Practice for EOR by Deep Profile Control and Oil Displacement in Old Oilfield with Near Limit Watercut–Take G979-938 Block as an Example

Abstract

Channeling communication often exists in strong heterogeneity reservoir after long time waterflood, causing problems such as water channeling, low pay-gross thickness ratio and poor waterflood performance even after well pattern modification. Deep profile control and oil displacement technology was adopted based on the reservoir development potential study, historical profile control treatment analysis, physical experiments and reservoir simulation. High strength crosslinking polymer gel and performed particle gel were used to block the strong channels and resist water channeling. Mid and low strength crosslinking polymer gel was to reduce the high permeability, correct heterogeneity, control profile, maximize sweep efficiency. Soft micro gel was to block, break, re-block and re-break the big pore throats distributed throughout high permeability area in deep formation and direct water into trapped, oil rich zones to drive out the remaining oil at the same time. Different agents and slugs were injected alternately for correcting reservoir heterogeneity from macro to micro reservoir and from near the wellbore to in-depth by combination of channel blocking, heterogeneity correction and oil displacement. After field test in G979-938 block with watercut as high as 97%, the watercut was decreased by 2.74% points, the natural decline rate decreased by 8.86% points, the oil recovery increased by 3.24% points and incremental oil was 122000 tons, which showed that it could be used for further improving oil recovery of the same kind of reservoirs.