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.
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