Abstract

The Monias Field is the largest Halfway Formation gas field in northeast British Columbia. The field was discovered in 1975 by the re-entry of the 14-15-82-21 W6M well. Monias is located 22 kilometres southwest of the city of Fort Saint John. The field is made up of a series of anticlinal structures, the result of Jurassic reactivation, of late Mississippian-aged faults with structural movement that continued into post-Albian time forming structural closure at the Triassic Halfway Formation level and also overlying Cretaceous reservoirs. Gas is trapped in the Halfway Formation sandstone and coquina reservoirs which were deposited in an upper shoreface setting that have an average porosity of 8.8% and average horizontal permeability of 5.2 md. Diagenetic overgrowths around detrital grains and fine pore-blocking dolomite and quartz crystals are the cause of low flows on drillstem tests during drilling operations. To date there are 33 producing gas wells in the Halfway Formation pools flowing 1239 E 3 m 3 /d (44 MMcf/d) with a cumulative production of 7184 E 6 m 3 (255 Bcf) to July 1, 1996.

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