Study Of Wastewater Reinjection Law Of Injuries On Chang-2 Reservoir In Yuanmao Wayaobao

Chang-2 reservoir in Yuanmao Wayaobao is a low-pressure,low porosity and permeability,micro-fractures in the reservoir.The main way of development mode is polluted Water reinjection,sewage main control indicators:oil content≤5.0mg/L,suspended solids≤1.0mg/L,median diameter≤1.0um.Because oil reinjection sewage treatment and operation management is difficult to deal and the high costly,resulting in treated sewage are often unable to reach the reinjection standards,but these re-injection of sewage,water pressure did not change significantly,also not show severe reservoir damage.Therefore,needing accord to low porosity and permeability,reservoir characteristics and development of micro-cracks,carrying out on the reservoir reinjection injury law sewage suspended solids and emulsified oil,for working out the appropriate effluent standards provide the basis for reinjection.In the aticle,Chang-2 reservoir in Yuanmao Wayaobao is deeded an object,Firstly,Using a variety of analytical methods and tools study the Chang-2 reservoir rock mineral characteristics and pore structure characteristics of reservoir properties;Secondly,Evaluate reservoir sensitivity experimental methods,analysising of reservoir potential harm and potential harm to the type and degree of injury;Finally,core flowing-experiments,a detailed analysis of the reinjection sewage solid particles and emulsified oil on low porosity,permeability porosity reservoir and fracture-porosity reservoir injury law.The results show that:（1）Chang-2 reservoir porosity is between 10%to 12%,permeability is between 1.0～16×10^-3um²,average pore throat radius 1.23um,reservoir fractures,fractures rate of 1.89%of the total face;（2）Reservoir has a strong stress sensitivity,moderate water sensitivity,speed-sensitive and weak alkali sensitivity,no or weak acid-sensitive;（3）As low permeability reservoir porosity roared small pore throat radius generally 2.0um or less in diameter≤1.0um reinjection sewage suspended particles easily cause deep into the core of internal injuries,and particle size≥1.0um suspended particles are mainly in the core section or the crack surface and very shallow range or near wellbore damage caused by blockage;（4）When suspended solids in wastewater reinjection diameter of 0.134μm,the permeability of the smaller,more serious harm to the core;the higher suspended solids content,the greater the harm;suspended solids particle size of 3.613μm then:the permeability is less than 40m D,the lower permeability and the smaller damage,the higher permeability（40.8m D）and the greater damage;（5）In fracture-porosity reservoirs,sewage reinjection suspended particles are deep into the microcracks clogging,reducing fracture permeability,water is forced into the pores of the matrix more improve the efficiency of water injection,for this type of reservoir layer may be appropriate to relax the reinjection of wastewater quality indicators;（6）Similar injury law wastewater reinjection of core damage emulsified oil law and suspended particles;（7）Because of reinjection of particles suspended in water and emulsified oil on core damage mainly in the injection a small amount of damage in the cake and the cake outside end surface near wellbore formation,the reverse displacement results showed that flooding can return more than 60%of core permeability recovery,it can be inferred:regular use of negative returns spit flushing water reinjection wells can relieve blockage injury problems.