ABSTRACT

Since the discovery of commercial gas and condensate from deeper Hosston sands below 15,000 ft at Bassfield field in 1974, the exploration effort seeking other similar reservoirs in the Hosston trend in south Mississippi continues to grow. From 1951 through 1970, a total of 32 new fields were discovered from Sligo/Hosston reservoirs: 30 being oil and 2 gas. However, in the last 10 years, from 1971 through 1979, 33 new fields were discovered, of which 28 are gas and 5 are oil. The striking relationship of more recent gas discoveries rather than oil is significant.

The increase in exloration activity for gas reservoirs was brought on by three major factors: the critical national energy shortage, the favorable success of finding commercial gas below 15,000 ft and the continued increase in the value of an MCF of gas, which skyrocketed from 15-20 cents per MCF prior to the early seventies to more than $3 per MCF in recent months. A series of very fine grained tight sandstones are present in the top 1000 ft of the Hosston Formation. The most favorable objective is the Booth Sand found about 600 ft below the top. However, other sands (above and below) have recently been proven to be equally favorable in distribution and thickness, as well as productivity. Prductive Hosston sands have a porosity range from 7 to 15%; permeability ranges up to 1000 millidarcies and although occasionally may be higher, generally averages in the low hundreds.

Many of the fields produce formation water along with gas and condensate having 100,000 to 160,000 ppm chlorides. Water yields vary from less than 1 BBL./MMCFG to 115 BBL./MMCFG. Condensate yields vary from less than 1 BBL./MMCFG to 80 BBL./MMCFG. Productive sand thickness varies from 5 to 70 ft. Commercial production depends more on sufficient permeability than net thickness of pay. Flow rates in some of the better fields have sustained production of more than 4 MMCFG per day per well. Recoverable reserves per 640 acre unit for an average Hosston reservoir having 20 ft effective pay will vary between 5-9 BDFG and 100-200 MBC.

As long as operators continue to find new fields of this magnitude, the efforts will continue to escalate and indications are that the future still looks encouraging for many more years to come. We have only begun to "scratch the surface".