Abstract
Abstract. The working environment in hot dry rock boreholes, encountered in deep geothermal investigation drilling and ultra-deep geological drilling (up to 5000 m), is very difficult at the present stage. We have developed a drilling trajectory measuring instrumentation (DTMI), which is based on the interference fiber-optic gyro (FOG). This can work continuously, for 4 h, in an environment where the ambient temperature does not exceed 270 ∘C and the pressure does not exceed 120 MPa. The DTMI is mainly divided into three parts: an external confining tube, a metal vacuum flask, and a FOG measurement probe. Here, we focus on the mechanical design, strength, and pressure field simulation analysis for the external tube, the structural design and temperature field simulation analysis for the vacuum flask, and the FOG Shupe error analysis and compensation in the temperature field. Finally, through the engineering applications of the SK-2 east borehole of the China Continental Scientific Drilling (CCSD) project and the geothermal well of Xingreguan-2, the data measurements of the drilling trajectory were used to analyze the stability of the DTMI. The instrument realizes long-duration, high-stability work in the process of making trajectory measurements in an ultra-deep hole. The instrument has the characteristic of anti-electromagnetic interference and enables work to be carried out in the blind zone of existing technologies and instrumentation. Therefore, DTMI has great potential in the promotion and development of geological drilling technology.
Highlights
With the recent rapid development of the national economy, shortages in resources and energy have become major barriers to economic development
We carried out pressure field simulation analysis for the pressure-bearing outer tube
The structural design of the metal thermos was examined, and we carried out temperature field simulation analysis, measuring with the fiber-optic gyro (FOG) in the probe
Summary
With the recent rapid development of the national economy, shortages in resources and energy have become major barriers to economic development. The depth of drill holes for mineral resource exploration and extraction is constantly increasing. The development of drilling engineering, in the field of high-temperature geothermal energy and shale gas, is included in the development plan of China (Chen et al, 2015). With increases in borehole depths, there is an increase in temperature. Areas of high geothermal energy, and other areas with anomalous geothermal gradients, the temperature will be higher (Osipova et al, 2015; Chen et al, 2015). When the depth of the borehole (well) increases, the degree of borehole deviation increases. With the increasing depth of deep mineral resource exploration and geothermal resource exploration and development, the drilling path or trajectory needs to be more and more accurate (Xu et al, 1996).
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