Filter Cake Removal Technology in the Palouge Oilfield in South Sudan

In horizontal wells in the Palouge Oilfield,South Sudan,the filter cake of drilling fluid on the screen tube and borehole wall cannot be completely removed with screen pipes during the well completion,resulting in the inability of the well to achieve target production levels.Taking into consideration the weak salt sensitivity,moderate water sensitivity,acid sensitivity,alkali sensitivity of the Palouge Oilfield reservoir,the drill-in drilling fluids used in the oil field mainly consisted of degradable organic treating agent,calcium carbonate and polyol,the acidic remover HBK-Lb was selected,the corrosion inhibitor and its dosage were optimized to form the acidic completion fluid for removing filter cake.Indoor performance evaluation results showed that the acid remover HBK-Lb could remove API filter cake and screen cake of Drill-in drilling fluid,with a removal rate up to 90.0%.The acid completion fluid could remove filter cakes inside and outside the core.The permeability recovery rate of the core that static polluted by filter cake is higher than 97.0%,and the permeability recovery rate of the core that dynamic polluted is higher than 102.3%.The acid completion fluid for removing filter cake was applied in the six wells,the completion fluid loss rate increased with the increasing immersion time,indicating that the filter cake was removed.After completion,the well production capacity increased by 12.4% on average compared with the neighboring wells which did not use completion fluid for removing filter cake.The study demonstrated that the acid completion fluid could remove the inner and outer filter cakes around the borehole wall,and improve the permeability of reservoir in the Plalouge Oilfield.