UV effective against sulphate reducing bacteria
Bacteria control has become an important topic for discussion in the oil and gas industry. Inadequate biocidal treatments can have negative consequences, ranging from souring the reservoir with hydrogen sulphide gas to microbial induced corrosion or the loss of fluid stability during stimulation.
With stricter regulations on stimulation fluid (also known as downhole injection fluid) additives there has been an increasing effort to reduce or eliminate hazardous chemicals such as biocides that are present in these fluids. This challenge has been complicated by water use restrictions, placing the oil and gas industry under increased pressure to move away from using fresh water. Instead, oil producers have turned to non-pristine water sources, such as produced or flowback waters, which can often have high levels of bacterial contamination.
The use of ultraviolet (UV) light for disinfection is well established in many industrial processes and Hanovia has been at the forefront of its implementation for the past several decades. Partnering with a major oil and gas servicing company, Hanovia helped prove this technology successfully in pilot trials that have been operating since early 2009. Using an enhanced version of its standard product, field experience has proven the robustness of the equipment in extreme conditions
A plethora of data is available on bacteria species that are human pathogens, and on the effectiveness of UV disinfection for these particular species. But in the oilfield, sulphate reducing bacteria (SRB) are the target of interest. Unfortunately, there is little published data on the effectiveness of UV disinfection on SRBs.
Through its development partnership, Hanovia has employed advanced laboratory testing to validate the effectiveness of UV disinfection against specific SRB species that are commonly found in fluids used in the oil and gas industry. These studies verified that UV disinfection can be an effective method for treating the target SRB species and revealed some other interesting results.
A typical Hanovia UV disinfection system is highly compact, modular and easy to install within existing pipework with minimal disruption. Shock dosing with chemicals does not require the complex monitoring equipment which is necessary if biocides are used as a primary disinfectant. In addition, UV does not produce any unwanted by-products.
Oliver Lawal, Hanovia’s Vice President of Technology, presented a paper at this year’s Singapore International Water Week (http://www.siww.com.sg/) which outlined some of the techniques used in the laboratory and field testing, while detailing the operational considerations unique to this application.