Which statement about reservoir sampling is true when the reservoir is above bubble point?

Which statement about reservoir sampling is true when the reservoir is above bubble point?

• A. Hydrocarbon composition can be determined
• B. Hydrocarbon composition cannot be determined
• C. Temperature is the only factor
• D. Sample quality is not affected by pressure

Answer: (A)

When the reservoir is above bubble point, the fluid exists as a single liquid phase with dissolved gas. In this state, a sample pulled from the reservoir remains representative of the overall hydrocarbon mix, so standard laboratory analyses can determine its composition accurately. There isn’t a separate gas phase forming and changing the proportions as pressure changes, so the measured hydrocarbon makeup reflects what’s actually in the reservoir. If the pressure were below bubble point, dissolved gas would come out of solution, causing fractionation: the gas phase would be enriched in light components while the liquid would be depleted, making it harder to infer the original reservoir composition without corrections. The idea that temperature is the only factor ignores the critical role of pressure and phase behavior, and the notion that sample quality isn’t affected by pressure isn’t correct because pressure changes can drive gas evolution or dissolution and alter the sample. So, the true statement is that hydrocarbon composition can be determined.

When the reservoir is above bubble point, the fluid exists as a single liquid phase with dissolved gas. In this state, a sample pulled from the reservoir remains representative of the overall hydrocarbon mix, so standard laboratory analyses can determine its composition accurately. There isn’t a separate gas phase forming and changing the proportions as pressure changes, so the measured hydrocarbon makeup reflects what’s actually in the reservoir.

If the pressure were below bubble point, dissolved gas would come out of solution, causing fractionation: the gas phase would be enriched in light components while the liquid would be depleted, making it harder to infer the original reservoir composition without corrections. The idea that temperature is the only factor ignores the critical role of pressure and phase behavior, and the notion that sample quality isn’t affected by pressure isn’t correct because pressure changes can drive gas evolution or dissolution and alter the sample.

So, the true statement is that hydrocarbon composition can be determined.