The Oil Drum

So what is a reserve? Can we wander into a meeting with one of them Eastern banker types wave a fistful of geological maps under his/her nose and get them to cough up $100 million so that we can go drill a hole in the back 40? Well not exactly. There is a fundamental definition that says that a proven reserve can only be counted where there is no "reasonable doubt of uncertainty" in the estimate of the oil/gas in place. And how do you overcome that doubt, why by drilling a hole down into the reservoir and starting to produce the oil.

But here's the thing, let's say I buried a container of soda in a sandbox and just left a straw sticking out of the sand. How do you know, short of digging it up, or fully draining it, whether I buried a soda can, a liter bottle or a full barrel's worth? That is the problem that you face when you finally drill to the bottom of an oil well and find that the cuttings that come to the surface are all nice and oily. And the answer is that you can place a special coring bit on the end of the drill string and take out a cored cylinder of rock all the way down through the pay zone, or you must log the well, and often you will do both.

This is one of the techie talks that turn up on this site on intermittent weekends. It tries to provide some basic information on topics that relate to oil and gas production and you are asked to bear in mind that it is a very simplified explanation, so that you can grasp the basics. A full list of previous posts is given at the end of the piece.