Optimization study on the slot width of slotted screen in heavy oil wells based on permeability loss law analysis

In one certain oil area of Xinjiang Oilfield, slotted screen is generally adopted in sand-production heavy oil thermal recovery wells for simple sand control, but the slot width design of slotted screen is absent of basis, which leads to the serious loss of oil well productivity after sand control. Therefore, it is in urgent need to carry out the studies related to the slot width design of slotted screen. The sand retention and plugging experiment of slotted screen was carried out by simulating the heavy oil, formation water carrying sand flow and formation sand conditions of the target oil area. Then, the permeability change laws and sand retention situations of slotted screens with different slot widths under the conditions of heavy oil plugging and combined heavy oil and formation sand plugging were analyzed. Finally, slot width was optimized based on the quantitative evaluation of sand control performance indexes. It is indicated that slotted screen permeability decreases significantly in heavy oil plugging stage and combined plugging stage and it drops to less than 0.3 μm² after the plugging reaches the balance state. With the increase of the slot width, the permeability increases in the process of sand retention and both permeability loss amplitude and permeability loss velocity present the trend of decreasing, but the reduction of slot width is beneficial to increase screen’s sand retaining ratio. As far as the formation sand with median particle size of 0.25 mm in the target oil area is concerned, the comprehensive sand control performance of the screen with slot width of 0.30 mm is the best. This study takes the sand production time of heavy oil thermal recovery wells into consideration and it can provide a reference for the productivity evaluation of similar oil wells after sand control and the optimization of sand control medium accuracy.