ABSTRACT
For oil sand reservoirs, the steam-assisted gravity drainage (SAGD) technique is one of the most efficient thermal recovery technologies. However, the high oil viscosity and the severe heat loss seriously affect the production effect of SAGD in developing thin oil sand reservoirs by the traditional SAGD technology. Therefore, it is essential to improve the SAGD technology to enhance the recovery of the thin oil sand reservoir. In this paper, SAGD with a combination of vertical and horizontal well (VH-SAGD) technology was adopted, and the influence of different well spacings (horizontal distance between vertical steam injection wells and horizontal production wells) on the development of steam chambers was investigated. By the similarity criterion, the experimental parameters were obtained. After that, an improved 2D visualization physical model was designed with 9 × 9 high-precision thermocouples installed inside the device to monitor the real-time temperature. This experimental physical model can not only accurately capture the temperature distribution but also display the continuous change process of the chamber inside the model by the visible window. Finally, different well spacing cases (10, 15, and 20 cm) were tested to observe the development of the steam chamber and analyze the production data. Both the temperature distribution and visual window showed that the steam chamber has four obvious stages, and reasonable well spacing can promote the development of the steam chamber. When the well spacing is relatively small, the unswept area of the cold oil on both sides is large, and the area of the steam chamber overlaps more. When the well spacing is relatively moderate, the steam chamber is the most complete and the recovery factor is the highest. When the well spacing is relatively large, although the unswept area of the cold oil on both sides is small, the middle cold oil area is larger than the previous two groups. Therefore, the best well spacing for oil sand reservoirs of about 15 m thickness is 15-20 m, where the VH-SAGD method has a better displacement effect and higher oil recovery. The experimental conclusions can provide theoretical support for the production of thin oil sand reservoirs.
ABSTRACT
We investigated the influence of altitude on aero-optic imaging quality degradation of the hemispherical optical dome. Boundary conditions for the aerodynamic heating effect of the optical dome were calculated by solving the Reynolds-averaged Navier-Stokes equations provided by FLUENT. The finite element model and the thermal-structure simulation results of the optical dome were obtained using ANSYS. The 3D nonuniform refractive index field of the optical dome was obtained according to the thermal-optical effect. The optical tracking method based on the fourth-order Runge-Kutta algorithm was adopted to simulate the optical transmission through the optical dome. The Strehl ratio (SR), encircled energy, distorted target images, and peak signal-to-noise ratio were presented for imaging quality evaluation. The variation rules of these imaging quality evaluation parameters were obtained in the altitude range of 0-45 km. The results showed that, in the same flight conditions, with the increase of altitude, peak signal-to-noise ratio (PSNR) of the distorted image, and SR result were increased, and radiuses of dispersion spots, including 80% energy, were decreased; therefore, the influence of aero-optics effect on imaging quality degradation was gradually weakened.
