Oil samples obtained by shutting the well in and sampling the oil at the bottom of the wellbore are called?

• A. Bottom-Hole Sample
• B. Subsurface Sample
• C. Surface Sample
• D. Downhole Core Sample

Answer: (A)

Bottom-hole sampling involves closing the well and pulling a fluid sample from the bottom of the borehole, capturing the oil at near formation pressure. This preserves the fluid’s composition as it exists underground, minimizing changes that happen when lifting to the surface. It’s distinct from a surface sample (taken at the surface) and from a downhole core sample (a solid rock sample), hence the term bottom-hole sample.