For improving the expansibility of natural Ca-based bentonite (Ca-Bent), the Ca-Bent was modified with sodium dodecyl benzene sulfonate(SDBS)-Na 2 CO 3 complex agent by microwave semi-dry method. And the ratio of Na 2 CO 3 to SDBS, microwave power, radiation time and initial temperature on the modification were studied. Furthermore, X-ray diffraction (XRD) patterns and infra-red spectrum (IR) were carried out to characterize , which obtain microstructure of samples. The result showed that the optimized experimental parameters are obtained as follows: Na 2 CO 3 to SDBS ratio 1:1, radiation time 2min, microwave power 600W and initial temperature 120K. Besides, under the optimization conditions, the modified bentonite has swelling volume of 68.5mL/g, cation exchange capacity of 56.2mmol/10 2 g and yield point and plastic viscosity ratio of 1.67, respectively. A comparison of the single factor experiment and orthogonal experiment indicates that the SDBS and Na 2 CO 3 have synergistic effect in the process of modification, especially, under the optimum microwave condition, Na 2 CO 3 increased the anion activity of SDBS, which enhanced the hydrophilicity of modified bentonite. The experimental result show that the process improves the swelling volume of bentonite and the comprehensive performance. So, the modified bentonite was a perfect additive in water drilling mud.
Abstract. To improve the performance of sodium-modified bentonite in drilling fluids, the natural Ca-base bentonite (Ca-Bent) was modified by microwave wet, which regarded the anionic surfactant SDBS is compounded with inorganic sodium salt as modifier. The effects of different sodium salts, the volume of modifier, the ratio of SDBS to inorganic sodium salt, temperature and time on the modification of bentonite were studied. Moreover, the applicability of modified bentonite in drilling fluid was also evaluated. The result showed that the optimized experimental parameters are obtained as follows: SDBS to Na 2 CO 3 ratio 1:1.5, modified volume 50ml, radiation time 3 mins, and initial temperature 50℃. Under the optimization conditions, the modified bentonite has a swelling volume of 45mL/g. And the pH of 8, the plastic viscosity of 18 mPa•s, yield point and plastic viscosity ratio of 0.25 and sand content less than 0.5% respectively. So, the modified bentonite is regarded as excellent drilling grade bentonite.
According to the reservoir characteristics and the current situation of CO2 utilization during thermal recovery in an unconsolidated sandstone heavy oil reservoir, the mechanism and law of porosity and permeability change in an unconsolidated sandstone heavy oil reservoir during CO2+steam and CO2+steam+ sodium alpha-olefin sulfonate (AOS) injection were studied by combining a static monomineral water-rock reaction and a dynamic polymineral sand pack displacement experiment. In the static water-rock reaction between CO2 and monomineral of reservoir rock, the dissolution degree of monomineral at 200°C is greater than that at 100°C and 300°C, and the order of mineral dissolution is illite, montmorillonite, kaolinite, and quartz. Besides, the dissolution rate of single rock minerals decreased significantly in the system of CO2 with AOS. In the polymineral sand pack displacement experiment, the porosity gradually decreases by CO2 multicomponent thermal fluid, and the permeability first decreases and then increases by CO2 multicomponent thermal fluid, but the permeability change is only about 0.5% by CO2+steam+ AOS, which is mainly attributed to the adsorption of AOS on the rock surface, and it is confirmed in the infrared spectrum of unconsolidated sand after displacement. This also shows that CO2+steam+AOS can stabilize the rock skeleton structure of the reservoir and prevent the deterioration of heterogeneity in the subsequent development of thermal recovery of heavy oil reservoirs; therefore, the CO2 multicomponent thermal fluid with chemical agents can improve the damage of a single CO2 thermal fluid to the reservoir.
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