Study On The Design And Application Of Flow Improver For Xinjiang Tahe Heavy Oil

Heavy oil,as an important component of oil and gas resource,is a research field receiving relatively high strategic concern.The first carbonate oil reservoir with ultra-deep buried depth and extra-high viscosity has been discovered at Xinjiang Tahe oilfield in China.It is characterized by high proportion of heavy viscous oil and high salinity of formation water,which makes the exploitation of heavy oil considerably difficult.The study investigated the factors affecting the viscosity of heavy oil,and analyzed the correlation among the factors through the gray entropy theory.Based on the molecular simulation method,both theoretical and experimental studies on the design of molecular structure of the flow improver were carried out.Flow improver with relatively good viscosity reducing effect,i.e.amphiphilic polymers,has been prepared using acrylic alkyl ester as the main component and monomers with various polarity as aided modification component on the basis of the high contents of resins,asphaltenes,and metal in the Tahe heavy oil,The corresponding application evaluation of the Amphiphilic polymers has been complemented.The main research contents and results of our work are as follows:The correlation among the various factors affecting the viscosity of heavy oil has been discussed using the grey entropy theory.The contribution of each factor has been quantitatively assessed by using scaling theory.In view of the complexity of heavy oil,the heteroatoms and metal with high content were intentionally selected out.Through the calculation results,the contribution of Fe and Ni to the viscosity of heavy oil has been discussed.Our experiments proved that Fe had the strong crosslinking and thickening effect on the heavy oil by the results acquired from the reversing-addition metal salts experiment under the condition of anhydrous and water solution condition.The infrared-radiation(IR)characterization of heavy oil and its components,and interactions between components and metal ions indicated that the resins and asphaltenes are responsible for the high viscosity of heavy oil.The importance and the mechanism of the interaction between the metal ions and heavy oil have been studied.The strong interaction between the metal ions and heavy oil has propounded influence on the fluidity of heavy oil in the case of Tahe geochemistry.The representative average molecular structures of various components of Tahe heavy oil were built by 1H-NMR,XRD and elemental analysis.The interactions between flow improver various fragments and modeling compounds of heavy oil,and water phase have been studied by assuming types of hetero-compounds and the structure of saturates.A reasonable and effective screening method used to select and design flow improvers was obtained.The viscosity reducing mechanism of heavy oil flow improver has been studied and discussed in depth.According to the molecular structure design principle and the composition properties of heavy oils from Tahe block 10 and block 12,monomers with different functions have been screened out for the preparation of octadecyl acrylate as the main component of flow improver by using direct melting copolymerization.Through application test method,amphiphilic MAP type improver that is suitable for Tahe heavy oil recovery process has been selected out,and fully meet the actual production requirements in Tahe oilfield by simulated production experiment.