JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III PETROLEUM RESERVOIR ENGINEERING Previous Question Paper (August - 2022 - R18)

Flow regimes in petroleum reservoirs refer to the specific patterns of fluid movement and pressure distribution within the reservoir as a function of time and distance from the wellbore. These regimes are defined by the geometry of the flow, the compressibility of the fluids, and the boundary conditions of the reservoir.

The fundamental equation governing radial flow in a porous medium is derived from the continuity equation, Darcy's Law, and the equation of state for slightly compressible fluids, resulting in the diffusivity equation:

The different types of flow regimes are described as follows:

• Transient Flow (Infinite Acting): Occurs immediately after a well is opened or closed. The pressure disturbance has not yet reached the reservoir boundaries. The pressure drop is proportional to the logarithm of time, and the reservoir behaves as if it were infinite in extent.
• Pseudo-Steady State (PSS) Flow: Occurs in a closed reservoir after the pressure transient has reached all boundaries. The rate of pressure decline becomes constant throughout the reservoir, and the pressure at every point in the reservoir decreases at the same rate.
• Steady-State Flow: Occurs when the pressure at every point in the reservoir remains constant over time. This typically requires constant pressure boundaries, such as an active water drive or fluid injection, where the rate of fluid withdrawal equals the rate of fluid influx.
• Linear Flow: Occurs when flow lines are parallel, typically observed in hydraulic fractures or long, narrow reservoirs. The pressure drop is proportional to the square root of time.
• Spherical/Hemispherical Flow: Occurs when flow converges toward a point or a limited entry interval in the wellbore. This is common in partially penetrating wells, where the pressure drop is inversely proportional to the square root of time.