Research and application of environment-friendly scale inhibitor

In order to address the problem of severe scaling in tubing and rod in oil wells on Yucha Block of Xiasiwan Oilfield, field research and sampling inspection revealed that the produced water had a high content of scaling ions like Ca2+, Mg2+, CO32– and SO42–, and also had a high content of bacteria, esp. SRB bacteria, which was up to 103/mL. In consideration of the main causes for scaling in oil wells on Yucha Block, the PESA (Polyepoxysuccinic acid) and PASP (polyaspartic acid) were used as the main agent in lab experiment and such additives as corrosion inhibitor, bactericide, dispersant, etc. were optimized, from which the environment-friendly scale inhibitor formula was chosen, and tests were made on its corrosion and scaling inhibition properties and biodegradation properties. The result of field application shows that the average retention rate of Ca2+ was up to 81.6% and the average inhibition rate was up to 80.6% in stimulated wells. The repair-free period of stimulated wells was increased from 75 d to 247 d. This scale inhibiting system has a double function of scale inhibition and corrosion inhibition, can address the scaling problem in oil wells on Yucha Block of Xiasiwan Oilfield, reduce the maintenance operations on oil wells and reduce oil well production costs.