ABSTRACT
Scale deposition in perforations and tubular goods has been a problem for decades in the oil industry. Years have been spent in research and in somewhat futile attempts to solve this problem. Classic treatment is with a fluid, usually an acid, which is designed based on the mineralogical content of the scale. Complicating these efforts is the relationship of down-hole bacteria to scale deposition. The above mentioned treatments do not address the presence of bacteria. The ability of organisms to thrive in hostile environments is sometimes difficult to overcome and the number of biocides on the market today attests to this. The problems caused by these scale deposits have cost producers millions of dollars and have been known to change sweet oil to sour in whole fields. Also, much money has been spent for cathodic protection and other corrosion inhibition treatments when the major cause of tubular corrosion may have been biological activity.
Typical scale identification consists of determination of constituents by chemical means, X-ray or microscopic analysis, and acid solubility tests. This series of tests is necessary for the design of scale removal treatments, but does not account for the causes of scaling. Computer programs which determine the scaling tendency of waters give an insight into the cause of scaling. However, none of these tests can show the influence of biological activity. In order to provide a more thorough analysis of the cause of scaling, the use of epifluorescence microscopy has been added to the testing scheme. Bacterial cells from a scale and/or water are dyed and their fluorescence observed microscopically. The lack of fluorescence indicates no biological activity. The information gained from this microscopic technique is then used to modify removal treatments and to design treatments to help prevent further deposition.
This paper will discuss (1) epifluorescence as a scale testing technique, (2) well conditions that contribute to bacterial growth, (3) areas in the Rocky Mountains where bacterial scaling is prevalent, and (4) removal and inhibition treatments.
