Productivity Index Case Study

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2.6 Productivity Index The productivity index is a measure of the well potential or ability to produce and is a commonly measured well property.The symbol J is commonly used to express the productivity index; as well as, being the preferred symbol by the Society of Petroleum Engineers. The productivity index of a well is a measure of the production rate achievable under a given drawdown pressure, which is the difference between the average reservoir pressure and the flowing bottom hole pressure. Defined as the flow rate per unit pressure drop, the productivity index gives an indication of the production potential of a well.

From the bpss equation above:

Therefore: From a reservoir point of view, well management …show more content…

Standing was one of the first to address the prediction of future well performance from IPRs. He used Vogel’s IPR with a modified multiphase productivity index to relate current well performance to future performance. Unfortunately, his relationship requires knowledge of fluid properties and relative permeability behavior. This makes Standing’s method difficult to use because one must estimate saturation, relative permeability, and fluid properties at a future reservoir …show more content…

2.5 Material Balance Equation (MBE) For gas, the MBE is defined as the relationship between the original gas in place, initial pressure (pi), cumulative gas production, and the current average reservoir pressure. The basis of the MBE for gas flow is the volumetric balance of all the fluids at a given time. The following equation proposed by Ramagost and Farshad (1981) is used to calculate the average reservoir pressure for gas systems. This equation considers that gas is the only mobile phase in the presence of residual fluid saturations (oil and water) in a compressible formation.

Note that this equation is only valid when the term ce(pi – p) < 1
For oil and water The MBE is defined as the relationship between the original fluid in place, initial pressure (pi), cumulative fluid production, total system compressibility (ct), and current average reservoir pressure. The following equation for liquid flow is based on the definition of total compressibility (ct) at a given time. This equation considers the selected fluid (oil or water) as the only mobile phase in the presence of residual fluid saturations, if present, in a compressible

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