In order to improve the accuracy of magnetic azimuth measurement,it is often necessary to establish a more accurate local geomagnetic model to obtain precise magnetic declination information.Compared with global geomagnetic model, local geomagnetic model contains magnetic anomaly information caused by underground magnetic ore veins at the surface.Considering the different burial depths and sizes of underground magnetic veins,their effects on magnetic declination at different borehole depths differ significantly.Therefore,it is necessary to consider the correction of the azimuth angle of medium and deep wells under the influence of underground magnetic veins.Based on ANSYS Maxwell numerical simulation software,the geomagnetic field model under the influence of magnetic veins of different burial depths and sizes was established.Through numerical simulation method and actual drilled borehole trajectory of a medium?deep well (Z well),a method of azimuth correction was given to quantitatively analyse the influence of underground magnetic veins on the azimuth and borehole trajectory.The results of the study show that the effect of underground magnetic veins on the azimuth of drilling within the 2 000 m thickness stratum is about 0.6° under the condition that the magnetic veins are buried at a depth of 2 100 m.After considering the influence of underground magnetic veins,the borehole trajectory is inevitably offset,and the offset increases with the depth of the well,which may cause off?targeting and other accidents for medium and deep wells.Therefore,it is of great significance to consider that the azimuth correction under the influence of geomagnetic veins can strongly improve the azimuth measurement accuracy and realise accurate guidance.

Heterogeneous Mn₃O₄/CuMnO₂ catalyst CMO-A is prepared by a one-step hydrothermal method using cupric chloride dihydrate and manganese chloride tetrahydrate as raw materials.The composition of the samples prepared at different temperatures is analyzed by X-ray diffraction analysis.Using mercury lamp as light source and 50 mg/L Rhodamine B(RhB) solution as contaminant model,the photo-Fenton reaction performance of the prepared CMO-A sample is tested.The results show that CMO-150 has the best degradation effect on RhB solution when the reaction temperature is 150 ℃,and the degradation rate reaches 98.01% when the reaction time is 15 min.The optimal reaction conditions and cyclic stability of CMO-150 catalyst are investigated.The experimental results show that the optimal reaction conditions are 0.2 mol/L H₂O₂,50 mg CMO-150 catalyst,50 mg/L RhB solution and pH=3.0.After 5 cycles,the degradation rate only decreases by 22.24% at 15 min.The main active species in the reaction is hydroxyl radical (·OH) through the sacrificial agent experiment,and the reaction mechanism is explored by combining with the control experiment.