JNTU B.Tech II DRILLING AND BLASTING Previous Question Paper (March 2022 - R13)

Core recovery is the ratio of the length of the core sample recovered to the total length of the hole drilled, expressed as a percentage. It serves as a critical indicator of the quality and integrity of the subsurface materials encountered during drilling.

A single tube core barrel consists of a single outer tube that rotates with the drill string. As the core is cut, it is subjected to the full rotational speed and the direct flow of drilling fluid, which can cause erosion or breakage of soft or fractured rock samples.

A double tube core barrel features an inner tube that remains stationary while the outer tube rotates. The core is protected from the rotational friction and the direct impact of the drilling fluid, significantly improving recovery rates in friable, jointed, or soft geological formations.

Wire line drilling is a technique where the inner core barrel can be retrieved to the surface through the drill string using a wire line and overshot tool, without the need to pull the entire drill string out of the hole. This significantly increases productivity by reducing the time spent on tripping operations.

Horizontal drilling involves drilling a borehole that deviates from the vertical to follow a horizontal path through a target formation. This is primarily used to maximize the exposure of the wellbore to a reservoir, thereby increasing the flow rate and recovery of resources.

Directional drilling is the practice of controlling the trajectory of a wellbore to reach a specific subsurface target that is not located directly beneath the drilling rig. It utilizes specialized tools like mud motors, bent subs, and measurement-while-drilling (MWD) systems to steer the drill bit along a planned path.