Activator Development for Controlling Degradation Rates of Polymeric Degradable Diverting Agents

摘要

Hydrolytically degradable polymers (generally aliphatic polyesters) have been used in a variety of applications in the oil field, such as fluid diversion, fluid-loss control, and filter cake removal applications. In general, diverting agents and fluid- loss-control materials are only necessary to perform the intended function for a finite amount of time. Once the well is completed or placed on production, it is desirable that the degradable materials be removed so that they no longer have any influence on subsequent fluid flow. With time and temperature, the degradable polymers will break down by forming water- soluble byproducts, leaving behind limited, if any, residual formation damage. The effective formation sealing by these materials while in place, and eventually during cleanup, has made them sought after for a growing number of applications. However, for cooler temperatures, and applications where the well must be placed on production more quickly, there have not been many options to controllably increase the rates of polymer degradation. This has considerably limited the realization of the full potential of the technology. There is an increasing demand for faster cleanup of the diverting agents and fluid-loss- control agents for applications at cooler temperatures. Strong acids and bases are known to accelerate the degradation of these polymers. Use of such materials can present several disadvantages, such as corrosion and/or undesirable reactions with the formation. Although enzymes are used for the activation of ester hydrolysis, the use of enzymes has not demonstrated effectiveness in all situations. There is a need for chemical activators that can controllably accelerate the degradation of polymers at wellbore temperatures without the detrimental effects of using strong acids or bases. This paper discusses specific activators that can degrade various types of polymers and polymer blends containing degradable functional groups in the polymer backbone. The polymers tested in this study had variable crystallinities and chemical compositions. This paper also presents a new approach to degradation activation that should be more desirable in oilfield applications where the degradation times can be controlled for wide range of temperatures and wellbore conditions.