Abstract: The compressive strength of rocks is very important to optimization of drill bits selection. Aiming at thesandstones which are frequently encountered in the oil drilling, a triaxial compressive strength model which is based on logging data is put forward. The model is established on the basis of acoustic logging, bulk density, gamma ray counts and the results of uniaxial compressive strength. The experiments’ results about the nature of confining pressure of sandstone mechanics and changes in sandstone porosity are also considered. It is shown that sandstone strength is influenced by confining pressure significantly. With the increasing of lateral pressure, the compressive
strength is also increased. Porosity is reduced with the increasing of confining pressures, which conforms to the rule of logarithmic function.

Key words: well-logging data, drilling engineering, sandstone, triaxial compressive strength, porosity