Oil and gas fields use a significant amount of water for oil and gas production. As the marine oil industry grows, strict regulations on marine discharges are implemented in most countries to protect the marine environment, and most oil and gas worldwide Companies are pursuing the complete elimination of pollutants in their production water. At this point, hydrocyclones emerged as an economical and effective alternative to oil removal and other uses from the water being produced. Hydrocyclone has advantages of low cost, simple design with no moving parts, easy installation and operation, and low maintenance cost. In order to increase the separation efficiency of the hydrocyclone, the separation efficiency according to the shape change was studied.