Research On The Characteristics Of Changes In Reservoir Properties In Panguliang Oil Fieled Of Changqing

Because of the changes of strata pressure and temperature, brushing of injected water anda series of injection-recovery measures in the procedure of long-peirod waterlfooding in anoilfield, the propertities of the reservoir may have changed obviously. In the future, thesechanges will affect the implementation about adjustment on development programs andoptimization measures. This paper studies the changes in the rese^oir characteirstics aboutsensitivity, prosity and permeability, wettability and the pore structure after the waterflooding, by combining indoor model experiment. According to the comparative analysis ofthe physical properties in different periods of time before and after the expeirment,thefollowing conclusions can be obtained:(1)The lfow rate sensitivity of study area in initial stage is weak and critical velocity is1.3ml/min. Water sensitivity and salinity sensitivity in initial stage are weak after waterflooding. Water sensitivity is almost unchanged, but salinity sensitivity changed slightly.Stress sensitivity and temperature sensitivity are strong，and with coupling effct of stress andtemperature, as the temperature decreases, the effective stress has great impact on the corepermeability to ihe same core with physical property.(2)The wettability of the reservoir changes from slight water wet to strong water wet.(3)The porosity and permeability of the reservoir have changed, despite the porosity haschanged slightly. Permeability becomes more complexityAfter long-term water injection, theaverage radius of communicating pore, the radius of flow structure and the medium radiushave raised.(4)Byanalyzing produced water，the results show that: the salinity of produced water hasincreased; the content of K++Na+，Ca2+, Mg2+, and CI" has increased, but the content of HCO3、CO23-、SO42" has reduced. This phenomenon shows that the injection of water taked placechemical and physical reactions with formation water or rock mineral in the cor^and filthymay generate in this strata.The objectivity understanding and evaluation on changes of reservoir and percolationcharacteirstics in Panguliang oil fieled, can be used as reasonable basis fowater plugging andprofile, opitmizingwater injection and adjusting development plan of oilifeld.