Ann: Rig 202 Contract Extended 2 years for future Cabora Bass, page-132

I disagree that you should only drill a vertical well if there are washedout coals and / or TLC is to be run. From my experience a vertical well definitely helps to minimise the risk of getting stuck in open hole. In addition, Scott mentioned in the fireside chat that the cable had probably cut a groove on the mud cake because the well was not vertical, and that led to increased filtrate loss and differential sticking.

After the M-1ST data was analysed, I pleaded for them to drill a vertical well, but it's obvious they either do not read the messages on Hot Copper or they believe only they are right. At first they said M-2 would be vertical, but after a few weeks things changed to "it's going to be nearly vertical". That was a bad decision that cost the shareholders dearly.

Drilling too deep in the same hole section is another example of not listening to advice from experienced engineers on HotCopper. Usually below 10,000 ft TVD, over-pressure can be found, which is why I did not want to risk damaging the Upper Angwa by increasing the mud weight. At 3400m MD (11033 ft TVD) the over-pressure has appeared a bit deeper than expected.

Even after the operational problems in M-2, there are people saying we've got MDT on TLC to fall back on if they don't manage to retrieve a sample on wireline. My recommendation is please do not run MDT on TLC because there is the CHDT cased hole MDT equivalent to fall back on. It takes too long, it's cumbersome and before you know it the hole has deteriorated and it's back to a failure scenario like M-1 and M-2 (hole open for 4 weeks in the Upper Angwa).


VSP and sidewall core samples are also important. If they fail to get a sample or two at surface via wireline, then it would be too risky to attempt VSP and swc on wireline.