Study On Synthesis And Properties Of Nano-composite Viscosity Reducer In Heavy Oil

Heavy oil is an important part of the oil and gas resources throughout the world. With the dramatically increasing demand and consumption for energy, reserves of the crude oil especially the light crude oil are reducing rapidly. The heavy oil resources are abundant relatively. so the demand for oil in the future will be met by the heavy oil. Due to large amounts of paraffin wax, resin and asphaltene in the heavy oil, it has the features of high viscosity and poor fluidity, bringing difficulties in both exploitation and transportation, and making the cost high. Therefore, reducing the heavy oil’s viscosity and improving its fluidity has been the hot and difficult problem in oilfield chemistry research in recent years.The method of adding Chemical viscosity reducer is considered to be the most promising method to solve the problem of exploitation and conveying for heavy oil, for the advantages of small adding amount, low power consumption, simple process and no post-processing. Nano materials viscosity reducer is a new type chemical viscosity reducer. It can change wax’s crystallization behavior and prevent colloid and asphaltene forming large-sized aggregation relying on special nanometer effect, then drastically reducing the viscosity of heavy oil, especially for high-wax crude oil.In this thesis, a novel KH550-C18/SiO2 composite viscosity reducer was prepared by modifying the surface of nano-silica with silane couping agent KH550 and stearic acid in ethanol as solvent. Taking grafting ratio as assessment index, the optimal ratio of modifying agent was investigated through experiment:the dosage of KH550 and stearic acid were 16% and 20% of SiO2 respectively. To improving the content of organic compound and introducing strong polar groups in nanocomposite, nano PSMA-AM/SiO2 composite viscosity reducer was prepared by initiating polymerization on the surface of nano SiO2 with KH570, octadecyl methacrylate and acrylamide as monomer. The structure and property of the two nanocomposites were characterized and analyzed by FTIR, TG, TEM, SEM and contact angle testing. The results showed that after surface modification, the nano-silica composite particles turned into hydrophobicity from hydrophily, and they were low agglomerated and could disperse in organic medium stably. Among the two nanocomposites, the grafting radio of nano PSMA-AM/SiO2 was higher, and its contact angle with water was larger too.Taking Daqing high-wax heavy oil as research object, tested the viscosity reducing properties of commercial oil-solubility viscosity reducer EVA and the two nanocomposites viscosity reducer. And the effect of temperature and dosage on reducing properties were investigated. With dosage rising, the viscosity-reducing rate increased first and after that it had an approximate constant. Under the optimal dosage of 600ppm, nano KH550-C18/SiO2 could lower the heavy oil’s wax precipitation point for 3.6℃, and its apparent viscosity reducing rate and pure viscosity reducing rate reached 66.9% and 40.3% respectively when 40℃. The other one nano PSMA-AM/SiO2 could lower the wax precipitation point for 5.5℃, and its apparent viscosity reducing rate and pure viscosity reducing rate reached 72.1% and 48.86% respectively when 40℃. The two nanocomposites both had better viscosity reducing properties than EVA. Nano PSMA-AM/SiO2 had a better property than nano KH550-C18/SiO2, because its organic compound content was higher and polarity was stronger.As temperature increasing, the viscosity reducing rate went down. The EVA’s lowering speed was the largest, and at 60℃, its viscosity reducing rate was only 19%. But for nanocomposites viscosity reducer, at the little high temperature 50℃ to 60℃, the pure viscosity reducing rate could still keep more than 30%.This thesis explored and analyzed the action mechanism of nanocomposites viscosity reducer. Relying on special surface effect, nano particles could become nucleating point to induce wax to crystallize on their surface, then change wax’s crystallization behavior and prevent wax-crystal forming three-dimensional network structure. Besides, the strong polar groups introduced into the particles’ surface could form new hydrogen bond with resin and asphaltene to break up the large-sized aggregations. Then the resin and asphaltene made a solvation layer on the surface which could prevent them connecting. Thus reduced the heavy oil’s viscosity drastically.