Research On Mechanism Of Removal Heteroatom Compounds In-situ From Heavy Crude Oil And Its Pilot Test

The high viscosity properties of heavy crude oil are the reflection of physical/chemical reactions between sulfur, nitrogen, oxygen, metal elements and aromatic ring structure and alkyl side chain in its molecular structure system. Therefore, the high content of heteroatom and condensed rings compounds is the inherent reason that cause high viscosity for heavy crude oil and difficult to be produced, transported and processed. In this paper, the chemical reaction mechanism and the applying technology that removal heteroatom in heavy crude oil with low sulfur content are researched. During thermal recovery, removing heteroatom in heavy crude oil by chemical method under steam injection conditions will result in viscosity reduction and upgrading for heavy crude oil. At the same time, high recovery and value of heavy crude oil production will be realized consequently.Before the removal of heteroatom from heavy oil, it is necessary to break and separate the macromolecular structure in the heavy oil, exposing part of the heteroatom-contained functional groups at the edge of the macromolecular, which is beneficial to promote the de-heteroatom reaction. Therefore, the gas phase catalyst for hydrothermal cracking of heavy oil is firstly developed and optimally selected in this dissertation, to solve the problem of low catalytic efficiency caused by the poor contact between the liquid phase catalyst and the crude oil in the thermal recovery formation. Results of laboratory experiment show that for the heavy oil treated by the gas phase catalyst without agitation, all of the index of viscosity reduction rate, molecular weight, composition, structure change and so on reach the levels of conventional liquid phase catalyst.Through the analysis of the existing form and the aquathermolysis activity of sulfur atom in heavy oil, the reaction mechanism of heavy oil oxidative desulphurization is revealed, the origin of hydrogen sulfide in the formation is discussed, and the technical route of wet oxidative desulphurization is put forward: after removal from heavy oil, the existence of sulfur atom in the water phase is in the form of sulfate radical rather than the form of toxic and corrosive hydrogen sulfide. The catalyst and oxidant of heavy oil desulphurization are developed and optimally selected, the formula system of catalytic-oxidative desulphurization is optimized, and the suitable desulphurization condition is investigated. As a result, the desulphurization rate of heavy oil is up to 49.4%.The results of chemical analyses show that oxygenated compounds are mostly carboxylic acids in Liaohe heavy oil. The way of decarboxylation reaction of carboxylic compounds is analyzed. Based on kinetics experiments, the paper obtains the data of the rate constant and activation energy of oxygenated compounds by decarboxylation in heavy oil .The experiments show that oil reservoir minerals possess catalytic function for decarboxylation reaction, and can make the activation energy of decarboxylation reaction decrease 16.97kJ/mol; introducing metal ions into oil reservoir minerals can make its catalytic activity enhance; the decarboxylation reaction may lead to the decrease of resin-asphatenes in heavy oil and viscosity.The content and existing form of metal elements is analyzed, and the reaction mechanism of removing nonporphyrins metal in heavy oil is proposed by chelated method. The demetallization agent PMAS is manufactured. The optimum conditions of the demetalation reaction with PMAS were obtained with the Liaohe super heavy oil being used as the treating object and with the removal rate of calcium, iron and nickel being used as the evaluation index. Under this condition, the treatment can make that Ca removal rate is more than 80%, Fe removal rate is more than 50% and Ni removal rate is close to 30% in liaohe super heavy oil.Mechanism of improving the quality of heavy oil underground to EOR is not limited to "viscosity reduction" by studying on the adsorptted and wetting properties to rock of the polar components in Heavy oil before and after removal of miscellaneous elements in heavy oil. After the removal of miscellaneous elements, the adsorption of heavy oil molecules and rock weakened, the oil wetting role of rock also weakened, improving the mobility of heavy oil, but also can enhance the recovery of heavy oil. useing series of chemical agents developed by autherto removal of miscellaneous elements in heavy oil,and designed appropriate site implementation process,carrying out field exploitation test of improving the quality of heavy oil underground.The result show that Heavy oil production over the test cycle, having a significant increase compare with the previous cycle; viscosity of produced oil decreased;the content of miscellaneous elements in heavy oil lowerer, reducing the content of heavy components, increaseing the content of light-weight fraction.In this paper, the results of the studies will help resolve or alleviate a series problems of heavy oil exploitation, gathering, transportation and processing caused by the the high content of miscellaneous elements in heavy oil.