2.2 Measuring Properties at Different Scales

The three main stages of field development are exploration (through to discovery), appraisal, and production. In exploration, one starts with a conceptual geologic model (Fig. 2.2), which may be based on geologic knowledge of the area, including basin evolution, structure, and stratigraphy (labeled 1 in Fig. 2.3). Conventional 2D or 3D seismic-reflection analysis (Fig. 2.2) normally is the next phase of exploration, because subsurface seismic profiles and 3D volumes can provide a regional-scale image of the area being explored (labeled 2 in Fig. 2.3). If the seismic data reveal potential drill sites, and a well is drilled, the well is logged with conventional logging tools (Fig. 2.2) to determine rock and fluid properties in the wellbore (labeled 3 in Fig. 2.3).

Figure 2.2: Diagram showing some of the different data types used in the study of reservoirs. Clockwise from upper left are conventional well logs, a conceptual geologic model, 2D and 3D seismic reflection data (shallow and deep), outcrops, cores and borehole image logs, and geologic reservoir models. Not shown are geochemical and biostratigraphic data, which also are important in reservoir characterization.

Figure 2.3: Exploration, discovery, development, and production stages in the evolution of a reservoir over time (steps 1 9). Geophysics, geology, and petroleum engineering all play dominant roles at different times in the life of a field.

If potentially economic accumulations of hydrocarbons are found in the exploratory well (labeled 4 in Fig. 2.3), the decision may be made to drill more wells...