Well Testing and Pressure Transient Analysis Flashcards

A pressure buildup test is shut in after a production time 'tp'. The Horner approximation works best when which condition is met?

Answer: Production time (tp) greatly exceeds shut-in time (Δt)

The Horner approximation (using superposition with a single producing time tp) is most accurate when tp >> Δt, ensuring that the transient is still within the early buildup response.

Which reservoir boundary condition produces a doubling of the semi-log straight line slope in a buildup or drawdown pressure transient test?

Answer: A sealing fault (no-flow boundary) at some distance from the well

When a sealing fault is encountered, flow transitions from radial to hemi-radial, effectively halving the drainage area and doubling the slope on the semi-log plot.

In a drill stem test (DST), the 'Initial Shut-In Pressure' (ISIP) measured at the start of the test is most useful for estimating which parameter?

Answer: Static reservoir pressure or pore pressure

The ISIP in a DST approaches static reservoir pressure as equilibration occurs, making it the primary indicator of pore pressure or original reservoir pressure.

What does the term 'pseudosteady-state flow' (PSS) describe in reservoir engineering and well testing?

Answer: Flow regime where reservoir pressure declines uniformly at a constant rate throughout the drainage area

Pseudosteady-state (PSS) occurs after transients reach all boundaries; the reservoir then depletes uniformly, with pressure declining at the same constant rate everywhere in the drainage volume.

In a pressure falloff test performed on an injection well, which parameter can be derived using the same analytical methods as a standard buildup test?

Answer: Formation permeability and skin factor

A pressure falloff test (shut-in after injection) is the injection-well analog to a buildup test; the same semi-log and derivative analysis yields formation permeability (k) and skin (S).

Which deliverability test method for gas wells involves flowing the well at four different stabilized rates to establish a flow-after-flow curve?

Answer: Backpressure (flow-after-flow) test

The backpressure (or flow-after-flow) test flows a gas well at four increasing rates, each to apparent stabilization, to construct the deliverability curve against backpressure.

When analyzing a naturally fractured reservoir using pressure transient data, the Warren-Root model predicts what distinctive feature on the pressure derivative plot?

Answer: A dip (valley) in the derivative between two parallel semi-log straight lines

The Warren-Root dual-porosity model exhibits a characteristic valley (dip) in the pressure derivative as fluid transfers from matrix to fractures, appearing between the early fracture-dominated and late total-system radial flow regimes.