John Waggoner - Technology Editor, Drilling & Production
West Africa continues to be an important region for offshore exploration and production. Angola and Nigeria remain foremost among the region’s countries for E&P but there have also been recent developments worthy of note in other countries.
Angola
The most important recent discovery in oil-rich Angola was by national oil company Sonangol and BP Angola. The find was with the Leda well in ultra deepwater block 31, representing the 17th discovery made by BP in this block. First offshore operations are expected to begin early in spring 2010. The BP Angola drilling program is expected to include more than 150 wells.
The block is 415 km (258 mi) northwest of Luanda and about 12 km (7.5 mi) southwest of the Marte field.
Leda was drilled in a water depth of 2,070 m (6,791 ft) and reached TD of 5,907 m (19,380 ft) below sea level. This is the fifth discovery in block 31 where the exploration well has been drilled through salt to access the oil bearing sandstone reservoir beneath. The well was tested at a rate of 5,040 b/d of oil through a 36/64-in. choke.
Operator BP has awarded Expro a multi-year contract for the provision of equipment and services on block 31. The contract covers the delivery of landing strings for use on PSVM (Plutao, Saturno, Venus Matre). BP Angola also has awarded Halliburton contracts totaling $600 million for the company’s four developments offshore Angola. The contracts encompass the key elements of well completions including upper and lower completions equipment and downhole flow control. In addition, Halliburton has been awarded the drilling and completions fluids business for these wells.
BP has awarded FMC Technologies an $80-million contract to manufacture and supply additional subsea equipment for ongoing deepwater projects offshore Angola. FMC’s scope of supply includes six subsea trees, control systems, wellheads, tubing hangers, well jumpers, and flow bases. The equipment will be manufactured at FMC’s Kongsberg, Norway, and Dunfermline, Scotland, facilities and will be delivered this year.
Operator Chevron, another important player in West Africa, has awarded Seadrill a $378-million contract for development drilling offshore Angola using the semi tender rigWest Berani II, which is currently under construction. The vessel’s five-year contract is scheduled to begin in 1Q 2010.
Nigeria
An independent assessment of the in-place oil and recoverable oil reserves has preliminarily confirmed a P50 STOIIP of 148 MMbbl of oil for the FB-1 and FB-2 areas. Recoverable oil reserves have been calculated at 41.2 MMbbl. The assessment also assigned 14 MMbbl of oil resources to the FB-1 and FB-2 field area.
An additional 21 MMbbl of contingent oil reserves and 33 MMbbl prospective resources have been assigned to other areas of the field including the Ebok West and Ebok North Fault blocks. Successful appraisal of the Ebok West fault block and northern area closures as well as down-flank potential in the FB-1/FB-2 areas during the initial development phase of the field is expected to lead to increased field production and a potential reserves upgrade in line with the resource assessment.
Total Upstream Nigeria (TUPNI) has started production from the Akpo deepwater development ahead of the planned start-up date. The field has proved and probable reserves estimated at 620 MMbbl of condensate (around 50° API), and more than 1 tcf of gas. The ramp up of production to 175,000 b/d of condensate and 320 MMcf/d gas plateau is expected to be reached during summer 2009.
The field, discovered in 2000, is 200 km (124 mi) from the Nigerian coastline in water depth ranging from 1,200 to 1,400 m (3,937 to 4,593 ft).
The field development calls for 44 wells (22 producers, 20 water injectors, and two gas injectors), out of which 22 already have been drilled. The subsea infrastructure to transport the hydrocarbons consists of 110 km (68 mi) of high pressure-high temperature subsea flowlines connected by steel catenary riser (SCR) pipe sections to an FPSO. In order to optimize gas use, Akpo is designed as a hybrid development capable of handling up to 530 MMcf/d of high pressure gas out of which 185 MMcf/d will be re-injected into the reservoir to maximize hydrocarbon recovery, and 320 MMcf/d will be exported by pipeline. This will enable additional supply to the domestic market and to the NLNG gas liquefaction plant, the company says.
The ultra deepwater drillshipWest Capella has begun operations for Total in Nigeria. The vessel is chartered to Total under a five-year contract.
Alliance Engineering has signed an agreement with Dover Engineering to provide support services for the design of offshore projects in Nigeria for Total. The agreement is for a three-year term.
Ghana
Afren is evaluating the Keta block offshore Ghana incorporating the results of the Cuda-1x well. The company also is evaluating further prospects and considering options for drilling on the block. The Cuda-1x exploration well, drilled by the Transocean drillshipDeepwater Discovery, was spudded in November 2008. The well was targeting a Cretaceous structure expected to contain 325 MMbbl of mean prospective resources in a setting comparable to those successfully proven by the recent Jubilee and Odum discoveries in the country. Operations had to be terminated due to abnormally high pressures encountered at the top of the Cretaceous. The primary objective of the well remains untested and still is considered highly prospective.
The government of Ghana, the Ghana National Petroleum Corp. (GNPC), Vanco Ghana, and LUKOIL Overseas Ghana have signed a new petroleum agreement covering the Cape Three Points deepwater block. The new agreement allows Vanco and LUKOIL to continue to explore the area with new 3D seismic and additional drilling activities planned. Cape Three Points encompasses an area of 5,146 sq km (1,987 sq mi) in water depths ranging from 200 to 3,000 m (656 to 9,843 ft) in the Tano basin.
The new agreement comes as the deepwater drillshipAban Abraham departs Cape Town, South Africa, after completing final retrofit operations to enable the unit to drill in water depths of up to 2,000 m (6,562 ft). The Aban Abraham was scheduled to commence the Dzata-1 exploratory well by the end of April.
In 1,874 m (6,148 ft) water depth, the Dzata prospect is a large anticlinal structure with numerous Upper and Lower Cretaceous potential reservoir horizons and distinct direct hydrocarbon indicators, including flat spots and a gas chimney, according to the companies. The well will be drilled to TD of approximately 4,786 m (15,702 ft), or 2,912 m (9,554 ft) below the mud line.
The Tweneboa-1 well, offshore Ghana, has been deepened to 3,938 m (12,920 ft) and encountered 4 m (13 ft) of highly pressured oil-bearing sands as well as an over-pressured zone at total depth, according to Tullow Oil.
The well has encountered oil of 26° API, which is independent of the shallower light hydrocarbon accumulation. Near the total depth of the well, an over-pressured zone was encountered which limited further progress.
Integration of the seismic and well data is ongoing and further exploration drilling will be required to test the extent of these deeper levels as well as the shallower accumulation where seismic indicates sands thicken away from the well.
The deepwater rigEirik Raude drilled the well in a water depth of 1,148 m (3,766 ft) west of the Jubilee field.
TGS-NOPEC Geophysical is acquiring a new 8,600-km (5,344-mi) multi-client, long offset 2D seismic, gravity, and magnetic data survey offshore West Africa.
The regional program ties to the recent Jubilee discovery on the west side of Ghana and extends across unleased shallow and deepwater acreage. The project is designed to help further define the extent of the petroleum system through the eastern prospective offshore area of Ghana, the company says.
Congo
Congo has approved SOCO Exploration and Production Congo’s acquisition of a 29.4% working interest in the Marine XIV block. This makes SOCO the operator of the block. SOCO acquired the interest from PA Resources Congo.
The block comprises three discontinuous sections in water depths up to 115 m (377 ft) and covers approximately 265 sq km (102 sq mi).
PA Congo retains a 12.5% interest and the national oil company, Société Nationale des Pétroles du Congo, holds a 15% carried interest. The remaining interests are held by fellow farm-in participants and joint venture partners on the Marine XI block, Raffia Oil SARL (21.55%) and a subsidiary of Lundin Petroleum (21.55%).
The operator is acquiring 3D seismic on the Marine XIV block which was to be completed during the first quarter of this year. It also expects to begin exploratory drilling on the adjacent Marine XI block during the third quarter of this year.
Previous exploration activity on the Marine XIV block has resulted in several oil discoveries and preliminary interpretation of 3D seismic data indicates a number of pre- and post-salt prospects. Post-acquisition processing is under way.
Chevron Overseas (Congo) Ltd. has awarded the front-end engineering and design for Lianzi development to Granherne. Lianzi is in a unitized zone including part of block 14 offshore Angola and Haute Mer offshore Congo.
Plans are to tieback Lianzi 27 mi (43 km) to the existing Benguela Belize host facility off Angola. Lianzi is in water depths of 2,700 ft to 3,500 ft (820 m to 1,070 m). Development will be with three subsea production wells, three water injection wells, and the capacity to add one more of each. Granherne’s work is to include FEED and design of the subsea system, connecting pipelines, and flowlines, and additional topsides equipment for Benguela Belize.
Equatorial Guinea
Gasol is now in a direct joint venture agreement (JVA) with Sociedad Nacional de Gas, GE (SONAGAS), the national gas company of Equatorial Guinea, after African Gas Development Corp. (AFGAS) assigned its rights and obligations under the JVA to Gasol as per the disclosure in the company’s June 2008 Admission Document.
Addax Petroleum has contracted Transocean’s drillshipDeepwater Pathfinder to begin a deepwater exploration campaign in the Gulf of Guinea. Addax Petroleum expects to receive delivery of the vessel at the end of the third quarter and intends to begin drilling on the Kina prospect in block 4 of the Joint Development Zone shortly thereafter.
TheDeepwater Pathfinder is a fifth-generation dynamically positioned drilling rig capable of drilling in water depths up to 3,048 m (10,000 ft).
The contract with Transocean requires the vessel to drill four wells with a minimum commitment of 120 days. The Transocean contract anticipates that the drillship will start drilling in the fourth quarter, once it has completed a drilling campaign for a third-party operator in Nigeria.
Senegal
First Australian Resources (FAR) has executed an agreement with Shell Exploration Co. to conduct an exploration program in the Sangomar offshore, Rufisque offshore, and Sangomar deep offshore blocks in Senegal, West Africa. Shell will fund a controlled source electro-magnetic (CSEM) data acquisition and geophysical evaluation program over part of the license area where a number of drilling prospects already have been identified. The CSEM acquisition phase was expected to begin in the second quarter. The results will allow Shell to determine whether or not to exercise an option to acquire a 70% interest in the block and enter the second renewal period that includes a well commitment.
Gabon
Production has begun from a new development well in the Ebouri field offshore Gabon, VAALCO says. The well was drilled from one of the three well slots on the Ebouri platform. The platform was installed in 250 ft (76 m) of water.
VAALCO also is drilling a second horizontal development well following successful results from the North Ebouri appraisal well and recently completed sidetrack.
