The Producibility of Coalbed Methane from Wilcox Coals in Louisiana

Abstract

ABSTRACT The producibility model for coalbed methane contains six controls. They are: (1) gas content, (2) permeability, (3) tectonic and structural setting, (4) depositional setting, (5) hydrology, and (6) coal rank and gas generation. Gas content in Central Louisiana Coalbed Methane Basin (CELCOM) coals was proven in 1989 when the Torch Operating Company perforated the No. 3 Greer well Sec. 21, T14N-R4E. The well immediately began flowing gas (50,000 cfg/d and 65 bbls water/d). The #3 Greer flowed approximately 2.8 MMcfg over a three month period and was plugged. Permeability is indicated by the separation (approximately 2 ohms) of the 16 short normal and the 40 conductivity curves in most, but not all, e-logs. Strongly developed Spontaneous Self Potential (SP) in many e-logs further indicates permeability. Tectonic and structural setting: The CELCOM is situated between the Sabine Uplift and LaSalle Arch on the west-southwest, the D'Arbonne Platform on the northwest, and the Monroe Uplift on the northeast. This location effected control on the Wilcox depositional environments. Depositional setting: The coals of the CELCOM were likely deposited on top of abandoned delta sequences prograding gulfward. Hydrology: The coals of the CELCOM do not outcrop at the surface, and, therefore, are not recharged with percolating ground water which must be removed during production. The thick Cane River shale section overlying the Wilcox separates the brackish and fresh water sands of the Sparta and Cockfield from the saline waters of the Wilcox. The coals have been compacted through the burial process and the amount and type of contained water is not known, although it is probably salt water. Coal rank and gas generation: Cores taken in equivalent sections in Concordia Parish, Louisiana, reveal a vitrinite reflectance value of Ro = 0.45, a coal rank of bituminous.