Large volume of water used for hydrocarbon production and processing can be an ideal place for bacterial growth and survival. Presence of bacteria can affect the quality of the product, asset integrity and the overall safety of the operations. Therefore, it is important to have a well-defined microbial control program, involving mainly proactive approaches in control of microorganisms. Monitoring, using different detection techniques, and control, using appropriate biocide treatments, are important measures in the program. Different types of biocides are available for microbial control programs in different phases of oil and gas operations. Understanding the application of biocides, their efficacy, compatibility and sustainability are critical in proper selection of biocides. There is no readymade check list available for the biocide selection and this often invites erroneous outputs because of numerous steps and manual interferences in developing a conclusion. A selection score card, based on numerical points on each step, could help in the better selection procedure and minimize the manual interpretation for conclusions.
Secondary oil production involves the injection of water into the reservoir, generally known as water flooding, to increase the reservoir pressure to its initial levels, to maximize the oil recovery out of the ground. The injected water flows through the formation to flush the oil from the formation into the production system. Injection systems are the portion of the field that is responsible for injecting the water into the formation. Source of water may be lake, river or sea water. Especially in Middle East countries, sea water is most preferred considering the availability and environmental conditions.
However, water injection raises various concerns such as the introduction of dissolved oxygen, planktonic bacteria and other undesirable chemicals. The injection water is generally pretreated to address these concerns before flooding the reservoir. The surface water is initially treated with an oxidizing biocide to kill the planktonic organisms and then de-aerated using physio-chemical methods. Since the deaeration tower can harbor a lot of bacteria, most of the fields inject non-oxidizing biocides before the water reaches the pipeline or formation.