Experimental and theoretical insight into the use of maleic anhydride copolymer and modified sulfamic acid for removing oilfield blockage

Abstract

In the process of oil production, the problem of oilfield production decline due to blockage is becoming more and more serious. To improve the exploitation efficiency of traditional fuel, it is very important to remove the blockage and inhibit the formation of the blockage. In this study, the primary constituents of the blockages in this oilfield were identified as asphaltene (organic blockage) and calcium carbonate (CaCO3, inorganic blockage). To address these blockages, maleic anhydride copolymer (MAC-1, MAC-2, and MAC-3) with different chain lengths were polymerized by maleic anhydride and allyl polyoxyethylene ether, which were used to disperse organic blockages. Additionally, modified sulfamic acid (MSA-1, MSA-2, and MSA-3) with different chain lengths were synthesized by sulfamic acid, polyethylene glycol, and lauroyl chloride, which were used to dissolve inorganic blockages. The efficacy of these agents in terms of blockage removal, scale inhibition capability, corrosion rate, and compatibility with formation water were comprehensively evaluated. Results showed that MAC-2, which possesses a moderate chain length, and MSA-1, which has a shorter chain length, demonstrated an optimal synergistic effect on blockage dissolution at concentrations of 4 wt% for MAC-2 and 5 wt% for MSA-1. The dissolution rate of this combination was 81.18 %, with a scale inhibition rate of 95.7 %. The corrosion rate increased with temperature, and the agents maintained good compatibility with the formation water. To elucidate the mechanism underlying the effectiveness of MAC, the interaction between MAC and asphaltene was simulated by molecular dynamics (MD). These simulations indicated that MAC-2 and asphaltene exhibit the highest interaction energy (-64.2618 kcal/mol). Furthermore, we investigated the dissolution kinetics of CaCO3 in MSA solutions and determined that the reaction between MSA and CaCO3 was first-order, with a reaction rate constant of 1.6 × 10−2 min−1. The insights gained from this study offer a valuable experimental and theoretical foundation for enhancing productivity in similar oilfields.