EXPLORATION Salt dome discoveries mounting in Mississippi

Rick L. Ericksen
Mississippi Office of Geology
Jackson

Exploratory drilling around piercement salt domes in Mississippi has met with a string of successes in recent months.

Exploration of these salt features is reported to have been initiated through the review of non-proprietary, 2D seismic data and subsurface control. This preliminary data and work were then selectively upgraded by the acquisition of additional, generally higher quality, conventional 2D seismic lines.

This current flurry of successful exploration and ensuing development drilling by Amerada Hess Corp. on the flanks of salt domes in Mississippi has resulted in a number of significant Hosston discoveries/producers at (Fig. 1) [26004 bytes]:

• Carson salt dome in Jefferson Davis County,

• Dry Creek salt dome in Covington County,

• Midway salt dome in Lamar County,

• Monticello salt dome in Lawrence County, and

• Prentiss salt dome in Jefferson Davis County.

The resulting production from these fields is gas and condensate, with wells being completed on 640 acre production units.

The trap, the problem

The trapping mechanism for this play is relatively simple-pre-existing, potential hydrocarbon reservoir beds are juxtaposed against the caprock/salt face of the salt diapir during salt movement and prior to hydrocarbon migration. The primary problem associated with seismically-based oil and gas exploration around these salt piercement features is the resulting high angle dip (30-70°+) of surrounding strata.

Without going into great detail, the following will provide an idea of why seismic imaging of these features has been so difficult and has not been totally achieved in most cases.

For example, in order to correctly seismically image strata at 16,000 ft with dips of 65° around a piercement salt dome one would need to have an offset of over 34,000 ft or nearly 6.5 miles to image in one plane, on one side of the dome. Further, to build sufficient fold would require at least another mile in addition to the 6.5 miles already required. So in total, to begin to evaluate, with a 2D seismic line, both sides of a salt piercement whose areal extent is approximately 1 mile in diameter would require roughly 16 miles of survey.¹

To my knowledge this has never been done, resulting in the relatively high risk nature of exploration around these features. If one were to image a salt piercement feature, assuming evaluation dollars were unlimited, a 3D seismic survey would be desired.

Using the same scenario as previously outlined for one 2D line, a 3D survey of the same feature would require a seismic grid of approximately 16 by 16 miles or 256 sq miles.

The resulting cost of this survey, assuming $50,000/sq mile in seismic acquisition and processing costs, would be on the order of $12.8 million and obviously would not be cost effective at today's prices. In addition to the difficulties already noted, problems may also be caused by side-swipe (out-of-plane imaging), diffractions associated with the salt diapir itself, as well as difficulties encountered in seismic imaging where salt overhangs may exist.

A more perplexing problem exists that may be tantamount to all of the seismic problems associated with exploration around piercement salt diapirs. That problem is the potential for reservoir compartmentalization due to the possibility of a myriad of radial faults and/or fractures created as the salt diapir pierced through the relatively competent strata. This potential will be evidenced only through the passage of time and production.

Previous exploration

Shell Oil Co., EP Operating Co. (Enserch), and Oryx Energy Co. conducted recent exploration around piercement salt features prior to Amerada Hess' activity.

The first of this activity resulting in commercial production on the flank of a piercement salt dome was Camp Shelby field, which Shell drilled in 1972, at Cypress Creek salt dome in Perry County (Fig. 1) [26004 bytes], No. 12. Shell encountered commercial production in the Tertiary Clayton and Lower Cretaceous Paluxy formations and also tested the Hosston formation at the rate of 169 b/d of oil, deemed noncommercial. As of December 1995, Camp Shelby has produced 353,681 Mcf of gas, 932,041 bbl of oil, and 274,419 bbl of water from Tertiary and Lower Cretaceous reservoirs.

EP's involvement in drilling on the flanks of piercement salt domes includes the discovery of Lower Cretaceous production at West Raymond field in Hinds County (Fig. 1) [26004 bytes], No. 38. West Raymond field, on the southwest flank of the Oakley salt dome, is structurally the result of salt movement and was delineated and drilled on the basis of 2D seismic and subsurface control.

EP discovered the field in 1985 with the 1 Prassel Trust 28-15, in 28-5n-3w. The well was completed from perforations at 11,743-818 ft and was swabbed at the rate of 41 b/d of 37.9° gravity oil with a trace of water from Rodessa A sand. As of December 1995, West Raymond has produced 1,712,759 Mcf of gas, 2,105,275 bbl of oil, and 297,765 bbl of water from multiple Lower Cretaceous reservoirs.

After most of the development drilling had been completed at West Raymond, EP shot a 3D seismic survey over the area to determine whether additional development drilling was warranted. The interpretation of the resulting 3D survey resulted in drilling of several more wells.

Also related to the Oakley salt dome are Oakley Dome and North Oakley Dome fields, which established Lower Cretaceous production. Oakley Dome is located in a southeastern fault block and North Oakley Dome is located on the northern flank of the dome in a horst fault block.

Oakley Dome has produced 28,719 Mcf of gas, 93,429 bbl of oil, and 29,174 bbl of water through December 1995. It is of interest to note that Oakley Dome had no production in 1995. North Oakley Dome has produced 10,316 Mcf of gas, 118,415 bbl of oil, and 510,010 bbl of water through December 1995.

Oryx (Sun) was involved with discoveries at Leaf River field in 1985, which is on the flank of Dont dome in Covington County (Fig. 1 [26004 bytes] No. 14), and Free State field in 1989, which is on the flank of Centerville dome in Jones County (Fig. 1 [26004 bytes], No. 10). As of December 1995, Leaf River has produced 6,876,565 Mcf of gas, 428,238 bbl of oil, and 23,911 bbl of water, and Free State has produced 3,520,121 Mcf of gas, 740,499 bbl of oil, and 39,675 bbl of water.

Fig. 2 [48532 bytes] is a seismic line shot across Centerville dome where Free State field is located. As the Centerville salt diapir punched through the overlying strata, pushing up the surrounding beds and causing them to dip away from the dome in all directions along with radial faulting and fracturing. Oryx drilled the discovery well on the south flank of Centerville dome.

The 1 Frankie Smith discovery was completed from overall Hosston perforations at 15,906-16,200 ft. The well flowed at the rate of 4.425 MMcfd of gas and 1,231 b/d of 42° gravity condensate on a 32/64 in. choke with 1,780 psi FTP and 600 psi casing pressure. GOR was 3,595-1.

As of December 1995 this well has produced 3,241,178 Mcf of gas, 663,874 bbl of condensate, and 25,769 bbl of water.

Recent discoveries

The following is an alphabetical listing of the recent Amerada Hess activity that includes pertinent information with respect to well locations, initial production, perforation interval(s), and other data.

Carson Dome field

The Carson Dome discovery well was the Amerada Hess 1 Lula Turner 24-10, in 24-7n-18w, Jefferson Davis County (Fig. 1 [26004 bytes], No. 8). Carson Dome field (Figs. 3-4) has been defined as being separate and distinct from Carson field, which was Shell discovered in 1977.

The 1 Lula Turner 24-10, was completed from overall perforations at 15,195-325 ft in Hosston and flowed at the rate of 3.156 MMcfd of gas and 499 b/d of condensate with a 6,325-1 GOR. The well was later recompleted from overall perforations at 14,706-15,325 ft and flowed 4.543 MMcfd of gas and 625 b/d of condensate on a 24/64 in. choke with 2,290 psi FTP and GOR 7,269-1. The well was again recompleted in Hosston at 14,656-696 ft flowing 2.528 MMcfd and 205 b/d of condensate on a 24/64 in. choke with 1,180 psi FTP and 12,332-1 GOR.

Fig. 4 [28541 bytes] shows the relationship of the now abandoned Shell 1 Amoco-Sabine, the discovery's original and sidetrack wellbores, and the salt face of the dome.

As previously noted, Carson Dome field is just east of and adjacent to Carson field, which produced from three wells, all from Hosston. The closest well to production at Carson Dome is the Shell 1 Amoco-Sabine, in SE NE 23-7n-18w. The discovery well for Carson field, it was productive from Hosston perforations from 15,076-084 ft. The well was initially completed flowing at the rate of 2.4 MMcfd of gas and 216 b/d of 48.1° gravity condensate on a 13.5/64 in. choke with 2,820 psi FTP and 11,111-1 GOR.

To date Amerada Hess has drilled one producer, the discovery well, on the south flank of the dome and one dry hole, the 1 John Bass Heirs, whose surface location is 1,500 ft FNL and 2,400 ft FWL of 18-7n-17w. The dry hole was sidetracked multiple times before being plugged and abandoned. Amerada has proposed to drill the 1 Hathorn in 13-7n-17w (Fig. 3 [27528 bytes]).

Dry Creek Dome field

The discovery well at Dry Creek Dome field was completed in the Hosston in 1993 (Fig. 1 [26004 bytes], No. 15). To date three additional producers have been completed-two in Hosston and one in Paluxy (Fig. 5 [26825 bytes]). The discovery well, the 1 Minerals Management 28-1, in 28-8n-17w, Covington County, was completed from perforations at 14,234-290 ft, 14,381-419 ft, and 14,516-530 ft.

The well flowed 3.313 MMcfd of gas, 209 b/d of 50.5° gravity condensate, and 14 b/d of water on a 14/64 in. choke with 3,330 psi FTP and 15,852-1 GOR. Permeability has been reported to range from 0.5-2.0 md, porosity is 10%, and connate water saturation 20%.2

Fig. 6 [26965 bytes] is a diagrammatic cross-section of Dry Creek Dome field showing the dry offset well, the Strata Energy 1 Booth, and the productive 1 McRaney in relation to the Dry Creek salt dome.

The second well, also a Hosston producer, is the 2 Minerals Management Inc., whose surface and bottomhole locations are in SW NW 27-8n-17w. The 2 Minerals Management well is about 1/4 mile south-southeast of the discovery well, the 1 Minerals Management 28-1. The No. 2 flowed from perforations from 14,532-704 ft at the rate of 4.724 MMcfd of gas and 240 b/d of 51.8° gravity condensate with no water reported on a 10/64 in. choke and with 4,330 psi FTP. GOR was 19,683-1.

The third Hosston completion was the Amerada Hess 1 Willie Von McRaney Sr., with surface location in NW NW 28 and bottomhole location in NE NW 28-8n-17w. The McRaney well was completed in Upper Hosston from perforations at 14,829-864 ft, 14,941-980 ft, and 14,984-15,018 ft. It flowed 6.619 MMcfd of gas and 398 b/d of 48.7° gravity condensate with no water on a 16/64 in. choke with 4,005 psi FTP and GOR of 16,613-1.

Paluxy production was established at Dry Creek with the Amerada Hess 1 Board of Education in SW SW 16-8n-17w from perforations at 12,068-116 ft. The well flowed 1.319 MMcfd of gas and 249 b/d of 39.6° gravity condensate on a 10/64 in. choke with 3,377 psi FTP, 90 psi casing pressure, and 5,297-1 GOR.

The well was drilled to TD 15,715 ft but did not encounter any commercial shows in Hosston and was plugged back to 12,478 ft. The 1 Board of Education reservoir discovery is 11/4 miles north-northwest of the 1 Willie Von McRaney well.

Amerada Hess has drilled only one dry hole in the field area, the 1 FICB, whose proposed bottom hole location was 1,100 ft FSL and 1,150 ft FWL of 15-8n-17w. The well was proposed for 16,500 ft but was drilled to a measured depth of 17,230 ft. After logs were run, the well was sidetracked to a depth of 16,383 ft and subsequently plugged and abandoned.

Dry Creek Dome has produced a cumulative total of 4,641,879 Mcf of gas, 200,707 bbl of condensate, and 1,847 bbl of water since its discovery through December 1995. According to the most recent reports, there is currently no drilling activity at Dry Creek Dome.

Midway Dome field

Amerada Hess discovered Midway Dome field at the 1 Allar Co., with surface location in SW SW 33-4n-15w, Lamar County and bottomhole location in the NW SW 33 (Fig. 1 [26004 bytes], No. 33). The Allar well was completed flowing 3.462 MMcfd of gas and 72 b/d of 47° gravity condensate with no water reported on a 10/64 in. choke with 5,503 psi FTP from Hosston perforations at 15,770-798 ft and 15,808-828 ft. GOR is 48,083-1.

Another reported test for the well was on a 14/64 in. choke with the resulting flow rate of 6.030 MMcfd of gas and 170 b/d of condensate with 5,160 psi FTP and 35,471-1 GOR.

The 1 Allar was drilled on a 640 acre gas unit taking up all of 34-4n-15w and located 9 miles northwest of Purvis and 13/4 miles northeast of the Tatums Camp field discovery well. The discovery well at Tatums was the Sun Oil Co. 1 Ross Beatty et al., in NW NW 9-3n-15w. The 1 Beatty was completed from Hosston perforations at 15,770-802 ft flowing 1.863 MMcfd of gas and 99 b/d of 49° gravity condensate through an 8/64 in. choke with 4,880 psi FTP and 18,818-1 GOR.

It was reported that Amerada Hess completed its directionally drilled confirmation well, the 1 Patterson, at Midway Dome flowing 5.096 MMcfd of gas, 319 b/d of 48.5° gravity condensate, and 117 b/d of water through a 15/64 in. choke with 4,231 psi FTP and 1,675 psi casing pressure.3

The well was perforated in Hosston at 15,112-128 ft and 15,342-370 ft. The GOR is 15,975-1. The Patterson was drilled from a surface location in NW SW 32-4n-15w with a bottomhole location in the SW SE 32. The reported bottomhole location is roughly 3/4 mile northwest of the bottomhole location of the 1 Allar discovery well.

There has been no production reported from this field other than that produced during test as of late May.

Monticello Dome field

Monticello Dome field was discovered by the 1 Dake, in NE SE 25-7n-10e, Lawrence County, on the southeasterly flank of the Monticello salt dome (Fig. 1 [26004 bytes], No. 34). The 1 Dake is 21/2 miles west of Monticello field and 11/2 miles west of the town of Monticello. The well was permitted and drilled on a 640 acre unit comprised of the southern three-quarters of section 25 and the northern one-quarter of section 36, same township and range.

The 1 Dake initially flowed at a reported 1.8 MMcfd of gas and 320 b/d of condensate on a 14/64 in. choke with 2,000 psi FTP and 5,625-1 GOR from unreported perforations in Lower Hosston.4

The well was later recompleted from Hosston perforations at 17,200-280 ft and tested at the reported rate of 1.7 MMcfd of gas and 250 b/d of condensate on a 14/64 in. choke with 2,000 psi FTP and 6,800-1 GOR.5

On official completion the Dake flowed at the rate of 1.351 MMcfd of gas and 293 b/d of condensate on a 12/64 in. choke with 2,460 psi FTP and 275 psi casing pressure from Hosston at 17,204-270 ft. GOR was 4,611-1. Monticello Dome field reported three months of production last year after coming on line in October, totaling 57,036 Mcf of gas, 19,168 bbl of condensate, and 21 bbl of water through December 1995.

As noted, the 1 Dake was drilled approximately 21/2 miles west of Monticello field, and the Louisiana Land & Exploration Co. 2 R. V. Dickey, in 28-7n-11e, tested noncommercial and the hole was abandoned in November 1981. The discovery well for Monticello field was the Inexco 2 James George, in 14-7n-21w. It was completed in June 1976 for 2.1 MMcfd of gas, 80 b/d of 51° gravity condensate, and 85 b/d of water on an 18/64 in. choke with 1,250 psi FTP and 26,250-1 GOR. Monticello field has produced 43,696,244 Mcf of gas, 772,866 bbl of oil, and 489,903 bbl of water as of December 1995.

Prentiss Dome Field

The Amerada Hess 1 Rankin, with surface location in NW NW 26 and bottomhole location in the SW NW 26-7n-19w, Jefferson Davis County, is the discovery well for Prentiss Dome field (Fig. 1 [26004 bytes], No. 42). The drillsite for the 1 Rankin is 31/2 miles south-southeast of the town of Prentiss, four miles southeast of Whitesand field, and 21/2 miles north of South Prentiss field.

The 1 Rankin tested at the rate of 6.949 MMcfd, 235 b/d of 51.5° gravity condensate, and 24 b/d of water on a 16/64 in. choke with 4,839 psi FTP from Hosston perforations at 16,444-624 ft and 16,650-765 ft. GOR is 29,570-1.

As of December 1995, the first month for which production is reported, Prentiss Dome produced over the reported period of five days 17,500 Mcf, 821 bbl of condensate, and 46 bbl of water.

As noted, South Prentiss field is located south of the 1 Rankin discovery well at Prentiss Dome field. The discovery well for South Prentiss field was the Pruet & Hughes 1 U.S. Lumber Co. Unit 2-14, in 2-6n-19w. The 1 U.S. Lumber well was completed in Hosston-age "Harper sand" from perforations at 16,122-135 ft and flowed at the rate of 685 Mcfd of gas and 40.4 b/d of condensate through an 8/64 in. choke with 2,200 psi FTP and 16,955-1 GOR.

South Prentiss field has produced 1,374,294 Mcf of gas, 22,272 bbl of oil, and 1,858 bbl of water since its discovery through December 1995.

Conclusions

Amerada Hess' impressive list of discoveries has generated intense interest around the remaining salt domes in Mississippi.

At least 40 domes have received little exploration.

Amerada Hess came up emptyhanded in early June due to mechanical difficulties at a 17,000 ft rank wildcat in northeastern Lawrence County at the previously untested Grange salt dome (Fig. 1 [26004 bytes], No. 21). It has development wells planned on several of its discoveries and has a well planned at Free State field associated with the Centerville salt diapir.

Overall it would appear that judicial application of 2D seismic data across these features has been well worth the time and money spent. As for ultimate recoveries and the overall potential for reservoir compartmentalization, only time will tell.

Acknowledgments

The author thanks Stanley C. Thieling and Stephen D. Champlin, both with the Mississippi Office of Geology, for allowing the use of unpublished data. In addition I also thank Michael Bograd, with the Office of Geology, who provided editorial/grammatical assistance and personnel with the Mississippi Oil & Gas Board who helped the author to obtain a portion of the information utilized in this article.

References

1. Morrison, C. A., geophysical consultant, personal communication, May 1996.

2. Mississippi Oil & Gas Production Annual Report 1994, Mississippi State Oil and Gas Board, 1995.

3. Southeastern Oil Review, Vol. LIX, No. 3, April 8, 1996, p. 1.

4. Southeastern Oil Review, Vol.. LVIII, No. 34, Nov. 20, 1995, p. 1.

5. Southeastern Oil Review, Vol. LVIII, No. 35, Nov. 27, 1995, p. 1.

Bibliography

Mississippi Oil & Gas Production Monthly Reports, January-December 1995.

Warner, J., and Moody, J., "The Flank Shallow Piercement Plays of Mississippi," Transactions, Gulf Coast Association of Geological Societies, Vol. 41, 1991, pp. 607-608.

The Author