Tai CPR comments24 May 2023 06:51
I have been short on time this week, so here are some comments on the Tai CPR, albeit a little late :-)
* Tai-1 drilling was a complete dog's breakfast. As well as losing the drill string, logging while drilling was only carried out on a small section, and this was sadly incomplete. Nothing was done on the Lake Bed Formation, since logging equipment was not ready in time. No porosity measurements were taken - critical for reservoir estimation. No water saturation measurements were taken, since the equipment was incorrectly calibrated - even if we knew the porosity, it wouldn't be known how much was filled with gas, or with water. No drill stem tests were performed because of hole conditions. Lastly, the mass spectrometer was broken, so helium/nitrogen levels were only partially measured. In summary, I have never seen such a poorly executed drill.
* ERCE have had to make a lot of guesses about the reservoir potential. If you look at the Y-axis of a seismic chart, you will see ms - this is not metres depth, but milliseconds two-way time (TWT), the time taken for a seismic pulse to travel down to a horizon and bounce back to the receiver. Sound waves move through dense rock more quickly than through soft rock, so you have to estimate the subsurface rock density in order to convert TWT to actual depth. This is particularly problematic for the LBF, which has interleaved beds of mud, sand, and other guff, all of unknown thickness. There is therefore an unusually wide range of interpreted thickness and areal extent for the Tai prospect - see figs. 2.6, 2.7 & 2.8.
*Porosity & permeability were not measured in the first Tai drill, so ERCE has estimated based on a very wide poroperm range seen in historical nearby hydrocarbon drills. Also important is the net:gross ratio, which is the %age thickness of a rock column which is likely to be reservoir e.g 100m of rock with 10m of likely reservoir is a 10% N:G. The figures for the LBF were: porosity 25-30% (excellent), permeability 10 -1000mD (cr@p - excellent), N:G - 25 -70% (good - excellent). For the Red Sandstone, porosity 15 - 20% (good), permeability 10 - 1000mD (cr@p - excellent), N:G 20 - 80% (good - excellent). No data for the Karoo.
* Helium concentrations in the original CPR were 4.4%, compared to surface readings of up to 10.6%. I was more than a little surprised that low/best est/high figures for Karoo & Basement were 0.5/1.1/1.75%, and for LBF & Nsungwe 0.1/2.1/3.25%.
In summary, this looks to me to be an extremely conservative CPR, with potential for much higher helium volumes due to low assumptions for reservoir thickness & areal extent, porosity, permeability & helium concentration. In particular, the assumptions by NHE are a lot more positive - but please note they do NOT have an independent CPR. I don't invest in resource companies without a CPR.
All my own opinion, do not invest based on my comments, read the CPR, make your own judgement.