Tuesday 11th March
Fracking shale gas: What on Earth is that all about?” by Professor Richard Selley
When we arranged this talk we were aware that it was likely to be a popular topic so we encouraged members to bring a colleague (or two) along. Our members did not disappoint, and a total of 77 members and guests heard an excellent and entertaining presentation from our speaker, Professor Richard Selley. Following the usual break for refreshments, we then had a very lively question and answer session.
Professor Selley began by outlining the history of fracking, which has its origins in the USA in 1860 (yes over 150 years ago) when explosives were used to release gases trapped in underground shales. In fact the history of shale gas extraction goes back even further, we were shown pictures of a monument in New York State dated 1821 where gas was being produced from naturally fractured shale. One well would supply the needs of a small village or a hospital and had a lifetime of about 30 years. The USA clearly has a lot of experience extracting shale gas by fracking and has drilled over 2 million wells.
Within the UK we have significant experience in oil and gas production from the north sea, and some 2000 onshore oil wells, one of the earliest being at Netherfield, near Hastings, which was drilled in 1875. Furthermore the UK has many years of experience of regulating the onshore oil and gas industry nationally, and one of the most tightly regulated regimes in the world.
Our speaker then described the process of fracking in detail. Shale is fissile rock that is formed by the consolidation of clay, mud, or silt. It has a finely stratified or laminated structure, and is composed of minerals essentially unaltered since deposition. The shale deposits that are of interest, i.e. those holding exploitable gas deposits, are located some 1500m or more below ground level. Like other oil and gas exploration or production, a bore hole approximately 1m in diameter is drilled and several stages of metal pipes (“casings”) are set in concrete within the well, to seal it and prevent contamination of surrounding groundwater. A well for shale gas will usually go down vertically to the shale layer and then run horizontally along it. For shale oil or gas, the rock is then fractured by injecting liquid at high pressure, an established technique for conventional oil and gas, but used more intensively for shale. Small particles (usually sand) are pumped into the fractures to keep them open when the pressure is released, so that the gas can flow into the well. The ‘liquid’ referred to above is 98-99% water and sand, with a small quantity of chemicals added to improve efficiency, for example to reduce friction. In the UK, operators must show the Environment Agency that all such chemicals are non-hazardous in their intended application. Once the rock is fractured, some of the fluid returns to the surface, where it is sealed in containers before treatment. The gas or oil can then flow through the well to surface operations which separate and process the gas or oil. If oil is recovered, it will be taken to an oil refinery or petrochemical plant. Resources (the quantity of gas/oil that is in the ground) is quite different from Reserves (the quantity that we
can actually extract) and economics dictate whether a test drilling will ultimately lead to production.
Professor Selley then discussed the current situation in the UK, in particular referring to some of the objections raised in the popular press:-
Impact on surface water – recycling water used within the extraction process will reduce any impact of additional emissions of methane and CO2 – reduced by carbon capture.
Earthquakes, of which two have so far been attributed to fracking within the UK, neither above 2.3 in magnitude on the Richter scale – each day there are 3-4 earthquakes within the UK, often the result of collapsing mines
Contamination of underground aquifers – aquifers rarely occur below 300m and all onshore wells drilled in the UK have to be fitted with sealed steel casings
In conclusion Professor Selley explained how developments in horizontal drilling techniques, improved hydraulic fracturing technology and progress in imaging technology using geo-phones will ensure that fracking in the UK would be capable of providing one of the solutions to our future energy needs as our reliance on coal and North Sea oil declines.
Tuesday 11th March