Research On Optimization Technology Of Weak Gel Shifting And Driving In Overseas River Oilfield

Haiwaihe Oil Field Block 1 is a typical high-temperature,low-salinity,heavy oil field.The formation permeability heterogeneity is at a quite high level,which leads to a very low sweep efficiency in oil recovery from petroleum reservoir.In order to enhance oil recovery,weak gel was used from 2010.Up to December 2012,residual oil in thief zone has been sweep out in some degree.However the water ratio in production wells hasn't been reduced largely.All in all,field application method needs to be optimized.A serious of experiments have been done to deal with those problems like lack of well optimization basic theory,low stability of week gel,variance feedback of field application,which are cring out for solutions.An application has been written for Haiwaihe Oil Field Blockl.It can help technical personel do the overall well optimization while using week gel treatment.This product provides a scientific method for selecting wells in oil field.To enhance the stability and profile control ability of week gel,we optimized the week gel composition and oil displacement slug combination,which is more suitable for the formation.Experiments have also indicated better injection treatment time,better treatment rounds,better slug combination using for high permeability heterogeneity formation.All the experiment results in this paper are exceedingly significantly for the successfully field application of week gel oil displacement method,not only in Haiwaihe,but also in other zones of Liaohe Oil Company.The mainly research results are as follows:(1)An application has been made to do overall well selecting optimization for Haiwaihe Oil Field Blockl.Using mathematical model,we found that three of the ten injection wells in Blockl are needless to do the week gel treatment,while the treatments are underway.Using the application,technical personel can exclude those wells before the application start.Thus it can save more resourse.(2)Lab experiment results show,-that optimized composition of week gel are HPAM 2000mg/L?3000mg/L+crosslinking agent 0.1%?0.2%.The formula gelation time is between 1.5d and 3d.It acts well in stability under formation conditions(temperature,salinity etc.),injection ablity and oil displacement.(3)Using combination slug can largely raise the injection pressure,and the profile changing rate can reach 97%,which is far more than single week gel slug.Optimized method is to inject partical gel fistly,then week gel.(4)Multiple round core flood experiments show:raise the injection round and cut down the week gel volume of each time can effectively reduce injection pressure,which is needed to ensure the wells' safty.It can also slightly enhance oil recovery,yet it not means the more round the higher oil recovery.After 3 round of displacement,oil recovery can hardly been uplifted.According to the lab result,we suggest the week gel flooding round of Haiwaihe Oil Field Blockl better be 3 or 4.(5)Since the major function of week gel in formation is oil displacement and profile control,we can largely enhance the oil recovery in high permeability heterogeneity formation by changing the stress of each slug and using combined slug.This has been proven in the paralledl connection core flooding experiments.By adding the stress of each slug each time,much residual oil has been diplaced out not only in low permeable zone,also the high one.(6)In order to find a suitable time for gel injection,we designed six different water saturation core flood experiments.The outcome indicates that,it is better to inject gel when water saturation is between 50%and 80%.At this time,recovery can be most largely enhanced.