Study on the oil/water separation performance of a super-hydrophobic copper mesh under downhole conditions

The existing downhole oil–water separation (DOWS) technology has disadvantages in terms of separation efficiency, cost, complexity, etc. The novel filtration separation technology using metal meshes has been investigated and it displays the potential to increase DOWS efficiency. In current study, a super-hydrophobic copper mesh was fabricated by a simple dip-coating method and then characterized. Focusing on the application in DOWS technology, the separation of the mesh materials in the lifting process of produced liquid from the wellbore was simulated and investigated by a designed indoor device for the first time. The results show that the highly hydrophobic copper mesh with water contact angle of 153 ° can be obtained by oxidizing 40 min, followed by immersing in a 50 g L−1 stearic acid solution for 25 min. The mesh can keep super-hydrophobicity and high separation stability after treatment at 100 °C or in the pH range of 5–7, while the separation efficiency is susceptible to the oil viscosity and the clay contents of the produced fluids. The super-hydrophobic copper mesh can be a promising candidate for DOWS in moderate condition. The inherent separation mechanism was further discussed by the variation of wettability and surface structure in microscopic scale.