Scaling Deposition Behavior in Sieve Tubes of Produced Water Filter in Polymer Flooding

Abstract

A green field development might face many challenges such as water source shortage, wastewater accumulation, discharging pollution, and purifying effect. The polymer flooding produced water (PFPW) with complex characteristics would lead to scaling deposition behavior, and the sediment compaction even appears in sieve tubes when filtering. Overall consideration of prevention and removal to scale in sieve tubes is an effective method to address the challenges. An investigation of produced water scaling and depositing in sieve tubes of sand filter in Daqing Oilfield was recently carried out, and a laboratory test was performed for characterizing the properties of scaling sediments. The scaling deposition behavior occurring in sieve tubes was identified and simulated, and the mechanism was discussed. The methods of scale prevention and removal were screened in consideration of operational feasibility and economical justification, and then the field practice effect was presented and assessed. The results show that the filter of disposing PFPW is mainly destroyed by the pressure locking which originates from the occurrence of scaling deposition in water collecting sieve tubes. The sediments are accumulated with sulphides, carbonate scale, silicate scale, dirty oil and degradable polymer. The deposition in sieve tubes is affected by the residual polymer in a great degree. The major impact of temperature threshold value is facilitating under-deposit corrosion. It is beneficial for the scaling deposition prevention by utilizing the anti-wear ceramics materials to replace carbon steel. The acid pickling operation could realize the effective removal to scale by integrating the dispersing, stripping, dissolving, deactivating, flushing, carrying and discharging mechanisms, and the acid fluid system is screened with which primary solvent is 10% hydrochloric acid. Furthermore, the field practice case indicates that the oil and suspended solids content of purified water reduced by 21.71% and 26.58%, respectively, the water consumption in backwashing process was multiplied, and the accumulation of sediments dropped by more than 50% in same running period. This study is significant to the understanding of scaling behavior in enhanced oil recovery (EOR) surface facilities, and it is also beneficial to provide an auxiliary technology of disposing PFPW.