Application Research Of CBM Well Drainage Monitoring System In Multi Seam Monitoring And Drainage

Coalbed methane(CBM)is a kind of associated mineral existing in coal seams.It adheres to the surface of coal matrix particles in the form of a large amount of adsorbed gas,partially dissociates in coal pores or dissolves in coalbed water.The main component of CBM is CH₄,is a kind of high quality clean energy rising in the world in recent ten or twenty years.The CBM extremely easily explosion caused safety accidents in the coal mine,is one of the most important threat to safety production,the rational exploitation of CBM in coal mine has very important practical significance,it can not only improve the safety index of coal mine and protect the personal and property safety of mining employees,but also serve as an important support in the consumption structure of natural gas to ensure the security of energy supply in China and improve the unreasonable energy structure in some areas.Although China is rich in CBM resources,the buried depth less than 2000m and the geological resources of CBM is 29.82×10¹²m³ and the recoverable resources are12.5×10¹²m³,but at present,the exploration,development and utilization of CBM in some areas are very backward,so it is necessary to introduce and develop relevant advanced supporting technologies to promote the low-cost and efficient development of CBM.Multiple coal seams are widely developed in coal bearing strata in many areas of China.It is one of the important measures to reduce the development cost of CBM and improve the production capacity is to implement the combined layer drainage technology in the area with multiple coal seams,coordinated multi-layer co-production is very important for the efficient development of CBM Wells,and the acquisition of down-hole parameters is very important for the co-production of multiple gas sources in CBM Wells.However,there is no general CBM drainage and production equipment to complete the acquisition of relevant parameters.Developed and improved a set of vertical well section suitable for multi-coal seam co-mining,installed down-hole drainage parameters monitoring instrument and relevant acquisition system,and obtained the production situation and productivity contribution of each gas layer by using the mining parameters,achieve timely understanding of CBM well production horizon state,carry out the study of the high rank CBM development process and reasonable scheme and to realize the efficient development of the CBM Wells has important practical significance.According to the production needs,this topic has developed and improved the"CBM well drainage and monitoring system".The monitoring system can collect production parameters at different depths of coal seam,the collected data is uploaded to the ground industrial control machine after the long-distance cable sends out the command on the ground,and the production situation and productivity contribution of each gas layer are obtained by calculation the parameters.Through the obtained situation,the production status of the CBM well can be understood in time,and the potential problems of the CBM well can be found,and the plan of production discharge can be adjusted in time.It has important practical significance to improve the efficient development of CBM wells.The thesis mainly focuses on the optimization of CBM underground drainage monitoring system.The main contents are as follows:In the first chapter,the development purpose and significance of the CBM are explained,and the related contents of analyzes the development of multi seam coalbed at home and abroad and the content of using relevant monitoring instruments to record parameters to improve the development efficiency,and puts forward the research content of this paper.The second chapter introduces the mining mechanism of the coal reservoir,studies the micro-structure of the coal reservoir,and analyzes the flow of the fluid in the reservoir and the production mechanism during mining.The pore structure characteristics of coal reservoir are analyzed,the occurrence characteristics of CBM reservoir are introduced,and the production characteristics of CBM wells are introduced.The main explanation from three aspects:desorption mechanism,diffusion mechanism and seepage mechanism.At the same time,the flow pattern of gas in the wellbore is analyzed,and the influencing factors of CBM flow in the wellbore are introduced.The third chapter the components of CBM drainage and production monitoring system are analyzed and explained.Firstly,the framework of the monitoring system is introduced,followed by the components of the bottom hole bubble monitoring device,focusing on the composition design and detection circuit of the bubble sensor,and then the selected pressure sensor and related parameters are introduced,and the pressure sensor is calibrated;Subsequently,the temperature sensor is selected and calibrated.Finally,the data acquisition system is introduced,in which the data acquisition,transmission and storage system are explained.The waterproof and compression sealing experiment was carried out on the acquisition board and cable of the coalbed methane drainage and production monitoring system.In the fourth chapter,in order to clearly grasp the movement of bubbles in the wellbore,when the bubbles pass through the bubble sensor,the data recorded by the probe is drawn into the relevant map through the software to observe the bubble flow pattern in the wellbore,This chapter analyzes the test data of CBM well drainage and production monitoring system.The velocity and volume of bubbles are analyzed,and the numerical model suitable for CBM production capacity is selected.According to the relevant formula,the gas production formula of single layer under the condition of combined production is obtained.In the fifth chapter,the typical CBM drainage well FS-4 in Fukang mining area of Junggar basin is selected to record the whole process of the drainage monitoring system configuration to the well.At the same time,the data of JS-064 well in Jincheng mining area of Qinshui Basin are selected to record the whole process of the drainage monitoring system configuration to the well.According to the relevant parameters obtained by the downhole monitoring probe,the parameters are substituted to simulate the situation in the wellbore,so as to understand the reservoir situation.In the sixth chapter,the application prospect of CBM drainage and production monitoring system is prospected.The seventh chapter draws the conclusion of this paper,points out the innovation of this research,and looks forward to the future in-depth research.In the sixth chapter,the application prospect of CBM drainage and production monitoring system is prospected.The seventh chapter draws the conclusion of this paper,points out the innovation of this research,and looks forward to the future in-depth research.The innovation points of this paper are as follows:(1)Change the independent upload of multiple short joints,multiple points and multiple lines in CBM wells to single bus upload.The monitoring system of CBM well lower drainage and production changes from the previous design that each underground main sub should upload data to the ground control device through the cable,to the current multi line convergence,upload through a bus,and upload the data detected by multiple underground main sub orderly through each underground main sub.(2)Complete the identification of flow pattern of gas-liquid two-phase flow in simulated wellbore.When the bubble passes through the bubble sensor,the data recorded by the probe can be drawn into the relevant graph by the software.Through the graph,the current gas-liquid two-phase flow pattern in the wellbore can be clearly understood,which provides some reference for the subsequent discrimination of the wellbore flow pattern in production.(3)Differentiation of gas production contribution of each layer by using multi gas source reservoir parameters collected.The bubble,pressure and temperature data collected from different coal seams in the wellbore annulus are calculated,and the relevant temperature,pressure and bubble data are derived.The gas production rate of each layer is calculated by using the productivity formula,so as to deduce the gas production contribution rate of each layer.The situation in the wellbore is simulated by using the multiphase flow steady-state simulation software.To sum up,the research and development of CBM well drainage monitoring system makes comprehensive use of multidisciplinary theory and technology,and completes the judgment of production horizon state in CBM well multi reservoir drainage.During the research and development of the monitoring system,it mainly studies the characteristics of coal reservoir,the mechanism of coal drainage,the composition design of sensor,the detection circuit of bubble sensor,and the underwater sealing of the monitoring system.However,there are still many related studies to be further studied in the follow-up work.