Selection and sand control precision optimization of sand control screen for horizontal wells in unconsolidated sandstone oil reservoirs

Unconsolidated sandstone oil reservoirs in the Pearl River Mouth Basin in the east of the South China Sea are characterized by shallow burial depth, high shale content and easy sand production. In order to select the sand control screen suitable for the horizontal wells in this oilfield, physical simulation experiments of sand control were carried out on different types of sand control screens by using the full-scale physical simulation experiment device of sand control screen, based on the reservoir characteristics (d₅₀=250 μm, heterogeneity coefficient 3.17, and shale content 12%) and actual working conditions in this oilfield. After the flow rate, pressure drop, sand content of oil and particle size of produced sand at different sand control precisions (150, 200, 250 and 300 μm) were measured, the modified star-hole composite screen and three metal-mesh composite screens with different structures were evaluated systematically from the aspects of sand control property, anti-blocking capacity and overall performance. It is indicated that metal-mesh composite screen II (protective sleeve + square hole net + dual-layer dense net + square hole net + base tube) and metal-mesh composite screen I (protective sleeve + square hole net + three-layer dense net + square hole net + base tube) are better in the indicators of sand control property, anti-blocking capacity and overall performance, and they are suitable to act as the sand control screen of horizontal wells in fine-moderate unconsolidated sandstone oil reservoirs with high water cut in the Pearl River Mouth Basin in the east of the South China Sea. And it is recommended to set the sand control precision at 200-250 μm. The research results provide the basis for the design of sand control scheme of this oilfield.