Overview

Evaluation of in situ rock mechanical behaviour requires relevant input data: What is the stress state and the pore pressure at the depth of interest? What are the elastic moduli and the strength parameters? Can we expect creep or other types of non-elastic behaviour to take place?

Our main data sources in order to answer these questions are core material and data recorded in the field (measurements while drilling, wireline logs, seismic data and various well tests). The logs provide data recorded continuously vs. depth, but do not measure directly the parameters that are needed for a rock mechanical analysis. For instance, rock strength can not be measured from wireline logs. Strength estimates may, however, be given if a proper interpretation procedure is applied. Field measurements of rock mechanical parameters are discussed in Chapter 8.

In this chapter we shall discuss rock mechanical core analysis. Cores provide a possibility for direct measurement of e.g. rock strength parameters and static elastic properties. We shall start by looking at the rocks to be tested: the cores in the laboratory may not be fully representative of the formation we intend to study. They may also have been altered during coring and subsequent handling. Some of these problems can not be solved, others can be overcome by proper sample preparation methods, test procedures and correction procedures. On the other hand, if proper preparation procedures are not applied, severe errors in the test results may be introduced. These factors will be discussed in...