Extracting Profits From Abu Dhabi's Sour Gas
Authors: Henni Abdelghani 
Published: February 2015

Sour Gas

An increase in local gas consumption in the UAE has caused Abu Dhabi National Oil Company to turn to development of the emirate’s sour gas fields, one of the most challenging types of fields. The development of the first sour gas field here, the Shah gas field in Abu Dhabi, is on track for 2014 startup with work on the project more than 70% complete at the end of 2012.

The USD-10-billion project is proceeding under the direction of Al Hosn Gas, a joint venture between Abu Dhabi National Oil Company (ADNOC) and Occidental Petroleum Corporation (Oxy), where Oxy holds a 40% participating interest in a 30-year contract. ADNOC holds the remaining 60% interest.

“The project involves construction of several gas-gathering systems, new gas and liquid pipelines, and processing trains. The development is expected to produce significant amounts of condensate and natural gas liquids [NGL],” said Saif Al Ghafli, chief executive of Al Hosn Gas.

In 2012, Al Hosn Gas constructed plants and a pipeline network, and completed almost four of the 20 wells targeted in the drilling campaign. In addition, the joint venture took over full operatorship of the drilling program from Abu Dhabi Company for Onshore Oil Operations (Adco) in April 2012, and finalized contracting of required services and materials for the drilling program.

The joint venture also obtained two rental drilling rigs that started drilling operations in July 2012, in addition to Adco’s assistance in lending a rig and drilling the first four wells in 2011 and 2012.

Al Hosn Gas’ Development Division, which includes geologists, geophysicists, reservoir engineers, drilling engineers, and drilling health, safety, and environment (HSE) and field-implementation specialists, will help ensure that the continuously updated reservoir development and drilling plans can aid in maintaining uninterrupted availability of the anticipated volumes of gas at the wellheads during the project’s expected 30-year lifespan.

The development team conducted the first well-production test on 5,000-ft lateral sections in the Arab C and D reservoirs in the Shah field. The subsurface group has continued to build and improve reservoir models based on the latest well data obtained to further optimize the ongoing drilling program. A seismic-data reprocessing pilot was successfully concluded, providing further technical insight for optimum well placement in the reservoir, and will move on to full field implementation later this year.

The Shah Gas Development (SGD) project consists of four major elements: the gas-gathering system, the Shah processing plant, product pipelines, and the Shah sulfur station. The field’s high hydrogen sulfide content—23% in the well fluid—means that in addition to key HSE design and implementation considerations, it will pose certain unique challenges due to the sheer scope of work to be done. The SGD project will also have a total of four trains for the massive Sulfur Recovery Units (SRU) that will process the 1 Bcf/D of sour gas. The SRUs will have a capacity of 2,500 tons per day (T/D).

The four main products expected to be produced from the billion-scf/day of feed gas at SGD, which lies about 180 km southwest of Abu Dhabi, are sales gas (500 MMscf/day), NGL (4,400 T/D), sulfur (9,200 T/D), and about 33,000 B/D of condensate.