In 2021, the El Tordillo Reservoirs team launched a polymer-gel injection project for tertiary recovery. They recently presented the results of this initiative at the IAPG Reserves Production and Development Congress; find out more below.

The lifespan of a well goes through a number of different phases, starting with the primary recovery stage, where it produces using its own pressurized energy. This is followed by the secondary recovery stage, when water is injected into a nearby well thus exerting pressure and prompting it to sweep across the rock layers to obtain gas or oil. This technique comes to a close when the results are no longer profitable and water is found in the final product. This is when the tertiary recovery phase begins.

Although its name indicates that it’s a new stage, tertiary recovery could be just as easily be considered a way of optimizing secondary recovery thanks to the application of various technologies. “By injecting polymer gels, we can improve the sweep, make it more uniform or identify new sources,” explains Rodrigo Santamaría, Development Engineer Lead Analyst in El Tordillo, at the IAPG Congress.

“These technologies are in fact among the most tested in the San Jorge Gulf basin, but they were discontinued in 2014 because oil prices were undermining our profitability margins,” details Santamaría. The good results obtained in YPF wells in the area meant that new investments could be made in this technique.

Zooming into the well

Applying the tertiary recovery technique in El Tordillo involves injecting a low-volume gel pill into the well, which solidifies to create a blockage so that water has to find new channels to get across. However, for the polymer gel to change state, a cross-linker is required that is activated at certain temperatures to become a plug so that the water redirects the injection.

“We’ve carried out 107 treatments in the history of El Tordillo with very good results. More recently, we reinjected three wells and achieved some promising results,” highlights the expert, who pointed out that “the selection of the right candidate wells is very important” to ensure that the practice is profitable. The results are clear: in all the wells where the technique was applied, the team saw an increase in extra oil production over the course of one year.

Based on the results presented to all the operators working in the country, the Reservoirs team is now readying itself for the next stage of the project to be carried out later this year. The new cross-linker, which is more efficient as it can withstand higher temperatures, means that the search for hydrocarbons can be carried out at greater depths. “While the previous cross-linkers were activated at 80° C, the new ones can withstand up to 150° C,” explains Santamaría. “Previously, we were limited to shallower areas, whereas now we can go further, to depths where gel treatment has never been carried out before,” he summarizes. “We believe that the prize to be had lies deeper today and that’s why we developed this technological innovation.”