Yoshihiro Masuda

Summary Simple simulation models are constructed to predict the performance of 1D polymer flooding. In the models, two phases of oil and polymer solution were assumed to be immiscible with each other. Because the displacing fluid was non-Newtonian, the BucldeyLeverett equation could be modified and a new approach developed to calculate fractional-flow curves. The rheological behavior of polymer solution was modeled with an Ellis type model and a viscoelastic model. To verify the models, two 1D f

In this study, we investigated the stability of asphaltene adsorption structures at the oil–water interface, focusing on the role of heteroatoms, by molecular dynamics simulations. We employed an oil (1:1 mixture of heptane and toluene, by volume)–water system and used 13 types of asphaltene molecules. Two sets of asphaltene models with the alkyl side chain at different locations were considered. For each set, six models were employed, which have essentially the same structures but with differen

Hydrate formation of a natural gas mixture is fascinating. Whereas both pure methane and ethane form a structure I (sI) hydrate, their mixture may form a structure II (sII) hydrate at certain compositions. Here, we investigated the underlying mechanisms of the methane–ethane mixture hydrate structural transition using an sII-hydrate–water–hydrocarbon three-phase interface system. The results indicate that sII hydrate formation is a function of methane concentration with a maximum at a mole conce

With the development of microscopy and sensor techniques, it becomes evident that nonswelling clays show swelling behavior under CO₂-water mixture environments at high pressures and temperatures. The examples include Illite, muscovite, and kaolinite-rich rock samples. Here, we investigated the underlying mechanisms of kaolinite swelling induced by CO₂ and water using molecular simulations and low-pressure gas adsorption experiments. The results suggest the cooperative adsor

Abstract In drilling horizontal wells and extended reach wells effective transport of drill cuttings is critical. Cuttings deposition and accumulation could lead to formation of deposit bed(s) inside the annulus, causing stuck drillpipe, eccentric borehole, poor penetration rate, etc. Experimental investigations reported in the literature previously focused on evaluation of cuttings transport performance in directional wells, as functions of mud flow rate, mud rheology, angle of inclination, pip

To investigate enhanced oil recovery processes, we constructed a molecular model of a live heavy crude oil (digital oil) and studied the crude oil properties at the reservoir temperature and a wide range of pressures. We identified the liquid phase components of the digital oil by flash calculation and calculated the density and viscosity by molecular dynamics simulations. The calculated density and viscosity were in good agreement with experimental data. To evaluate the effectiveness of various

We constructed a molecular model (digital oil model) for heavy crude oil based on analytical data. Crude oil was separated into four fractions: saturates, aromatics, resins, and asphaltenes (SARA). The digital oil was constructed as a mixture of representative molecules of saturates, aromatics, resins, and lost components (low boiling-point compounds vaporized during drying), while asphaltenes of ∼0.4 wt % in the crude oil being ignored. Representative molecules were generated by quantitative mo

Methane hydrate (MH) is the best-known unconventional energy resource and has begun to open its promising future, especially for Japan. In 2017, the second offshore gas hydrate field test was conducted in the Eastern Nankai Trough, Japan, where a depressurization technique was adopted for producing methane gas. Alongside the depressurization method, the replacement of CH4 from gas hydrates by a N2–CO2 gas mixture was suggested and adopted to increase performance for both methane gas recovery and

Recently, some mathematical models for the prediction on progress of carbonation of concrete were reported. These models were taking account of CO2 diffusion and chemical reaction of Ca (OH) 2 and CO2. These models were based on the assumption that CO2 diffused in the carbonation zone and reacted with Ca (OH) 2 at the boundary face of carbonation zone and uncarbonation zone. In these models did not coexist. According to previous studies, however, it was know that Ca (OH) 2 and CaCO3 do coexist i

CO2 injection is an effective enhanced oil recovery technique for energy security with the benefits of carbon neutrality. To reach the maximum oil recovery, the miscible condition between CO2 and oil needs to be maintained in the reservoir, which requires the operation pressure to be higher than the minimum miscibility pressure (MMP). There are two types of MMPs: the first-contact MMP (FC-MMP) and the multi-contact MMP (MC-MMP). In this study, molecular dynamics simulations were performed for th

We investigated asphaltene adsorption behaviors at the oil–water interface, focusing on the effect of oil solvents, by molecular dynamics simulations. Heptane, toluene, and their mixtures with ratios of heptane to toluene of 25:75, 50:50, and 75:25 by volume (namely, heptol25, heptol50, and heptol75) were used as the oil models. Two asphaltene models with essentially the same structure were employed: one contains a basic pyridine-type nitrogen heteroatom; another contains no heteroatoms. The asp