ZADCO has taken a huge leap away from traditional production platforms by building production islands to boost output at the giant Upper Zakum Field
Abu Dhabi’s Zakum Development Company (ZADCO) is working at full stretch on the enormous expansion of drilling and production to achieve its goal to produce 750 000 barrels per day (bpd) of crude oil by 2015 – dubbed the UZ 750 project – raising output by 200 000 bpd.
In order to achieve the huge ramp up, ZADCO is shifting from traditional offshore platform production to a network of four artificial islands (three satellites and one main central island), from which greater production is anticipated. Drilling reach will be extended from 10 000 feet to around 30 000 feet from the new islands using ZADCO shareholder ExxonMobil’s extended reach drilling (ERD) technology.
The contract to construct the four artificial islands (three satellites and one main central island) was awarded to the Abu Dhabi based National Marine Dredging Company in November 2009. After a series of trials construction of the South Island began in August 2010 with the first visible signs appearing above the waves in October. Although there are many more months of work ahead to place three million cubic metres of dredged material to complete the island, the appearance of sand above the high water level marked a milestone in the transition from wellhead platform tower (WHPT) based facilities and jack-up rig drilling to island based facilities and land rig based drilling.
Creative concept
Initially the development plan to achieve the 750 000 bpd target (and sustain it for 25 years) was based on an additional 25 WHPTs, together with hundreds of kilometres of new flow lines. Major facilities upgrades on existing satellites and the central processing platform were also planned. Inherent in these development plans was the need to more than double the jack-up drilling rig fleet in order to achieve the necessary production build-up rate.
The flexibility to manage long term reservoir performance, well integrity issues, corrosion and aging of existing structures and subsea flow lines has led ZADCO to seek out a better and more economical future development concept.
ZADCO embarked on an assessment of possible alternative concepts, the findings provided a compelling case for change from the conventional development plan to one that consolidates drilling centres and processing facilities on artificial islands, and using new technologies in ERD and maximum reservoir contact (MRC) to effectively develop the entire field.
The concept of artificial island based drilling and production facilities was evaluated relative to expansion of the current, traditional steel piled structures. The island concept was found to offer significant advantages in overcoming bottlenecks in the existing processing facilities and intra-field pipeline network, as well as providing a foundation for land rig based drilling. To support this concept, ZADCO has established its own drilling division in collaboration with ExxonMobil.
Historically, ZADCO has drilled wells up to approximately 10 000 feet deep. However, with this new technology it is planned to reach up to 30,000 feet or more. To date ZADCO has successfully drilled two MRC pilot wells, each nearly 20,000 feet total drilled length, setting several new records for ZADCO. The data and experience gained from drilling these wells will be used to guide the design of future wells and their completions. Many of the island wells will be more complex and expensive than previous Upper Zakum wells but the higher production rates and reduced number of wells will justify the higher capital investment in each well. ExxonMobil will be supported by Abu Dhabi’s National Drilling Company (NDC).
Island Advantages
Artificial islands provide a more flexible and robust development base for the redevelopment of the Upper Zakum field. This will significantly reduce life-cycle development costs and enable long term maximum recovery levels to be achieved. The ‘green fields’ development on islands accelerates oil development rate and is safer and more capital efficient. Gas lift application on the islands will be much easier than from WHPT and will help improve long term reservoir recovery. The current development plan could potentially extend the production plateau to more than 15 years and significantly delay the need for full field Enhanced Oil Recovery (EOR) and further investment.
First Mover
Redevelopment of Upper Zakum will present many technological and operating ‘firsts’ for ZADCO which will provide opportunities for additional development applications in the Gulf. The centralised drilling and production centres coupled with ERD and MRC technologies open opportunities in offshore shallow waters.
ZADCO is the first ADNOC company to intensively apply these complex drilling completions in terms of extended reach drilling and maximum reservoir contact.
