SPE Well Testing and Pressure Transient Analysis 1

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

The slope 'm' on a Horner plot is directly related to the permeability-thickness product (kh) via the equation m = 162.6 qBμ / kh, allowing calculation of formation flow capacity.

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

A positive skin factor indicates near-wellbore damage (e.g., from drilling mud invasion or scale), which creates an additional pressure drop and reduces well productivity.

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

Linear flow, which occurs in hydraulically fractured wells or elongated reservoirs, produces a half-unit slope (0.5) on the log-log pressure derivative plot.

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

A drawdown test acquires pressure transient data while the well flows, avoiding the production loss associated with a buildup test shut-in period.

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

Wellbore storage occurs because the wellbore volume contains compressible fluid; after shut-in, continued influx from this volume (afterflow) or fluid compression masks the true reservoir response.

(SPE) Society of Petroleum Engineers Certification Practice Test

(SPE) Society of Petroleum Engineers Certification Practice Test

SPE Well Testing and Pressure Transient Analysis 1