Study On The Synthesis And Dehydration Process Of High-Efficiency Demulsifiers For Aged Oil In Tuha Oilfield

Aged oil has long occupied the volume of storage tanks,and its recycling treatment has been a persistent problem in oilfield production.The difficulty in processing aged oil is mainly reflected in the difficulty in dehydration,and if the water content of the treated aged oil does not meet the standard,it cannot be directly transported to the refinery.However,conventional treatment methods such as thermochemical demulsification and centrifugation are not effective in large-scale and efficient treatment of aged oil in oilfields,bringing significant negative impacts on the gathering and transportation system.Storage of aged oil in storage tanks for a long time will inevitably increase maintenance costs.Open pit storage poses a risk of infiltration pollution to both groundwater and soil,and is bound to have an impact on the environment.Therefore,based on the research on the treatment methods of aged oil at home and abroad,this article proposes an innovative design idea for efficient demulsification and dehydration of aged oil with high solid content:Firstly,the high-efficiency demulsifiers for aged oil suitable for the target oilfield blocks were selected,and the DX series of high-efficiency demulsifiers for aged oil were synthesized indoors,and the various performances of the synthetic demulsifiers were systematically evaluated;Aiming at dehydration of aged oil in storage tanks of Tuha Oilfield,common demulsifiers were synthesized and modified,and a process design for deep dehydration of aged oil with low water content was constructed.The corresponding dehydration equipment was designed and studied,and its key technologies were systematically evaluated;Laboratory experiments and on-site experiments have verified the effect of synthetic modified demulsifier TDX on the dehydration of aged oil and the deep dehydration process of the system.The aged oil in the storage tank has been efficiently treated.The specific research mainly includes the following aspects.（1）The composition and physical properties of aged oil from Tuha Oilfield were analyzed,and it was found that the content of saturated and aromatic components in the composition of aged oil was similar to that of conventional oil.The content of solid phase impurities（organic asphaltene and inorganic solid phase）in aged oil was found to be much higher than that of conventional oil by infrared spectroscopy and four component analysis.Solid impurities in aged oil,especially excessive colloidal Fe S,will be adsorbed on the interface film between oil and sewage,forming a stable emulsion.The aged oil from Tulufan Oil Production Plant,Shanshan Oil Production Plant,and Santanghu Oil Production Plant in Tuha Oilfield has a high content of colloidal Fe S,with an average particle size of 27.31,respectivelyμm、23.60μm and 14.79μm.The peak values of particle size distribution are respectively 40μm、33μm and 24μm,which leads to difficulties in demulsification and dehydration of aged oil in the conventional treatment technology of the oilfield.（2）A series of DX and MC demulsifiers were selected for demulsification and dehydration experiments,and it was found that the demulsifier suitable for the treatment of aged oil in Tuha Oilfield was DX4 type.The demulsification and dehydration effects of aged oil were tested using this demulsifier,and factors affecting the demulsification and dehydration effects of aged oil such as additive addition,demulsification time,temperature,and p H value were analyzed.Adding additives（10%Na Cl aqueous solution,10%Na OH aqueous solution,and 1%ABS aqueous solution）to aged oil is beneficial to improving the demulsification and dehydration effect of demulsifiers on aged oil.The dehydration effect of demulsifiers on aged oil was most significantly improved after adding 10%Na Cl aqueous solution;During the 2h dehydration time,the dehydration rate of the demulsifier to the aged oil is very fast,and then the rate slows down;The dehydration rate has a significant impact on the initial stage of temperature rise,and the appropriate dehydration temperature is 80℃;When p H=8 shows weak alkalinity,the dehydration rate of aged oil is the fastest.When p H value deviates from 8,new active substances will be generated on the oil-water interface facial mask,forming a stable interface facial mask,reducing the dehydration effect of aged oil.（3）According to the physical characteristics of aged oil from Tuha Oilfield,a fluorine-containing phenolic resin initiator was synthesized from formaldehyde,trifluoromethylphenol,and tetraethylenepentamine at a controlled temperature of 110℃.The DX series of fluorine-containing polyether type demulsifiers were synthesized by polymerizing with different amounts of PO and EO at the conditions of-0.09 MPa and 130℃in the synthesis experiment.In DX series demulsifiers,when the EO group proportion is kept constant,the cloud point,water number,RSN value,HLB value,and hydrophilicity of the aqueous solution will decrease with the increase of the PO group proportion,and the hydrophilicity will increase.When the PO group ratio is constant,the cloud point,water number,RSN value,HLB value,and hydrophilicity of the mixed aqueous solution increase with the increase of the EO group,but the hydrophilicity decreases.When the demulsification temperature is 60℃,the demulsification experiment lasts for 120 minutes,and the demulsification rate of aged oil can reach 75%.Among them,DX14940 demulsifier has the highest demulsification rate on aged oil,reaching 86.52%,indicating that the synthesized DX series fluoropolyether demulsifier has a good demulsification and dehydration effect on Tuha aged oil.（4）In order to further improve the treatment effect of demulsifiers on aged oil from target oilfields,it is proposed to cross-link the synthesized DX fluoropolyether demulsifier by adding toluene diisocyanate（TDI）to synthesize a new type of TDX fluoropolyether demulsifier.Comparing the infrared spectra of the demulsifiers before and after the modification,it was found that a new absorption peak appeared at 1728 cm^-1,confirming the successful introduction of new groups into the molecular chain of the DX fluoropolyether demulsifier.Comparing the cloud point,molecular weight,and surface tension of the demulsifier mixture before and after modification,it was found that the modified TDX demulsifier was oil soluble,with a molecular weight much higher than that of the unmodified demulsifier,with higher surface activity and better ability to reduce surface tension.TDX oil soluble demulsifier is more suitable for demulsification and dehydration of aged oil in Tuha Oilfield.The modified TDX polyether demulsifiers were evaluated from four aspects:demulsification rate,water color removed,wall adhesion,and oil-water interface state.The results were superior to the unmodified DX series demulsifiers,with a maximum demulsification rate of 95.53%.The optimum demulsification temperature and concentration of TDX demulsifier are 60℃and 50mg/L,respectively.（5）In order to meet the export requirements for dehydration of aged oil by demulsifiers,a deep dehydration process of aged oil after dehydration by demulsifiers was designed,and an experimental platform for deep distillation and dehydration system of aged oil was established,verifying the feasibility of deep dehydration of aged oil distillation system.After distillation and dehydration,the water content of aged oil decreases to below 0.5%,meeting the requirements for crude oil export.The effect of adding modified demulsifiers during distillation dehydration was investigated.It was found that adding demulsifiers can shorten dehydration time.In addition,the mechanism of aged oil boiling has been studied through indoor high-definition camera observation experiments and theoretical model construction.Due to the different boiling points of water and oil,water preferentially vaporizes on the heat transfer surface,forming bubbles,and bubbles leap away from the heat transfer surface to form vapor in oil bubbles in the liquid.When the heat flux on the heat transfer surface increases,many small vapor bubbles in the vaporized oil package form on the heat transfer surface.Due to the bubble generation speed being faster than the burst speed,the liquid level quickly fills the entire container,causing the aged oil to boil violently.Aiming at the problem of boiling during the treatment of aged oil,the deep dehydration equipment of the distillation system has been optimized and improved,which can play a role in preventing boiling of aged oil.（6）According to the special properties of aged oil in the storage tank of the oil production plant in the research block of Tuha Oilfield,a dehydration process for the entire process of aged oil was designed,and the scheme of"thermochemical washing+thermal sedimentation+distillation dehydration"for the treatment of aged oil was optimi zed.A split cavity design theory was proposed to solve the heat transfer problem in multiphase flow,and a deep dehydration device for aged oil was optimized and design ed.The reliability of the device has been tested through on-site experiments.The wate r content of aged oil after random detection and treatment is less than 0.5%,meeting the crude oil export standards.