| In oil and gas drilling process,a large amount of drilling fluids is needed to carry the cuttings,balance the formation pressure,lubricate,and cool the drill bit.When the drilling is completed,the drilling fluids which complete their mission become drilling waste.These waste drilling fluids contain a great deal of organic treatment agents,clays,inorganic salts,etc.,which are very complex,have certain toxicity and are difficult to degrade.If waste drilling fluids can not be effectively treated,it will cause serious pollution to the ecological environment after discharge,and it will endanger the health and safety of animals,plants and humans with the biological chain.The existing waste disposal methods are all terminal treatment methods,and the pollution source cannot be completely eliminated,and secondary pollution is easily formed,and the treatment cost is pretty high.With the continuous improvement of environmental awareness and the continuous improvement of relevant laws and regulations,the environmental protection requirements for drilling operations are becoming more and more strict.The problem of drilling fluid pollution has become one of the bottlenecks restricting the development of China's oil and gas exploration and development.The most thorough solution to the above problem is to control from the source,use environmentally friendly water-based drilling fluid to reduce the pollution of the drilling fluid to the environment;and to recover and reuse the drilling fluid on site to reduce the discharge of waste drilling fluid to achieve"zero pollution,zero emissions",making clean and integrated production of the drilling process a reality.In this regard,the environmental impact mechanism of the current on-site drilling fluid system and its organic treatment agents were studied in the lab.Through the comparison of pollution assessment methods in various fields at home and abroad,a set of drilling fluid pollution assessment methods and indicators were formed to evaluate the environmental performance(petroleum content,biotoxicity,biodegradability and raw metal content)of on-site water-based drilling fluids.Through Fourier-transform infrared(FT-IR)spectroscopy and other methods,the molecular structure of common drilling fluid treatment agents were analyzed and their environmental impact mechanism were deeply studied,revealing the influence of molecular structure on the environmental performance of the treatment agents,providing theoretical basis for the development and screening of environmentally friendly drilling fluid treatment agents.At the same time,lab researches on water-based drilling fluid sub-micron useless solids removal technology was carried out.The composition of the on-site water-based drilling fluids was analyzed,and the root cause of the deterioration of the performance of the on-site water-based drilling fluid was found to be the accumulation of useless solids,especially submicron particles.A new technical idea of removing sub-micron useless solids is proposed by means of chemical flocculation and solid control equipments to recover and reuse the water-based drilling fluids.To this end,a series of flocculants CMS-g-PDMDAAC of removing the useless solids in water-based drilling fluids was developed.The molecular structure was analyzed by proton nuclear magnetic resonance(~1H NMR)spectroscopy and FT-IR.The flocculation effect and mechanism for the clay suspensions were studied through the turbidity,particle size and zeta potential.With micro-solids flocculants as the core and on-site solid control equipments,the water-based drilling fluids micro-solid removal technology was designed,and the treatment effect of the technology was tested and evaluated in the used water-based drilling fluids from the site. |
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