Technical Committee Reservoir Engineering
Carrier damage due to frac fluids
The aim of the project was to investigate carrier damage caused by frac fluids under simulated reservoir conditions. The work included investigations on the property of the filter cakes and the description of the "leak off". The core material used for the experiments with a commercial chemical system from Schlumberger GmbH covered the large permeability range of 2×10-12 - 1×10-20 m2.
The frac gel used forms compressible filter cakes in the temperature range from 120° to 150 °C. The filtration behaviour can be described mathematically on the basis of a physically plausible model based on a pressure-dependent compressibility. The parameters of the derived function are valid for a permeability range of at least 2×10-12 - 4×10-16 m2. The assumption of a "spurt lost" is not necessary.
No relevant invasion of damaging, polymeric gel components into the carrier occurs. However, the high pH value of the filtrate leads to dissolution reactions in the rock matrix and thus to changes in the rock properties. The effect of retention of gel components in the reservoir rock is to be assessed as low at high temperature.