No abstract

The technical problems existing in deep well drilling are becoming more and more predominant during the exploration and development of oil-gas field. The poor formation drillability, low drilling rate and complicated pressure system cause the underground accidents frequent, extend well construction cycle, and make the cost of the project much higher. Therefore, it is urgent to develop new technologies to improve the efficiency of the exploration and development in deep unconventional oil-gas reservoir. The particle jet technology is a new energy-saving way which has a broad application prospect. It can take the way of sucking in particles in annulus space to cycle use the particles, and promote the drilling rate. The feasibility of particle jet as a drilling medium is verified by the theoretical and experimental study, which provides the basis for the design of particle jet tool.

A Realizable k-ε turbulence model in conjunction with a standard wall function has been applied to the prediction of a fully-developed two-dimensional jet impinging within a semi-confined space. A single geometry with a Reynolds number of 10,000 and a nozzle –to-plate spacing of eight diameters has been considered at different inlet boundary conditions. The numerical results, including the time-averaged velocities and the turbulent intensity, have been compared with the experimental data reported by Yoshida (ref 5). It is found that the trends in the axial velocity, the radial velocity and the turbulent intensity are fairly predicted. The fully-developed boundary condition is generally better than the constant velocity boundary condition. The differences between the numerical and experimental results can be attributed to the turbulence model and the treatment of the low Reynolds number zone near the wall.

The technical problems during the development of unconventional oil and gas reservoirs are becoming more and more difficult to handle with conventional drilling and production methods. Supercritical carbon dioxide has so many good properties such as high rock-breaking drilling efficiency, strong dissolved displacement performance and unharmful effect on the reservoir that it can be used as a drilling, completion and production medium to effectively exploit the unconventional oil and gas reservoirs. The global distribution of unconventional oil and gas resources is introduced, application status of carbon dioxide in oil and gas development is discussed, and development prospects of supercritical carbon dioxide in the unconventional oil and gas reservoirs are systematically analyzed. Using supercritical carbon dioxide as a medium in the whole development process is an important trend of unconventional oil and gas development technologies.

The effects of well type, water extraction time and water extraction quantity on the control of bottom water coning are studied by analytical method. The results suggest that a reservoir with low vertical permeability and interlayer above the water oil contact would have good effect of water extraction and cone control. The effect of water extraction with horizontal well is better than vertical well; the earlier the water extraction is applied, the better the effect of water control is obtained; the larger the quantity of water extraction is, the more obvious is the water control effect, and water extraction time and water extraction quantity has optimal value. In addition, water extraction and cone control is not effective to all bottom water reservoirs that are developed with horizontal well. If the vertical permeability of reservoir is high and have not effective block off of interlining or interlayer above the water oil contact or the water body is giant, the water cut of horizontal well will go up rapidly and the effect of water extraction will be difficult to achieve.