The Use of Residual Oil as Nutrient for Microbial Enhanced Oil Recovery - JIP Proposal

Statoil are applying a novel aerobic microbial enhanced oil recovery technique to the development of Norne. The DTI and several UKCS Operators are keen to extend the approach but feel that currently there is insufficient data to make a sound technical and economic appraisal of the process. A one year JIP of principally laboratory work is proposed to fill this gap. The cost of participation is around £40k assuming five sponsors. For a detailed Proposal please contact Nigel Brealey ( n.brealey@senergyltd.com ), principal reservoir engineer with Senergy Ltd.

Background

Following laboratory research and pilot trials, Statoil are using a novel process to enhance recovery from their Norne Field. The process involves stimulating naturally occurring bacteria that feed on oil to create conditions that release residual oil from the rock.

Such bacteria are not at all rare. One estimate is that 20% of sea-borne bacteria feed on oil. In the process of metabolising the oil, the bacteria produce chemicals which have a surfactant-like effect in releasing oil. Similar microbial activity is used to clean up oil spills.

The particular approach differs from most historical MEOR application since it avoids having to supply an external carbon source which is considered logistically impossible in an offshore or other location remote from suitable chemical sources. Other nutrients are still required, but in much smaller volumes.

Statoil consider that the technique will produce about 32 million incremental barrels; about 6% above what would otherwise have been recovered.

The nutrients used are simple fertilizers, consisting largely of nitrates and phosphates, and oxygen. In addition to improved sweep, the nitrates injected inhibit sulphate reducing bacteria (SRBs). This can represent a cost saving since this can eliminate the need for alternative inhibition.

The Norwegian Petroleum Directorate awarded their 2001 IOR prize to Statoil and their researcher, Egil Sunde, who developed the approach ( http://www.npd.no/English/Emner/Ressursforvaltning/iorpris2001.htm ).

The UK DTI and two major oil operating companies have expressed interest in possibly extending the application of this MEOR approach. The UK DTI has estimated there could potentially be well over 200 million incremental barrels from UKCS fields alone. Also, the process could be have potential in many other areas of the world.

Why a JIP is Being Proposed.

It is understood that the Norne application was quite inexpensive since the decision had already been taken not to remove oxygen from the sea water injection by using corrosion-resistant materials. There were also savings from avoiding the need for other chemicals to guard against reservoir souring.

Some individuals believe that it should be possible to proceed to field trials or application without further laboratory work. However, no other known offshore Operator has been prepared to undertake such an application without further understanding and quantification of the process.

The concerns expressed have been:

• Costs would normally be quite substantial, even for a field trial
• Although some of Statoil's laboratory results have been made public [1], there is only limited information. It is also noted that there were a number of practical problems encountered during the experiments.
• Public information on other pilot results mentioned by Statoil is very limited.
• There should be data available to adequately design a pilot to ensure the response is sufficient to be evaluated
• Although blockage effects from the microbes may cause a diversion effect improving sweep, this could also reduce injection and impair shorter term production.

The requirements for a forward programme have been discussed by a panel of industry representatives. The laboratory work is defined in a "Statement of Requirement." It has been sense checked with a number of suitable laboratories. The elements of the first phase of the programme are:

• Enrichment of aerobic hydrocarbon-oxidising bacteria from a source representative of those in seawater flood operations.
• Determination of nutrients required for maximum effect on crude oil
• Measurement of impacts in releasing oil and other properties on a core scale, using outcrop rock at relatively low temperatures (25 - 40°C).
• Initial projections for a pilot flood response.

It is recognised that the programme could stop or need re-directing at various points depending on outcomes from different phases. Decisions about milestones and details of the subsequent laboratory studies outlined above would be made by a panel of experts drawn from the sponsoring JIP members.

We have also been in communication with Statoil. It is uncertain whether they would participate in this JIP financially given their own research. However, it is intended to maintain communication with them; inputting their experience where possible.

The overall objective is to obtain reliable laboratory results which, if sufficiently encouraging, will persuade one or more Operators to proceed to a field trial. This may require further work beyond this first Phase depending on the needs of the JIP sponsors.

A tentative overall outline programme is given below showing £200,000 in Phase 1 and £400,000 tentatively in a future phase:

Patent Issues

Mention must also be made of a potential patent issue. Statoil have taken a patent on their process. We understand that Statoil do not wish to stifle research in this area by the concern about any benefit being lost in licence fee. Statoil advise that the patent protects their position, and their ability to market their capability overseas. They see advantage in more general take-up, but it is not entirely clear what the impacts might be on others. A necessary pre-curser to the bulk of the programme described here is adequate assurance from Statoil that any sponsor here would not be disadvantaged by Statoil's patent.

One suggestion has been to ask Statoil for a statement to say they would be prepared to licence the technology which would allow each JIP participant to negotiate an agreement with Statoil.

Reference

1. Aerobic Microbial Enhanced Oil Recovery. Torsvik, Gilje and Sunde. Published in International Conference on MEOR & Related Technology for solving Environmental Problems. Plano , Texas Sept 1995.

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