Use of Layered Formation Models in Deformation Analysis

Davis, Eric ¹
(1)Pinnacle, San Francisco, CA.

Deformation measurements are used on a regular basis to map the orientation of hydraulic fracture treatments, determine the subsurface location of steam in EOR projects, measure the magnitude and areal extent of subsidence due to production, and track injected fluids including sequestered carbon dioxide. Determining the best fit strain source to match the measured deformation requires the use of a model that predicts the deformation induced by a given strain, together with an inversion process that can manipulate the source to find the best possible match to the measured deformation. Typically, the model relies on the assumption that formation properties are homogeneous. The simplification is used primarily to save computation time, since the calculations for a layered system are far more complex. A further issue is that layer properties, particularly going all the way from the reservoir back to the surface, are often difficult to obtain within reasonable precision.

This paper explores the implications of this simplification using rigorous testing for two and three layer systems, plus select examples of more complex systems with the intent of establishing ground rules for when the introduction of a more complex layered model is justified to improve the results.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.