Oil field production geology / Геология разработки нефтяных месторождений

There are widespread concerns about the future of oil resources. The volume added by new oil discoveries has declined since the 1960s while the global demand for hydrocarbons is rising as the world population increases. Although less oil is being discovered as a result of exploration for new fields, a significant volume of reserves is being added because of improved oil recovery from existing fields. Reserves are the volumes of petroleum that a company expects to produce from a field by the end of its life. Recent data suggest that the volume of exploration finds and reserves growth in producing fields are now roughly similar (Table 1).
So why is so much oil being added as reserves from existing fields? Where is this oil coming from? To start answering these questions, the basic observation is that the amount of oil recovered from the world’s oil fields has historically been poor. Typically, more oil has been left behind in oil fields than they have ever produced. Today, out of the total amount of oil that has been found in the world, it is anticipated that only about 30–35% of this volume is likely to be recovered under current estimates (e.g., Conn, 2006). The remaining 65–70% of the oil is expected to be abandoned in the world’s oil fields once these have become unprofitable to produce from.
A combination of factors resulting from geological heterogeneity, physical forces, and economics is responsible for this poor oil recovery. Reservoir complexity creates the situation where it can be: difficult to establish where the oil is to be found within individual reservoirs; hard to estimate what the remaining volumes are; and then a major technical challenge to produce the oil economically. Yet despite these problems, continuing efforts are being made by oil companies to understand their oil fields in more detail with the aim of improving recovery. Every decade since the 1950s has seen new and better techniques for extracting additional reserves from hydrocarbon accumulations in the subsurface (Table 2). Specialist petroleum geology journals are full of examples of how modern reservoir characterization methods have led to a better understanding of the geological configuration of reservoirs. These have resulted in increased production rates in oil fields and substantial reserves additions (Figure 1).
It is interesting to speculate as to how much the recovery factor for conventional oil resources can be improved globally by better reservoir management. The question was addressed by Keith King of Exxon Mobil at the 2006 Hedberg AAPG Oil Resources Conference. The range in the possible increase in recovery was estimated as an additional 4% to close to an additional 13% (based on the maximum resource case). The low case may arise if the current improvements in recovery start to moderate. The high case will depend on future technological advances in enhanced oil recovery techniques and the application of these globally, particularly in the world’s giant oil fields. Worthy of note is that an upside improvement in recovery of 13% would add almost as much oil supply as has been consumed by the world to date. It would take a heroic effort to get this much oil out of our reservoirs, but if we could, then this would go a long way to providing a solution for the world’s energy problems. Whether this will happen or not is open to debate. Nevertheless, it is clear from these figures that there is a very large hydrocarbon resource available in our existing fields. <...>