Abstract
While polymer flooding has proven to be an effective technique to improve oil recovery from mature reservoirs, the new objective pursued by the main stakeholders consists now in optimizing the overall costs and decrease the risks associated to the implementation of chemical enhanced oil recovery methods.
Several options do exist to tackle these challenges. Developing more costeffective polymers is one of these. Traditional partially hydrolyzed polyacrylamides (HPAM) are sensitive to brine hardness and temperature; increasing both lead to a drop in viscosity which could be detrimental to the success of the project. As a result, it is generally necessary to increase the dosage of the HPAM to reach the targeted viscosity and balance for the viscosity drop induced by polymer collapse, but always at the expense of the economics of the project. In extreme cases, the project can be aborted for economic reasons. This paper describes a new class of polymers, called “stimuli-responsive”, which has been designed to overcome the aforementioned challenges.
This new family of polyacrylamide-based polymers has structurally modified to counterbalance the negative effect of salinity and temperature encountered during the transit through the reservoir. The placement, number and quantity of stimuliresponsive grafts can be finetuned to each reservoir condition to develop its full potential in the subterranean formation. This variable comes on top of other possible adjustments made to the polymer backbone including molecular weight, hydrolysis and incorporation of thermostable groups such as ATBS (acrylamide tertio butyl sulfonic acid) and/or NVP (Nvinyl pyrrolidone).
A series of rheological tests has been performed to demonstrate several features of the solutions prepared from these polymers, including salinity resistance, effect of temperature and longterm stability tests. Moreover, injectivity and retention tests have been performed to evaluate the behavior of these polymers in porous medium. A reduction in the polymer dosage on the injection side and the stimuli responsive behavior of the polymer also open new opportunities to minimize the impact of the presence of said polymer in the coproduced water on surface facilities. Some preliminary experiments have been performed in these directions.
The objective of the study is also to demonstrate the possibility to develop innovative and costeffective polymers for each reservoir condition. It encompasses an early and particularly close cooperation between the polymer manufacturer and the company willing to improve oil recovery from its reservoirs.
