What is Annular Space?

• A. Space between the well casing /well screen and the wall of the borehole
• B. Space inside the well casing
• C. Space above ground
• D. Space around the surface appliance

Answer: (A)

In well construction, the annular space is the gap that exists around the outside of the casing or well screen within the drilled borehole. It lies between the outside surface of the casing (or screen) and the borehole wall. This space is typically sealed with cement or grout to create a barrier that prevents groundwater from moving between formations and to stabilize the casing. It’s a critical area for maintaining well integrity and preventing cross-contamination. The space inside the casing is simply the interior of the pipe, the space above ground is not part of the borehole, and the space around surface equipment isn’t the borehole annulus.