Mechanical behaviour of clastic formations at shallow – medium depths which bear hydrocarbon reservoirs could exhibit an important non-linear influence of the strain on the formation stiffness during depletion. Particularly in the early reservoir production stage, characterized by high uncertainty and little ground movement data for back-analysis, reliable determination of formation stiffness at very small strain and its degradation with increasing strain via experimental testing can play a key role in realistic subsidence predictions. The standard set of data acquisition by the oil industry represents a good starting point, but the information must still be corroborated and extended by dedicated lab tests analysis. The scope of this paper is to review a selection of the most used in situ data acquisition as well as laboratory techniques for the determination of the formation stiffness at (very) small strains and its non-linear degradation with increasing strain.

Mechanical behaviour of clastic formations at shallow – medium depths which bear hydrocarbon reservoirs could exhibit an important non-linear influence of the strain on the formation stiffness during depletion. Particularly in the early reservoir production stage, characterized by high uncertainty and little ground movement data for back-analysis, reliable determination of formation stiffness at very small strain and its degradation with increasing strain via experimental testing can play a key role in realistic subsidence predictions. The standard set of data acquisition by the oil industry represents a good starting point, but the information must still be corroborated and extended by dedicated lab tests analysis. The scope of this paper is to review a selection of the most used in situ data acquisition as well as laboratory techniques for the determination of the formation stiffness at (very) small strains and its non-linear degradation with increasing strain.