Shozo Tanaka

Simulation study of fireflooding (Part 3) - On the influence of residual oil saturation, oil density and air injection rate.

Simulation study was carried out to investigate the behavior of fireflooding and to obtain basic information for designing and/or screening fireflood projects. The simulator used has been reported elsewhere (JJAPT 52, 5, 1987). Parameters investigated were (1) residual oil saturation, (2) oil density, and (3) air injection rate, which was the only one parameter that could be controlled directly.Results are summerized as follows;(1) In general oil production methods other than fireflooding, oil recovery is low as residual oil saturation is high. Because the amount of oil used as fuel is little in fireflooding, the oil recovery is less affected by residual oil saturation, though the combustion reaction zone w ould be extinguished if the residual oil saturation is too small to leave sufficient amount of oil being supplied as fuel.(2) In fireflooding, the cork formed by the thermal decomposition of heavy components would be the fuel, so that the fireflooding would be impossible unless the oil density is high enough. However, the recovery and the prodution rate are higher as the oil is lighter in the range of operating condition.(3) Production rate would vary with air injection rate. But the optimum air injection rate may exist from the economical point of view.

Simulation study of fireflooding. (Part 1). On the behavior of displacement and flow of oil.

Simulation study was carried out to investigate the behavior of fireflooding in reservoirs and to obtain basic informations for designing and/or screening fireflood projects, through a sensitivity study. The simulator used has been reported elsewhere (JJAPT 52, 5, 1987). Parameters selected were (1) initial water saturation (or initial oil saturation), (2) absolute permeability, (3) porosity, (4) thickness of reservoir (as a parameter representing heat loss to the upper and lower strata), (5) residual oil saturation, (6) density of oil, and (7) air injection rate. As a part of the study, general phenomena of fireflooding is described in the present report.It should be noted that the whole process of fireflooding can be understood to consist of four processes; that is (1) the initial air injection process, where the air injection rate required is achieved, (2) the initiation of in-situ combustion and subsequent oil accumulation to form oil bank, (3) main production process following the oil bank formation process, and (4) process of little oil production after the production of oil in oil bank. It was also shown that the duration of the production period as the third process described above depended on the initial oil saturation, but the production rate was independent of the initial oil saturation.

A preliminary investigation of in-situ combustion for the enhanced oil recovery. (Part 4). Combustion tube tests and comparison of theoretical and experimental results.

Combustion tube experiments were carried out to investigate the basic behavior of fireflooding as an EOR method. And it was found that the vaporization-condensation mechanism was important to accumulate oil for making oill banks and oil banks formed moved toward the exit (production well).As to the production, three stages would be seen. These are (1) the production of oil movable at a liquid state, (2) production of oil from the oil bank formed by means of fireflooding mechanism mentioned above, and (3) little production of oil after the production of oil bank. When the oil is at the residual oil saturation in the reservoir, no oil production at the first stage would be expected.Adequacy of the simulator developed in the present study and described in the last paper was examined in detail by means of comparing results obtained both theoretically and experimentally. And it was shown that the simulator was preferable.

Practical measuring method of thermal conductivity of drilling mud at high temperature and high pressurs.

The transient hot-wire method have been used to measure the thermal conductivity of gases and liquids acculately using a very thin wire of diameter from 15 to 40μm, recently. On the other hand a practical method to measure thermal conductivities of viscous suspensions contained fine and/or coarse grains easily with practically enough accuracies at a high temperature and high pressure is needed in the fields of drilling technology and others. A needle probe type sensor having 2mm in diameter and 1, 000mm in length with a thermopile of six magnifications of sensitivity of temperature and the measuring system were developed. The thermal conductivites of three standard and test samples were measured by analyzing the data of smooth curve relations at an early period between the temperature increase of the probe and the constant heat supplied time to the probe using a theory of unsteady hot thick wire method and the multivariate analysis. Measurement errors of this method were estimated at less than ±10%. Thermal conductivity of montmorillonite-water based muds having concentrations of 3.0, 6.0 and 10.0% were measured at the temperature range from 20 to 180°C. From the measurement characteristic temperature and concentration dependencies on the thermal conductivity of the mud were obtained.

A preliminary investigation of in-situ combustion for the enhanced oil recovery (Part 2) - Measurement of functional dependencies of properties of crude oil as a multi-component mixture.

For the investigation of the performance of in-situ combustion as an FOR method by means of mathematical simulation, physical and chemical properties of crude oil must be expressed mathematically.First of all, combustion characteristics of a crude oil-silica sand system was experimentally obtained using a gravimetric technique. Resultant equations of high temperature burning rate and thermal decom-position rate for Ishinazaka crude oil (18.2°API) are Eqs. (1) and (2) in the text, respectively.In our mathematical Model to be presented in the next report, a crude oil is assumed to be a mixture of two hypothetical components, one of which can represent the lowest gravity component and the other the highest gravity component of the crude oil. Their fraction is determined to express the gravity of the oil, and other physical properties are expressed as functions of temperature, pressure, and gravity of the oil. Then the saturated vapor pressure of oil and the gravity of vaporized oil were experimentally determined. These are shown, respectively, as Eqs. (3) and (4) in the text.

A preliminary investigation of in-situ combustion for the enhanced oil recovery (Part 1) - Development of a simulator for Laboratory Experiments.

A model was developed to simulate laboratory combustion tube experiments. This paper describes a one-dimensional simulator of three phases, gas, water and oil phases, and five components, oxygen, nitrogen, carbon oxides, water and oil, in which fluid flow, heat transfer, combustion and vaporization/condensation are appropriately modeled. A crude oil is a mixture of many hydrocarbons but in the simulator it is treated as one component, the physical and chemical properties of which vary consistently with pressure and temperature, so that the model developed is different from ordinary three phase, five component models. The applications demonstrate that the simulator can be used to interpret laboratory results and predict the effects of reservoir characteristics and operations.

The Forecast of the Temperature of Groundwater by the Simulation Model: Heat Transfer on Steady Flow in a Confined Aquifer@@@被圧帯水層中の定常流に伴う熱移動

The temperature distribution of groundwater in a confined aquifer was numerically analysis by the simulation model shown in Fig. -1. These results offer substantial benefits when caning out hot water injection into water

A Study on Two Phase Flow of Air and Water in Gas Lift Well

The writers undertook laboratory study for the purpose of examining relation between factors affecting f factor in gas lift well. By the results of the experiment, writers obtained the equation, f=aρbwhere f is f faxtor; ρ is fluid density; a and b are the function of the flow rate of liquid and the inside diameter of lift pipe, respectively. By application of the equation, writers are able to calculate f factor for a much wider range of gas-oil-ratio.