East Flour Bluff (Deep) Cycling

The East Flour Bluff (Deep) Field is composed of a series of abnormal pressure gas reservoirs. A production test of the J-55 zone indicated a condensate yield of more than 100 BPM. Laboratory analysis showed that the dew point pressure was near the 7800 psi reservoir pressure and indicated severe retrograde behavior. Initial production from the zone, which reduced the reservoir pressure to 6800 psi, confirmed the analysis as condensate recovery dropped to 80 BFM. An additional zone was tested and found to have initial condensate yield of 45 BPM. This paper describes how cycling operations were evaluated. Reservoir performance calculations were made for natural depletion and for several possible cycling cases using a compositional reservoir simulator. In these calculations the B-W-R equation of state was used to predict phase behavior. Economic analyses of these cases combined with anticipated deliverability requirements for depletion of area reserves under the existing gas sales contract resulted in selection of the optimum cycling plan. Of interest is the flexibility designed into the compressor installation which is capable of high pressure injection as well as low pressure sales compression without requiring recylindering. Introduction The East Flour Bluff (Deep) Field is composed of 13 abnormal pressure gas reservoirs. Production is from Marine Frio sandstones which Production is from Marine Frio sandstones which occur from 9,000 to 11,000 feet subsea. The field is located in the Laguna Madre waterway near Corpus Christi, Texas, as shown in Fig. 1. Gas from this field is committed for sale along with gas from the Flour Bluff, East Flour Bluff, and Pita Island Fields. All leases in the East Flour Bluff (Deep) Field are included in a single royalty unit. In mid-1968, the East Flour Bluff (Deep) J-55 reservoir was tested and found to have an original yield of 102 barrels of condensate per million standard cubic feet of gas produced. Laboratory analysis of a recombined gas sample showed a dew point close to the original reservoir pressure of 7800 psi and indicated severe retrograde behavior. Subsequent production from this reservoir indicated a dew production from this reservoir indicated a dew point of about 7500 psi; condensate yield has point of about 7500 psi; condensate yield has dropped to 80 BPM at a reservoir pressure of 6800 psi. The other major reservoir, the J-77, was tested and found to contain a 45 BPM gas condensate. From these results, it was apparent that gas cycling of these reservoirs should be evaluated in an attempt to maximize condensate recovery.