SPE Well Testing and Pressure Transient Analysis

Question 1

During a buildup test, the Horner plot is constructed by plotting shut-in bottomhole pressure versus the Horner time ratio. What does a slope of 'm' on this plot represent?

Accepted Answer

Formation permeability-thickness product (kh)

Answer

Skin factor indicating near-wellbore damage

Answer

Reservoir drainage radius

Answer

Reservoir pressure gradient

Question 2

In pressure transient analysis, what does a positive skin factor (S > 0) indicate about the wellbore condition?

Accepted Answer

Near-wellbore damage reducing effective permeability

Answer

Enhanced permeability near the wellbore due to stimulation

Answer

A naturally fractured reservoir

Answer

Gas slippage effects in a tight formation

Question 3

Which flow regime appears as a half-slope straight line (slope = 0.5) on a log-log plot of pressure derivative during a pressure transient test?

Accepted Answer

Linear flow

Answer

Radial flow

Answer

Bilinear flow

Answer

Spherical flow

Question 4

What is the primary purpose of performing a drawdown test rather than a buildup test in well testing?

Accepted Answer

To evaluate productivity without sacrificing production time by shutting in

Answer

To measure static reservoir pressure more accurately

Answer

To determine original oil in place using material balance

Answer

To measure wellbore storage effects only

Question 5

In well testing, 'wellbore storage' (afterflow) distorts early-time pressure data. What causes wellbore storage in a producing oil well?

Accepted Answer

Fluid expansion or compression within the wellbore volume after shut-in or opening

Answer

Reservoir compressibility changes near the wellbore

Answer

Skin damage reducing flow into the wellbore

Answer

Fracture closure pressure exceeding reservoir pressure

Question 6

The dimensionless wellbore storage coefficient (CD) accounts for afterflow effects in pressure transient analysis. Which well characteristic most directly increases CD?

Accepted Answer

Larger wellbore volume (e.g., larger casing ID or deeper well)

Answer

Higher formation permeability

Answer

Greater reservoir thickness

Answer

Higher bottomhole temperature

Question 7

On a pressure derivative plot (Bourdet derivative), radial flow is identified by what signature?

Accepted Answer

A flat (horizontal) straight line

Answer

A unit slope (45°) straight line

Answer

A half-slope (0.5) straight line

Answer

A negative quarter-slope line