| During the process of drilling, directional engineer and geologist want to know timely more about formation parameters of borehole and control the borehole trajectory in terms of higher drilling and recovery efficiency. Generally the value of natural gamma ray of virgin formation is related to its mud-content. Therefore, a kind of natural gamma ray tool service for logging while drilling (briefly called LWD) has been developed already.This paper systematically introduces all parts of the tool including design, methods and apparatus. there are as follows. Fisrt: bring forward dissertation necessity and its main contents after analyzing to national and international situation. Second: introduce of basic principle, calibration and survey methods, factors affected on gamma response and main technique specifications of gamma tool. Third: main introduce circuit design involved in downhole electrical system and communicational interfaces and downhole software programming consisted of subprograms of gamma count, real time communication with measure-while-drilling (briefly MWD) system, parameters correction and data recollection. Fourth: study of stability and reliability related to anti-noise technology. Last: introduce tests and conclusion during tool development. natural gamma ray tool is feasible confirmed by experiment and field application.
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