Error Correction Method Of Measurement While Drilling And Its Application In Shale Gas Horizontal Well Drilling

In the development of the Changning shale gas field in Sichuan,the method of cluster horizontal wells or wells is widely used.In order to prevent the collision of the upper dense cluster sections and accurately control the wellbore trajectory of the inclined and horizontal sections,the vertical section during the well construction process The construction uses conventional MWD monitoring,and the directional and horizontal section drilling uses a rotary guiding tool.Due to the geographical location of the Changning area and the speciality of geological complexity,when the azimuth is in the special case of 90° or 270°,the magnetometer is most affected by the magnetic field,and the measured azimuth angle will have an error.The rotary guiding tool used in the directional and horizontal section drilling construction is a combination of the gamma probe and the MWD measuring module.Since the measurement of the gamma probe is susceptible to the vibration of the drilling tool in the formation and the potassium chloride content of the drilling fluid is too high,When the diameter of the well is enlarged,the gamma value of the drilling will be deviated,which will affect the accuracy of vertical well anti-slope and well trajectory control.In this paper,the problems of well inclination,azimuth and gamma correction while drilling and accurate control of well trajectory are studied in the above horizontal well drilling construction.Through the measurement of the parameters and the analysis of the influencing factors of the calculation error,the indoor test experiment,the test well verification and the actual engineering application,the temperature compensation correction method of the inclination angle,the magnetic flux measurement error correction method of the azimuth angle,and the chlorination in the drilling fluid are respectively established.Potassium content and wellbore expansion method for measuring gamma value error correction,and formed a set of engineering application measures suitable for the region.Laboratory calibration and test wells and field applications show that after correction by the established method,the relative error of the inclination angle can be controlled within 0.02%,the azimuth relative error is within 0.56%,and the relative error of gamma value is within 2.04%.It meets the engineering requirements for precise control of drilling anti-collision and well trajectory in the area.