Metgasco goes deep into CSG

One of Metgasco’s test wells at Sextonville Road.

There is a lot of concern in the community about the processes used to extract coal seam gas, particularly the practice of hydraulic fracturing or ‘fracking’. The concerns are generally about the chemicals used and the potential for them to get into groundwater.

Metgasco’s chief operating officer Mick O’Brien said the company had done one hydraulic fracture in the Northern Rivers region, at the Kingfisher site near Casino, where they found the largest conventional gas field in NSW.

A full list of chemicals used was supplied to Industry & Investment NSW, who regulate the industry.

“We’re happy to give a list of chemicals, the names aren’t generally recognisable but they’re all relatively common chemicals; every one of the chemicals will be in most people’s houses,” Mr O’Brien said. “The Kingfisher frack was done at 1450m. The deepest water table in that area – and nobody’s drawing from that – is 400m. So it was done 1000m below water table and there’s a very hard sandstone barrier just below the major aquifers there so it’s inconceivable that the frack could get into the water aquifer in Kingfisher. All the chemicals are actually food grade chemicals.”

The National Toxics Network recently put out a briefing paper calling for a moratorium on fracking (see story page 8, with a list of chemicals used by Metgasco at Kingfisher).

“There are a number of issues of concern with that report,” Mr O’Brien said. “One of the major comments from their report is that most of the chemicals are unknown and unregulated. At a meeting in Lismore with the Environmental Defender’s Office, we gave a list of chemicals and took them through all the information related.”

Mr O’Brien said Metgasco was trying to be as open as possible with members of the community.

“For people who have concerns there are an awful lot of sources of information, it’s not confidential, not secret, there are a very large number of reports that are publicly available and we can direct people to those or provide copies if they need them. This is not a new industry, it’s been operating in Australia since 1969. It’s a very safe industry.

“The prime purpose of those involved in the industry is to get a cheaper energy source. This will be a low cost source energy for that area and enhance development of that part of NSW.”

Metgasco managing director David Johnson walked The Echo through the drilling methods they are planning to use for CSG extraction:

“There are two types of test wells, stratigraphic wells and core wells.

With a stratigraphic well, we use a percussion drill bit and, as it goes down, it basically crushes the rock into little chips and drills a hole. It’s a common method that all of the water well drillers (bore water holes) use.

The core drilling method involves using a bit on a drill that has a diamond or a tungsten carbide encrusted drill head, that’s sort of circular, like a ring. When that drill rotates it goes through the rock, which allows you to recover a cylindrical specimen of rock (a core sample).

We basically use a series of increasingly smaller drill parts as we drill for depth, very much like what you see on one of those old-style pirate telescopes – how they slide out from each other.

We drill with an auger type fit til theblade won’t go further into hard rock, generally around 5m. That means you’re through soil or colluvium, then we cement around that. That top bit of pipe, the conductor pipe, is injected with cement so that the conductor pipe is solidly placed, then the bottom of the conductor pipe set in what’s effectively bedrock.

Then we come back with a smaller diameter bit of drill pipe and we generally drill to about 180m, then go through same process there – so we run in some steel casing, commonly 8 or 9 inches, then again we envelope that with a sheet of cement, for safety reasons, so if there were a gas blowout, we would be able to control the well.

Then we come back and again drill inside that pipe to 450-500m, into a particular rock found in the area, Maclean sandstone, very hard sandstone. Now we drill from the surface down to 450-500m, repeat the process, once in Maclean sandstone, inject cement, which comes up outside what’s the open hole so you have steel drill pipe surrounded by cement. What that gives us is a steel pipe surrounded by cement all the way down to 450-500m, which ensures at no time can any of our drilling or subsequent activity have any contact with any of the aquifers that may be present.

We’ve done this for more than 20 drill holes, so we have a good understanding that that method ensures there is no aquifer contamination.

Next step is to fill inside the casing below the Maclean sandstone into the unit known as Walloon coal measures, that unit contains various layers of coal, shale and lithic sandstone, so that gives you exposure to reservoirs. Gas is contained within those coal layers.

There is an enormous amount of work that then goes into the data we collect at that point. To give an example, we collect wire line log surveys, lower a probe down into those coal-bearing formations and those probes measure a number of different rock properties, such as rock density, the sonic response to rocks, the electrical character of the rocks, ferrousity. Where using core drilling we can physically recover core samples of the reservoir, then dispatch to labs for analysis. Tests that we will commonly conduct are tests on gas composition, gas content, chemical properties of the coal, carbon, hydrogen, nitrogen contents, so the character of the coal, the micro structure of the coal, can be studied.

Extraction

After production testing, you step back a bit. There’s a lot of information to collect from exploration. You’re trying to collect information that will tell you something about the nature of the gas reservoir as a function of how the gas can be accessed.

With a test well, what you’re trying to do is to get information at the exploration stage and to use that information to design your drilling method to how much gas you can recover.

I think there’s a misconception that if you drill a hole, it suddenly produces gas, but the contrary is the case. There are only a limited number of areas that contain the appropriate reservoir conditions that are conducive to flowing gas.

With the test wells

we’ve tried a number of different methods; there are two methods we’ve identified so far that seem to be able to deliver gas.

With horizontal drilling technology, you have a drill hole, vertical in the manner described, then it bends about 90 degrees, travels horizontally along the coal seam, like keyhole surgery. What you’re doing there is almost like building an underground communication network, which allows the gas to flow along underground passageways.

The second method we’ve identified is peculiar to this basin and what’s known as ‘air drilling’. What we’ve discovered we normally wouldn’t divulge because of our competitors, but we want the public to understand we are operating in a regulated and safe manner.

We’ve discovered this geological basin is post mature, that means it has been subjected to degrees of pressure and temperature that have affected the gas maturation process for any gas. We believe that relates to the separation of Australia and New Zealand 100,000,000 years ago, and also the volcanic activity that occurred with the intrusion of the Mount Warning and Mount Barney volcanic complexes about 20,000,000 years ago. The consequent associated temperature and pressure effect means that the gas occurs in the coal largely without the presence of any water. What we’ve seen is most of the water has been driven off.

People who have been looking at Four Corners think gas is integrally associated with water. Our experience is that that is not the case in this basin. In fact, normally when we use those exploration or test drilling methods, the drill bit is encased in water as it goes down, but if you use that method and go into reservoirs we damage the reservoir, so that means when we drill some of these test wells, we now switch over drilling once below Maclean sandstone, and use the air drilling method, where we basically use an air compressor and air takes the place of water. Then we drill into the reservoir and that ensures there is no damage to the formation and allows gas flow.”