– Damage Mechanisms and Mitigation
Significant improvements have been made in hydraulic fracturing over the past few decades, particularly in modeling, materials, delivery equipment and monitoring, and the technology footprint has gone beyond tight or unconventional gas into higher permeability reservoirs such as frac and pack applications. Despite its tremendous successes, hydraulic fracturing often does not deliver its full expected potential. The literature is replete with examples of treatments in which production or well test data have indicated an effective fracture length much shorter than predicted. Among the many factors that can contribute to this discrepancy are various damage mechanisms that often accompany hydraulic fracturing treatments.
This presentation will review a number of damage mechanisms associated with hydraulic fracturing, and their impact will be quantified using a customized 3-D multiphase reservoir simulator. Of particular interest is a new understanding of the damage caused by the concentrating of the frac fluid polymer. Much of this understanding has resulted from an extensive experimental study conducted by an industry JIP that was initiated in 2002. It will be shown that contrary to popular belief, the polymer concentrates only in the filter cake, and a significant yield stress can result when the filter cake thickness dominates the proppant pack width. The effect of this yield stress on effective fracture lengths and techniques for mitigating this problem and restoring production from the full length of the created fracture will be discussed.