Report on the Mamou Field Pressure Maintenance Project

The Mamou Field, located in Evangeline Parish, La., is an elongatedanticlinal structure on the downthrown side of a major east-west fault with oiland gas production from the upper part of the Wilcox formation. Two mainproducing horizons occur at an approximate depth of 11,500'Ft and have beendesignated the Morein sand and the Deshotels sand. The upper sand (Morein) had an original bottom-hole pressure of 6,788 psig, which is some 1,500 psi above the normal pressure for that depth. Oilproduction with high gas/oil ratios and fluid analyses giving high shrinkagefactors prompted a study of the reservoir in its early stages. The resultsindicated a closed reservoir producing under solution gas drive with lowexpected ultimate oil recovery. The early study of the Wilcox formation and its contained hydrocarbonsresulted in the presentation of the data to the Department of Conservation ofthe State of Louisiana, with suggestions for field rules and a request forpermission to inject extraneous water into the Morein sand. The water injectionplans eventually led to complete unitization of working and royalty interests, to the construction of a gasoline plant, and to a central tank batteryinstallation for the field. Deshotels sand wells were reworked to the Moreinsand, and the water injection system was installed and ready for continuousoperation in the early part of 1949. The injection of water was started in timeto arrest the bottom-hole pressure decline at or near the bubble-pointpressure. This injection was calculated to increase the ultimate recovery andto conserve natural resources. Pressure maintenance, the extraction of LPGproducts, and the sale of residue gas (early 1950) represent an attempt toproduce an oil field with utmost efficiency. Introduction The two principal Wilcox oil horizons in the Mamou Field are the Morein sandand the Deshotels sand, occurring at 11,500'Ft and 11,700'Ft subsea, respectively. Minor oil production has been encountered in Morein stringersands. (Fig. 1.) This paper deals only with the Morein sand, which is blanket over the MamouField. It is, however, segmented by the northwest-southeast "E" faultas shown in Fig. 2. The west segment is the area involved in the waterinjection pressure maintenance program. To date the east segment has operatedlargely under the influence of a strong water drive. The paper presentsbrief history of field development,resume ofreservoir conditions which led to the decision to inject extraneous salt waterinto the principal producing horizon, andsummary of reservoir analysisand performance. T.P. 3192