Dual Kinetic Hydrate Inhibition and Scale Inhibition by Polyaspartamides

Polyaspartamides are a recently developed class of kinetic hydrate inhibitors (KHIs) with good biodegradability, made from polysuccinimide (PSI). Because polyaspartates are well-known biodegradable scale inhibitors (SIs), which are also made from PSI, we have investigated the possibility of using PSI to make a single product that would function as both a KHI and a SI. We have synthesized an extended range of PSI derivatives and tested them as KHIs in high-pressure autoclaves with synthetic natural gas and as SIs for both calcium carbonate and barium inhibition in a high-pressure dynamic tube blocking rig. In comparison to earlier work, we have further improved the ICHI performance of the polyaspartamide class by incorporating a high percentage of isopentyl groups into the structure without losing water solubility. We have also found that, for some polymers, good scale inhibition can be obtained for both types of scale without compromising the KHI performance when dosed at several thousand parts per million (ppm), a typical KHI dosage. The polyaspartamides have high cloud points and are compatible with brines containing calcium ions up to a concentration of at least 2000 ppm. Thus, use of certain polyaspartamides as KHIs for gas hydrate control should not require the extra use, where needed, of a specialized SI for topside carbonate or sulfate scale inhibition.