Injection Of A Bactericide-Surfactant During Hydraulic Fracturing - A New Method Of Corrosion Control
Authors: Hawsey Jerry D. , Whitesell L.B. , Kepley J.A. 
Published: December 2007

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Abstract
Microbial corrosion and plugging have been recognized as problems in waterfloods for some time; however, only recently has it been realized that they may be equally as troublesome when introduced to a reservoir by hydraulic fracturing or some other similar means. Continental Oil Company's Petrochemical Department has introduced what is believed to be a new concept in arresting and controlling this microbial activity. This concept consists of injecting a bactericide-surfactant into the formation during hydraulic fracturing or squeeze-type treatments.

I Introduction
Extensive laboratory and field data have been accumulated to prove that producing formations are often contaminated by micro organisms during hydraulic fracturing treatments. Contamination has occurred when fluids containing micro organisms are used to create a hydraulically fractured system and to carry propping agents into the fracture system. Desulfovibrio (sulfate reducing) and Gallionella (iron) bacteria often have been found in return water after completion of the fractured well. As a result of this microbial contamination, evidence has been found that wells will produce various quantities of hydrogen sulfide, iron sulfide, and various other products of corrosion. Corrosion rates have increased in contaminated wells and plugging, especially due to a combination of iron sulfide and crude oil sludge, has been found. It is general knowledge that bacteria can constitute a problem in waterflood systems, including source and injection wells but too little thought has been given to the possibility that they might also have an adverse effect on producing wells. Work performed in past months has proven conclusively that micro organisms can be the source of many corrosion difficulties encountered in producing wells. Hydraulic fracturing can be a major source of this contamination. Sulfate reducing bacteria are a major source of hydrogen sulfide gas and can initiate corrosion or pitting of metal surfaces. They can survive in almost any kind of water and commonly are found in streams, ponds, or subsurface water beds. They are introduced to the reservoir by water from one of these sources being used in a drilling fluid, cement job, squeeze job, or in hydraulic fracturing. Once in the reservoir they quickly adapt to the environment. The Gallionella, or iron bacteria, are troublesome in that they cause iron hydroxide precipitation and slime build-up in the wellbore area. In general, bacteria can cause permeability plugging of the formation through the deposition of their by-products, or because they are present in large numbers. The number of bacteria required to initiate plugging action varies with the permeability of the formation, but the presence of any sulfate reducing bacteria or iron bacteria can be the beginning of a serious corrosion or plugging problem. Extensive field testing has shown that the proper use of a good bactericide-surfactant can assist in controlling this type of corrosion.