Study On Prediction Of In-situ Stress Of Coal Reservoir And Improvement Of Wear Resistance Of Measuring Instrument In Changzhi Block

The in-situ stress is one of the key parameters affecting the permeability of coalbed methane reservoir,and it is also the key factor controlling the fracturing and drainage measures of coalbed methane wells.Thus,the in-situ stress plays a crucial role in the exploration and development of coalbed methane.At present,there are two main scientific and technical problems in the study of in-situ stress coalbed methane reservoir:On the one hand,the existing in-situ stress of coal reservoir are mostly based on log data.So the accuracy of existing in-situ stress data has a strong dependence on log data and greatly influenced by the choice of calculation model.Therefore,it is necessary to evaluate and verify the relevant parameters and applicability of the calculation model.Meanwhile,for the area lacking log data,this method cannot be used to obtain the insitu stress data;On the other hand,the direct measurement of in-situ stress is usually used as a supplement to the log data calculation method to obtain the in-situ stress data for the area without log data.However,the measuring equipment of in-situ stress is easily affected by the underground complex environment.The hostile environment leads to the decrease of reliability and service life of the equipment,and leads to the decrease of data accuracy and the increase of cost.In view of the above two problems in the in-situ stress data acquisition,this paper carried out researches on in-situ stress prediction of coal reservoir based on well log data and the material performance improvement of in-situ stress measurement equipment.This paper studies the log data calculation results and coupling analysis of the insitu stress based on the data from Changzhi block of southern Qinshui basin,and proposed an Anderson model with residual tectonic stress to predict the in-situ stress distribution of research area.The results show that: 1)the prediction method is suitable for the calculation of in-situ stress data in the simple geological structure area,and it can reflect the distribution of the in-situ stress accurately in this area;2)in the research area,the influence of the buried depth is greater than the tectonic in the eastern part of the area,meanwhile the influence of the tectonic is greater than the buried depth in the western part;3)there is a high correlation between the distribution of the in-situ stress and the production of coalbed methane well.For the problem of reliability of in-situ stress instrument working in the complex geological conditions,this paper carried out a surface modification study by magnetron sputtering on the guide head,protective cover and other easily worn parts of the in-situ stress measuring instrument.The Cr N coating was used to cover the easily worn parts to improve their wear resistance,high temperature resistance and corrosion resistance,so as to improve the reliability of the equipment.The results show that the preparation parameters have great influence on the properties of the samples,and the friction and wear properties of the Cr N coated samples obtained under appropriate parameters are greatly improved.It has great application potential to improve the performance of worn parts in the in-situ stress measuring instrument.