What specific data is required from a pressure transient analysis test to determine the skin factor near the wellbore?

To determine the skin factor near the wellbore from a pressure transient analysis test, several specific data points are required. First, the initial reservoir pressure (Pi) before the test begins must be accurately known. This represents the undisturbed pressure of the reservoir before any production or injection occurs. Second, the wellbore pressure (Pwf) as a function of time during the test is essential. This pressure is continuously measured by a downhole pressure gauge. The data is used to construct a pressure drawdown or buildup curve. Third, the production or injection rate (q) during the test must be precisely controlled and recorded. This rate, combined with the pressure data, forms the basis for the analysis. Fourth, reservoir fluid properties are needed, including fluid viscosity (μ), formation volume factor (B), and fluid compressibility (ct). These properties influence the pressure response in the reservoir. Fifth, the reservoir's permeability (k) and thickness (h) need to be determined, often estimated from other well tests or geological data. Finally, the wellbore radius (rw) must be known. The skin factor (s) is calculated using the pressure data, production rate, and reservoir properties by analyzing the pressure transient data using methods such as Horner analysis or type curve matching. The skin factor is a dimensionless value that quantifies the degree of impairment or stimulation near the wellbore. A positive skin factor indicates damage or restriction to flow, while a negative skin factor indicates enhanced permeability near the wellbore.