Experimental Study on the Draw-Down Pressure Control of Horizontal Wells with Gas-Cap/Edge Water Narrow Oil Rims

To better understand the influence of draw-down pressure control strategy on the development result of gas-cap/edge water narrow oil rim, and to improve the recovery percentage of such reservoirs, a large-scale three-dimensional physical model was designed by taking an offshore gas-cap/edge water narrow oil rim as the prototype on the basis of similarity criteria. Production experiments on the different adjustment timing and adjustment modes of horizontal well draw-down pressure were conducted, and the influence of those adjustments on the development results of gas- cap/edge water narrow oil rim was analyzed. The results showed that the draw-down pressure increased after gas channeling in the horizontal wells, and the recovery percentage increased from 28.32% to about 40.00%. When gas channeling lasts for a period of time, the recovery percentage from draw-down pressure increase was better than that when gas channeling occurs instantly, and the recovery percentage can increase by 2.09%; In addition, the development result from draw-down pressure increase in single step mode is better than that in multi-step mode, and the recovery percent can increase by 2.47%. The research results showed that draw-down pressure increase in single step after gas channeling lasts for a period of time is the best strategy to improve the recovery percentage of this type of reservoir. This pressure draw-down adjustment strategy has been applied in an offshore gas-cap/edge water narrow oil rim, and oil production increase is remarkable.