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With complex fractured-vuggy heterogeneous structures, water has to be injected to facilitate oil production. However, the effect of different water injection modes on oil recovery varies. The limitation of existing numerical simulation methods in representing fracturedvuggy carbonate reservoirs makes numerical simulation difficult to characterize the fluid flow in these reservoirs. In this paper, based on a geological example unit in the Tahe Oilfield, a three-dimensional physical model was designed and constructed to simulate fluid flow in a fractured-vuggy reservoir according to similarity criteria. The model was validated by simulating a bottom water drive reservoir, and then subsequent water injection modes were optimized. These were continuous (constant rate), intermittent, and pulsed injection of water. Experimental results reveal that due to the unbalanced formation pressure caused by pulsed water injection, the swept volume was expanded and consequently the highest oil recovery increment was achieved. Similar to continuous water injection, intermittent injection was influenced by factors including the connectivity of the fractured-vuggy reservoir, well depth, and the injection-production relationship, which led to a relative low oil recovery. This study may provide a constructive guide to field production and for the development of the commercial numerical models specialized for fractured-vuggy carbonate reservoirs.Keywords Multi-well fractured-vuggy unit Á Three-dimensional physical model Á Similarity criteria Á Bottom water drive Á Optimization of water injection mode

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A starch graft copolymer (SGC) gel is proposed to assist CO2 huff-n-puff for further enhanced oil recovery in a water channeling reservoir. The SGC gelant can form a 3D solid-like gel, and then effectively enlarge CO2 sweep efficiency.