It is well known fact that some part of drilling fluid can get inside the reservoir through filtration channels of the rock during drilling-in the oil reservoir. Well drilling is made with the pressure that is much higher than formation. It is done to prevent oil and gas inflow during drilling. The magnitude of the hydrostatic repression depends on the density of the drilling fluids, the height of the fluid column and the reservoir pressure. And it is obvious fact that the oil layer is sensitive to contamination and clogging with drilling fluid. Also, under certain conditions, a flocculation and sedimentation of solid particles can occur during water oil contact. And as a result, obstruction of pore space occurs. Suspension particles can scale on the surface of the pore space.

This problem can be partly solved with help of using progressive types of perforation (sometimes with using of expensive fluids and stimulation methods). But even this cannot restore the permeability of the pay zone completely. Based on different sources, the losses in productivity due to well completion factors can reach 30% and more.