The Impact of EOR Polymers on Scale Inhibitor Adsorption

Abstract

With the current trend for application of Enhanced Oil Recovery (EOR) technologies, there has been much research into the possible upsets to production, from the nature of the produced fluids to changes in the scaling regime. One key question that is yet to be addressed is the influence of EOR chemicals, such as hydrolysed polyacrylamide (HPAM), on scale inhibitor (SI) squeeze lifetime. Squeeze lifetime is defined by the adsorption of the inhibitor onto the reservoir rock, hence any chemical that interacts with the adsorption process will have an impact on the squeeze lifetime. This paper experimentally demonstrates potential changes to inhibitor adsorption from a polymer EOR project by demonstrating the complex interactions between HPAM and phosphonate scale inhibitors with respect to adsorption. This work presents a detailed coreflooding programme, supplemented with bottle tests, to identify the impact of HPAM on a diethylenetriamine penta(methylene phosphonic acid) (DETPMP) squeeze lifetime. A range of pH values, representing the expected inhibitor injection pH, have been studied on consolidated and crushed Bentheimer sandstone. A temperature of 70°C is used throughout as it represents the likely maximum temperature at which HPAM would be applied and the typical temperature at which DETPMP would be used in squeeze applications. The results presented show that scale inhibitor application pH is key in defining the impact of HPAM on DETPMP adsorption. Neutral pH displays a reduced squeeze lifetime, believed to be due to reduction of adsorption sites by HPAM. However, this impact could be countered by injecting this type of scale inhibitor at a low pH (e.g. pH 2). Static tests performed alongside the corefloods show that even low inhibitor concentrations (as found in SI pre-flushes) are sufficiently acidic to fully precipitate the HPAM from solution, but did not impact the adsorption. This study suggests, contrary to the commonly held view in the industry that EOR polymers may negatively impact squeeze lifetime, that with the correct selection of inhibitor type and their application pH it is possible to achieve the same results as in a conventional reservoir.

Effect of engineered water and scale inhibitor concentration on the adsorption performance of gypsum inhibitors on multi‐walled carbon nanotubes and crushed sandstone

“…[ 43 ] In a different study, using hydrolyzed polyacrylamide (HPAM) as the EOR chemicals resulted in a decrease in SI adsorption at both neutral and low pH. [ 42 ] Another study demonstrated that using nanomaterials like CNT and GO in a brine that contains calcium ions can improve the SI adsorption more than DW, but the SI concentration reduction at their ideal experiment (83%) is lower than the optimal condition of this study (93%). [ 44 ] As a result, the ideal scenario for improving scale inhibitor adsorption is to eliminate monovalent cations from SW that may block the adsorbent's surface active sites and keep the divalent cations (both Mg 2+ and Ca 2+ ).…”

“…-Gypsum nucleation inhibition in the presence of HEDP and PBTC using dynamic light scattering Popov et al [41] DETPMP Seawater À30 μg/g -HPAM Investigating the effect of HPAM and lowering pH on DETPMP adsorption Beteta et al [42] PVS Synthetic brines 22% increase -PEC nanoparticle Increasing the lifetime of PVS in sandstone rock by adding PEC Veisi et al [43] EDTA CaCl Ghorbani et al [45] HEDP PBTC other organic and inorganic substances are among the impurities that are found in oil and gas when they are taken from the ground. These impurities have the potential to precipitate, which can lead to equipment inefficiency, pipeline obstructions, and other operational issues.…”