The Research On Treatment Technology Of Waste Oil-Based Drilling Fluid

With the development of China’s oil and gas exploration and development, multi-branch well, horizontal well and complex geological well drilling is increasing in a large number and wellbore stability problems are becoming more and more serious. The oil-based drilling fluid technology is payed more and more attention to and constantly developing, in response, produced waste oil-based drilling fluid growing in a large quantity. At present, a considerable amount of waste drilling oil-based mud is not treated and directly buried or re-injected back to strata, not only to waste a lot of mineral oil resources, but also to cause soil, surface and groundwater pollution, directly or indirectly doing enormous harm to plants,animals and human health. Current overall level of environmental treatment of waste oil-based drilling fluid technology is not high, existing high cost, poor effect, poor technical support problems. The waste oil-based drilling fluid harmless treatment technologies seriously prevent development of oil-based drilling fluids technology and has become one of the bottlenecks which restrict business of our oil and gas exploration and development.Because requirements of China’s environmental protection department to environmental pollution management become increasingly strict and the development of green recycling economy has become the key to sustainable development. A lot of waste oil-based drilling fluid of no safe and effective way out has become a serious burden on the oil fields. On environmental protection and economic benefits point of view, looking for a economic-effective waste oil-based drilling fluids treatment and oil recovery technology is particularly urgent and important. Therefore, we carried out the research of waste oil-based drilling fluid harmless treatment technologies. Forming a technically feasible and economically reasonable processing technology, achieving clean drilling, and promoting coordinated development of oil and gas exploration and environment protection has a very important significance on the development of entire oil industry.In this paper, chemical demulsification treatment of waste oil-based drilling fluids was studied, sifting out the best demulsifier, recovering the mineral oil and optimizing demulsification process parameters (the demulsifier SA increase the amount of coagulant PAC plus the amount of flocculant PAM plusvolume, temperature, demulsification time, centrifugation speed and centrifugation time) to determine the optimal process conditions. under the optimum conditions, the verification experiment was done and the adaptability of demulsifier SA to different waste oil-based drilling fluid was studied; Isolated from wastewater was treated with the method of Fenton oxidation. Impacts of H2O2/COD mass concentration ratio and Fe2+/COD mass concentration ratio, temperature, initial pH and reaction time on COD removal efficiency in wastewater treatment were investigated to attain optimum process conditions; Isolated sludge conducted harmless treatment with a curing agent, optimizing out curing agent and further discussing the best dosage of the curing agent. Finally, bringing up two sets of on-site pilot testing program, the final scene pilot testing program was optimized. In accordance with the processing of material consumption, energy consumption and labor costs, the economics of waste oil-based drilling fluid processing technology were preliminarily analyzed.Through experiment research, the results are as follows:The waste oil-based drilling fluid the demulsification processing technology results show that:the waste oil-based drilling fluid after demulsification, through comparing oil recovery rate, precipitation water quality, middle layer thickness and reagents cost, the best demulsifier SA was sieved out, determining optimum demulsification process parameters:the amount of demulsifier SA is8‰(volume ratio), the PAC dosage is600mg/L, the PAM dosage is8mg/L, reaction time is1hour, the temperature is55±0.5°C, centrifugation speed is3000r/min and centrifugation time is4minutes; under the optimum conditions, demulsification result of the waste oil-based drilling fluid is very good and the oil recovery rate reachs94.36%. Demulsification effect is consistent with theory. The demulsifier SA can dispose of different waste oil-based drilling fluid, the demulsification result is also quite good, oil recovery rate is as high as93%.Fenton oxidation treatment of separation wastewater results show that:Fenton best process conditions are that reaction temperature35±0.5°C, Fe2+/COD mass concentration ratio of0.2, H2O2/COD mass concentration ratio of3.0, the initial pH value of2.0, the reaction time of40minutes. By the Fenton process, COD of isolated wastewater dropped to120mg/L, the COD removal efficiency up to97.35%, and concentrations of main pollutants of the effluent were lower than secondary standard limits value of the Integrated Wastewater Discharge Standard (GB8978-1996).The isolated sludge harmless treatment research results show that:comparing pollutant concentrations of leaching solution and tightness of sludge curing compounds, the best curing agent G3was sifted. Investigating impacts of the dosage of curing agent G3curingthe on pollutant concentrations in the leaching solution and tightness of sludge curing compounds, the best dosage of G3is15%and the curing intensity is up to grade Ⅳ. The concentrations of main pollutants in leaching solution of the curing compounds is within secondary standard limits of the Integrated Wastewater Discharge Standard (GB8978-1996).Proposed two sets of on-site pilot testing program, the optimum scene pilot testing program is "solid-liquid separation—chemical demulsification—oil recovery—waste water and residue harmless processing ". Preliminary eonomic analysis of studied waste oil-based drilling fluid treatment technology in this paper reveals that presuming annually processing300m3waste oil-based mud, the annual direct treatment costs are estimated at between440.5and463.25thousand yuan and the direct income of recovery oil is between500to795thousand yuan. By comprarison, it shows that the annual overall economic efficiency of treatment is36.75to354.5thousand yuan, the treatment technology with good economic benefits.Through the research of waste oil-based drilling fluid processing technology,it is found that the technology can effectively separate petroleum, water and residue in drilling waste oil-based mud of Daqing Oilfield. Oil recovery rate is high and quality of the recovered oil is good. Isolated wastewater and sludge easily are conducted harmless disposal, to provide a new treatment technology of practical and environmentally friendly for waste oil-based drilling fluid treatment and resource recycling. The technology is at advantage of mild conditions, simple processing technical and lower costs and has broad prospects for industrial applications. Using the technology to deal with waste oil-based drilling fluid, it can not only improve the level of clean drilling production and promote the development of oil and gas exploration and development, but also achieve organic combination of oilfields’ healthy and sustainable development and environmental protection, Humanities and efficiency.