The good oil on fracking

01:57, Nov 08 2012
tdn frack stand
The Todd Energy Mangahewa-D wellsite on Rimutauteka Rd

Todd Energy says it wants to provide full transparency about its fracking operations in New Zealand.

That's why it has written what it describes as a plain-language, comprehensive picture of its operations - and made it public.

In what is an extremely unusual move by a member of New Zealand's normally secretive energy industry, Todd's submission to the parliamentary commissioner for the environment's investigation into fracking has opened the books on what is happening at the Mangahewa gas and condensate field inland from Waitara.

Out there, every well that is being drilled is being hydraulically fractured. Todd claims this is the only way supplies of what is known as "tight" gas can be unlocked and therefore continue to make the field economically viable.

The Todd report explains that oil and gas forms over millions of years from organic plant and animal matter in what are known as source rocks. Some of the petroleum then migrates into reservoir rocks, just as water would soak into a bucket of beach sand.

In the Mangahewa field, all the gas-bearing reservoir rocks are located 3400 to 4400 metres below ground level and therefore trapped by at least 2500m of impermeable sealing rock far below known freshwater aquifers which stretch to about 400m below ground level.


The gas and oil lies in low-permeability reservoir rock formations - known as ‘tight' formations - that will not naturally flow commercial quantities of gas or oil without some form of help. This assistance comes via being hydraulically fractured. In this process, fluid is pumped down the drill pipe at high pressure, creating fractures in the reservoir rock that are typically about the width of a straw and extend several hundred metres laterally away from the well.

Fracking is undertaken by specialised international oilfield services contractors. Well integrity is central to its success, and several layers of steel casing and cement isolate a well from the surrounding rock layers.

The fracture fluids used are 97 to 99 per cent water and proppant (either sand or ceramic particles which keep the fractures open), with the remainder made up of chemical additives, most of which have common applications around the home, says the submission. Fluids returned to the surface are safely disposed of through consented processes.

Fracking has enhanced production to the extent that in 2011 the Mangahewa field alone produced as much energy as 89 per cent of New Zealand's 456 wind turbines combined.

But several recent events overseas have prompted public concern about the environmental effects of fracturing, Todd admits. These events have included an increase in fracking in shale gas developments in the United States, shallow coal seam gas developments in Queensland, and seismic events in Britain and North America that may have been related to fracking.

The main concerns being expressed about fracking are:

possible fresh groundwater contamination;

the possibility of triggering earthquakes;

migration of natural gas and fracture fluids to the surface;

inappropriate handling and disposal of wastes at the surface.

"Some critics also oppose it because they believe it will defer the shift to renewable energy and prolong our reliance on emissions-intensive fossil fuels, and thus increase global warming," it says.

"Natural gas is in fact the next- best energy source from a climatic perspective after renewables, and is doing much more to reduce global greenhouse gas emissions than all renewable energy sources combined."

The report says rigorous, independent studies have been commissioned into the effects of fracking in New Zealand and other countries, including a landmark study in Britain, and these have all concluded that the risks are minor if industry best practice and regulations are implemented and enforced.

It adds that the types of chemicals used for fracking have changed substantially over the last 20 years. Most are now environmentally benign and are common in many household products.

The submission admits that by its very nature fracking does induce some seismic activity, but on a geological scale it is below magnitude 2M (micro earthquake) and not felt at the surface.

"Many of the environmental risks raised as concerns related to hydraulic fracturing apply to all exploration and production drilling," says the report.

"They are well recognised by the industry and managed through adherence to high-quality well construction and best practice in all aspects of the operations."

Taranaki Daily News