PREVENTING BLOWOUTS IN GEOTHERMAL WELLS
It is not only only oil and gas wells that can experience blowouts. The same can happen when targeting hot water or steam, as a country such as Japan only experienced last year when a blowout occurred whilst drilling on the flanks of a volcano. Until very recently, though, I was unaware that the way pressure is managed is different between deep-water offshore wells and onshore geothermal boreholes. The crux is in the temperature of the returning fluids. In the case of deep-water drilling, temperatures of the returning fluids are very manageable because of the long distance the fluids travel through the riser. In the case of onshore drilling, that effect does not exist, which means temperatures at the well head are much higher and, therefore, require tools to be of a totally different spec to be able to cope.
IT WAS A MATTER OF FAITH, NOW IT IS REAL SCIENCE
We recently published an article about exploration and whether to think of it as a science or more like an art. Many people commented on it, with some showing a sense of frustration with the notion to associate exploration with art. I don’t really see what you would think of an art being inferior to science, but that is a by the by. During a presentation in Aberdeen the other day, Helge Løseth from Equinor used the dilemma art or science when talking about the development of the Mariner field in the UKCS. “In the early days of the project,” he said, “the seismic did not allow the accurate positioning of the development wells. Thanks to much better data, the internal structure of the (Maureen) sands is resolved at such a level that it has become more of a science”, he said.
KUDU GAS IS NOT A TYPICAL GAS
The stranded Kudu gas field was founded in 1972 by Chevron but has remained undeveloped since. I spoke to someone who had looked at Kudu quite closely in recent years, and he shared that the gas is not a typical gas from a type-III source rock such as found in the Southern North Sea, for instance. In the case of Kudu, the gas has a signature that points to a cracked oil origin instead. It makes sense, as the known source rocks offshore Namibia are supposedly marine, and oil is, therefore, likely to have been generated first. And, it was Marcio Mello who researched the Kudu gas origin for his PhD thesis. Did he realise at the time that he would be back in Namibia drilling three high-profile exploration wells?
UNCONSOLIDATED OR NOT
“What looks like an unconsolidated sand to a geologist might actually be a not-so-unconsolidated sand to a coring engineer”, someone told me the other day. It just depends on how you look at it. “From a coring perspective, as long as the formation can be cored with a standard core barrel, to me, it is normal sand”, I was told. “At the same time, when the core is inspected by the geologist and he or she is able to stick a finger into the reservoir without too much friction, will unsurprisingly conclude something else when it comes to the integrity of the sand.” It just depends from which angle you look at it, I suppose.
