Thermal-Poro Elastic Stress Effect on Stress Reorientation in Production and Injection Wells

Presented at: Brasil Offshore, Macaé, Brazil, June 2011.


Stress reorientation is an important issue for the cuttings injection batching, refracturing design and stimulation candidate well selection. Long term production/injection causes the principal stresses to reorient. Temperature differences and pore pressure differentials induce thermal elastic stress and poroelastic stresses. These induced stresses are the fundamental reasons for the reorientation of the stress field. A model and numerical scheme are developed to study the effects of thermal differentials and pressure differentialss on stress reorientation. The model couples thermal diffusion and convection with hydraulic diffusion to obtain the temperature distribution reflecting the cumulative impact. The effective poro-elastic and thermo-elastic stresses result from the 1-D displacement equilibrium equations in a radial system. The 3-D in-situ analytical effective stress is superimposed on the 1-D solution. Application of this methodology simplifies the modeling of the 3-D stresses in a deviated borehole. The method makes it practical to obtain the stress distribution at any given injection/production time. The thermal stress and poro-elastic stress effects on the stress reorientation are compared and evaluated. Field examples are presented to show that in some cases the thermal stresses play an important role on stress reorientation. The quantified results of the model will give guidance on fracture treatments and well plans during injector or producer construction.