Satoshi Akibayashi

Experimental Modelling of the SAGD Process 3/4 Enhancing SAGD Performance with Periodic Stimulation of the Horizontal Producer

Experiments on initial stages of the steam-assisted gravity drainage (SAGD) process were carried out, using 2-D scaled reservoir models, to investigate production process and performance. Expansion of the initial steam chamber, its shape and area, and temperature distributions were visualized using video and thermal-video pictures. The relationship between isotherms and steam chamber interface was investigated to study the drainage mechanism. The temperature at the interface where the steam chamber was expanding was observed to remain nearly constant at 80°C. Effect of vertical spacing between the two horizontal wells on oil recovery was also investigated. For the case of conventional SAGD, oil production rate increased with increasing vertical spacing; however, the lead time for the gravity drainage to initiate oil production became longer. The results suggest that L can be used as a governing factor to evaluate production rate and lead time in the initial stage of the SAGD process. Based on these experimental results, the SAGD process was modified: the lower production well was intermittently stimulated by steam injection, in conjunction with continuous steam injection in the upper horizontal injector. Using the modified process (named SAGD-ISSLW), the time to generate near breakthrough condition between two wells was shortened, and oil production was enhanced at the rising chamber stage compared with that of the conventional SAGD process.

A Calculation Model for Liquid CO2 Injection into Shallow Sub‐Seabed Aquifer

Abstract: This study provided a model for calculating the aquifer transmissibility, the CO2 injection rate, the inner diameter of the injection well, and the number of wells for liquid CO2 disposal in the aquifer. The possibility of disposing liquid CO2 in an aquifer just beneath the sea floor was shown, based on the equilibrium lines in the pressure and temperature map. Our study focused on the feasibility of liquid CO2 disposal below the critical temperature because CO2 can be denser in the low‐pressure range (below the critical temperature) than above the critical temperature. An aquifer about 200 m under the sea floor, at a water depth of around 500 m (700 m below the sea surface), will serve for liquid CO2 disposal. In the aquifer the absolute pressure is approximately 7.3 MPa, sea‐floor temperature is about 4–6°C, and aquifer temperature is about 15–20°C. Therefore, it can be assumed that CO2 dissolves in the aquifer water, and liquid CO2 replaces the water. This means that under the previous conditions, more CO2 can be injected into the aquifer compared to supercritical conditions. Furthermore, by forming a cap of CO2 hydrates, the sediment between the sea floor and the aquifer, prevents CO2 leakage to the sea. Even without the cap, liquid CO2 and CO2 hydrates form at the sea floor, so the CO2 exerts no large environmental impact.

A theoretical approach for estimating the surface area of a rough-walled fracture from well logging data

Abstract A theoretical approach is presented to estimate the surface area of a rough-walled fracture artificially induced in a hot dry rock. In this approach the concept of parallel-plate model, measured values of permeability, average fracture aperture obtained from the injection test and by the televiewer, are used. This approach was also applied numerically to analyze the transport, deposition and dissolution of silica in the non-isothermal problem when a cool water was injected into the hot dry rock fracture through the injection well. From the results of the analysis, the effect of fracture surface area on the dissolution and precipitation of silica in the fracture and the computational error in this approach was evaluated.

Outline of the development of water dissolved natural gas in Japan and the world

Natural gas is one of the important energy resource compairing with petroleum, coal and nuclear energy. Water dissolved natural gas accounts for one fourth of the natural gas production in Japan. In this paper, we present the geology and development technology of water dissolved natural gas in Japan, especially of Minami Kanto and Niigata gas fields. The situation of water dissolved natural gas development in the world is also presented.

Simulation of high GWR behavior in the water-dissolved natural gas reservoir.

A numerical model was developed to study the production behavoir in the Mobara type water-dissolved natural gas reservoir which was composed of horizontal beds of alternating mudstones and sandstones. The model consists of the mathematical description of a horizontal, two phase (water and methane gas) flow in the two-dimensional sandstone layer, assuming the vertical, one dimensional diffusion of the desorbed gas from the mudstone.The methane adsorbtion volume for the mudstone was calculated assuming the Langmuirs adsorbtion isotherm. The model was applied to simulate the behavior of the reservoir of the Mobara type gas field.From the results of simulation, it was concluded that the model was valid for the Mobara type gas reservoir and that the effects of desorbed gas from the mudstone on the GWR behavior could be simulated by the proposed model.

A numerical model for simulating production behavior of multi-wells in the Mobara-type water-dissolved natural gas reservoir.

This paper describes a simplified three-dimensional numerical model for production behavior of the Mobara-type water-dissolved natural gas reservoir composed of alternating beds of sandstones and mudstones. It is assumed that water and gas flow horizontally through the sand-stones and vertically (in one dimension only) through the mudstones. Finite difference approximation method is used to solve the differential flow equations.Application of the model to a practical Mobara-type field in Chiba Prefecture shows very good coincidence between the calculated and the measured values for the average gas-water-ratio of all the production wells.Calculation results show that the production behavior remains ordinary-type if gas does not migrate from the mudstones to the sandtones even though pressure is maintained at a constant and a large amount of free gas is supplied at the boundaries, provided that the reservoir be isotropic and homogeneous.

Estimation of Transmissivity is the Water-Dissolved Gas Field

The spatial distribution of transmissivity in the water-dissolved gas field (G6 formation) in the Nishikanbara district, Niigata prefecture, was estimated using time histories of the groundwater heads which were calculated from the production data such as flow rate, gas-water ratio and wellhead pressure etc. at a number of wells. A quasi-linear approach was used to estimate the transmissivity.The estimated values of transmissivity were in the region of 2.0×10-4-7.8×10-2m2/s, and in the same accuracy as the values of transmissivity which were estimated using time histries of the groundwater heads including the errors which were expressed by random numbers of normal distribution N (0, 4.92).

Simulation of the gas water ratio behavior in the Mobara type water-dissolved natural gas field. Radial flow model.

A mathematical model is developed for predicting reservoir behavior in the Mobara type water-dissolved natural gas field. The model consists of the mathematical description of the flow of water and gas in the reservoir which is composed of the alternation of sandstone and mudstone. This description considers gas exudation at the face of the mudstone and horizontal radial flow in the sandstone.An application of the model to the practical reservoir problem (in the Sencho district) has revealed that the calculated values of gas water ratio and bottom hole pressure are in general agreement with the measured ones and that gas exudation at the face of the mudstone is a principal cause of the peculiar performance such that the gas water ratio rapidly increases with production in the field.

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