Research On Viscosity Change Of Displacement Fluid In Pipe Fittings Of Dispensing System And Sampling Device With Low Shear Action

Ternary compound flooding is a chemical flooding tertiary recovery technology,by mixing polymers,alkalis,surfactants,and water in one system and injects it into the ground,displacing crude oil that could not affected by traditional oil recovery methods,thereby improving crude oil recovery yield.The addition of polymers could increase the viscosity of the displacement fluid,expand the displacement volume of the displacement fluid in the oil layer,thereby improving the displacement efficiency.But the viscosity loss of the displacement fluid will occur when it is subjected to a certain degree of mechanical shear.This phenomenon affects the oil displacement effect of the ternary compound flooding.In order to maintain the viscosity of the displacement fluid as much as possible,it is necessary to study the viscosity change rule of the displacement fluid in the dispensing pipe and propose effective measures to reduce the viscosity loss.According to the injection process of the weak alkaline ternary compound flooding test station,pipe fitting models such as elbows,tees,and reducing joints are established.The viscosity change situation of the displacement fluid flowing in the pipe is numerically simulated.The apparent viscosity of displacement fluid be found reduced with the increase of flow velocity,and the dispensing flow velocity should not be greater than 0.2 m/s.The elbow with small radius of curvature cause large shear,so the elbow with big radius of curvature should be selected;the shear caused by the diversion on both sides is greater than the branch pipe diversion,the shear caused by the direct variable diameter shunt is greater than the transitional variable diameter shunt,and every effort should be made to avoid the situation of both side diversion and direct variable diameter shunt;Reduce joint will cause great flow shear,the reduction ratio cannot be greater than 4 : 3.Aiming at the problems that the existing multiple samplers have larger shear,produce more waste liquid and low sampling efficiency,a piston sampler was designed.the diameter of the inlet short tube is 1.5cm,the inner diameter of the sampling chamber is 6cm,the length of sampler is 16 cm,and the sampling capacity is 400 m L.The numerical simulation of the sampling process by moving grid technology found that when the piston movement speed is 0.0053m/s,that is sampling time is 1 minute,the displacement fluid in the sampling chamber is not subject to flow shear.The shear between the sampling chamber and the inlet short tube can be reduced by rounding.The piston was designed with modular and its control method adopts screw thread connection.So there is no need to inject water to balance the back pressure when sampling,in the same time the amount of waste liquid could be reduced.So the sampling efficiency be improved.