All articles in the Oil patch Sub-Sahara Section:

CGG Completes Carpet Seismic Coverage of Gabon’s Pre-Salt

CGG has acquired and processed over 25,000 km2 of new 3D BroadSeis™ multi-client seismic data over available and licensed blocks in Gabon’sCGG-Gabon-Map South Basin. It is to aid companies participating in the country’s on-going 11th deepwater licensing round.

“A fast-track pre-stack time-migrated dataset for this survey is available now, along with sample pre-stack depth reverse time-migrated (RTM) data in one area”, the company says. “The final RTM for the whole of the survey area will be available this summer”.

The world’s top geophysics company is excited that it was able to carry out a project of such a scale, in conjunction with the state hydrocarbon firm Direction-Generale des Hydrocarbures of Gabon (DGH)- at a time of  depressed oil prices.

The survey’s objective, CGG explains, “is to image potential prospective structures at base salt level without compromising the shallower post-salt image quality”.

Then the company boasts: “The data do not disappoint. Even a preliminary ultra-fast-track dataset produced onboard was described as “way beyond expectations” by a major oil company interpreter”.

On the full fast-track dataset, more detail below the salt is being revealed than has ever been seen before, revolutionizing the understanding of the geology of the area. Early seismic imaging results indicate the presence of thick syn-rift and sag sequences below the salt, which are the key intervals of a pre-salt petroleum system and indicate many exciting prospects, some of which continue beyond the borders of the survey so that their full extent cannot be gauged.

CGG claims that the Gabonese bid round“has generated considerable interest from both International Oil Companies (IOC’s) and newcomers alike, encouraged by the success of exploration in the conjugate margin offshore Brazil, as well as recent pre-salt discoveries such as Ruche, Tortue, Diaman and Leopard in nearby Gabonese waters. CGG has worked directly with the Direction Generale des Hydrocarbures of Gabon (DGH) to acquire and process to enable evaluation of this prospective area”.  The Gabonese government has not yet corroborated that claim.

The company says the survey is being processed using the latest high-end imaging technology to produce the clearest images. “The fast-track PSTM volume shows clear uplift over the existing data, while the fast-track PSDM shows the full benefits of advanced velocity modeling and depth-migrated modern broadband 3D seismic data. The uplift in subsalt imaging that will be achieved in the final dataset is dramatic; the RTM fully depth-migrated example shows clearly defined tilted fault blocks and horst features as well as the highly complex nature of the thrusted and distorted salt and sediment overburden.

“Multi-layer tomography (TomoML) and full waveform inversion (FWI) are being used to create the final velocity model, with RTM being used in the velocity model building iterations. The high-quality, low-frequency data acquired using the BroadSeis solution is particularly beneficial for FWI as the low frequencies prevent cycle-skipping. The imaging improvement from the FWI velocity model can be seen both in the shallower section, where pull-up/push-down image distortions are precisely corrected, and in the deeper salt bodies, where salt flanks and subsalt reflectors show improved focus and continuity due to better overburden description.

“Although this dataset delivers unprecedented images of the subsurface in this area, additional data are being acquired to improve the imaging still further in the most complex geology to the southeast of the survey. Tailored multi-vessel survey design is enabling longer offsets, up to 14 km in the same orientation as the original data, to be acquired over block F14. In block F15, adjacent to the Congo border, a second orthogonal azimuth of the full range of offsets, including those up to 14 km, is being acquired.

Longer offsets and dual azimuths are expected to improve the sub-salt illumination and provide even greater clarity of the most challenging structures. In order to acquire these long offsets an additional source vessel is being deployed. Synchronized source technology and blended acquisition are being used to enable the shot interval to be less than the record length, so that source density, and therefore fold of coverage, can be maintained”.

Angolan Rig Count Reaches A New Bottom

AngolaThe number of active rigs drilling in Angola was reduced by three in April 2016. The total fell from 17 to 14. The Maersk Delivererdrilling for Chevron was cancelled; so was the Transocean’s Global Santa Fe (GSF) Driller I, drilling for ExxonMobil.

Deliverer and Driller I were drilling in Block 14 and Block 15 respectively in March 2016.

The Ensco DS-6, which was in action on Block 31 for BP in March, is now on standby and not even in Angola.

Find the full details of the rigs active in Angola here..


With One Disappointing Well, Dana Can Justify Its Retreat from Africa

Dana Petroleum was winding up its portfolio in Africa, with the exception of Egypt, as of the time it drilled Manatee-1, in Cameroon’s Bakassi West Permit, in March 2016.

The well encountered some gas shows, and although the result derisks the 12 other prospects and leads in the permit, the site of Manatee-1 remains the most optimum on the acreage’s play map.

Although the permit is in the Cameroonian segment of the prolific south east offshore of the Niger Delta, Manatee-1 was drilled on two dimensional (2D) data, acquired in early 2014, two years after Dana Petroleum won the licence. The U.K.-based subsidiary of South Korea’s state-owned KNOC had pulled out of Mauritania and Guinea but was committed to Manatee-1 as an obligatory exploration well.

Drilled with the jack up Paragon M825, Manatee-1 reached total depth of 1,447 metres, intersecting 26metres of gas bearing section of varying quality throughout the wellbore. “Wellbore conditions did not permit the acquisition of a full suite of logging tools in the deeper sections of the hole which makes the analyses of these lower intervals inconclusive at this time”, a press release on the well indicated. ”Additional technical work will be completed with the samples and material collected from the well to improve the understanding of their quality in a post well analysis”, the release explained.

Dana Petroleum holds 55% participating interest in Bakassi West, with two Canadian minnows SDX Energy and Soft Rock Oil Co Ltd, holding 35% and 10% respectively. “The secondary objective was to see whether we could make a commercially viable gas discovery”, notes Paul Welch, Chief Executive of SDX Energy, the 35% partner. “At this stage it is too early to quantify the Manateee-1 gas potential

and our technical team will be working closely with our partners to evaluate the well results to determine if the gas volumes on the block have commercial potential”. SDX may be keen on staying in West Bakassi, but Dana Petroleum prefers to focus on Egypt as its preferred country of interest in Africa. The three other countries that the company has interests are entirely on the North Sea: the UK, Norway and the Netherlands.

Tullow Plays Word Games with Sub-commercial Probe in Kenya

By Toyin Akinosho, Publisher

The phrase: ‘Strong Oil Shows’ do not mean a discovery

Tullow has plugged and abandoned the new field wild cat Cheptuket-1 in Block 12A onshore Kenya.

The well, drilled by PR Marriott Rig-46, had “good oil shows”, a way of saying it is non-commercial. But Tullow and its partner, Africa Oil say the well wasn’t drilled for commercial success.

The companies refrained from using the term ‘Discovery’, because  the well didn’t encounter a single commercial pool of oil. However, by claiming that Cheptuket-1 had ‘strong oil shows’, a phrase unknown in exploration lexicon, they led the energy media to interprete it as a discovery. Read what Tullow and Africa Oil said about the well: “The objective of the well was to establish a working petroleum system and test a structural closure in the south-western part of the basin. The strong oil shows(emphasis ours) encountered in Cheptuket-1 indicates the presence of an active petroleum system with significant oil generation and represents the most significant well result to date in Kenya outside the South Lokichar basin. Post-well analysis is in progress ahead of defining the future exploration programme in the basin”. Cheptuket-1 is the first well to test the Kerio Valley Basin and was drilled to a final depth of 3,083 metres”.

It is clear that Tullow and Africa Oil’s geoscientists are trying to say that the result of this well has given hints on better prospects elsewhere in the Kerio Valley, but there’s not even a guarantee that it has significantly de-risked the basin, otherwise the partners would have said so. The report on Cheptuket is, geologically misleading.

Nigeria: Marginals Are More Prominent on the Rig site Than Other Players

On a per capita basis, Nigerian marginal field operators are more

→   Read the rest of this entry

BP Drops one, Chevron Maintains Count in the Angolan Fleet

British oil major BP dropped one rig from its Angolan fleet, to two rigs whereas Chevron’s  count remains flat, at five, in the January 2016 Angolan Rig Count compiled by Africa Oil+Gas Report.

The total number of rigs active in the country dropped to 17 in January 2016 from 18 in December 2015.

ExxonMobil, TOTAL and ENI were also busy with the drill bit.

Full details are available in the Volume 17, No 1, 2016 of the Africa Oil+Gas Report

Multi-Client Seismic Survey Planned For ‘Equatorial Transform’

Geoex International plans a two dimensional (2D) multi-client seismic data acquisition along the transform margin of Ghana, Togo and Benin.

It is the first phase of a larger regional programme, that would tie in to similar programmes in Nigeria and the conjugate margin of South America.

Data acquisition is expected to commence in the latter part of the first quarter of 2016, with Pre- Stack Time Migration data targeted for delivery in August and Pre-Stack Depth Migration data targeted for delivery in December.

The African equatorial transform margin has proven to be an exciting exploration province over the last decade with the Upper Cretaceous deep water fan play in Ghana, so far proving the most successful part of the system, according to Robertson Safi, Managing Director of Ghana Geophysical Company Limited, a partner in the project. ‘”Yet along with the successes have come a number of high profile failures, which have highlighted the need to fully understand the petroleum systems from basin architecture through to reservoir development and migration and trapping mechanisms.”

The Ghanaian portion of the offshore survey is about 6,000 km, for which Geoex, in conjunction with Ghana Geophysical Company and other partners, signed an agreement with Petroleum Commission- the State’s regulatory body and concessionaire. “The data would be interpreted in the broader context to allow geoscientists to evaluate both sides of the margin as it evolved and to identify other potential petroleum systems offshore Ghana”, Safi explains.

“This is the first Reconnaissance License that the (Ghana) Petroleum Commission (the industry regulator) has signed since its establishment”, notes Theophilus  Ahwireng, Chief Executive Officer (CEO) of the Commission.  “This strategic project will include the acquisition of long offset, long record 2D regional seismic data that will be migrated to depth and integrated with available offshore well data to calibrate key stratigraphic horizons and ties in major discoveries in the area to provide the regional context and enable a full evaluation of petroleum plays.”

Tullow Encounters “The Best Quality Reservoir” in Kenya’s Most Prolific Basin

By Sully Manope, in Nairobi

Etom 2’s the most northerly well in South Lokichar.. opens a new fairway

Irish independent Tullow Oil says the 102 Metre net pay in two columns it encountered in Etom 2, “confirms a new potential exploration fairway in the northern portion of the Lokichar Basin”.

The well was consequent on the interpretation of a 247 km2 three dimensional (3D) seismic data acquired over the Etom area (Block 13ST) earlier in 2015; Etom-2 was not even a part of the proposed 2015 drilling set out in late 2014. But the new data identified the prospect on the north flank of the Etom structure in an untested fault block

In the event, the stars are all aligned for this new find:  “Oil samples, sidewall cores and wire line logging all indicate the presence of high API oil in the best quality reservoir encountered in the South Lokichar Basin to date,” the company explains. Tullow says additional prospectivity identified on the 3D seismic in the Etom Field area and in the northern portion of the basin, including the Erut and Elim prospects, will now be considered as part of the future exploration drilling programme.

“Discovering this thick interval of high quality oil reservoirs further underpins the development options and resource base. The result demonstrates how we have improved our understanding of the South Lokichar Basin,” says Angus McCoss, Tullow Oil’s Exploration Director.

“This discovery confirms a new potential exploration fairway in the northern portion of the Lokichar Basin.  This result also suggests significant potential in this under explored part of the block as it is the most northerly well drilled in South Lokichar and is located close to the axis of the basin away from the basin-bounding fault.

The PR Marriott Rig-46 drilled the Etom-2 well to a final depth of 1,655 metres and will now move to Block 12A where it will spud the Cheptuket-1 well around year end, the first well to be drilled in the Kerio Valley Basin.

Sterling Will Finalise Ambilobe’s Early 3D Interpretation In Q1 2016

London listed Sterling Energy has completed a three dimensional (3D) seismic survey of approximately 1100 km²

→   Read the rest of this entry

Angolan Rig Count Drops

The number of rigs actively drilling on locations in Angola has fallen to 18 in November, from 22 in September 2015, according to the November 2015 edition of the Africa Oil + Gas Report.

Chevron and TOTAL have dropped one rig each, while ExxonMobil increased its rig count by 1. Cobalt has finished drilling on Block 21 and released the rig. ENI retains the two rigs it had last September.

The busiest company at the drill bit remains Chevron.

Full details of who is drilling what and where in Angola is available to paying subscribers of the monthly edition of the Africa Oil + Gas Report.

© 2018 Festac News Press Ltd..