New JDZ offers deepwater opportunity

São Tomé and Príncipe has recently found itself at the forefront of oil industry interest with political and technological developments combining in 2002 to propel São Tomé and Príncipe and its jointly-controlled Joint Development Zone with Nigeria into a highly anticipated license round.

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Tom Ziegler,PGS

São Tomé and Príncipe has recently found itself at the forefront of oil industry interest with political and technological developments combining in 2002 to propel São Tomé and Príncipe and its jointly-controlled Joint Development Zone with Nigeria into a highly anticipated license round. The potential for significant hydrocarbon accu-mulations in this deepwater area is thought to be one of the highest worldwide. Initial analysis of multiclient PGS 3D data acquired prior to the license round announcement supports this assertion.

São Tomé and Príncipe

São Tomé and Príncipe are volcanic islands lying in the Atlantic Ocean 200 km south of the Nigerian coast. The islands represent the smallest country in Africa, with a land area of 1,001 sq km and supporting a population of 165,000 people. Granted independence from Portugal in 1975, the island economy is increasingly dependent on cocoa exports. However, there is optimism that significant petroleum resources will be encountered offshore in the near future.

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The offshore of São Tomé and Príncipe is separated into the JDZ with Nigeria and the EEZ.
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The islands' territorial waters are large, encompassing fairly deep waters but with a sediment cover that is unusually thick for such oceanic regions. This thick sediment cover represents the distal pro-deltaic sediments of the Ogooué Delta of Gabon, which was the main sediment outlet of West Africa during the Cretaceous, and the Niger Delta, the main sediment outlet during the Tertiary. The offshore territory of São Tomé and Príncipe is separated into the Exclusive Economic Zone and the JDZ with Nigeria.

JDZ

The JDZ represents an area of overlapping maritime boundary claims Nigeria and São Tomé and Príncipe will jointly develop. The key provisions of the treaty include the joint development of hydrocarbons and other resources based on a split of 60% for Nigeria and 40% for São Tomé and Príncipe. The duration of the treaty is 45 years, with a review after 30 years. Both parties accept that there is no renunciation of claims to the zone by each country.

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PGS' multiclient 3D survey in the JDZ illustrates the structuring of this distal part of the Niger Delta.
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The JDZ is governed by the Joint Authority, chaired by Dr. Taju Umar and based in Abuja, Nigeria. The Joint Authority is an independent legal entity and acts accordingly in its management of the affairs of the JDZ. The Joint Authority itself is supervised by the Joint Ministerial Council, which has overall political responsibility, and is formed by ministers from both countries.

Political developments

President Fradique de Menezes of São Tomé and Príncipe and President Olusegun Obasanjo of Nig-eria formally inaugurated the JDZ and the Joint Authority on Jan. 16, 2002, in Abuja. In a subsequent speech given by Dr. Rilwanu Lukman (member of the Joint Ministerial Council and leader of the Nigerian delegation) in Abuja on April 19, the Nigeria-São Tomé and Príncipe Joint Authority first announced its intention to offer acreage in the JDZ for licensing in 2002.

At the formal opening of the round, expected to be by year-end, the Joint Authority will provide information on the petroleum regulatory regime, the petroleum tax regime, the production sharing contract, and the tender guidelines.

Both Nigeria and São Tomé and Príncipe attach great importance to the success of the JDZ.

Technological developments

Exploration activity has taken large leaps in recent years into waters previously considered unacceptably deep for drilling and production. The deepest well offshore Africa was drilled offshore Gabon in 2,791 m of water. Exploration well success rates have more than tripled from 10% to over 32% worldwide, primarily due to the advent of 3D seismic surveys in the early 1990s and their increasing use as an exploration tool. In 2001, deepwater exploration success rates in Africa were an unparalleled 47%.

The deepwater Niger Delta shares certain characteristics with other deepwater basins worldwide that are attracting substantial attention, and this applies equally to the area covered by the JDZ: The initial phase of exploration has proven the presence of high quality reservoirs, good source and seal, together with the existence of giant accumulations in the delta. There is a large existing seismic database of 2D and 3D surveys and reasonable well control. The data helps constrain risk and reduces the uncertainty associated with deepwater exploration. Reasonably favorable lease terms exist for deepwater exploration and production, and the delta has good accessibility to key markets.

Geology and structure

The JDZ includes the southernmost extent of the outer compressional fold belt of the Niger Delta. The PGS survey shows that the structuring is complex and characterized by large distal toe-thrusts trending northwest-southeast, terminating toward the southern part of the 3D survey against thrusts that trend more east-west. The toe-thrusts are relatively recent features that deform thick sedimentary successions of Oligocene-Pliocene age.

Ninety percent of deepwater hydrocarbons found to date in the Niger Delta have been trapped within turbidite sandstones. In addition, two-thirds of deepwater reserves in the delta have been found in traps with a stratigraphic component. Although large structures are currently being drilled in the region, they more often that not have a stratigraphic overprint. Explorationists need to understand the often-complex relationship between the turbidite systems, and the structuring observed.

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This JDZ seismic section shows a toe-thrust. Seismic facies indicate turbidites and DHIs.
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The survey data show excellent seismic facies resolution of numerous turbidite channel systems within the Agbada formation equivalent. Anal-ogues of theses facies can be seen in present day channels observed traversing the JDZ area. Direct hydrocarbon indicators (DHI) are also numerous and will help define potential hydrocarbon accumulations.

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Seabed topography shows present-day channels.
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The JDZ is part of a proven prolific play fairway, with several significant discoveries in Nigerian waters, such as the world-class fields of Agbami, Bonga, and the adjacent Akpo field in OPL 246. Indeed, the reduced Tertiary overburden above the source rocks in the area suggest the fairway may well be more oil prone in this area.

Conclusion

The technological capacity to drill in these water depths and the acquisition of multiclient 3D seismic have combined with the significant political accomplishment of offering a license round in the JDZ only eight months after its inauguration.

Lessons learned during Africa's exploration history indicate that technical risk is significantly lower when exploring for deepwater extensions of proven petroleum systems than in the exploration of completely unproven systems. Regional fairway mapping of the Niger Delta has already high-graded the JDZ. PGS' 3D survey confirms that this is an area that has significant exploration potential. The Nigeria-São Tomé and Príncipe JDZ License Round presents an opportunity for oil companies to stake a claim to this world-class deepwater hydrocarbon province. For more information visit the website: http://www.nigeriasaotomejda.com/.


PGS survey reduces cycle time

PGS has entered into an exclusive agreement with the government of São Tomé and Príncipe to assist the country in promoting its offshore acreage in all territorial waters, including the JDZ. In support of this agreement, PGS has embarked on a program to acquire and market high quality 2D and 3D seismic data prior to future license rounds. This agreement, together with a separate exclusive agreement signed with the Nigerian government for non-exclusive 3D acquisition in Nigerian deepwater areas, allowed the acquisition and processing of a 3,000-sq-km multiclient 3D (MC3D) survey in the highly prospective northern part of the JDZ. The fully processed data became available in July, with the intention of reducing technical and economic risk and uncertainty for the oil industry prior to the submission of bids for the JDZ license round.

The immediate availability of MC3D will benefit São Tomé and Príncipe and oil companies by accelerating time to first oil with a large corresponding increase in project net present value.

Contact: Tom Ziegler, tel: +44 1932 26 00 01, fax: +44 1932 26 64 84, email: tom.ziegler@pgs.com, website: www.pgs.com.

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