Nuclear logging is one of major areas of logging development. This paper presents an empirical investigation to bring the drilling and completion of wells from an ill-defined art to a refined sci-ence by using radioactive source to “look and measure” such as formation type, formation dip, porosity, fluid type and numerous other important factors. The initial nuclear logging tools rec-ords the radiation emitted by formation as they were crossed by boreholes. Gamma radiation is used in well logging as it is powerful enough to penetrate the formation and steel casing. The ra-dioactive source is reusable so that after engineer finished the job the radioactive source is sent back to bunker. In this case inventory level of radioactive source is relatively high compared with monthly movement and the company must spend large amount of cost just for inventory. After calculating and averaging the monthly movement in 2014 and 2015, we detected a big pos-sibility to cut the inventory level to reduce the inventory cost.

This research presents detailed notes on the penetrating geological formations of the wellbore. Logs can be presented in two forms of good geological logs, means visual inspection of surface-carrying samples, and geophysical logs, means physical measurements by instruments that are lowered into holes. Logs that are created during drilling are called real-time logs. LWD tool is produced from real-time data transmitted to the surface computer from downhole. Three common services are Natural Gamma Ray, Resistivity, and Porosity and Bulk Density. The output of an LWD service is a log. A log is a graphical representation of the properties of the formation. Some factors that affect data quality are Depth Calculation, Sensor Malfunction and LWD Tools Measurements Fault. During drilling, borehole path monitoring is the important thing to be maintained because the quality of LWD data is critical for the success of any LWD job. Therefore, the field engineer has to understand the factors that affect data quality. Quality Control Process is the key to ensure that the tools are working properly.

The present invention provides a modular drilling assembly having a module for contactless power and data transfer over a nonconductive gap between rotating and non-rotating members of a steering module. The gap usually application data contains a non-conductive fluid, such as drilling fluid, or oil for operating hydraulic devices in the down-hole tool. The down-hole tool in one embodiment is a modular drilling assembly wherein a drive shaft is rotated by a down-hole motor to rotate a drill bit attached to the bottom end of the drive shaft. Generally, there are two main sections on mud motor which are bearing section and power section. The power section generally includes a housing which houses a motor stator within which a motor rotor is rotationally mounted. The power section converts hydraulic energy into rotational energy by reverse application of the Moineau pump principle. The stator has a plurality of helical lobes which define a corresponding number of helical cavities. The rotor has a plurality of lobes which number one fewer than the stator lobes and which define a corresponding plurality of helical cavities. Generally, the greater the number of lobes on the rotor and stator, the greater the torque generated by the motor. Fewer lobes will generate less torque but will permit the rotor to rotate at a higher speed. Based on torque and rotate speed, determine the optimum power can be produced by power section configurations.