A Discussion Of Stress Evolution During The Lifetime Of A Field And The Impact On Field Development Design

Abstract

The stress-depletion response of reservoirs has been recognized since the 1970s, where the minimum horizontal stress magnitude reduces linearly with pore pressure decline. The evolution of minimum horizontal stress magnitudes accompanying both depletion and injection has been measured in a number of fields.

Along with the minimum horizontal stress, the maximum horizontal stress and vertical stress magnitudes also evolve with pore pressure, though these changes are not directly measured, but estimated through either analytical or numerical modeling.

Reservoir stress evolution is most marked in overpressured and HPHT fields where the pore pressure decrease is most severe. In these fields, stress reduction may not be linear, and will change as the rock properties evolve from elastic to plastic responses. Key factors controlling reservoir stress evolution will be discussed.

Prediction of the stress evolution response of reservoirs with simple analytical models has proven to be problematic. A rigorous approach using 3D modeling and field and test data produces more realistic results. Field examples are presented which highlight the impact of the depletion-stress evolution on field development, and in particular the influence on initial well planning, infill drilling, and completion design.

AAPG Datapages/Search and Discovery Article #90324 © 2018 AAPG Asia Pacific Region GTW, Pore Pressure & Geomechanics: From Exploration to Abandonment, Perth, Australia, June 6-7, 2018