Study on acidizing effect of β-cyclodextrin-PBTCA inclusion compound with sandstone

One of the main stimulation techniques to enhance oil production in reservoirs is acid treatment. The acid that can decrease the corrosion rate with formations and may control the reaction is the key to a successful stimulation. In this study, a new supramolecular retarded acid system has been developed to treat the sandstone. The inclusion action between β-CD and 2-Phosphonobutane-1,2,4-Tricarboxylic Acid (PBTCA) was investigated by UV–Vis Spectroscopy. The result showed that the stoichiometric ratio of inclusion compound was 1:1. The dissociation constant of PBTCA before and after including was measured by acid base titration. The result illustrated that the inclusion compound did not change the multiple ionization property of PBTCA, but it could effect on the value of pK. This is because the carboxy group of PBTCA partly dissociates to form anion inclusion compound with β-CD. Experiments have been conducted in the laboratory to prove the efficiency of reaction control using the new acid system. The experimental results that demonstrated β-CD-PBTCA had lower reaction rate and limited corrosion with sandstone compared to the mud acid and PBTCA. The molecule recognize test results showed that oil molecules can interact with β-CD-PBTCA and drove the guest of β-CD-PBTCA out of the cavity to react with ammonium bifluoride.

Research Highlights► We prepared the β-CD-PBTCA inclusion compound under appropriate conditions. ► We measure the corrosion rate of cyclodextrin-organic phosphonic supramolecular acid system with sandstone. ► Cyclodextrin supramolecular acid system not only owns the advantages of phosphonic retarded acid but also can recognize oil molecules in some degree so as to possess the premise of deep aciding. ► We give the acidizing process schematic drawing. ► This paper is only the preliminary laboratory study, and the effect of field application will be discussed in future work.