Droshky Field, Gulf of Mexico, United States of America
Droshky Field lies in Green Canyon Block 244 in the Gulf of Mexico. The deepwater oil and natural gas field was earlier known as Troika Deep. It lies at a water depth of 3,000ft and is situated about 257km off the coast of New Orleans.
The field is 100% owned and operated by Marathon Oil. The company has invested $900m in the field development.
First production from the field occurred in July 2010. The field life is estimated to be about seven years with complete abandonment planned in 2016.
The Droshky field was discovered in 2007 with the drilling of the Droshky #1 well. This well was drilled by the GSF Celtic Sea semisubmersible rig in April 2007 to a depth of 21,190ft. It encountered 250ft of net oil pay.
Geology and reserves
The Droshky field is of the Upper Miocene age, with reserves estimated at 80-90Mmboe. The oil produced at the field has a gravity of 30-32° API.
Following the drilling of the discovery well, the field was appraised by drilling two sidetrack wells. Marathon contracted Transocean's Henry Goodrich semisubmersible rig to drill the two wells. The first was a downdip sidetrack well which struck 600ft of net oil pay. The second was a lateral sidetrack well which struck 300ft of net oil pay.
A third sidetrack well and a delineation well were drilled in 2008. In 2009, Marathon contracted the Noble Paul Romano semisubmersible rig to drill a fourth development well. By August 2009, drilling operations were completed and well completions were nearing.
The four wells are tied back to the Bullwinkle Tension Leg Platform (TLP) (owned by Superior Energy) through dual, 18-mile flowlines. The fourth well has not commenced production due to problems with the equipment. Marathon is planning to re-enter the fourth well in early 2011.
The field is expected to produce 50,000boepd at its peak. In September 2010, production from the field was 45,000boepd, which included 39,000bpd of liquid hydrocarbons and 39MMcf/d of natural gas. Production forecast for 2010 is 4.6MMbbls of oil and 3.96Bcf of natural gas.
Bullwinkle Tension Leg Platform
The Bullwinkle TLP is the world's tallest offshore platform at 1,736ft. It weighs 78,000t and has a processing capacity of 20,000boepd. The platform features a 49,000t single piece jacket. The jacket has 60-well slots and two deck sections.
The platform was installed in 1988 in 1,353ft of water. The legs of the platform are 120ft-long and 54ft in diameter. The cross bracing is 48ft. The platform was designed to operate in harsh environmental conditions such as hurricane winds and massive waves.
The contract for the $500m platform was awarded to Bullwinkle Constructors, a joint venture of Peter Kiewit & Sons and Gulf Marine Fabricators. The world's biggest barge and 12 tugboats were used to transport the platform to the location.
In 1996, the platform was expanded to include 4,000t of equipment and piping. Apart from Droshky, other fields which are tied to the platform include Manatee, Aspen, Angus, Arnold and Lorien.
Subsea 7 was awarded a $45m contract in August 2008 for providing subsea equipment for the field. The contractual scope included engineering, manufacture and installation of two 8in flowlines totalling 36 miles and two 1,900ft 8in risers.
Subsea 7 also supplied the termination pipeline end structures and manifolds. The company completed the installation works in May 2010 using its Seven Oceans vessel.
In October 2007, Technip won a contract during the feasibility stage of the field development. Technip provided engineering and support services for subsea trees, flowlines and other subsea equipment of the field.
Lonestar Deepwater provided technical lead management for the subsea tie-back of the Droshky wells to the platform.