Abstract
Process fluids used for operations with productive formation are considered to be a decisive reason of decreased well productivity. Application of special-purpose fluids allows eliminate the negative effect of the process fluids; these fluids don't make through a formation during operations of wells completion and workover and could be easily removed after the operations have been finished. Well- killing operation with process fluids without tunable properties is a standard well- killing technique during workover operations. Such method doesn't protect a formation from liquid penetration, and oftentimes after such workover operations it is getting rather difficult to reach the process stabilization of the well.
Visco-elastic gels (VEG) act as a "flexible packer" and are designed for temporary protection of productive formation on the stages of wells’ completion and development, during workover and insulation operations. Over 350 well- killing operations by using VEG have been carried out in the territory of Perm region within 2012-2013. Application of this technique provides specified effect concerning decrease of well- killing liquid volume and saving time needed for the process stabilization. However the well pumping equipment failures have been registered due to fouling with VEG residues. Noted problems could be eliminated by applying the proposed well- killing technique by using the composition with specified destruction time.
Cross-linked polymer systems gain widespread acceptance in formation fracturing operations. Provided that a considerable amount of breakers are offered at the market, they include "encapsulated" breakers designed to destruct fluids after proppant has been injected into formation. By that the induction period prior the breakers start action doesn't exceed 2-3 hours upon they have been injected into the system. For well- killing operations by VEG application it's typical to provide retention of the fluid bridging properties at least 2-3 days. In this regard conceptually new approaches are required to reach such conditions in order to control VEG "lifetime".
This study presents the results of laboratory research on VEG development with controllable service life. Introduction of this technique will allow reducing the likelihood of equipment failures and accelerating the process of reaching design basis conditions of the wells.
