Synthesis and Testing of Oil Field Scale Inhibitors

Abstract

Scale formation is one of the major problems faced during production in the oil industry. A common method to control scale is the utilization of chemicals known as scale inhibitors (SIs). Several SIs are available commercially but with one or more disadvantages. Poor biodegradation of PVS, ATMP and DTPMP limited their use in environmental restricted regions. Polyaspartate (PASP) is an eco-friendly SI but is not stable thermally. Moreover, SIs containing a greater number of phosphonate groups has less calcium tolerance. None of them is good enough to overcome inhibition efficiency, thermal stability, calcium compatibility and biodegradability issues altogether. So, in this study, we focused on the synthesis of green and thermally stable SIs to increase squeeze lifetime and their versatility. In project 1 poly aspartate was modified with phosphonate and sulphonate functional groups due to known biodegradability of PASP and good thermal stability of phosphonate and sulphonate groups. Inhibition performance of the final products was evaluated against carbonate and sulfate scales using a high-pressure dynamic tube blocking rig at 80 bar and 100oC. The calcium compatibility and thermal stability of synthesized SIs were also examined in this study. Results indicate that the performance of all modified scale inhibitors was improved after modification for both carbonate and sulphate scales. Phosphonated-PASP SIs showed good thermal stability against carbonates and sulphates while other was not thermally stable against both carbonate and sulphate scales. Moreover, phosphonated inhibitors showed limited calcium compatibility after modification than others. In project 2 a novel series of hydroxy bisphosphonate SIs was synthesized by the substitution of carboxylic acid using different amino and dicarboxylic acids. The inhibition performance, thermal stability and calcium compatibility of final products were tested the same as above. The results exhibited that the products containing one hydroxy bisphosphonate functional group showed excellent inhibition efficiency against carbonate than sulphate scales before and after thermal ageing. Products that contain two hydroxy bisphosphonate functional groups exhibit a reasonable performance against both carbonate and sulphate scale before and after thermal ageing. The results represent that the compatibility of all inhibitors with calcium was limited except SI-10 that was compatible in all given concentrations of calcium ions.