Premature coiled tubing (CT) failures have occurred in the United States, in areas such as the Eagle Ford and Haynesville formations, and the Permian Basin. In Canada, these failures once were not considered as prevalent. However, a presentation at the 2015 SPE/ICoTA conference in The Woodlands, Texas, changed that perception. A paper presented there detailed how a major Canadian CT service provider experienced a series of CT string failures while performing bridge plug millout operations in the Montney formation in northeastern British Columbia (Edillon et al., 2015). With each trip in or out of the wellbore, CT strings incur fatigue that can be estimated using simulation software based on the CT outside diameter (OD), material grade, and operating conditions.
Eibergen, Nora (The Dow Chemical Company) | Maun, Philip (The Dow Chemical Company) | Caldwell, Brittany (The Dow Chemical Company) | Widera, Imke (The Dow Chemical Company) | Morris, Brandon E. L. (The Dow Chemical Company) | Wunch, Kenneth (The Dow Chemical Company) | van der Kraan, Geert M. (The Dow Chemical Company)
The pipelines and vast infrastructure required for the production and transport of oil and gas are largely constructed of carbon steel. This material is highly susceptible to damage and failure as a result of direct or indirect Microbially Influenced Corrosion (MIC). One approach to reduce and/or remediate MIC is the application of microbicides to affected assets such as storage tanks, pipelines, heat exchangers and pumps. The objective of this paper is to generate efficacy data for biocidal formulations against corrosion-associated biofilms grown under anoxic and flowing conditions, which is difficult to obtain due to the distinct nature of biofilms and growth conditions. This data can be more representative when mimicking petroleum and water transporting pipelines. Thus, to facilitate the testing and comparison of products that successfully attenuate MIC under field-relevant conditions, a method that allows consistent corrosion measurements to be made, for corroding biofilms grown on steel surfaces under flowing and anoxic conditions, has been developed. This method utilizes microorganisms that were enriched on carbon steel from a North Sea sediment sample that, when grown in recirculating flow circuits, can generate corrosion rates of up to 65 mpy after four weeks of growth. The samples taken for the enrichment of corroding cultures came from a low tide anoxic sediment sample (black sand). In this presentation and paper, this method and its application to the benchmarking of field-relevant biocidal chemistries in MIC control experiments are described. Attention will be given to the reproducibility of the method as well. Distinct differences can be observed in biocidal performance against biofilms developed on metal surfaces.
Ferreira, Joalene A. S. (Federal University of Bahia, Brazil) | Almeida, Paulo F. (Federal University of Bahia, Brazil) | Nunes dos Santos, Jacson (Federal University of Bahia, Brazil) | Sampaio, Igor C. (Federal University of Bahia, Brazil) | França Figueirêdo, Lais (Federal University of Bahia, Brazil) | Tereska, Daniel (Federal University of Bahia, Brazil) | Chinalia, Fabio A. (Federal University of Bahia, Brazil)
Biocide injections are used for controlling biological souring in mature oil wells, but unpredictable results of such practices are also frequently reported. To address this problem, this research aimed to quantify the effect of four new biocides, and one commonly used biocide, within a dynamic system (packed-bed bioreactor) without using batch testing. The bioreactor was operated for 591 days, and the results showed that sulfate-reducing-bacteria (SRB) activity could recover within a period that varied from 15 to 60 days. Neem-oil (NO) (1.5% vol/vol) and 3,5-dimethyl-1,3,5-thiadiazinane-2-thione (Dazomet, DZ) (0.5% vol/vol) were the most efficient in controlling SRB activity. The tests showed that the mechanistic interaction controlling souring is not only associated with the compounds’ toxicity. Immiscible biocides not only killed cells, but they also can control SRB-recovery rates after the injection of biocides.
Broussard, Zach (Nalco Champion, an Ecolab Company) | Tidwell, Timothy J. (Nalco Champion, an Ecolab Company) | De Paula, Renato (Nalco Champion, an Ecolab Company) | Keasler, Victor (Nalco Champion, an Ecolab Company)
An oil transmission pipeline in the Eagle Ford area was being treated with 150ppm of active biocide based on a five percent water hold up but good control of the microbial population was not being maintained based on cATP data obtained from swabbing coupons within the system. Based on field data and recommendations, 3750ppm of active biocide was chosen to replace the incumbent biocide treatment and a sessile kill study was requested to validate the treatment plan before being implemented in the field. Subsequent sessile kill studies and biofilm regrowth studies indicated that an initial biocide treatment was not successful in killing or removing biofilm but that a second biocide treatment, performed two weeks after the initial treatment, was much more effective. Several mechanisms of biofilm resistance to biocide treatments are discussed to help understand the efficacy of this biocide treatment plan.
Microbial contamination of oilfield pipelines can lead to microbiologically influenced corrosion (MIC) and other issues including hydrogen sulfide (H2S) souring and biofouling. A typical program used to mitigate microbial populations and their resulting issues often includes a biocide application either through batch injection or continuous injection, with the latter typically not being recommended. Typical batch injection concentrations range between 100-1000ppm (μL/L). It is of the opinion of the authors that to be considered a successful treatment, batch biocide treatments must reduce the microbial population by approximately 99% of planktonic cells and 90% of sessile cells. However, because biofilms have been shown to be the primary cause of MIC and can be much harder to treat than planktonic microorganisms, biocide efficacy against sessile populations should be the deciding factor when choosing a biocide treatment strategy.1,7
It is well known that biofilms often exhibit decreased susceptibility to antimicrobial agents and mechanisms of this decreased susceptibility have been well studied and reviewed. These mechanisms include slowed cellular growth, adaptive stress responses, horizontal gene transfer, presence of tolerant persister cells, and efflux of antimicrobials (1,2,3) Additionally, the extracellular polysaccharide (EPS) matrix, made up of biopolymers secreted by microbes, provides a biofilm’s first line of defense against biocides and other anti-microbials by excluding or preventing the penetration of these molecules into the biofilm.(3,4,5) Due to the decreased susceptibility caused by these mechanisms, it is important to validate biocide treatments against biofilms representative of the system to be treated.
Biocides play a critical role in the exploitation of low permeability oil and gas formations via hydraulic fracturing by protecting the integrity of fracturing fluids and preventing the souring of the wells. Traditionally, biocide selection for a well is determined though a limited battery of tests used to evaluate initial biocidal activity and biocide effects on performance of the fracturing fluid. This paper presents the results of an enhanced biocide selection evaluation that extends past the traditional selection process to include stability and performance with a larger range of fracturing additives, environmental conditions, and secondary biocidal properties. Results show when using this enhanced process, a more accurate view of performance advantages and limitations of commonly used biocides emerge. In the expanded laboratory experiments, limitations with stability and performance were better elucidated with biocides such as 2,2-dibromo-3-nitrilopropionamide, glutaraldehyde, and glutaraldehyde/quaternary ammonium blends. Whereas with phosphonium polyammonium blend-based biocide, additional performance advantages were revealed. Comparative field assessments confirmed the validity and benefit of this expanded biocide evaluation for fracturing applications.
Advanced stimulation techniques, such as hydraulic fracturing of horizontal wells, have made the exploitation of low permeability oil and gas formations possible in recent years. Water, sand, and various chemical additives are injected into the ground to fracture open a formation and unlock the oil and gas. Biocides play a critical role both during and after the fracturing process protecting the integrity of the fracturing fluid and preventing souring of the well, respectively. Although biocides play a critical role in the overall effectiveness of a frac job, the traditional selection process is usually limited to laboratory tests to evaluate their biocidal activity and effect on the performance of the frac fluid, which doesn’t tell the entire story.1
We report here on an enhanced selection process that takes biocide evaluation a step further by considering additional factors that affect biocide stability and performance in the presence of a wide range of frac additives, environmental conditions, and secondary properties of the biocide. The results indicate that when the enhanced selection process is used to evaluate biocides for frac applications, performance limitations of the commonly used frac biocides, such as DBNPA, glutaraldehyde, and glutaraldehyde/quaternary ammonium blends, become apparent while a biocide based on a phosphonium polyammonium blend stands out as having superior applicability and performance in frac applications. Results from successful field applications of the phosphonium polyammonium blend have confirmed the usefulness of this biocide and the benefit of the enhanced frac biocide selection process.
Eibergen, Nora (Dow Microbial Control ) | Maun, Philip (Dow Microbial Control ) | Wier, Matthew (Dow Microbial Control ) | Caldwell, Brittany (Dow Microbial Control ) | van der Kraan, Geert (Dow Microbial Control ) | Wunch, Kenneth (Dow Microbial Control )
Pipelines and other carbon steel assets that are exposed to water, mixed phases, or water-laden hydrocarbons are highly susceptible to microbiologically influenced corrosion (MIC). This process, caused by either direct or indirect attack of metallic iron by microorganisms, causes costly damage to carbon steel assets and, in some cases, failure of the asset altogether resulting in loss of primary containment. One approach to reduce and/or mitigate the negative impact of MIC is the implementation of an effective biocide treatment strategy.
In laboratory studies, the impact of multiple biocides and treatment strategies on MIC were evaluated. Several commonly used biocides were applied under anoxic flowing conditions to sessile organisms enriched from anoxic North Sea sediment. This benchmarking study involved both the application of biocides to reduce biofilm formation on clean carbon steel and the application of biocide to established biofilm. The impact of biocide choice and mode of application on effective microbial control and corrosion management in these studies will be discussed.
The pipelines and vast infrastructure required for the production and transport of oil and gas are largely constructed of mild steel. This material, while less expensive and easier to fabricate than stainless steel, is highly susceptible to corrosion. Indeed, it has been estimated that the annual cost of corrosion associated with oil and gas production alone is 1.4 billion USD1 and that 25% of all failures experienced in the oil and gas industry can be attributed to corrosion.2 In particular, MIC has been estimated to account for 10-20% of this costly corrosion damage to steel oilfield assets.3
MIC is characterized by accelerated rates of metallic corrosion in the presence of microorganisms and is often associated with sulfate-reducing bacteria (SRB) and acid-producing bacteria (APB). These microorganisms can grow in sessile communities on metallic surfaces and can directly or indirectly contribute to the corrosion of the metal surface on which they grow. Through the production of biogenic hydrogen sulfide and acids near the metallic surface, SRB and APB are well known contributors to biocorrosion. This indirect mechanism of corrosion is sometimes referred to as chemical microbiologically influenced corrosion (CMIC).4 Biocorrosion can also occur via a direct mechanism in which bacteria use electrons from the metal to drive their own metabolic processes. This mechanism, discovered more recently, is referred to as electrical microbiologically influenced corrosion (EMIC) and has been demonstrated to be a particularly aggressive form of biocorrosion.4,5 Microorganisms utilizing this mechanism have been shown to induce corrosion at rates exceeding 25 mpy.4
Biocide chemicals are an essential control in the oil and gas industry. From drinking water to hydrocarbon production streams, it is necessary to use the correct chemical, at the correct dose to prevent uncontrolled microbiological activity. The objective of this review is to discuss an example of a biocide evaluation that tested seven (7) different biocide chemicals (from the same chemical vendor) against planktonic and sessile microbial populations by both traditional and molecular microbiological monitoring techniques.
The methods used in the biocide evaluation were in accordance to internationally recognised standards; NACE TM0194-2014 ‘Field Monitoring of Bacterial Growth in Oil and Gas Systems’ and NACE TM0212-2012 ‘Detection, Testing, and Evaluation of Microbiologically Influenced Corrosion on Internal Surfaces of Pipelines’. The procedure stated that 7 biocides at 2 concentrations (500ppm and 1000ppm of product) were to be tested against bacterial populations (planktonic and sessile), in relation to appropriate water chemistry and microbial consortia. The microbiological techniques used to determine the biocide efficacy were; traditional Most Probable Number (MPN) bacterial enumeration of; Sulphate Reducing Bacteria (SRB), General Heterotrophic Bacteria (GHB) and Acid-Producing General Heterotrophic Bacteria (APGHB), Quantitative Polymerase Chain Reaction (qPCR) with pre-selected primers for SRB, Sulphate Reducing Archaea (SRA), and lastly, Next Generation Sequencing (NGS).
The results from the microbiological techniques allowed for an evaluation by ranking each biocide chemical in comparison to the total test group of chemicals, against untreated controls. Performance was based on the reduction of microbiological populations from the untreated control populations and greater microbiological community detail was achieved through interpretation of the molecular techniques data.
The inclusion of molecular microbiological monitoring techniques to biocide evaluations is a novel approach to understanding the direct impact of biocide chemicals in greater detail. In turn, this approach will provide knowledge and valuable information for chemical addition optimisation and cost saving.