Rheology and Special Requirements on the Flow System and Equipment for Large Scale Injection,Production and Gathering of Viscous-Elastic Polymer Fluids in Chemical Floods and Methods to Solve the Problems that Emerge

摘要

Most flow systems and equipment for the injection, productionand gathering of large amounts of fluid are designed forNewtonian fluids. Now, an increasing number of oil fields areon viscous-elastic flooding (for example, Daqing Oil Fieldalone injects and produces more than 70 million m3 ofviscous-elastic fluid containing polyacrylamide [PAM] peryear). After flooding by PAM fluids, besides an increase inrecovery (in Daqing, the recovery increases more than 12%OOIP [original oil in place]), decrease in water cut (from morethan 90% to about 70%), increase in production (in year 2001,Daqing produced about 9.8 million tons of oil by PAMflooding), it was seen that the flow of this type of fluid inproduction and surface systems and equipment has its specialcharacteristics which in turn require special designs for theequipment and flow process. Otherwise, the efficiency andservice life of each equipment and system will be low, energyconsumption and mechanical degradation of polymer fluidhigh and vibration in the whole system serious. Sometimes,normal operation cannot be maintained.This paper introduces the actual performance of theproduction and surface flow systems and equipment, pointsout the influence that the special rheologic characteristics,especially the viscous-elastic nature of the fluid, has on thesystem and the modification made. For example, there is anormal force acting on the beam pump sucker rods that causepronounced eccentric mechanical wear on one side of thesucker rods and thereby very short service life span of beampump wells; this normal force significantly lowers theefficiency of centrifugal pumps; increases the vibration andmechanical degradation in triplex pumps and the wholesystem; lowers the efficiency of maturing tanks and staticmixers etc.The modifications on the system and equipment and itsresults are shown. For example, the service life of beampumps more than doubled; mechanical degradation of polymerin the system and triplex pumps decreased more than 50% and70% respectively; and the energy consumption of mixingequipment decreased 80% etc.The above should be of value to oil fields preparing to uselarge amounts of viscous-elastic fluids to increaseoil recovery.