A NOVEL OILFIELD SCALE CONTROL APPROACH IN SITU ION DIVERSION THROUGH ELECTROKINETICS

Sulfate scaling in oil well and near wellbore formation is a common phenomenon in a water flood recovery system where sea water, rich in sulfates mixes with formation water rich in Ba, Sr and Ca ions. This leads to a chronic flow assurance problem and warrants frequent well intervention for chemical squeeze and well cleaning operation. Apart from production loss, in offshore operations this could lead to a significant addition to production cost. To find a long term solution for this commonly occurring problem, we experimented on a novel idea of applying electrokinetic phenomena on controlling incompatibility scale in‑situ. The concept of electro‑kinetic scale remediation is derived from our successful experience with electro‑remediation of heavy metals in highly contaminated coastal area of Abu Dhabi, where di/tri‑valent cations were separated by applying DC current through metal electrodes. In the present study we focused on Barium Sulphate scaling through a series of experiments conducted in sand‑packed glass electrokinetic‑cell with multiple electrode positioning and fluid injection options. DC power was applied at 2V/cm through a single electrode configuration. Cation injector (500 ppm Ba+2) is converted to cathode and anion (SO4‑2) injector as anode. Salinity of fluid varied from 0‑40000 ppm and flown for equal period at flow rate 1 ml/min for all the flow studies. Results of pressure build up (due to scale deposition) compared with control, show that under electrokinetic application, scaling rate reduced to 1/10th or less. ICP‑MS mapping of scale deposits at various points show high localized concentration near electrodes and 50% (or less) deposition near the production well, indicating arresting/diverting of scaling ions in the vicinity of electrodes. Effect of salinity on flow pressure and current is analyzed and used for current/cost optimization.