OCT COMPANY, INC.

Bacteria Control

 

Bacteria control in oilfield environment is achieved by killing a majority of the bacteria in a system or by maintaining the bacteria in a static "no growth" state. Most of the modes of action that microbiocides take to kill bacteria occurs at the bateria's cell membrane. The cell membrane controls the osmotic regulation, the active transport of food stuffs through it, and is the site of respiration in bacteria. 

 

The most effective biocides have been determined to be cationic and can kill both aerobic and anaerobic bacteria. These biocides are effective against gram-positive and gram-negative bacteria. 

 

Anionic materials are primarily effective against only gram-positive bacterial. Non-ionic materials have been found to have little effect against bacteria. 

 

Chemistries in commercially available biocides include:

• Chlorine

• Hydrogen peroxide

• Formaldehyde

• Thiocarbamates

• Glutaraldehydes

• Glutaraldehyde Quat Blends

• THPS

• ADBAC Quats

• DDAC Quats

• Cocodiamine

• Peracetic Acid

• DBNPA

• Isothiazoline 

• Oxazolidine

• Bronopol 

 

System Evaluation for Bacteria Control

 

A thorough evaluation of production system for bacteria control would require the following information:

• Temperature profiles

• Water, oil and gas production data

• Comprehensive water analysis

• System SRB / APB enumeration test data

• Microscopy and genetic fingerprinting of bacteria

• H2S concentration

• Occurrence of pitting corrosion

• Current bacteria control program

 

Bacteria Test Method

 

There are numerous techniques can be used to evaluate bacteria levels in oilfield environment. 

 

Liquid Media - Classical serial dilution detection method

• Various types of sterile culture media are inoculated and incubated for the detection and quantification of specific types of bacteria

• Commonly used medias for the oil/gas industry are (formulas are specified by the NACE Standard for oil/gas microbial detection TMO-194 2011)

  • Modified Postgate’s B (MPB) for the detection of sulfate reducing bacteria (SRB)

  • APIRP-38 (API) for the detection of SRB

  • Phenol Red Dextrose (PRD) for the detection of acid producing bacteria (APB) and general heterotrophic bacteria (GHB)

  • NRB media for the detection of nitrate reducing bacteria (NRB)
     

Fluorescence Microscopy

• DNA and RNA in bacterial cells are stained using Acridine Orange or DAPI and then analyzed using a fluorescent microscope

• DNA and RNA within bacterial cells (or any other organism present) is stained with these chemicals. The DNA and RNA is then illuminated using different wavelength light filters by the microscope and the bacteria are counted or photographed. The illuminated bacteria are then quantified based on volumes and microscope viewing area formulas.
   

Fluorescence In Situ Hybridization - Genetic RNA hybridization

• This technique has been used for years in the medical industry and in recent years, has been adapted to the oil and gas industry. Highly specific fluorescent tagged RNA probes are designed, and then used to hybridize with 16s ribosomal RNA within targeted bacterial cells. If the type of bacteria that are targeted are present, the fluorescent tagged probes will fluoresce when analyzed with a microscope.

 

Luminultra ATP Based Microbial Activity Analysis

• Adenosine Triphosphate (ATP) is an energy molecule used by living organisms. Active bacteria will have ATP present within their cells. With the Luminultra method, ATP molecules are isolated from bacteria in water samples, and the amount of ATP is calculated using a luminometer. These ATP readings can give the level of bacterial activity in a sample. 
   

Sulfur Isotope Ratio Analysis

• Sulfur Isotope Ratio Analysis (SIRA) is a technique that can be used to determine if H2S production is due to microbial activity (e.g. sulfate reducing bacteria {SRB}) or geochemical processes  
  It Is well known that SRB reduce sulfate to hydrogen sulfide and in so doing enrich the sulfide phase in S-32.