Progress at Bab: Shell and ADNOC’s strategy for the Bab Sour gasfield

Abu Dhabi

Shell is a partner in Abu Dhabi Gas Industries and an original member of the Abu Dhabi Company for Onshore Oil Operations (ADCO). Country chairman Andrew Vaughan spoke to TOGY about the development strategy the Abu Dhabi National Oil Company (ADNOC) and Shell are looking at for the Bab Sour gasfield. In 2013, ADNOC selected Shell as its development partner for the field.

How does the Bab sour gas project complement the production of the Bab oil and gasfield?

The Bab reservoir contains a lot of fields stacked on top of each other. The field operated by ADCO has for many years been producing gas that is reinjected to improve oil recovery. The layers we are working with for the Bab sour gas project are deeper in the reservoir and have not yet been developed, but we are keen to apply the seismic and geological knowledge, as well as the production experience, we have received from our long history onshore Abu Dhabi as part of the ADCO concession.

In partnership with ADNOC, we are now conducting a subsurface appraisal of the Bab sour gasfield to know exactly what we are going to be developing. We are also in the process of awarding contracts for pre-front-end engineering and design for the project. The scope of the project is defined in this process. It is very important we get the front-end engineering and design right so that the project execution and ultimate production will be cost-effective and safe.

How is Shell seeking to avoid potential hazards resulting from the corrosive nature of sour gas?

There are many tried and tested ways to solve this problem, such as using corrosion-resistant alloys or corrosion inhibitors. Part of the design process is obtaining the best approach to the problem, given the feedstock available and the operating conditions.

From our contractors, we will look for sound integrity in design and construction, as well as sound operating practices. Well-trained and well-prepared operators can significantly improve onsite safety levels. We will bring experience, particularly from our sour gas operations in Canada, to develop the right operating practices for the field. We will also look to our partners at sour oil and gasfields in Oman, which have experience working in this type of climate.

What precautions must be taken for the project to avoid affecting communities in close proximity to the field?

When developing a sour field, it is critical to consider the impact on our neighbours in the vicinity. Despite the field’s relative proximity to communities in Western Region, there are plenty of ways in which safety can be optimised. These include creating safety exclusion zones, implementing emergency shutdown procedures, introducing processes to mitigate operational risks and designing the plant to reduce the number of potential leak paths for the gas. The experience Shell has had from developing these techniques over the last six decades will be brought to bear in this context.

Where can the sulphur produced at the field best be used to add value to existing industries?

The global market for sulphur is volatile but robust, and booming in 2014. Sulphur can be used to produce products and chemicals, such as fertiliser and sulphuric acid. We see potential in using the sulphur extracted from the Bab development for both purposes, but particularly in fertilisers. For example, by marrying it with a phosphate source, value-added fertilisers could be created towards supplying the global demand for food.

Where has Shell amassed the relevant experience to handle the sulphur present at the Bab field?

Our research on sulphur recovery and handling was mainly cemented in Canada. We first started developing sour fields in order to produce sulphur. The gas present both there and in the Bab field is not just contaminated with hydrogen sulphide, but also with other sulphur compounds, such as mercaptans and disulphides.

All of these complex chemicals can be dangerous and difficult to handle, but we have developed technologies that allow us to treat them. Our Sulfinol process technology removes hydrogen sulphide, carbon dioxide, carbonyl sulphide, mercaptans and organic sulphur components from natural and synthesis gas.

Which specific technologies will Shell look to apply in Abu Dhabi?

We are still looking at some of the technologies we can apply to the field for sulphur recovery, one of them being the use of high-performance column internals and amines for absorption and separation of hydrogen sulphide and carbon dioxide. With challenging reservoir conditions, everything we engineer must be tried and tested. That said, dealing with the elemental sulphur present at the Bab field will require us to scale up techniques as tried elsewhere. We may implement a large-scale sulphur recovery unit with a high capacity.

Bab is one of the largest sour gas projects in the world. It will produce 14.2 mcm (500 mcf) of sales gas per day, with around 13,000 tonnes of sulphur and 7,000 tonnes of carbon dioxide, which we are seeking to capture for enhanced oil recovery applications. It provides room for everything we have already engineered for in previous sour gasfield developments to be enhanced and developed further.

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