Depositional Environments and their Flow Characteristics
The theme of this section is that specific depositional environments, deltas for instance, show common patterns of production behavior. Many of these themes repeat again and again from field to field in different basins and in various geographical areas around the world. The knowledge of the production patterns from one field in a specific environment may be applicable to reservoirs with the same depositional environment elsewhere.
Each of the depositional environments has a specific character in terms of the flow geology. The macroforms making up a reservoir will have a typical size range and geometry for a particular depositional environment. These combine to give one of the distinctive geometric types; shoreline deposits are commonly layer-cake in geometry whereas meander belts are labyrinthine in form. Certain lithofacies will act as flow barriers; for example, marine shales in deep-water marine reservoirs or coals in fluvial reservoirs. Permeability profiles can be particular to a specific type of depositional environment; channel fills commonly show upward-decreasing permeabilities whereas sediments prograding into standing water will typically exhibit an upward-increasing permeability profile. Production characteristics, the sweep efficiency, and the location of bypassed hydrocarbon volumes can to a large degree be predicted according to the particular depositional environment.
The flow character of a reservoir is strongly influenced by how the various macroforms within a reservoir connect to each other (Larue and Friedmann, 2005). Although individual sand-prone packages tend to link up as connected volumes, on occasion, the boundary between two sand prone macroforms can form a flow restriction.
Figures & Tables
Oil Field Production Geology
This book was written for students, new professionals in oil companies, and for anyone with an interest in reservoir geology. It explains the background to production geology in the context of oil field subsurface operations. It also gives practical guidelines as to how a production geologist can analyze the reservoir geology and fluid flow characteristics of an oil field with the aim of improving hydrocarbon recovery. Advice is given on how to search for the remaining oil volumes in a producing field, where these pockets are typically found, and then how to plan wells to target these volumes.