Deep shale gas development is viewed by many as critical to future global energy security and many countries are eyeing this abundant resource to help diversify their energy supplies. However, the hydraulic fracturing process –fracking – has been the subject of much debate amidst concerns about earthquakes, gas migration and the contamination of natural water resources. Rapid on-site analysis is therefore necessary to ensure that contamination is dealt with appropriately and this monitoring activity is seen as crucial to public perception of this controversial technology
Shale is the most common sedimentary rock on Earth. Exemplifying the potential for shale gas, Poland, which is seeking to reduce its dependency on Russian gas, is planning to begin commercial shale gas production from 2014. Most of the projects are currently at the phase of seismic surveys but some have already entered the drilling phase and this is expected to intensify after 2014. According to the US Department of Energy, the natural gas trapped in shale rock in Poland could provide the country with enough fuel to last for 300 years.
It is believed that the UK also has significant shale gas potential – estimated to be roughly equivalent to about half of the current North Sea natural gas reserves. However, many believe that it will be significantly more difficult for the UK to make shale gas cost-effective in comparison, for example, with the United Sates, which already has an established drilling infrastructure. In addition, the population density of the UK is much higher so there is likely to be greater opposition and in the US landowners own the mineral rights so they have a strong incentive to drill.
The potential for fracking to improve energy security is tempered by concerns that existing legislation may not be adequate to protect the environment. A recent report undertaken for the European Commission, covering Sweden, Poland, France and Germany concluded: ‘Neither on the European level nor on the national level have we noticed significant gaps in the current legislative framework, when it comes to regulating the current level of shale gas activities.’ The report argues that activities relating to the exploration of shale gas are already subject to EU and national laws and regulations, such as the Water Framework Directive, the Groundwater Directive and the Mining Waste Directive, and that the use of chemicals is covered by the REACH regulation. However, many commentators believe that tighter, more specific regulations will be needed if shale gas operations expand.
In February 2012, an influential group of scientists from the University of Texas called for better policing of shale gas operations with stronger regulations to reduce environmental and health risks. The report highlighted a need for better guidelines to avoid surface spills at shale gas works, and to ensure the safe storage and disposal of toxic fluids used in fracking operations. It also said that while some US states have updated old oil and gas regulations to encompass fracking and shale gas work, many lag behind and lack enough qualified people to enforce the regulations properly.
The scientists found ‘little or no evidence’ to support claims that fracking had contaminated aquifers, but recommended that more should be done to prevent accidents, such as spillages, underground leaks and gas explosions. In addition, they found that regulations should be established to ensure that responsibility for any groundwater contamination by fracking activities were clearly defined and that guidelines should be in place for replacing water supplies when drinking wells are affected.
The scientists found ‘little or no evidence’ to support claims that fracking had contaminated aquifers, but recommended that more should be done to prevent accidents, such as spillages, underground leaks and gas explosions
Climate change and increasing demand for freshwater are placing greater pressure on groundwater, rivers and streams, so there are additional concerns about the volume of water used for fracking. It has been estimated that around 5 million gallons of water are needed per well so the management of flowback and produced water is a key issue. Procedures need to be established to ensure that such large volumes of potentially contaminated water are handled in an appropriate manner and that the environment and public health are protected.
Testing and monitoring clearly has a vital role and the measurement of oil in water is an important indicator of contamination from fracking. The results of such tests on wastewater can inform decision making on issues such as reuse, treatment or disposal. Furthermore, oil in water measurements can help to provide reassurance that the environment has been protected if reliable results are available quickly.
Fast oil in water measurements can be undertaken onsite using infrared instrumentation such as the Wilks InfraCal TOG/TPH Analyser (in photo 1). Versions of this instrument have been used in the oil industry for more than 40 years and over 2,500 InfraCal analysers are now in use worldwide – primarily for measuring the amount of oil in produced water on off-shore and on-shore oil rigs. The main reason behind this instrument’s popularity is that it enables users to perform accurate on-site tests without having to incur the cost and delay of laboratory analysis. The same technology is ideal for testing the wastewater from fracking or for water quality testing. In the case of fracking, fast results would demonstrate that no contamination has taken place or enable a swift response to any leak or spill of contaminated water.
Portable, lightweight and battery powered, the InfraCal TOG/TPH analysers enable oil in water testing at the well site in less than 10 minutes. Testing requires a few simple steps that can be performed by non-technical personnel; the water is simply mixed with the extraction solvent, shaken, and then presented to the InfraCal analyser for measurement.
This analyser exploits the fact that hydrocarbons such as oil and grease can be extracted from water or soil through the use of an appropriate solvent. The extracted hydrocarbons absorb infrared energy at specific wavelengths and the amount of energy absorbed is proportional to the concentration of the oil/grease in the solvent. This can be directly calibrated or converted to the amount of oil in the original sample if the ratio of solvent to water is carefully controlled.
The oil concentration is determined by a calculation of the logarithm of the ratio of the light transmission at the reference wavelength to the light transmission at the analytical wavelength (Beer-Lambert law). The Beer-Lambert law assumes a linear relationship between absorbance and concentration. Deviations from linearity are determined by obtaining absorbance values from known samples and an internal point-to-point calibration table is prepared so that actual concentration is directly presented on the display. If the concentration ratio used during extraction (typically 10 parts sample to 1 part solvent for liquid samples and 1:1 for soil samples) is taken into account during calibration, the display will read directly in the desired units.
The same portable analyser can also be used for the measurement of TPH (Total Petroleum Hydrocarbons) in soil if a spill or pond leak occurs, to determine the area of contamination.
At a gas well, the first water to emerge after hydrofracking is flowback water, which is a mix of the fluid used to facture the shale and water from the formation that includes solids, metals, salts, chemical additives and trace amounts of oil. Once the gas well is producing, naturally occurring water from the shale formation flows to the surface as produced water. This has high levels of Total Dissolved Solids (TDS); minerals such as barium, calcium, iron and magnesium that are leached out of the shale along with dissolved hydrocarbons.
There are a number of water management options that include removal to an off-site treatment facility, evaporation ponds, injection into disposal wells, recycle and reuse for hydrofracking and treatment for surface discharge. Often the first step in any of these options is an oil/water separator, at which a portable infrared analyser has the capability of quickly giving an on-site result allowing the operator to verify the oil/water separator has functioned correctly and removed oil to the specified level.
Gas wells are typically drilled down as far as 2 to 3km or more; much deeper than private wells, so contamination could occur if there is a leak in the subsurface steel and cement casings that line the well. If surface containment pits or tanks that are used to store the flowback and produced water before treatment or transport off-site gets cracked or damaged, contaminated fluids could leak into the ground or groundwater. Improper disposal is also a potential source for water or soil contamination.
In summary, relatively small quantities of hydrocarbon have the potential to contaminate enormous volumes of water resources, so fast, on-site oil in water analysis is an important protective measure in a wide variety of applications such as fracking and those involving the production, handling, storage and distribution of oils and fuels. From a UK perspective, if fracking is to gain acceptability, on-site analysis will be necessary as one of the measures to address the environmental concerns of those that oppose the technique.
Dr Andrew Hobson, Quantitech Ltd