Study On The Waste Water-based Drilling Fluid Used For Profile Control And Water Plugging In Oil Wells

Waste water-based drilling fluid contains various functional additives,heavy metal ions and organic matter inside,which will seriously pollute the environment without any treatment.After relevant treatment,it is used for profile control and water plugging,which reduces the pollution to the environment,and is a low-cost treatment agent with good profile control and water plugging performance.The composition characteristics and rheological properties of waste drilling fluid.It can be divided into upper low solid phase liquid and lower high solid phase heavy liquid according to the composition characteristics,and the performance of the two is quite different.There are great differences in mineral composition,the content of NaCl in supernatant is higher,91%,and the content of barite in sinking pulp is obviously high,accounting for 54%.In the solid phase content,the solid phase content of sinking slurry is up to 30.8%,and the supernatant is only 3.05%.In the rheological properties,the apparent viscosity of the supernatant is 2.5 mPa·s,the dynamic plastic ratio is 0.25 Pa/(mPa s),the apparent viscosity of the sinking slurry is 12.5mPa·s,and the dynamic plastic ratio is 0.39 pa/(mPa s).Because it contains a large amount of inorganic salts and calcium and magnesium ions,the mineralization of supernatant and sinking slurry is 33127 mg/L and 23522 mg/L respectively.The supernatant and sinking slurry contain a large number of fine(less than 20?m)solid particles,which provide material protection for filling the pores of the formation.In the performance evaluation of the cross-linked polymer system of waste drilling fluid,T-type polymers have better viscous effect at a certain temperature and salinity in three kinds of polymers,such as T-polymer,active polymer and SAP.From the aspects of polymer,sinking slurry addition,system stability and rheology,0.06% crosslinking agent and 10% sinking slurry were added according to mass volume ratio(w/v)in the suspension system of 4000 mg/L T polymer supernatant.In the suspension system of 5000 mg/L T polymer supernatant,0.08% crosslinking agent and 15% sinking slurry are added according to mass volume ratio(w/v),and the above system has strong suspension stability ability of sinking slurry.The performance evaluation of the phase conversion cementation system of waste drilling fluid,the consolidation system of supernatant and sinking slurry,the low density crosslinking agent(?)was selected according to the mass volume ratio(w/v),the optimum addition was 10~15%,the low density crosslinking agent(?),and the optimized addition was 1%.It has good rheological properties and consolidation strength,and can meet the basic requirements of site construction.The regularity of injection and blockage of waste drilling fluid can be evaluated,and the waste drilling fluid after quality treatment has good injection.The sealing rate of suspension profile of waste drilling fluid is around 90%,the breakthrough pressure is higher,can reach more than 6 MPa,basically can meet the needs of water injection well plugging.The plugging rate of the consolidated waste drilling fluid plugging system is more than 90%,the maximum breakthrough pressure is close to 10 MPa,and the scour resistance is good.