Effect Of Clay Minerals On Air Oxidation Characteristics

In recent years, Air injection technique has received considerable attention as an effective IOR process worldwide with the successful commercial implementation of high pressure air injection (HPAI) in light oil in America. Air, as an abundant injected gas. can be obtained locally which gives a low cost. Air injection can be used in both carbonate and sandstone reservoirs, especially in those reservoirs where other recovery processes are uneconomic or can not be applied effectively, for instance, low permeability or ultra low permeability reservoirs in which water injection is difficult, high water cut reservoirs, mature ploymerflooded reservoirs and high-temperature and high-salinity reservoirs in which chemical flooding is infeasible. Air injection is different from other traditional gas injection technique. The injected air can react with crude oil in reservoirs. The reaction between oil and oxygen make air injection not only has physical displacement process as other gas injection does but also has other additional chemical and physical displacement processes mainly including flue-gas displacement after oxidation, thermal effect-distillation effect of thermal front,the changing of oil component and oil properties because of the oxidation reaction ect. Flooding mechanism is more complicated. Oil recovery can be greatly improved under the synthetic action of all mechanisms in air injection process.As the flooding mechanisms primarily rely on the low temperature oxidation (LTO) air injection, the investigation on the LTO is very important. The LTO between crude oil and oxygen is controlled by many factors. Rock mineral and clay mineral types as one of factors have a significant impact on the LTO. Thus, it is really necessary to study how the clay minerals influence the LTO.This study is carried out for a heavy oil from T reservoir in X oilfield and a light oil from C reservoir in L oilfield. A literature review was made to analyze the field application of air injection, development history of flooding mechanism, the effect of clay minerals on LTO, the methods and equipments for investigating the LTO. X-ray diffraction (XRD) was employed to analyze rock and clay minerals types and content. Simultaneously. SEM was also employed to observe the micro for further verifying the results obtained by XRD, and use the X-ray fluorescence spectrometer (XRF) to test the element content in the four kinds of clay m inerals.Four clay minerals, including chlorite, illite, kaolinite and montmorillonite, were chosen to conduct oxidation tube physical simulation experiments. The effect of the clay mineral on the LTO of the heavy oil (from T reservoir in X oilfield) and light oil (from C reservoir in L oilfield) was analyzed by measuring the O2,CO2and C1～C6levels before and after oxidation. Four clay minerals exhibited obvious difference in catalytic effect.The catalytic abilities of four clay minerals are mainly influenced by the species and content of metal salts.Thermogravimetry/Differential thermal analysis (TG/DTA) was employed to study the oxidation behavior of the heavy and light oil. The results indicates, for both light oil and heavy oil in oxidation with air. three distinct reaction regions were identified known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). There are obvious differences in the TG, DTG and DTA curves for the two oils. Comparative analysis was made to clarify the influence of the two rocks, carbonate and sandstone, on the oil oxidation. The results showed that the sandstone with high clay levels has a greater impact than the carbonate with97.95%calcite levels. Arrhenius method was used to calculate kinetic parameters of the oil oxidation reaction and the oil oxidation reaction in the porous medium. And the effect of clay minerals on the oxidation kinetics was analyzed by comparing the activation energy obtained. The results were consistent with that of physical simulation experiments. The catalytic ability followed by chlorite, kaolinite, illite and montmorillonite. The investigation on the effect of clay minerals on the oil oxidation behaviour and kinetics is significant for evaluating the applicability of air injection technique to different rock types reservoirs (mainly refer to clay minerals types and levels).