Petroleum Engineering

Stability of Coated Proppants

CProppants stabilize fractures stimulated during hydraulic fracturing and allow for fluid flow along these fractures during production of tight gas and unconventional oil and gas. Coated proppants additionally stick together to prevent them from being washed out during clean up or production. Another desired effect of the agglutination is the enlargement of the specific surface and hence a higher stability of the single grains against confining pressure. Fines derived from crushed grains can lower the permeability of the proppant grain framework and should therefore be avoided. Experience from the field, however, shows that coated proppants do not always fulfil all these expectations.
Here the stability of coated and uncoated proppants was tested under in situ conditions. The influence of formation water, clean-up fluids and acids was evaluated. An experiment set-up was built, which allows for the measurement of the permeability of a proppant pack under reservoir conditions. Clean-up procedures against salt evaporation were simulated and optimized.
As part of the first phase of the project, a test cell for proppants was set up to allow flow through the proppant packing to determine the hydraulic conductivity under reservoir conditions.
In the second phase of the project, the existing test cell was used to conduct studies on the effectiveness and optimization of frac scrubbing against salt precipitation.