Comprehensive Utilization of Formation Water Scale to Prepare Controllable Size CaCO Nanoparticles: A New Method to Improve Oil Recovery.

Formation water scale blocks pipelines and results in oil/gas production decreasing and energy consumption increasing. Many methods have been developed to inhibit scale formation. However, these previous methods are limited by their complications and low efficiency. A new method is proposed in this paper that uses the scale in formation water as a nanomaterial to improve oil recovery via controlling particle size. A series of ligands were synthesized and characterized. Micrometer-CaCO was formed and accumulated to form scale of a large size under uncontrolled conditions. The tetradentate ligands (L) exhibited an excellent capturing yield of Ca (87%). The particle size was very small, but they accumulated to form large particles (approximately 1300 nm) in the presence of NaCO. The size of the CaCO could be further controlled by poly(aspartic acid) to form sizes of about 700 nm. The flooding test showed that this material effectively improved oil recovery from 55.2% without nano CaCO to 61.5% with nano CaCO. This paves a new pathway for the utilization of Ca in formation water.