| Stabilization and solidification treatment of tight oil and gas drilling waste was an urgent problem to be solved in the development of tight oil and gas reservoirs.The key lay in the recycling utilization of waste and secondary leaching pollution.In this paper,the high-strength solidification and surface coating technologies for drilling waste in tight oil and gas reservoirs was put forward and studied in view of the pollution in tight oil and gas drilling waste.The formed technologies could promote the development of environmental protection technology of drilling waste,and realized the environment-friendly exploration and development of tight oil and gas reservoirs.The abandoned solid in Shengli Oilfield was retrieved,and the high strength curing system formulation was optimized by orthogonal test and single factor analysis.The hydration substances and microstructure of the solidified substance were analyzed.The high strength formation mechanism of the solidification system was studied.The sealing performance of the solidification system on pollutants was tested,and the influence of different factors on the system strength was investigated.The built solidification system formula was 100g drilling waste+5g water+28g MgO+19g MgCl2+0.4g modifying agent+21g flyash.The compressive strength of the system was 39.65Mpa after 28d,and waste disposal rate was 69.78%.The peak solidification strength was reached when the dense needle-like hydration substance 5Mg（OH）2·MgCl2·8H2O was in a staggered space network structure resulting in an effective mechanical interlock,and the environmental protection performance met the national environmental standards.The strength of the system was affected by many factors such as forming pressure,soaking,and waste composition.The increase of forming pressure,quartz,NaCl,and barite content could increase the strength of the system.Soaking,the increase of oil and clay minerals content had a negative effect on strength.There were the problem of the highest high-strength solids strength loss ratio was 63.19%after soaked for 7 days,with the Cd,Mn,Cr ions leaking in the leaching solution in the study of high strength solidification,which limited the resource utilization environments.The surface coating process was optimized by orthogonal test and single factor analysis,and the surface modification and sealing effect of the coating layer on the solidified substance were studied.Coating layer and coating effect on the solidified substance were evaluated,and the surface coating mechanism was analyzed.The obtained surface coating process was:age over14d+hydrophobic resin 2 layers+brush+room temperature maintained for 1d;surface contact angle of the coating solidified substance was 79.56°,water absorption rate was3.036%,strength loss ratio was 21.091%after soaked for 7 days.The surface had the strong hydrophobic effect and good waterproofness.Good resistance to temperature,H2O,10%HCl,10%H2SO4 solution after soaked for 7 days,poor 10%NaOH solution resistance.The COD of the leaking solution met the national primary standard without any heavy metal ion.The surface coating mechanism was analyzed by the contrast of effect evaluation results.The surface of the solidified substance was rough with the pore developed,which was beneficial to the adhesion and infiltration of coating material,and resulting in the pore structure disappeared after coating.According to the infrared spectrum analysis,the characteristic peaks of esters appeared on the surface of the solidified substance.The coating layer was tightly bonded to the surface of the solidified substance.The comprehensive performance of the coating solidified substance was similar to the coating layer.The solidified substance retained the excellent properties of the coating layer and improved the surface performance,which enhanced the sealing performance and environmental performance of the solidified substance. |
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