Preparation Of Modified Attapulgite Nanocomposites And Their Demulsification Performance For Crude Oil Emulsion

With the wide application of tertiary oil recovery,the water content of crude oil produced fluid is greatly increased,accompanied by more complex components and higher degree of emulsification,which greatly increases the difficulty of oil-water separation.Nano particle(NP)demulsifier has become a hot spot in the field of oilfield development in recent years.Based on the related research work of our research group in recent years,a variety of attapulgite(AT)based nano-particle demulsifiers were prepared by modifying and functionalizing the AT materials.Their demulsification performance for O/W type crude oil emulsion were studied.The demulsification mechanism was discussed and proposed.The main research results are as follows:(1)Demulsifiers of AT-APTES,AT-APTES-STA and AT-OTS were designed and prepared by grafting long chain molecules onto the surface of AT materials.The structure and morphology of various AT demulsifiers were characterized by FT-IR,SEM and zeta potential measurement,which confirmed the formation of the target products.The measurement of contact angle and the distribution of nanoparticles at the oil-water interface showed that the ATAPTES-STA nanomaterials had good amphiphilicity and interfacial activity.It is found that the AT-APTES-STA nanoparticle is a new type of NP demulsifier which can rapidly and efficiently demulsify crude oil emulsion at low temperature.The demulsifier dosage,emulsion p H and demulsification temperature have important effect on the demulsifying performance.The demulsification efficiency is up to 96.7% at the demulsifier dosage of 900 ppm and p H=7.In contrast,the demulsification efficiency of AT-APTES is relatively low,while AT and AT-OTS have almost no demulsification performance.By comparing the demulsification performance of these modified AT nanomaterials,it is revealed that the NP demulsifier with excellent demulsification performance needs to have the follow characteristics: a)the demulsifier should have good amphiphilic and interfacial activity;b)The composition and structure of the NP demulsifier need have the surface functional groups which can strongly interact with the active molecules at the oil-water interface.(2)A novel attapulgite-Graphene Oxide Nanocomposite(AT-GO)was prepared by grafting graphene oxide onto attapulgite.The structure of the AT-GO composite was characterized by FT-IR and TEM,which confirmed the successful preparation of the at-go composite.The zeta potential of the AT-GO composite and the oil droplet was analyzed.It was found that they exhibit opposite charge in the range of p H = 4-8,which was very important for the demulsification performance of the material.The surface wettability of the material was evaluated by the partition of the nanoparticles in the oil-water mixture.The results showed that the AT-GO composite has good amphiphilicity and interfacial activity.The demulsification performance of the AT-GO composite for crude oil emulsion was evaluated by bottle test.It was found that the demulsification performance of AT-GO increased with the increase of GO content in the composites.It is further found that the AT-GO nanocomposite can effectively demulsify crude oil emulsion in a wide p H range.The demulsification conditions of the AT-GO nanocomposites were optimized.It was shown that the demulsification efficiency can reach95.2% at the demulsifier dosage of 700 ppm,p H=8 and room temperature,indicating that the AT-GO nanocomposite is a kind of NP demulsifier with excellent demulsification performance,which can realize rapid and efficient demulsification of crude oil emulsion at room temperature.(3)Compared with the traditional chemical demulsifier,the modified attapulgite nanoparticles can demulsify crude oil emulsion rapidly and efficiently at room temperature.The Demulsification Mechanism of NP material on crude oil emulsion was proposed.The NP demulsifier with good amphiphilic and interfacial activity can be able to disperse well in the continuous phase of emulsion,and can quickly reach the oil-water interface to firmly combine with the emulsified active molecules such as asphaltenes on the oil-water interface.The binding force between the NP materials and emulsified active molecules generally includes electrostatic attraction,hydrogen bonding and ?-?/n-? interactions.Once the NP materials firmly combined with the emulsified molecules,the mechanical forces of external stirring and vibration provide sufficient kinetic energy for the NP material to destroy the protective film at the oil-water interface,which promotes the combination of dispersed droplets,and realize the efficient separation of oil and water.In this process,the NP demulsifier material is not needed to replace the original emulsified molecules at the oil-water interface.Under the help of external mechanical energy,rapid and efficient demulsification at room temperature is realized.