The presence of sulphate-reducing bacteria in live drilling muds, core materials and reservoir formation brine from new oilfields

Abstract

The sulphate-reducing bacteria (SRB) produce the toxic gas hydrogen sulphide (H2S) and cause numerous problems in the oil and gas industry. It has been suggested that these organisms are either introduced to the formation by drilling or water injection or that they may be indigenous. Little is known of the activity and survival mechanisms of the SRB under reservoir conditions. In this study a number of samples from hydrocarbon reservoirs were inoculated into sulphate-rich growth medium to determine the presence and activity of the SRB. The samples studied included freshly drilled core material and live drilling muds. The majority of samples analysed contained SRB which produced HzS to varying degrees following different incubation times. Organisms capable of producing H2S at temperatures up to 95~ were detected. Often long incubation periods, in excess of 6 months, were necessary before H2S was produced.

Minimizing Formation Damage in Drilling Operations: A Critical Point for Optimizing Productivity in Sandstone Reservoirs Intercalated with Clay

“…Microbes or bacteria can trigger oxidation reactions involving loss of hydrogen a result of corrosion, pitting, and stress cracking of downhole and surface equipment [31]. Microbes or bacteria can also trigger the loss of sulphates, ultimately producing hydrogen sulphide gas, which can have adverse health impacts on rig personnel throughout drilling operations; these bacteria are either natives of the reservoir or have been brought into the reservoir during drilling operation [33]. Mcgovern-Traa et al [33] reported that the behaviour of these bacteria under reservoir conditions are not completely understood [33].…”

“…Microbes or bacteria can also trigger the loss of sulphates, ultimately producing hydrogen sulphide gas, which can have adverse health impacts on rig personnel throughout drilling operations; these bacteria are either natives of the reservoir or have been brought into the reservoir during drilling operation [33]. Mcgovern-Traa et al [33] reported that the behaviour of these bacteria under reservoir conditions are not completely understood [33]. However, if these sulphatereducing bacteria (SRB) are indigenous and feed on nutrients contained in reservoir drilling fluid (RDF) or injected water, this means that the associated formation damage reactions will extend beyond the near-wellbore region, reaching rather deep into the sandstone reservoir [34].…”

Evaluation of a More Environmentally Sensitive Approach to Microbiological Control Programs for Hydraulic Fracturing Operations in the Marcellus Shale Using a Nitrate-Reducing Bacteria and Nitrate-Based Treatment System

“…Because of being the last addition to the reservoir, treatment of the fracturing fluids represents an appropriate location to apply remediation strategies to help maintain integrity of the future well and minimizing production of sour oil or gas. Additionally, the drilling process is another possible source of contamination in the wellbore because drilling muds are circulated through thousands of feet of subterranean formations while being recycled into an open tank or pit (Mcgovern-Traa et al 1997;Struchtemeyer et al 2011). Regardless, when microbes are introduced, adequate treatment is necessary to mitigate the possibility that these detrimental bacteria establish viable colonies in the wellbore and in the formation (Johnson et al 2008).…”

Microbially Induced Formation Damage in Oilfield Reservoirs

“…The presence of microbes in oilfield reservoirs is widely accepted, and have been isolated from oilfield reservoirs world wide (1 & 2). These microbes while often native to the reservoirs can also be introduced as a result of drilling operations and/or water injection (3).…”