Introduction to Well Log Interpretation: Finding the Hydrocarbon

This chapter presents a general overview of the problem of log interpretation and examines the basic questions concerning a formation’s potential hydrocarbon production that are addressed by well logs. The borehole environment is described in terms of its impact on the electrical logging measurements, and all of the qualitative concepts necessary for simple log interpretation are presented. Without going into the specifics of the logging measurements, the log format conventions are presented, and an example is given that indicates the process of locating possible hydrocarbon zones from log measurements. Although the interpretation example is an exercise in the qualitative art of well log analysis, it raises a number of issues. These relate to the extraction of quantitative petrophysical parameters from the logging measurements. This extraction process is the subject of subsequent chapters. Once these relationships are established, more quantitative procedures of interpretation will be described.