Experimental Study On The Flow Behavior And Enhanced Oil Recovery Of Nanofluid Flooding

China’s low-permeability oil reservoirs are rich in resources,accounting for as much as 60%to 70%of the currently proven petroleum geological reserves.Efficient exploration and development of low-permeability oil reservoirs is the focus of strategic deployment of petroleum resources.However,the low permeability reservoirs are characterized by low permeability and low porosity,with complicated formation mechanism and strong heterogeneity,and the water flooding recovery rate is less than15%,so the early stage of enhanced recovery is entered.At present,nanofluid flooding technology has caused widespread concern among reservoir workers.Nanofluids are homogeneous,stable and highly thermally conductive suspensions prepared by adding nanoscale metal or oxide particles into the liquid in a certain manner and proportion.In this paper,two kinds of nanofluids were prepared at first,which were Nano-SiO₂water solution dispersed with deionized water as base liquid and Nano-SiO₂-SDS compound solution dispersed with sodium dodecyl sulfate solution as base liquid,and conducted performance evaluation studies on dispersion stability,particle size distribution,viscosity characteristics,flow characteristics,and enhanced oil recovery to understand the flow behavior of nanofluids in low-permeability cores and provide theoretical guidance for the application of nanofluid displacement technology in low-permeability reservoirs.The experimental results showed that both Nano-SiO₂water solution Nano-SiO₂-SDS compound solution could maintain a certain dispersion stability,and Nano-SiO₂-SDS compound solution behaved better dispersion uniformity and stability.The viscosity of nanofluids increased with the increase of the concentration of nanoparticles and decreased with the increase of the system temperature,and the viscosity of Nano-SiO₂-SDS compound solution was higher than that of Nano-SiO₂water solution under the same conditions.The flow pressure difference of nanofluids in low-permeability cores increased first and then stabilized with the increase of injection volume;in the core of the same permeability,the pseudo-starting pressure gradient values of different types of fluid flow were ranked as:deionized water>Nano-SiO₂water solution>Nano-SiO₂-SDS compound solution>sodium dodecyl sulfate solution.When the concentration of nanoparticles was 0.05wt%,the two kinds of nanofluids had the best recovery efficiency.Under the same injection condition,the recovery degree of the Nano-SiO₂-SDS compound solution was 7 percentage points higher than that of Nano-SiO₂water solution and the pressure reduction ratio was 8.3 percentage points higher,showing a better potential for enhanced oil recovery.