Drilling practices: The good, the bad and the ugly (2)
A mudlogger is a specialist responsible for the interpretation of drilling and geological data. To this end, he has different specialized sensors mounted in strategic parts of the drilling rig.
These sensors measure different signals and send them to his computer workstation. It is the signal’s signature he looks at to make expert opinion on how well or badly the drilling is progressing. He/she monitors over 50 parameters per second! The mudlogger is the nerve centre of any drilling operation.
Unfortunately, their rates do not reflect their status which in itself is a local problem and not an industry problem. Because they are not well paid in Nigeria, their opinion and interpretation is hardly respected. Because they monitor so many parameters and understand the language of the well better, it is very easy to prey on them. Because the mudlogger is aware of these challenges, he is always on his toes and on top of his game. Whether the operator believes him or not, he is always sure to do his job as professionally sound as possible.
Reputable operators often use mudloggers as a check on the drilling contractors which is why the drilling contractors are seldom friendly with them. In spite of all their efforts, some operators still believe they can do without them and are actually drilling without them in Nigeria. It is because of such ignorant operators the series in this column (The Good, The Bad and The Ugly) was put together.
Circa 1998, the then Elf Petroleum Nigeria Limited contracted Saipem drilling Limited to drill the first in a set of wells lined up onshore Omoku in Rivers State, Nigeria. The geological field of that area was predominantly gas and the well name was Ibewa-1. The drilling rig was Saipem-92. Service providers, among who were a mudlogging crew of six personnel, were mobilized to site and drilling operations commenced.
The mudlogging crew comprised of two pore pressure analysts, two mudloggers and two mudlogger trainees working a 12 hour tours in between (The Elf standard). The surface hole section was successfully drilled to completion with casing set and cemented in place. Drilling progressed without hitches until the intermediate section was completed. All these while, everything was fine with the driller, the client representative often referred to as the “Companyman”.
Drilling resumed in the reservoir section and everything was going well with the operations except from the mudloggers perspective. It happened during the night. First, the mudlogger saw and immediately reported to his pore pressure analyst increase in the return flow from 30% to 40% without any noticeable increase in the pump rate. The sample catcher quickly dashed to the shale shaker screen for samples which was quickly analyzed. The shale samples were found to be over-pressured. With these details, the mudlogger reported to the client representative on nightshift.
The client representative summoned the night toolpusher who immediately summoned the rig superintendent. Mr Maurizio Scarabeli, the rig superintendent, the man in charge and the chief of mission, told the client representative to forget about what the mudloggers were reporting. He said his gauges were the very best in the industry and should, therefore be relied upon better than a locally fabricated junk. The client representative, a man of little experience, deferred to Mr Scarabeli’s and immediately dismissed the mudlogger.
The mudlogger has done that which he’s required to do and so, he went back to his shack to resume live commentaries on the flow-out readings. In under 45 minutes, the flow-out has increased from 40% to 70%! At this point, it was clear to the mudlogger that a disaster was waiting to happen and he advised accordingly! The client representative by this time had been joined by the day “companyman”, a French man who ordered for the well to be shut-in with all pressure readings taken.
Lo and behold, the rig’s sensors recorded nothing because they picked nothing! They picked nothing because they were not working! The rig superintendent, Mr Maurizio Scarabeli, an Italian, still confident of his rig and himself, instructed his driller to circulate bottoms up which actually, is a term to bring the last drilled rock samples to surface for inspection.
The moment the driller switched on his pumps, there was a terrible kick of about 600 barrels of mud displaced into the mud pits. In a nutshell, all the drilling mud in the hole was displaced. The master bushing, the weight of a power bike, was lifted from the rig floor 95ft above, the height of a 9 storey building, for the gas to escape! That was the fury of nature and the reward for a bad drilling practice.
The well was eventually controlled with the gas circulated out for over three days.
If with this example of the BAD, an operator still believes he can drill his well as he pleases without due diligence and best practices, such operator should wait for the concluding column; the UGLY!
• Kayode Adeoye is an energy expert in Lagos.