Flow Law And Mechanism Of Oil Recovery By Branched-preformed Particle Gel (B-PPG) Flooding

This paper studied the flow law and the mechanism responsible for the enhancement of oil recovery using viscoelastic preformed particle gel(PPG)in heterogeneous reservoir,investigated the moving way of B-PPG in porous media in microscopet.At last,the recovery of the residual oil of polymer flood by branched-preformed particle gel(B-PPG)injection was also studied.Single-core flooding and heterogeneous parallel-dual-core flooding tests were carried out to investigate the plugging performance and conformance control ability of viscoelastic branched pre-formed particle gel(B-PPG).Then the mechanism responsible for the enhancement of oil recovery using viscoelastic preformed particle gel(PPG)in heterogeneous reservoir was studied systematically through heterogeneous parallel dual core flooding test,micro flooding and visual sand-packed glass model flooding test.At last,the recovery of the residual oil of polymer flood by branched-preformed particle gel(B-PPG)injection was also studied.The results showed that B-PPG travels in the core in the manner of plugging-alternating-pass by deforming and restoring its particles' shape alternately.The high permeability channels in the core can be blocked effectively by B-PPG and a high resistance factor can be achieved.Both the resistance factor and plugging efficiency increase with the increase in core permeability,B-PPG concentration,and brine salinity;however,both factors decrease with the increase in injection rate and temperature.The water injection profile in the heterogeneous parallel cores can be significantly improved because B-PPG can selectively block high permeability core and divert the displacement to the low permeability core.B-PPG exhibits a good performance in profile control when the low to high permeability ratio of the two parallel cores is smaller than 1:7 and the injected B-PPG slug is between 0.25 to 1.0 PV.The increment of oil recovery enhanced by B-PPG after water flooding increased with temperature,heterogeneity and B-PPG slug,while decreased with the salinity of formation water.Select the appropriate concentration of B-PPG has important significance for oilfield application.The micro experiments show that with the ability of plugging different pore throats with different diameters dynamically and alternatively,B-PPG can adjust heterogeneity and increase sweeping efficiency significantly.The residual oil in the small pores after polymer flooding can be displaced by B-PPG.Furthermore,the oil film in the pore throat can be effectively stripped by B-PPG particles.B-PPG is capable of adjusting the flow resistances of different permeability zones of a heterogeneous reservoir and preventing the injected water from channeling.Making a dynamical flow diverting and increasing sweeping efficiency is the main mechanism of PPG to enhance oil recovery in heterogeneous reservoir.