Richards, W.L., Methane Drainage Ventures

Abstract

A joint venture test project for methane drainage was conducted by Methane Drainage Ventures (MDV) at Australian Iron and Steel Pty. Ltd's (AI and S) Appin Colliery, Appin, Pty. Ltd's (AI and S) Appin Colliery, Appin, New South Wales, Australia. The project for methane drainage in advance of long wall mining included five (5) horizontal boreholes into the Bulli Coalbed of the Illawarra Goal Measure in the south Sydney Basin, Australia.

Peak gas flowrates from a total of 1380m (4500 ft) of horizontal boreholes reached 17,000 m3 per day (600,000 standard cubic ft/d). The total horizontal drilling project was conducted in eight months of project was conducted in eight months of 1981. Produced gas of 97% methane was safely vented both during and after the test project due to the efforts of the colliery operators.

Test drilling was successfully conducted from two separate mining sections on opposite sides of the colliery. Data collected during and after the drilling campaign were used to define the properties of the coalbed. Computer simulation was used to predict commercial gas production. production. The Appin project and a concurrent exploration corehole project were conducted to provide data to evaluate the Sydney Basin. Results of the evaluation indicate commercial feasibility of methane drainage for natural gas production. A subsequent design was completed for a natural gas production facility utilizing methane production facility utilizing methane drainage technology.

Introduction

The coal fields of the south Sydney Basin are well known gassy mining regions. Collieries on the south coast have experienced gas problems in mining activity since mining began there in the 1800's. As is true with most coal seams, the Bulli coalbed's gas content increases with distance from the outcrop and overburden depth.

At the Appin Colliery, the distance to the outcrop is approximately 19 km (12 mi) and the overburden is greater than 300 m (985 ft). Appin Colliery is located at Appin, New South Wales (NSW), Australia, shown in the map of Figure 1. The Bulli coalbed at Appin averages 3.0 m (10 ft) in thickness. Bulli coal at Appin is medium to low volatile bituminous coking coal used by AI and S for steel production. An analysis of Bulli coal is shown in Figure 2.

Planning for the Appin Project and the associated methane drainage evaluation of the Sydney Basin began in 1980. A working agreement was reached between Occidental Petroleum Corporation (OPC) and the Petroleum Corporation (OPC) and the Australian Gas Light Co. (AGL) to jointly pursue a three-pronged evaluation program. pursue a three-pronged evaluation program. This program included an in-mine evaluation project to assess gas production capability, an exploration core drilling project and an engineering evaluation to project and an engineering evaluation to assess the gas reservoir and economic potential. A further agreement was reached potential. A further agreement was reached with AI and S to coordinate an in-mine project at the Appin Colliery.

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