SPE Formation Evaluation and Logging 3

Question 1

Which parameter is determined by the Waxman-Smits model that the standard Archie equation does not account for?

Accepted Answer

Clay conductivity contribution to measured resistivity

Answer

The Waxman-Smits model accounts for the additional electrical conductivity contributed by clay-bound water and exchange cations on clay surfaces, which Archie's equation ignores.

Question 2

What is the main advantage of Logging While Drilling (LWD) over wireline logging?

Accepted Answer

Measurements taken before significant invasion and borehole deterioration

Answer

LWD acquires data immediately after bit penetration, before substantial mud filtrate invasion alters formation fluid distribution and before borehole wall degradation.

Question 3

A formation with a photoelectric factor (PE) of approximately 4.65 is most likely composed of:

Accepted Answer

Limestone (calcite)

Answer

Calcite (limestone) has a PE value of approximately 5.08, and dolomite is about 3.14; a PE near 4.65 is characteristic of limestone or a limestone-dominated mixture.

Question 4

In nuclear magnetic resonance (NMR) logging, the T2 cutoff is used to distinguish:

Accepted Answer

Bound (irreducible) water from free (producible) fluids

Answer

The T2 cutoff separates short T2 signals (clay-bound and capillary-bound water) from longer T2 signals representing moveable fluids like free water and hydrocarbons.

Question 5

The dual water model for shaly sands treats clay-bound water as having:

Accepted Answer

Zero salinity (effectively fresh)

Answer

The dual water model treats clay-bound water as essentially fresh (zero salinity) because cations balance the charge, making it behave like distilled water electrically.

(SPE) Society of Petroleum Engineers Certification Practice Test

(SPE) Society of Petroleum Engineers Certification Practice Test

SPE Formation Evaluation and Logging 3