The drilling bottom hole assembly (BHA) is one of the components of the Drilling String which is below the Drill Pipes. The most common components of the BHA are Drill Collars, Stabilizers, Shock Absorbs, Jars, Reamers, Heavy Weight Drill Pipe, and The Drilling Bit.

The bottomhole is the lowest or deepest part of a well. Drillers use mud pumps to circulate drilling fluid through the central well annulus to the bottomhole of the peripheral well.

There are three different types of bottom hole assembly packed BHA: Mild Crooked Hole Packed BHA. Medium Crooked Hole Packed Bottom Hole Assembly BHA.

A bottom hole assembly (BHA) is a component of a drilling rig. It is the lowest part of the drill string, extending from the bit to the drill pipe. The assembly can consist of drill collars, subs such as stabilisers, reamers, shocks, hole-openers, and the bit sub and bit.

Bottom hole pressure is the pressure at the bottom of the hole, usually measured in pounds per square inch. In a flowing well the bottom hole pressure is equal to the pressure drop in the tubing plus the wellhead pressure. The reservoir or formation pressure at the bottom of the hole is known as bottom hole pressure.

The function of drilling muds conduct cuttings away from the drill face, provide a hydrostatic head that counters the pressure of gas or oil, and provide a physical and chemical means of stabilizing and protecting the rock formation that is being drilled.

“Bottom-hole location” means the subsurface point at the greatest measured penetration of a well or a well branch.

The bottom hole assembly (BHA) is a portion of the drillstring that affects the trajectory of the bit and, consequently, of the wellbore.

Two types of BHAs are commonly used to drill a vertical hole: slick and pendulum. A slick BHA consists of a drill bit, drill collars, heavy-weight drill pipe, and regular drill pipe. The name slick is related to the absence of stabilizers.

Bottom-hole pressure determinations can be an important aid in determining the reservoir condition, ability of the well to produce and, if the hole is in condition for the well to produce to the best advantage. They can also be used to determine the condition of the screen or liner.

Bottom Hole Pressure Relationship

1. Bottom Hole Pressure (BHP) = Surface Pressure (SP) + Hydrostatic Pressure (HP)
2. The first case: Hydrostatic column is water which is equal to formation pressure gradient so SP is equal to 0 psi.

Three main types of mud have been used and any or all of them may be present in the drill cuttings piles: (1) water-based muds, (2) oil-based muds, and (3) synthetic muds (SMs).

In general there are three types of Bottom Hole Assembly BHA In drilling: This type of bottom hole assembly (slick BHA) consists of a Drill Bit and Drill Collar without Stabilizer. Slick BHA is suitable for formations which have mild crooked hole tendencies.

The bottomhole assembly (BHA) is the component of the drill string located directly above the drill bit and below the drill pipe. The primary component of the BHA is the drill collar. Therefore, it has a signifi cant effect on drill bit performance.

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A typical build assembly uses two to three stabilizers. The first (near-bit) stabilizer usually connects directly to the bit. If a direct connection is not possible, the distance between the bit and the first stabilizer should be less than 6 ft to ensure it remains an angle-building assembly.