scope:

This standard describes field test methods for estimating bacterial populations commonly found in oil and gas systems. Although these techniques have been successful in the oil field, they are not the only methods that are used. It is not the intent of this standard to exclude additional techniques that can be proved useful. However, caution should be exercised with any technique that is at variance from those outlined here.

A glossary of terms used in this standard is provided is Appendix A.

This standard deals only with bacteria and does not consider other organisms that may be found in oilfield fluids, such as archaebacteria, phytoplankton (algae), protozoa, or fungi. In addition, these methods are not applicable to marine organisms such as zooplankton (copepods).

Because effective sampling is essential to any successful analysis, emphasis is given to sampling methods that are suitable for use in oilfield conditions.

Media formulations for enumerating common oilfield bacteria are given.

This standard describes dose-response (time-kill) testing for evaluating biocides used in oilfield applications.

Methods for evaluating sutface attached (sessile) bacteria are addressed. The importance of these bacteria in oilfield problems is usually not adequately considered. Attached bacterial populations are often the most important component of a system's microbial ecology.

Emerging technologies for the rapid determination of bacterial populations and bacterial activity are addressed (See Appendix B). While these technologies are not specifically recommended, it is not the intent of this standard to prevent the use of any technology that can be useful. However, the user must determine the applicability of these new methods to the site/system. Similarly, there are a number of commercially available "test kits" for detecting various types of microorganisms; these are not discussed in this standard. However, the user could use this standard to evaluate the suitability of these test kits for any particular situation.

The simple presence of bacteria in a system does not necessarily indicate that they are causing a problem. In addition, bacterial populations causing problems in one situation, or system, may be harmless in another. Therefore, "action" concentrations for bacterial contamination cannot be given. Rather, bacterial population determinations are one more diagnostic tool useful in assessing oilfield problems.

Further information on the corrosion problems associated with bacterial growth in oilfield systems is given in NACE Publication TPC #3.