Development And Application Of Azimuth Gamma While Drilling Measurement System

The conventional natural gamma while drilling measurement system can not accurately judge whether the current wellbore trajectory enters or leaves the reservoir from the bottom or top of the reservoir.Azimuth gamma while drilling measurement system can tell whether the hole is at the top or bottom of the reservoir according to the shape of the azimuth measurement curve.The dip angle and thickness of the reservoir can be calculated by using the shape of azimuth gamma curve and the geometric parameters of borehole trajectory,thus providing a more accurate basis for the adjustment of wellbore trajectory.Therefore,it is of great significance to develop and apply azimuth gamma along with measurement system.Based on the research of gamma ray characteristics and direction measurement technology of formation,the theoretical foundation of gamma ray measurement method while drilling is established,which is based on the electronic measurement technology of special sensor and related downhole information,signal processing and signal transmission technology.The overall design scheme of azimuth gamma while drilling measurement system is put forward,the relative factors of interference azimuth gamma measurement data accuracy are analyzed,and the detection signal is converted from time domain to frequency domain by FFT(Fast Fourier transform)technique.The interference signal in the detection signal is identified in the frequency domain,and the frequency band of the interference signal is determined.The method of filtering interference signals by digital filtering technique is obtained,and the formation structure model of borehole trajectory at different lithologic strata and interface of different lithologic strata is established.The response characteristics of azimuth gamma measurement curve are simulated.The lithologic distribution and characteristics of drilling strata corresponding to azimuth gamma measurement curves are obtained when the azimuth gamma measurement curves show different shapes.According to the morphological characteristics of azimuth gamma curves and the geometric parameters of borehole trajectory,the reservoir dip angle is derived.The calculation method of reservoir geometric parameters,such as reservoir thickness,is used to simulate the sandstone reservoir whose borehole trajectory is in a sandstone thin layer and the dip angle changes in the process of azimuth gamma-while drilling geological guidance.The response of azimuth gamma two-dimensional imaging map in sandstone reservoir with multi-layer mudstone thin layer and fault is analyzed and the response characteristics of azimuth gamma two-dimensional imaging map to different types of complex stratigraphic environment are obtained.The successful application of azimuth Gamma system in Well Yingping 18-4H and Hongtai 23-P5-3 well shows that the system is successful and can meet the requirement of improving the drilling rate of reservoir in the process of geological guidance.