in the late ‘90s barred any interest in a CO2 pipeline to southeast Mississippi (figure 4). In 1997, Shell elected to abandon its tertiary recovery efforts in Mississippi and sold its CO2 properties to Air Gas Inc. for specialty gas marketing and dry ice manufacturing. In early 2000, Simpson negotiated lease extensions through 2005 in Goshen Springs from one of the largest mineral owners in Madison and Rankin counties.
Golden Age: Denbury and Hidden Treasuries
In February 2001, Denbury Resources Inc. purchased the CO2 production and pipeline assets from Air Gas Inc. for $42 million. This acquisition included the same properties that Shell Oil had sold to Air Gas Inc. five years earlier.
Denbury purchased 10 producing wells, three undeveloped discoveries, a 182-mile pipeline to Donaldson, La. and other related infrastructure. At the date of purchase, sweet CO2 proved developed producing (PDP) reserves were estimated at 800 BCF with a current production rate of 90 MMSCFD. Fifty-five percent, or 50 MMSCFD of this CO2 production stream was sold to commercial users and 40 MMSCFD was purchased by Denbury.
Denbury had purchased Mississippi’s first CO2 flood, Little Creek field, in 1999 from J.P. Oil Company Inc. This acquisition marked Denbury’s first venture into CO2 tertiary operations.
Denbury’s acquisition of Simpson’s interest in the Goshen Springs Field further consolidated their control of Jackson Dome’s CO2 reservoirs.
At the end of the first quarter of 2003, with compression facilities updated, deliverable rates of 250 MMSCFD were possible; with the completion of two new CO2 wells, PDP reserves of approximately 1.6 tcf were booked.
Over the last 14 years, Denbury has produced over 3 TCF of natural sweet CO2 from approximately 45 wells with nearly a billion dollars invested in CO2 production. To date, 11 CO2 fields have been developed and 10 are currently producing.
Denbury’s discoveries at Dri Ice, South Ross Barnett, Ophelia and Monroe Fields added an additional 3 TCF of recoverable reserves. Dry holes have been limited to four because of 3-D seismic data sets. Remaining PDP reserves are over 5.5 TCF with an additional 2.1 TCF possible. A CO2 pipeline infrastructure of over 480 miles has been laid for the redevelopment of 11 oil fields within the state of Mississippi.
Cumulative oil production from tertiary operations is over 100 million barrels for the state with an additional 250 million barrels possible under current pricing.
Currently, more than 50 percent of Mississippi’s oil production, or 31,000 bbl per day, is from CO2 tertiary operations.
One factor in Denbury’s early success was the understanding of CO2 deliverability in the abnormally pressured Norphlet reservoir. Production rates of 50 MMSCFD per well have facilitated the average 20-25 mcf per barrel net utilization rate for these Mississippi miscible and immiscible tertiary floods.
Denbury’s organic growth in the Mississippi oil patch helped fund their domestic operations into Texas, Montana and Wyoming. A company with total assets of $790 million in the fourth quarter of 2001 ended 2011 valued at $10.2 billion.
In 2010, Chuck Simpson, who had retained a 20-year contract at 20 MMSCFD from Denbury for sweet CO2 delivery, sold the contract to Tellus Operating Group. Tellus uses this CO2 for pressure maintenance and EOR projects at its Stampede, Raleigh (figure 5) and West Yellow Creek fields, respectively.
Unfortunately, as Shell experienced in the 1980s, the recent precipitous reduction in commodity prices constrains economic viability of many Mesozoic and Cenozoic CO2 tertiary floods in the Gulf Coast region. Gulf Coast CO2 net utilization rates are two- to three-times greater than West Texas net utilization rates.