JNTU B.Tech III SURFACE PRODUCTION OPERATIONS Previous Question Paper (August - 2022 - R18)

Process flow diagrams (PFDs) utilize standardized symbols to represent equipment and instrumentation in surface production operations. Key symbols include:

• Vessels: Represented by horizontal or vertical cylinders for separators, treaters, and storage tanks.
• Pumps and Compressors: Represented by circles or triangles indicating the direction of flow and mechanical energy addition.
• Heat Exchangers: Represented by rectangles or shell-and-tube configurations showing fluid paths.
• Valves and Piping: Lines represent pipes, with specific symbols for gate, globe, check, and control valves.

Salient points for PFDs include the representation of primary flow paths, major equipment items, and process control loops. They focus on the functional relationship between units rather than physical layout, ensuring clarity in fluid processing sequences, pressure ratings, and material balance requirements.

Separator stages are employed to efficiently remove gas from liquid hydrocarbons and separate water from oil through pressure reduction. The process typically follows these stages:

• High-Pressure Stage: The wellstream enters the first separator at high pressure, where bulk gas is removed. This stage handles the highest volume of gas and reduces the pressure to a level suitable for downstream processing.
• Intermediate-Pressure Stage: The liquid from the first stage is flashed into a second separator at lower pressure. This stage recovers additional gas that evolved due to the pressure drop.
• Low-Pressure/Stock Tank Stage: The final stage operates near atmospheric pressure. It allows for the stabilization of the crude oil by releasing remaining dissolved gases before the oil is sent to storage or pipeline transport.

The diagrammatic representation involves a series of vessels connected by piping, where each vessel is equipped with inlet diverters, mist extractors, and level controllers. The primary objective of multi-stage separation is to maximize the recovery of liquid hydrocarbons (stock tank oil) while minimizing the loss of valuable light ends into the gas stream.