The Oil Drum

With your indulgence I am going to try and explain a little bit more about some of the stages that an oil reservoir might go through, to clarify some of the topics that have arisen in discussing oil production from large oil reservoirs. To do this I am going to build a simple model, to try and illustrate the odd point, concerning production and reservoir collapse. (This might help in understanding some of the debate between Matt Simmons and Jim Jarrell, as reported by Marco. Please bear in mind that this is a very simplified example, to illustrate the points - to those more knowledgeable, I apologize. But please jump in and clarify what I have not made clear or not explained correctly.)

Let me start by assuming that I have a layer of rock that is 300 ft thick, five miles wide and thirty miles long. Let us then assume that this has been folded in the middle, so that it now has trapped oil within all the pores of the rock. And, for the sake of discussion let's assume that it has a porosity of 20%. Now having found this reservoir - which is, let's say some 6,500 ft below the current surface of the ground - back some years ago, the oil moguls of the time decided to drill into it and extract the oil.