Beaver River Middle Devonian Carbonate: Performance Review of a High-Relief, Fractured Gas Reservoir With Water Influx
Authors: Davidson D.A. , Snowdon D.M. 
Published: December 2007

Beaver River Middle Devonian Carbonate: Performance Review of a High-Relief, Fractured Performance Review of a High-Relief, Fractured Gas Reservoir With Water Influx

This paper discusses the performance history of Beaver River Field, located in British Columbia and the Yukon Territory. Development in this frontier location was supported by reserve estimates of more than 1 Tcf and high well deliverabilities. After production began in 1971, a severe decrease in recoverable reserves and deliverability resulted from water influx.

Introduction

When first produced, Beaver River Field [located 100 miles northwest of Fort Nelson on the border of British Columbia and the Yukon Territory (Fig. 1)] was thought to be British Columbia's largest gas field, with recoverable reserves estimated at more than 1 Tcf. Initial production rates of more than 200 MMcf/D from six wells were production rates of more than 200 MMcf/D from six wells were reduced after 2 years because of increased water production. Although production was curtailed to determine the cause of water production, this problem soon was overshadowed by reduced capacity resulting from increasing water/gas ratios. In 5 years, field rates have decreased from 230 MMcf/D to 3 MMcf/D. The field was shut in Oct. 1978. Because of the effects of water influx, ultimate recoverable reserves are estimated at 178 Bcf.

Field Discovery and Development

The Beaver River Anticline first was recognized in 1944 by the Geological Survey of Canada during a reconnaissance project. Amoco Canada Petroleum Co. Ltd., began exploring project. Amoco Canada Petroleum Co. Ltd., began exploring the area in 1954; the A-1 Beaver River well was drilled in 1958. This well was abandoned with lost drillstring in the hole in the Middle Devonian carbonate at 11,752 ft. However, the well indicated the presence of a potential gas-bearing horizon.

In Jan. 1961, drilling began for Well A-2. This 13,500-ft well penetrated 1,200 ft of Middle Devonian carbonate without reaching the water contact. Testing established an absolute open flow (AOF) of 85 MMcf/D, while core analysis indicated average porosity of 3%. The success of this well justified exploratory drilling in the adjacent Pointed Mountain Anticline and supported the drilling of more Beaver River wells.

From 1967 to 1970, continuous drilling led to successful completion of four additional gas wells at Beaver River. AOF potentials of up to 100 MMcf/D at Beaver River and 200 MMcf/D at Pointed Mountain, a 20-day high-rate flow test at Pointed Mountain (showing no apparent depletion), and evidence of good porosity all contributed to a favorable view of the area's potential.

A sales contract based on reserves of 1.47 Tcf was signed, which led to the design and construction of a dehydration plant and transmission line. Production from the field began Oct. 1971.

Stratigraphy and Structure

Beaver River Field is located in a structural belt known as the Liard Plateau or the Liard Fold Belt, bounded by the Mackenzie Mountains on the north and the Rocky Mountains and foothills on the south. The main production at Beaver River is from a thick sequence of highly altered dolomites. Although these dolomites range in age from Middle Devonian through Ordovician, production is from the upper portion of this sequence. Here, the reservoir is called the "Middle Devonian carbonate.

The Middle Devonian carbonate was deposited as a relatively monotonous carbonate and evaporite sequence in shallow subtidal to supratidal environments on a broad carbonate bank.

JPT

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