MYACIDE® AS - APPLICATIONS IN OIL AND GAS

Myacide AS is a broad spectrum bactericide with a relatively high level of product safety combined with the effective biocidal activity required in the oil and gas industry. The following examples demonstrate the efficacy of Myacide AS in typical treatment conditions in a wide range of applications found in this industry. It has been tested in both laboratory-based studies and in field trials.

LABORATORY TRIALS
Suspension Tests

In "time to kill" tests, Myacide AS at 100ppm and Kathon WT achieved 100% kill of aerobic bacteria in production water obtained from a North Sea oil rig.

Other treatments showed lower log10 reductions after equal contact times of 48 hours. Against the anaerobic sulphate reducing bacteria (S.R.B.), Myacide AS achieved complete kill in less than 3 hours with a starting inoculum of >106 colony forming units (c.f.u.)/ml production water, demonstrating superior performance to the other biocides.

Biocidal Activity in Drilling Muds

A bentonite/starch based drilling mud was inoculated with a mixture of laboratory and naturally occurring bacterial and fungal isolates to give an initial population of 104 c.f.u./ml. The mud samples were treated with Myacide AS at 40 to 100ppm for six days at 25°C. At two different pH's (7.3 and 9.5) and with two separate inocula, Myacide AS showed equally good activity at 40 to 100ppm reducing the inoculum levels to between 101 and 102 c.f.u./ml at 1 to 6 days after treatment.

Effect of Myacide AS on the Physical Characteristics of Drilling Muds

In another trial, a bentonite/starch mud with an initial pH of 8.4 was treated with Myacide AS at 50 to 150ppm. Various other commercially available biocides were also included; Dowicil 75 at 1000ppm, Proxel GXL at 200ppm, Basamid at 200ppm, paraformaldehyde at 2800ppm and Phylatol at 2.5%. A mixed microbial inoculum containing several species and strains of Pseudomonas, Desulfovibrio and cellulolytic bacteria plus natural fungal isolates and isolates from cooling towers was added to the mud samples to give 106 c.f.u./ml SRB, 107 c.f.u./ml aerobic and cellulolytic bacteria and 104 c.f.u./ml fungi.

After incubation for 8 days at 25°C, the samples were assessed for apparent viscosity, yield value and fluid loss. The untreated control experienced a rapid breakdown in physical stability with an associated drop in pH from 8.5 to 5.0 over the 8 days. Except for Dowicil 75 at 1000ppm, the physical stability and pH of the mud was maintained by the other biocides and by Myacide AS due to their activity preventing adverse effects from the contaminating organisms.

The Use of Myacide AS to Control Microbial Growth in Contaminated Fuel

In a laboratory test, contaminated fuel/water samples obtained from a diesel oil storage tank were treated with Myacide AS at 50, 250, 500 and 1000ppm. The three higher rates of Myacide AS gave complete reduction of aerobic bacteria (initially 105 c.f.u./ml), anaerobic SRB (104 c.f.u./ml) and filamentous yeasts (103 c.f.u./ml) at 2 days after treatment. The same effect was observed with 50ppm of Myacide AS at day 5. Control was maintained for 7 days except against SRB where numbers rose to 101 to 102 c.f.u./ml at day 7 with the three lowest rates of Myacide AS.

The Efficacy of Myacide AS in Contaminated Fracturing Fluids

Myacide AS at 80ppm in an HP Guar-methanol fracturing fluid led to a reduction from 1 x 104 c.f.u./ml to 1 x 102 c.f.u./ml after several days. The Myacide AS affected neither the performance of the enzyme breaker system nor the rheology of the fluid.

FIELD TRIALS
Studies in Drilling Muds

In the Middle East, Myacide AS shock dosed in a starch/bentonite drilling mud at 100ppm every 1 or 2 days, prevented mud spoilage problems at a water well drilling site over a 12 week period.

In Alberta, Canada an initial dose of 100ppm Myacide AS followed by daily applications of 50ppm over a 5 week period performed well with no stability problems due to bacterial spoilage. The drilling mud was composed of starch, oil, KCl, NaOH, bentonite and polyacrylamide with a pH of 10 to 10.5. A mud volume of 1500 to 2800 barrels was circulated for 8 hours to a depth of approximately 12,000 feet with a bottom hole temperature of 185°F. A microbiological sample showed a reduction from 1 x 107 c.f.u./ml to 5 x 103 c.f.u./ml following treatment.

Control of SRB in Produced Waters

At an oil well site in Alberta, Canada the oil flow lines from 12 wells had undergone frequent failures due to severe pitting corrosion. This corrosion, which was probably due to S.R.B., had already led to the replacement of several lines. In a trial, Myacide AS at 50ppm in 150 litres of produced water was pumped into the producing well and the casing valve was closed for 24 hours. Normal production continued and Myacide AS was injected again on the following day. At 10 of the wells with initial SRB contamination, the Myacide AS led to significantly reduced levels of infection in four wells with complete control in the other six wells.

Well Squeeze Fluids

At a site in Canada, 5 gas wells were treated with well squeeze fluids containing 50ppm Myacide AS. In one well the H2S level in the gas was reduced from

250ppm to 0 but this and another well showed a return to 40ppm of H2S after 3 months. The other three wells remained clear of souring for 5 months.

Note: Conditions for microbial growth are likely to vary considerably between oil and gas wells and in different processing fluids. For this reason, it is important to fully evaluate any new biocide regime before commencing the treatment program.

ENVIRONMENTAL SAFETY
Myacide AS, like other effective biocides, is toxic to some algae species and is therefore potentially dangerous for the environment. However, its inherent biodegradability, rapid photolysis in water, low bioaccumulation characteristics and hydrolysis at low concentrations indicate that it is unlikely to cause significant, long-term adverse effects in the aquatic environment.

For further information consult Environmental Safety Product Information Sheet (PBP 07).<![endif]>

REGULATORY APPROVALS
In the UK, the Department of Energy lists Myacide AS as a Category 2 product, which allows offshore installations to discharge up to 10 tons of product/year without notification. In the USA, the EPA have cleared the discharge of up to 25ppm into the Cook Inlet of Alaska concluding that toxic effects would not occur due to the hydrolytic instability of Bronopol.

For further information on Regulatory Approvals consult Product Information Sheet (PBP 10).

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The information contained in this sheet is believed to be accurate but is given without warranty.