Honest Tom - not quite right! Neil Ritson of Solo supported Mike Rego of Aminex's proposal to deepen the Ntorya well, at a TCM held in Aminex's London office that Tullow attended by Skype. The technical and budgetary case was put forward by Mike Rego based on his seismic interpretations the previous week whilst waiting for the 'hotshot' biostrat data, etc, and supported by the available resources at the rig site, logistics, etc., that meant that the well could be deepened by 250m without exceeding the planned budget or requiring a further shift rotation of drilling crew etc. The drilling to 2,500m had not been encouraging in terms of oil or gas shows on the mudlogs (unlike Likonde), and to have plugged and abandoned the well at 2,500m as originally envisaged in the plan but without much positive news would have been a disaster for both Aminex and Solo. You must remember that this was, and still is, very much a frontier area with limited 2D seismic of variable quality at the time, and little knowlege of the subsurface geology from nearby wells because other than Likonde there were none. The feature that Mike Rego identified on the seismic as a deeper target was not something that stood out and had not previously been recognised by anyone as a primary or indeed a secondary target. Mike Rego had prepared a detailed technical and logistical proposal and justification for deepening the well in the TCM, that Neil Ritson then supported, and it was at that point that Tullow announced their withdrawal from the farmin agreement, as they felt that they had fullfilled their two well obligation to the farmin.
Tullow did not give up their share because "they were not interested in gas". They gave up their share when the bit was at 2,500m, BEFORE the reservoir was penetrated, and no-one knew if the well would be a discovery or dry hole. NT1 was a wildcat well - the original target was a Base Tertiary pinchout, updip of a sand penetrated at Likonde, a wildcat well that was operated operated by Tullow as part of their farm-in agreement, whereas operatorship for NT1 had reverted to Aminex. When the original prognosed Base Tertiary target depth was penetrated and found to be deeper than prognosed, the well was paused for 'hotshot' biostratigraphic checks to calibrate stratigraphy with depths and seismic. At this point Tullow felt that they had 'fulfilled their obligations as as a partner' and withdrew, as they had been hoping to build an East African cost centre to support a deepwater exploration strategy, and to Tullow, further spending on what appeared to be a dry hole at Ntorya was clearly an unnecessary anchor. Aminex proposed deepening the well a further 250m to test a possible channel feature on the 2D seismic, and as the well at the time was under budget, with enough drilling supplies on site for several hundred more metres and and rig time to go deeper could be achieved before the next crew change, Solo supported the proposal to deepen at a 75%/25% partnership. NT1 came in within 5m of the revised prognosis at 2,665m, at the downdip edge of the GWC which is why it was only a 3m gas column at discovery. This was a wildcat well, limited depth or lithology data was available from existing data, that is how exploration works. Aminex and Tullow had more to lose from NT1 being a dry hole than Tullow, who were wanting to chase bigger fish.
i think you'll find that it was nt-2 that suffered from high mud weights, not nt-1.
nt-1 was the discovery well. it's primary target was a sand pinchout at the base tertiary, updip from sands encountered at likonde, with the location defined by seismic amplitudes on a sp**** grid of 2d seismic. as it turned out, the well was probably drilled a little too far updip just beyond the sand pinchout, such can be the vagaries of amplitude analysis on sp**** grids of onshore 2d seismic in such a complex stratigraphic environment.
it would possibly make sense to re-enter nt-1 as a possible producer, but only if the well was re-entered and sidetracked, to penetrate the reservoir updip, as after the disappointment of the base tertiary, aminex made the decision - supported by solo - to deepen the well to a very poorly defined possible channel feature some 150m below the then bottomhole depth, as there were sufficient drilling supplies on site and the well was within budget, and a dryhole would not have been good news for aminex or the markets. it was at this point that tullow withdrew. aminex deepened the well and penetrated the gas-bearing reservoir 155m deeper. there was only 3m or so to test because being - as it turned out - the location at this target level was on the very edge of the trap, close to the gas-water contact. you have to remember this was a wildcat exploration well, and at the time the available seismic imaging was poor and the detailed stratigraphy poorly defined, and the well was never intended to go so deep, it was only after a revised in-house review of data by aminex based on drilling information that the proposal to deepen the well was made. the sands at this depth had not been proposed as a secondary target, and up to this point all the commercial successes in the region had been in shallower tertiary sands. an updip sidetrack at nt-1, subject to a valid location based on the new 3d seismic, and within the technical capability of the drilling rig, could be a very sensible low-cost option to complete nt-1 as a future producer.
Tom Mackay is the only Director with geological expertise, but I very much doubt that he has been hands-on for quite a few years now personally evaluating 2D or 3D seismic data or conducting petrophysical analyses of well logs, etc! What sort of exploration department is there beneath him? Is there anyone? It is all well and good having oil & gas financial and legal experience, but that does not help you evaluate oil and gas potential of a new country or exploration licence, read a well log or interpret seismic, or plan an exploration programme. Exploration opportunity reviews, exploration analysis and interpretation and evaluation of basic geological and geophysical data to evaluate risk of success (or failure!) is a full-time occupation and requires specialist support, ideally with a degree of local knowledge and experience. I am not sure that Aminex has that strength in-house any more.
Does Aminex still have access to anyone in-house with any real exploration expertise, other than the technical team at ARA who own 29%(?). All Aminex's in-house exploration knowledge and experience was lost after Battercharjee took over as CEO and relied on a series of independent consultants who seemed happy enough to write one-off reports and take the money, but not to stay stick around and see things through, (and lack of revenue income from Kiliwani North probably didn't help either).
This is old, old news! Oil seeps in Rufiji and Ruvuma Basins have been recorded for years, Aminex published a lot of work since their first field trip to the region in 2003, and the ex-Aminex personnel involved have continued to work on the source rock story of the region and have published papers on this as recently as 2022 detailing the potential of all the various source rocks believed to be present. There isn't much new in the Sabuni 2023 paper. The source rock history is complex, but much of the gas is derived from source rocks that were originally oil prone. Also, despite the claims of some people it is unlikely that Cenozoic source rocks have the capability (i.e., kerogen type or presence) to generate oil in anything but small quantities in localised areas in Rufiji and Ruvuma.
Not quite so, the well was never classified as a 'duster'. It was a wildcat frontier well, the prognosed reservoir lithology was not present at the predicted depth, Aminex made a decision independently and in advance of any communication from Solo to propose deepening the well based on careful re-examination of the available 2D seismic over about 4 days, using the knowledge gained from comparison of lithologies encountered to seismic whilst drilling to the original planned TD, and Neil Ritson from Solo fully supported the proposal, having also developed a similar re-evaluation. The well to the original planned TD (just below target zone) was drilled under budget and there were supplies on site to allow another 250-300m drilling before the next crew change. The top gas was encountered approx. 155m below the original planned TD, within less than 5m of the depth prognosed by Aminex from the re-evaluated 2Dseismic. Aminex gave a detailed presentation at the East African Community Petroleum Conference in Arusha, Tanzania, in February 2013.