DRA-2-retarded acid: breaker intensifier

By Maxim Mikitin, Chief Geologist of LLC Newco Well Service

Maxim Mikitin, Chief Geologist of LLC Newco Well Service explains the advantages of DRA-2 for hydrofracturing.

Today many oil producing companies facedecrease in the number of frac candidates in developed oilfields on the one hand and the necessity to maintain production and comply with license agreements on the other hand. The main reason for this is that the majority of “good” wells were already fractured before, some of them many times, and the remaining well stock has restrictions on performance of conventional fracs.

As a solution to the problem specialists of LLC Newco Well Service offer a technology of residual fracture conductivity improvement which is based on application of DRA-2, assisting to initiate formation of retarded acid. Results of experimental industrial application of this technology proved increase in fracture performance.

DRA-2 – is a new chemical that was successfully introduced by Newco during oilfield fracturing operations. When added to water solutions at high temperatures this liquid additive slowly disengages organic acid. Such acid disengagement has numerous advantages that are essential for fracturing systems with high pH, such as Quantum. The most obvious advantage is slow pH decrease in the course of acid disengagement. The pH decrease below 8 completely removes borate x-linkers both from hydrated polymer chains and from polymer chain fragments after decomposition by oxidizing breaker. This results in decreased number of unbound polymer fragments, thus minimizing a potential for sedimentation that reduces conductivity of proppant pack.

Application of DRA-2 in combination with  the oxidizing breaker results in synergetic degradation of fracturing gel. One more advantage of DRA-2 application is that an organic acid, when disengaged, can completely decompose fracturing gel. A long time period and high temperatures assist organic acid to hydrolyze polymeric chains. This reaction is similar to oxidation, incidentally chains are degraded into smaller fragments.

A synergetic effect of adding two breakers is in retarded chemical reactions. Since DRA-2 is fluid and conventional oxidizers are encapsulated solid substances, DRA-2 mixes with fluid that penetrates reservoir while oxidizer is in fracture. As a result breaker is distributed with frac fluid to everywhere is flows. The final frac fluid with low pH has a number of advantages. It is known that fluids with high pH cause significant damage to sand formations with high concentrations of swelling and migrating clays. The majority of clay minerals highly tend to hydrate at high pH levels (over 7). Water that penetrates a formation causes less damage to clay if frac fluid is decreased by DRA-2. Beside obvious advantages of adding DRA-2 to frac fluids this unique additive has other functions. Laboratory tests proved that DRA-2 can be applied in combination with enzymatic breaker to decompose frac fluids with high pH, such as Quantum gels. A conventional  cellulose enzyme becomes a denaturated enzyme at high pH (over 7). However DRA-2 decreases pH the enzyme may partially deactivate. Enzyme breakers are usually more preferable versus oxidizers, since enzymes do not require any catalyst, and polymer decomposition is this case is more efficient and complete than when treated with an oxidizer.  DRA-2 may also be useful in combination with foaming additives (chemicals that form water at high pH and do not foam water at low pH). Deactivation of foaming additive has obvious advantages while fracturing with foaming agent or foaming cleaning fluids. DRA-2 is a cost-effective, non-evaporating, non-flammable and odorless  additive. This product is successfully applied in some oilfields in the Western Siberia, the application analysis confirms efficiency of the additive for the group of wells.