Proppant-Pack and Formation Impairment During Gas-Well Hydraulic Fracturing

Abstract

Summary Equipment has been constructed to give a realistic laboratory simulation of the in-situ conditions during and after a hydraulic fracturing treatment of tight gas reservoirs (TIGRE). The equipment measures the permeability of both the "natural" core material and the proppant pack with gas under in-situ conditions before and after exposure to fracturing fluid. The rate of cleanup of the proppant pack and the core sample is measured after the fracturing fluid has broken. Various fracturing fluids commercially available from the major service companies have been evaluated. Little damage to the proppant/rock interface has been measured, but massive damage to the proppant pack was observed. The damage is caused by fracturing-fluid residue, filter cake, and non-Darcy flow effects. This damage is observed only in the experiments described above and has not been reported in other less sophisticated laboratory simulations of the fracturing process. The least damaging of the commercially available products tested has been identified. Procedures have been developed for placing "overdesigned" (or increased-conductivity) proppant packs during field hydraulic fracturing treatments. This has resulted in large increases in well productivity during field treatment, which is particularly noticeable during the early (transient) production phase. It is concluded that there is scope for the development of less damaging fracturing fluids to optimize economics.