Speciality Chemicals

Down the well

Chemicals suppliers to the oilfield industry must develop green products while contending with ever more difficult operating conditions. We report from the latest RSC event

'Chemistry in the Oil Industry' is a symposium and table-top exhibition organised every other year by the UK's Royal Society of Chemistry (RSC). The twelfth event in the series, held in Manchester last November, highlighted two themes, which both make life more difficult for suppliers of oilfield chemicals.

First, legislation is getting more stringent, often requiring suppliers to reformulate their products. It is also becoming more complex as the Oslo-Paris (OSPAR) Convention for the Protection of the Marine Environment of the North-East Atlantic that regulates this industry is progressively harmonised with REACH, bringing the initial substitution deadline of December 2012 sharply into focus.

Secondly, the conditions under which oil and gas are being extracted are becoming tougher, which itself poses major demands on the chemistry used. The low hanging fruit has long since been picked. Oil and gas are being extracted from more challenging environments, like the Arctic regions or deeper sub-sea wells, with Enhanced Oil Recovery (EOR) techniques being increasingly needed to flush out more oil from existing wells.

Nonetheless, there was plenty of new chemistry on show in Manchester. As well as launching of showcasing new products, chemicals suppliers had stories to tell of how their products have been developed and applied to meet the twin demands of harsher conditions and more exacting legislation.

Corrosion inhibitors, among the most vital chemicals in oil and gas production, are under particular pressure. As several speakers noted, many ingredients in them have been earmarked for substitution under OSPAR's Harmonised Mandatory Control Scheme because they do not meet the requisite tests for biodegradation, bioaccumulation and/or aquatic toxicity.

A further complication is that many of these ingredients are classified as surfactants, raising concerns about biodegradation, particularly in the cases of base ingredients with long alkyl chain sequences, like benzyl quaternary amines and alkyl imidazolines. Indeed, since 2007 the UK authority CEFAS has ceased to accept the traditional Log P_ow measurements for bioaccumulation for surfactants. Consequently, substitution warnings are being applied to surfactants with molecular weights of <700 that are either <60% or 70% biodegradable in 28 days or have an EC₅₀/LC₅₀ score of <10 mg/litre, unless there is evidence that they should not bioaccumulate.

Dominique Dugué of oilfield chemistry specialist Baker Hughes noted that corrosion inhibitors are "among the most complicated of oilfield treating chemicals, perhaps second only to emulsion breakers". Their composition varies greatly with the relative amounts of the fluids being treated and the corrosive nature of the fluid content. Moreover, by their nature corrosion inhibitors are "inherently toxic to aquatic life".

Corrosion inhibitors are intrinsically dangerous to marine life

Formulating suitable corrosion inhibitors, remarked consultant Dr Henry Craddock of Roemex, is "a chemistry challenge", as the most effective chemistries do not have the required environmental characteristics. "Even more frustrating, in producing more acceptable environmental profiles for inhibitor products, it is possible to compromise the very technical effects you are trying to design," he added.

Various chemistries have been tried, notably amino acid and aspartic acid, polyaspartates, phosphates and phosphonates, phosphate esters and their related alkoxylates and others. The problem remains of a "significant trade-off between inhibitor efficiency and ecological properties, in particular the mismatch between persistency and biodegradation," Craddock said.

In response, said Andrew Miles, oilfield chemicals specialist Champion Technologies has sought "to identify environmentally acceptable corrosion inhibitors, including developments of both novel and traditional chemistries". Aquatic toxicity was investigated for various commercial surfactants that "illustrated a number of useful structure-toxicity relationships which can be used to guide the selection of more environmentally acceptable components".

Miles particularly cited case studies on alcohol ethoxylates and alkyl imidazolines, plus ways to achieve a balance between toxicity and corrosion inhibition performance and exploiting synergies to improve corrosion inhibition. This has all led Champion to a toolbox of products and combinations that continues to grow, with one unnamed new formulation looking particularly promising.

Craddock described the use of alkyl polyglucosides (APGs) as corrosion inhibitors for oil and gas production, particularly in Teekay Petrojarl's Banff field. APGs, he said, "have been developed to tackle the specific regulatory and environmental challenges relating to application in the marine environment of the North Sea Basin".

Called RX-2055, this new formulation outperformed the incumbent in trials and field applications. It offered excellent corrosion protection on produced fluids under both flow regimes and the process system was less sensitive to it, so increased corrosion protection was achieved. There was no increase in water in oil or oil in water throughout the system and no effect on produced water characteristics.

Corrosion inhibitors and scale inhibitors are increasingly used in combination as operators in sub-sea systems try to make savings in chemical consumption and process design. Such chemicals, said Dugué, must combine the physical properties for application and meet all environmental criteria, while also protecting the integrity of the flowline and ensuring that no flow assurances issues are created.

Baker Hughes has recently developed and qualified a new, multi-component combined scale and corrosion inhibitor for a TAQA Britani platform in the North Sea. This had to be applied via a sub-sea umbilical line, which involved the danger of it coming into contact with produced gas under severe pressure and leading to hydrate formation.

Oil and gas are increasingly being sought in inaccessible, environmentally sensitive regions of the world

Various chemistries were assessed before a polycarboxylic acid-based scale inhibitor was chosen for use in the formulation. This was essentially because polycarboxylic acid is readily biodegradable in oilfield applications, thus clearing the most common stumbling block, as well as being thermally stable and an excellent inhibitor of carbonate and sulphate scale.

Dugué described in detail the corrosion and other testing on a series of blends, followed by umbilical, viscosity and both material and product compatibility testing. 'Blend 18' came out on top, with the likely result, he said, being "improved corrosion protection in the production system and consequently reduced chemical consumption and ultimately discharge into the environment".

The event was not all about corrosion and scale inhibitors, of course. For instance, John Kennedy of MacDermid Offshore Solutions described the development of potassium formate in place of monoethylene glycol (MEG) as a freeze point depressant for subsea hydraulic fields in the Arctic Circle, where conventional hyudraulic fluids are not tolerated.

Unlike MEG, Kennedy said, potassium formate is non-toxic and exerts a significantly lower COD and BOD demand, as well as being readily biodegradable. MacDermid has developed a novel fluid that offers an 85% reduction in COD "which significantly reduces the potential for cultural eutrophication of sensitive Arctic seabed environments".

From Momentive Performance Materials, meanwhile, Kalman Koczo reported on the development of "a new class of silicon-based surfactants that provide enhanced demulsification performance in a variety of crude oil systems". In studies of their adsorption characteristics and interfacial tension, these silicon-modified outperformed other tested groups and also performed well as a booster to conventional organic demulsifers. Further bottle testing is now planned.

Also in the surfactants field, Kevan Hatchman of Rhodia Novecare looked at surfactant synergies in the development of foamers for gas well deliquification, a common means to prolong well productivity. This found both synergistic and antagonistic behaviours in different combinations of commercial surfactants and Hatchman tentatively suggested some ways forward.

Among the poster presentations, James Donovan of Dow Oil & Gas presented Elevate CO₂. This is a suite of CO₂-soluble surfactants that, when injected with supercritical CO₂ into a mature reservoir during EOR, can address the two key problems of conventional CO₂ flooding: mobility and conformance control. Elevate CO₂ can thus, Dow claims, reduce the amount of CO₂ injected and improve the oil yield.

Similarly, Jonathan Wylde presented Clariant Oil Services' development of an alkoxylated solvent as a replacement for 2-butoxyethanol (2-BE). 2-BE has been widely used as a pre-flush additive in fracturing oil and gas wells but is environmentally suspect has been linked to birth defects. The replacement has good mutual solvency and wettability modification properties and the same ready biodegradability as 2-BE but has far superior toxicity and bioaccumulation properties.

The University of Manchester itself has a Corrosion & Protection Centre (CPC), within its School of Materials. In early February, the CPC announced a "strategic partnership" with another exhibitor at the November event, AkzoNobel, which claims to be the world's largest manufacturer of corrosion protection coatings, as well as a major supplier of speciality chemicals to the oilfield and related markets.

This will include endowing a chair in corrosion control, with Professor Stuart Lyon having already appointed to it, employing post-doc researchers and PhD students to work on projects with active technical involvement from AkzoNobel and giving AkzoNobel access to the CPC's specialist measurement equipment techniques. The work will mainly be focused on anti-corrosion coatings. It is estimated that corrosion costs some $2.2 trillion/year, over 3% of global GDP.

As the oil age enters what could be a long, slow decline, ever more ingenious ways will have to be found to exploit ever more difficult-to-access sources with what operators at least hope will be zero discharge and minimal environmental impact. Chemistry - as so often - will be the means by which they try to achieve this.

 

 

From Online Issue: February 2012