🔍 Key Concepts

• Wellbore geometry – how the drilled hole, casing, and pipe are arranged • Clearance/space between two cylinders – inner object (pipe) vs outer boundary (borehole or casing) • Common oilfield terms: bore, open hole, down hole, and the term for the space between two concentric pipes

💭 Think About

• Visualize a cross‑section of the well: what is the term for the gap between the outside of the inner pipe and the inside of the outer wall? • Which option names a space or ring‑shaped gap rather than the pipe itself or the drilled hole as a whole? • Think about which term is used when talking about circulating fluids (like mud or cement) around the pipe rather than inside it.

✅ Before You Answer

• Make sure the term you pick refers to a space/gap, not the solid pipe or the full hole. • Check which choice is commonly defined as a ring‑shaped space between two cylindrical surfaces. • Verify that the term you choose is the one used in context of fluid flow outside the pipe but inside the wellbore/casing.