eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-06-09 11 Spl.Edn.1 201 206 10.13005/bbra/1411 11823 article B. Antony Fayaz 1 Akhil Sunny 1 Nazeel 1 BE (Petroleum Engineering) AMET University, Chennai - 603 112, India. The success of any drilling operation especially directional drilling operations depends upon the selection and design of Bottom Hole Assembly. Therefore, it is very important to know the components and its working in a BHA. Any failure to BHA design may result in complete failure of the drilling operation. For this purpose there should a complete knowledge of what the BHA is compose of and what are the factors that have to considered while design of a BHA. Certain parameters like maximum permissible dogleg severity, maximum bending stress, neutral point of compression and tension etc. has to be calculated for designing a BHA. When there is a miss calculation in any of these factors it may lead to complete or partial failure of the BHA.Down Hole Mud Motors are also another important criterion in directional drilling. Therefore, it is equally important to know the components and its working principle of the down hole mud motor or positive displacement motor. This paper deals with the components of BHA and Down Hole Mud Motor and their working for directional drilling. Proper understanding of the components is critical in design concept of the BHA and mud motor. Knowing what component if required where is vital. So this paper gives a clear idea of all the components and their role in the BHA and mud motor as well. https://www.biotech-asia.org/vol11_nospl_edn1/bottom-hole-assembly-and-mud-motor-for-directional-drilling/ Bottom hole assembly; mud motor; directional drilling