Abstract

The Fairfax Foster Sutter No. 2 well located in the East Franklin area of St. Mary Parish and the Beulah Simon No. 2 well located in the Kaplan area of Vermilion Parish, Louisiana were the first successful tests of Parish, Louisiana were the first successful tests of geopressured-geotherman (Geo 2) aquifers under the Well of Opportunity (WOO) program. Gruy Federal assumed the Fairfax Foster Sutter operation on March 8, 1979 when the operator abandoned attempts to discover conventional hydrocarbons at a total depth of 16,340 ft. The Simon No. 2 well was acquired under similar circumstances approximately one month later at a total depth of 15,265 ft.

In both tests, the objectives were all accomplished and data were obtained which will contribute to the overall assessment of the geopressured-geothermal resource of the upper Gulf of Mexico basin. In both instances, the gas solubilities (22.8 and 24.0 scf/bbl) indicated that the waters were saturated with gas at reservoir conditions. The produced water was more saline than expected (190,000 mg/l in one instance, 104,000 mg/l in the other). {The high concentrations of dissolved solids in these waters created a scaling problem that required significant attention and will problem that required significant attention and will have to be addressed in future tests.}

TEST OBJECTIVES

The Well of Opportunity program was intended to take advantage of non-productive oil and/or gas wells for geothermal-geopressured testing at a much lower cost than the alternative of drilling a well. Utilization of the Geo 2 resource requires a reasonably extensive reservoir with petrophysical properties capable of sustaining production at high rates (40,000 bbl/day). The test objectives for the WOO wells were essentially as follows:

  1. Determine the reservoir geometry and extent.

  2. Assess the petrophysical properties of the Geo test horizon, in particular permeability, porosity and formation damage resulting from the drilling and completion operations.

  3. Obtain chemical analysts of the gas and brine produced.

Since the solution gas is expected to comprise a significant portion of there source, measurements of the solubility of the gas in the brines was deemed essential. The constituents and caloric value of the dissolved gas, as well as the thermal content of the brine was also of interest. 4) Assess the disposal problems to be expected in the development of the resource. The range of potential problems varied from fluid incompatibility to aquifer charging.

GEOGRAPHY AND GEOLOGY

This general area occupies a portion of the Gulf Coast geosyncline, a large arcuate depositional geosyncline extending from Florida westward to Mexico (Figure 1).

Sediments of recent to Cretaceous age have been encountered as well as diapiric salt of Jurassic age. The Tertiary, from which most oil and gas is produced, consists almost exclusively of a regressive sequence of sands and shales. Oil and gas accumulations are found most often in sand reservoirs deposited in an inner to middle neritic environment, ranging in age from Miocene to Oligocene.

The area is a south dipping monocline with regional dips of about 150 feet per mile at 10,000 to 12,000 ft. Interruptions of this dip are caused either through vertical uplift by flowage (salt or shale), by gravity slumping along normal faults, by differential compaction between sand and shale bodies, or by a combination of the three.

Salt domes are formed by the movement of salt from its "mother" layer, the Louann Salt, which underlies the area at an estimated depth of at least 40,000 feet. Shale also acts diapirically, and many salt domes are complicated by shale flowage. Faulting associated with salt domes is generally complex. On piercement domes in which the salt has intruded most piercement domes in which the salt has intruded most of the sediments, radial faulting predominates. On deep seated domes, "graben" faulting is a more common feature.

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