TABLE OF CONTENTS In the earlier chapters, I have discussed both the origin of oil in geological terms and the history of the industry. Now, I approach the heart of the matter, and turn to how much has been found, how much is yet to find, and, most important of all, how much remains to produce, not only in quantity but when. It is, however, first of all, necessary to decide what we are talking about, for, as explained, petroleum is a slippery substance that comes in many different forms, each having its own characteristics and depletion pattern. It is essential at the outset to distinguish conventional from nonconventional oil and gas, but that is easier said than done.
As already discussed, the unfettered production of oil, as in an uncontrolled blow-out, rises rapidly to a peak and then declines exponentially until the reservoir is exhausted. To understand this, it is necessary to think of the reservoir. The oil lies in pore-space within the reservoir rock under enormous pressure. When the wellbore taps the reservoir, the pressure in the adjoining pores is sufficient to force the oil into the well through which it flows to erupt at the surface. In an uncontrolled well, or blow-out, there is a plume of escaping oil several hundred feet high (see Figure 3-22). As the pressure in the immediate vicinity of the wellbore is depleted, so oil farther and farther away has to be tapped, but instead of flowing through a pipe several inches in...
