Branch News

PESA NSW Field Trip
To Sydney Gas Company's Johndilo Pilot Project And Energy Developments' Appin Power Plant, March 23rd, 2001
By Malcolm C Galloway

The day began with the attendees meeting at the Central Railway bus terminal where we boarded a bus for the trip to Camden. We were joined there by a few Sydney people who had traveled by car, as well as a contingent from AGSO in Canberra. Mr Charles M Wright, Manager Corporate and Government Affairs of Sydney Gas Company, welcomed us. He introduced Mr Mike Roy Operations Manager who was formerly with Schlumberger Oilfield Services. He described the various completions that had been tried and the varying degrees of success.

Sydney Gas holds PELs 2, 4 and 267 in the Sydney Basin. The current work is being undertaken on an Assessment Lease where a pilot project, including production facilities and pipeline to the AGL Distribution System, is being completed. The gas treatment facility was 80% complete when PESA visited the plant.

From the days of Australian Oil and Gas (AOG's) exploration work in the Camden area in the 1950s and early 1960s, attempts to produce the gas of this area have met with little success. Typically, in those early days, there would be a major flow of gas when the prospective horizon was reached but within a day this would dwindle to near nothing. By comparison with what is being done today, AOG had little hope of success with only the technology of 1950/60 era at their disposal. AMOCO in the 1980s did a lot of excellent work in the area but did not proceed because of more attractive exploration targets in other countries. Now that Sydney Gas has taken up the area, and with the data and knowledge gained from previous operators such as AMOCO, AGL and AOG, and staff with Coal Bed Methane experience from the USA and elsewhere to guide them, they have had quite encouraging results.

The primary target is the Bulli Seam which has a low water content. The secondary one is the Tongara Seam some 100 m further below.

The evolution of well completions is shown in Figure 1 and described below.

Open Hole Completions:
Initially wells were drilled through the target horizon and cased to immediately above the Bulli seam at about 700 m. However, problems associated with the migration of coal fines, due to the open nature of the well bore, caused production difficulties.

Cased Hole Completions:
These holes were drilled to below the Tongarra Seam and cased to about 830 m. They were then perforated in the Bulli and Tongarra seams. These wells have proved to be successful in the control of the well bore and coal fines migration. This completion style is currently the preferred technique.

Proposed Horizontal Completions:
In the USA this form of completion has been very successful. Similar completions are planned for wells to be drilled later this year. The planned procedure will be to initially drill a conventional hole to the target horizon, log it and case it to 650 m. The horizontal section would then be kicked off immediately below the casing shoe, rapidly building angle. Once the seam is reached the well will be continued for about 1000 m horizontally along a line approximately midway between the bottom and top of the seam.

During this evolution in completions, various combinations of drilling fluids, fraccing procedures and injection fluids have been used until the present scheme was devised. The details of this will be the subject of a paper currently in preparation.

Environmental considerations
The company has been particularly conscious of environmental considerations and of reducing, as much as possible, their impact on the local residents. Work in this fairly closely settled area has had its problems. Normal 24 hour drilling shifts have had to be abandoned and instead 'builders' hours have had to be kept, will work commencing at 7 am and ceasing at 6 pm. As anyone knows, this is hardly conducive for maintaining well bore conditions and getting to the desired target as quickly as possible, as well as many other jobs such as running casing. Even with these restricted hours, some residents have complained about noise and, to overcome this, the sound barrier shown in Figure 2 is used. It consists of a trailer loaded with hay positioned across the line of sight with a tarpaulin to keep the load relatively dry. This does a remarkably good job of deadening and diverting the sound. It is a relatively inexpensive solution to the problem and can easily be moved from drill site to drill site. Unfortunately, the four legged local fauna has a taste for the hay, hence the holes in the load.

Disposal of the produced water has not been a problem as it is quite fresh and certainly potable to stock. It is certainly far more pleasant to taste than the waters from the Great Artesian Basin of Queensland. Consequently, the water is either run into farm dams or released onto the ground to irrigate crops, with the prior consent of the property owner.

Drilling mud pits are dug and lined with plastic. When finished with, the pits are cleaned out, the plastic removed and the topsoil graded back over the hole. Thus the ground is restored to its original contours.

From the Camden headquarters we moved to the pilot gas plant and treatment facility.

Figure 3 shows the attendees being addressed at the then nearly completed pilot gas plant. In the background is a large butane gas cylinder. Butane is added as required to increase the calorific value of the gas so that it meets the specifications of the local distribution system, notwithstanding that gas being produced is pipeline quality. Also shown is a dam which was formerly used in conjunction with drilling the nearby
Apap #1 well. This dam is now being used for farm water as well as for an emergency supply should it be needed for the gas plant.

Figure 4 shows the now completed pilot gas plant, which is in operation.

Figure 5 is of the gas plant flare pipe ready for initial use.

Figure 6 shows Mr Charles Wright beside a nearby completed well and shows all that will normally remain on the land after a well has been completed and placed on line.

Fig. 2.	Fig. 3.	Fig. 4.
Fig. 5.	Fig. 6.	Fig. 7.

From the gas plant we traveled to a newly completed well to demonstrate the ease with which the wells unload water. Figure 7 shows Mr Ken Bull, Field Superintendent, with his hand on the well head separator for the newly completed Logan Brae #5 well. Also shown is the pipeline leading to the water storage pit. Figure 8 shows Logan Brae #5 unloading water under its own head of pressure.

We then moved on to a well that was being prepared for cementing. Figure 9 shows the truck mounted workover rig, trailers of cementing fluids, and pumping truck in place for the cementing job on the Logan Brae #9 well. Figure 10 shows Mr Ken Bull, Field Superintendent, addressing attendees at the Logan Brae #9 well. The cementing truck is in the background and various pieces of equipment in are the foreground.

This concluded the visit to the Sydney Gas field operations after a most informative time. We then adjourned to a nearby hotel for drinks and lunch before progressing on to the Appin Power Plant.

Fig. 8.	Fig. 9.
Fig. 10.	Fig. 11.

Appin Power Plant
This plant runs in conjunction with the Appin Coal Mine which is an underground mine operated by the BHP Group. Methane gas is continuously extracted from the mine to maintain safe working conditions. The methane is treated by wet scrubbing and filtration and is then supplied as fuel to the generating plant. Natural gas supplied by pipeline is utilised as supplementary fuel if there is a shortfall in methane supply from the mine.

The generating plant comprises 54 gas engine generator sets, each of 1MW nominal rating. Figure 11 shows part of one bank with eight gas engine generator sets. Reciprocating gas engines were selected for this project due to their ability to use low pressure gas with low methane content. Generation voltage is 415 volts. Voltage is increased to 22 kV by unit transformers (one transformer per two generator sets). A high voltage substation is installed to further increase voltage to 66 kV. Interconnection with the utility network is at 66 kV.

The project is wholly owned and operated by Energy Developments. The power is supplied to Integral Energy, the local electricity distribution utility. It has a power generation capacity of 56 MW.

Another similar plant operates in conjunction with the BHP Group's Tower Hill Coal Mine, NSW. It has a power generation capacity of 41 MW.

Energy Developments' plants utilise landfill gas at a number of locations to produce electricity. These include:

1. Belrose (Sydney) NSW (power generation capacity 4 MW)
2. Lucas Heights I and II (total power generation capacity 18 MW)
3. Clayton Victoria (power generation capacity 11 MW)
4. Broadmeadows Vic (power generation capacity 7 MW)
5. Corio Vic (power generation capacity 1 MW)
6. Berwick Vic (power generation capacity 7 MW)
7. Springvale Vic (power generation capacity 9 MW)
8. Browns Plains Qld (power generation capacity 1 MW)
9. Highbury SA (power generation capacity 2 MW)
10. Tea Tree Gully SA (power generation capacity 3 MW)
11. Wingfield SA I and II (total power generation capacity 6MW)
12. Pedler Creek SA (power generation capacity 3 MW)

Though all of these plants have far lower capacity than the Appin or Tower Hill plants, they drain methane which would otherwise escape to the atmosphere, and produce electricity. This all helps to reduce greenhouse gas emissions and produces electricity with less thermal release than the burning of coal. Sadly we were told that today it would be uneconomic to build similar plants because of the reduction in the price for electricity resulting from the deregulated market.

The author wishes to thank the staff of Sydney Gas, particularly Will Barker, geologist, for reviewing this paper and making various corrections.