Microbially-influenced corrosion (MIC) contributes to the general corrosion rate (CR), which is typically measured with carbon steel coupons. Here we explore the use of carbon steel ball bearings, referred to as beads (55.0 ± 0.3 mg; Ø = 0.238 cm), for determining CRs. CRs for samples from an oil field in Oceania incubated with beads were determined by the weight loss method, using acid treatment to remove corrosion products. The release of ferrous and ferric iron was also measured and CRs based on weight loss and iron determination were in good agreement. Average CRs were 0.022 mm/yr for eight produced waters with high numbers (105/ml) of acid-producing bacteria (APB), but no sulfate-reducing bacteria (SRB). Average CRs were 0.009 mm/yr for five central processing facility (CPF) waters, which had no APB or SRB due to weekly biocide treatment and 0.036 mm/yr for 2 CPF tank bottom sludges, which had high numbers of APB (106/ml) and SRB (108/ml). Hence, corrosion monitoring with carbon steel beads indicated that biocide treatment of CPF waters decreased the CR, except where biocide did not penetrate. The CR for incubations with 20 ml of a produced water decreased from 0.061 to 0.007 mm/yr when increasing the number of beads from 1 to 40. CRs determined with beads were higher than those with coupons, possibly also due to a higher weight of iron per unit volume used in incubations with coupons. Use of 1 ml syringe columns, containing carbon steel beads, and injected with 10 ml/day of SRB-containing medium for 256 days gave a CR of 0.11 mm/yr under flow conditions. The standard deviation of the distribution of residual bead weights, a measure for the unevenness of the corrosion, increased with increasing CR. The most heavily corroded beads showed significant pitting. Hence the use of uniformly sized carbon steel beads offers new opportunities for screening and monitoring of corrosion including determination of the distribution of corrosion rates, which allows estimation of the probability of high rate events that may lead to failure.

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Samples of (I) produced waters, (II) central processing facility (CPF) waters and (III) pipeline solids were collected from a light oil-producing field. The biocide, tetrakis(hydroxymethyl)phosphonium sulfate (THPS) was routinely used in the CPF. Samples monitoring indicated that THPS was effective in microbial control but also increased concentrations of sulfate and phosphate in transitioning from Type I to Type II waters. Type II waters had high concentrations (up to 60 mM) of acetate but low most probable numbers (MPNs) of acid-producing and sulfate-reducing bacteria, indicating the presence of active biocide, as high MPNs were found in Type I waters. Solids had high phosphate and high MPNs, indicating that THPS was inactive. Solids had oil and an anaerobic community dominated by Acetobacterium, which may contribute to conversion of oil to acetate. The presence of THPS prevented the use of this acetate in Type II waters, where it accumulated to unusually high concentrations.

Microorganisms contribute to souring and corrosion in oil and gas field systems. Biocides and/or nitrate can be used to mitigate the negative effects associated with these microbial activities. In order to determine the success of or the need for these measures we use a number of analytical tools on aqueous or solid field samples: (i) spectrophotometric and HPLC assays are used to monitor key analytes (sulfate, sulfide, nitrate, nitrite and others), (ii) microbial assays are used to determine numbers and activities of key microbes and (iii) sequencing of PCR amplicons, typically of a portion of the 16S rRNA genes is used to determine microbial community compositions in field samples. The trick is to combine the information to arrive at a comprehensive view of what is happening and what action may be needed. For instance, a shale gas and a shale oil field in North West Canada, appear to have similar water chemistry. Both are highly saline but halophilic (salt loving) SRB were only found in samples from the shale oil not in those from the shale gas field, which appears related to the different temperatures in these fields of 30-35°C and 75-100°C, respectively. Hence, mitigation measures aimed at killing bacteria downhole may be appropriate for these shale oil but not for these shale gas environments.

The larval species Atlantocaris gigas Ortmann is shown to be conspecific with Heterocarpus ensifer A. Milne Edwards, while Procletes biangulatus Bate is the larva of Heterocarpus levicarina (Bate). Each species passes through 13–15 zoeal stages and 3–4 megalopal stages. The later zoeal stages are large, have a long toothed rostrum, a carinated carapace and dorsal abdominal spines. The carinae on the carapace are retained in the adult; the rostrum becomes shortened and the abdominal spines modified at metamorphosis. Larval characters support the retention of Heterocarpus in the Pandalidae. New information on the distribution of both species is included.