Shah Gas Field: Defying the Environment
The development of the first sour gas field in the United Arab Emirates, the Shah Gas Field in Abu Dhabi, reached more than 75 percent by the end of 2012, the company said.
The $10 billion project is being developed by Alhosn Gas, a joint venture between Abu Dhabi National Oil Company (ADNOC) and Occidental Petroleum Corporation (Oxy), where Oxy holds a 40 percent participating interest in a 30-year contract. ADNOC holds the remaining 60 percent interest.
Located about 130 miles (210 kilometers) south west of Abu Dhabi, the Shah gas field covers an area of 5.8 square miles (15 square kilometers), and is expected to start up in 2014.
The Shah Gas project is the biggest of its kind in the world. Although this sour gas field was discovered in the mid-1960s, its remoteness and the complexity of gas extraction made development virtually impossible. Only in recent years has technology advanced to an extent that makes processing such sour gas feasible.
"The project will involve 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, the company also constructed special plants and pipeline network, and completed almost 20 percent of the special wells of the field, which total 20 wells. In addition, the company has taken 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 company has also obtained two rental drilling rigs that started the 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.
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 H2S content - 23 percent 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 – the largest in the world - for the massive Sulphur Recovery Units (SRU) that would process the 1 billion cubic feet per day of sour gas. The SRUs will have a capacity of 2,500 tons per day (TD).
The four main products expected to be produced from the billion scf/day of feed gas at SGD which lies about 112 miles (180 kilometers) southwest of Abu Dhabi, are sales gas (500 million scf/day); NGL (4,400 TD); sulfur (9,200 TD) and about 33,000 barrels of condensate per day.
Challenging the Environment
The development of the Shah gas project is very challenging. The main design technical challenges result from the gas and reservoir characteristics of the Shah Field. The gas is extremely sour, as 23 percent of its content is hydrogen sulfide, and 10 percent is carbon dioxide. The underground temperature and pressure are equally daunting. The temperature is about 150 degrees Celsius and the pressure is as high as 5,500 pounds per square inch.
In addition, the production of sour gas and its conversion to the usable sweet product poses technical and financial challenges, because hydrogen sulfide is toxic and highly corrosive to certain metals. Raw sour gas is generally treated at the well-head stage, to remove the sulfur impurities.
Despite of all these challenges, the soaring local energy consumption has pushed Abu Dhabi to tap the development of the Shah field, and currently mauling of developing other sour fields like Bab and Hail fields.
In August 2008, ADNOC selected ConocoPhillips as a partner for the development of the project, followed in July 2009 by a joint-venture and field-entry agreement. Under the deal, ConocoPhillips was going to have a 40 percent stake in the joint-venture development, with ADNOC to hold the remainder.
But in April 2010, ConocoPhillips decided to pull out from the project without given details about the move. In January 2011, ADNOC selected Oxy as a partner to develop the field.
The remoteness of the location offers up its own set of unique challenges as far as logistics is concerned. Originally, the concept was to transport sulfur in liquid form all the way from Shah via hot water jacket pipelines down to Ruwais for granulation and export. It would take 360 trucks to transport the 22,000 tons of sulfur per day produced from the field.
But, as the UAE decided to create a national rail system, the opportunity arose for the project to take advantage of that and utilize that railway to transport sulfur from Shah to Ruwais. Therefore, they actually have shorter sulfur pipelines – only about 6.8 miles (11 kilometers) long – that will take the sulfur from the Shah plant to the nearby sulfur station where the sulfur is granulated, loaded on railcars and sent down to Ruwais for export.
To use the railway, ADNOC signed a contract with Etihad Railway to build the first phase of its railway network - the 165-mile (266-kilometer) Shah-Habshan-Ruwais section. The rail line will be built to transport granulated sulfur for export from ADNOC's oil and gas fields, including Shah, in the three points. The Habshan-Ruwais link is scheduled for completion by the end of 2013, and the Shah gas field-Ruwais link by the end of 2014, according to the agreement.
In early January 2013, Etihad Railway announced that the first shipment of wagons, to be used in Stage One of the rail project linking Shah and Habshan to Ruwais in the Western Region arrived at Abu Dhabi's Mina Zayed port. The wagons' top-hatch covers for loading maintain the purity of the sulfur at 99.9 percent.
Furthermore, train transport allows for a capacity of up to 22,000 tons of sulfur per day.
The development of the Shah gas will also allow the UAE to increase its production capacity of sulfur to 22,000 TD by 2015.
"By 2015 the field is expected to produce around 9,200 TD of sulfur," said Tareq Sahoo, supervisor of operations at ADCO. "Once the Shah project starts, we expect sulfur production in the UAE to reach 22,000 TD which will be the largest production in the world, surpassing Canada," he said.
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