Experimental study on selection of mechanical screens and sand retention precision design for horizontal wells in a gas field

Key words:  sand control screens  characteristics evaluation  throughput capacity  sand retention ability  displacement experiment  sand retention accuracy  sand control in gas wells

Abstract:

Mechanical screen is a key component for downhole sand control in unconsolidated sandstone reservoirs, and its type and comprehensive characteristics have a great impact on sand retention capability, well productivity and service life. In order to select a proper screen type and optimize sand retention for X gas filed in South Sea with typical sandstone formation and severe sanding problem during production, various parameters, such as screen conductivity, sand retention capability and a corresponding evaluation index, can be used to characterize the screen 's comprehensive sand control capability. A series of sand control experiments were conducted using an in-house experimental set up with sand samples from the field and under the production conditions. Six types of screens were tested, including a single-layer mesh compound screen, a two-layer mesh compound screen, a slotted linear screen, a wire-wrapped compound screen, a multi-layer mesh screen and a star-hole metal cotton screen. The performance index of each screen tested was calculated based on the experimental results. It indicates that, to control the fine sands from the gas reservoir with no water production, the two-layer mesh compound screen and the multi-layer mesh screen are the bests for use, which exhibited a good performance for sand retention, flow deliverability and anti-plugging. To optimize the sand retention precision, the two-layer mesh compound screens with six different sand retention accuracy from 0.1 to 0.15 mm were tested using simulated formation sands with median size of 0.08 mm. The experimental results show that the optimum sand retention accuracy is 0.1-0.115 mm for X gas field.