| Coal powder production is one of the main issues controlling the well productivity.The gas,water and solid flow model and numerical simulation researches are the technical difficulties of coalbed methane simulation.The motivation and main research of this thesis comes from the scientific problem in China 12th FIVE Major Project coalbed methane vertical well testing and numerical simulation research in South Qinshui Basin(2011ZX05060-004).The current stages of coalbed methane production do not consider the influence of coal powder,of which migration has a dramatic effect on well productivity.The desorption on coal powder migration in coalbed has multi problems,including(1)the coal powder type,production stages,flow channels and physical production stages;(2)establishing the flow model considering coal powder migration,sediment and plug;(3)the solution and simulation method of the math model considering the coal powder.This thesis is based on coal powder generation,migration,sediment and plug processes modeling and realizes the simulation method.Then five production experiments are designed with reference to analysis of coal powder sources,stages,types and flow channels to explore the simulation with coal powder influence.The main content of achievements of this thesis are following.1.Compared the coal component from neighbouring region by analysis of industry composition,XRD,and mercury injection,it is concluded the average moisture,ash,mineral,clay content of SZ block are 4.02%,18.33%,19.38%,68%,respectively.The average porosity is 5.41%,of which huge pore takes 4.43%,The coal matures with fractures,of which density is 5-15 per centimeter.As the fractures are filled with kaolinite and illite,the coal powder is easy to produce during production.2.Based on coal powder size,the coal powder production is divided into 3 stages with different generation mechanism.The first stage is controlled by shearing damage.The second stage is controlled by shearling,stretching and cementing damages.The third stage is controlled by stretching and cementing damages.The coal powder production depends on production schedule and the fractures are the main channels of coal powder migration based on lab analysis of core.3.Based on the coal powder production stage and methane production,the coal powder,formation water and methane flow model is established.This model including the velocity model between coal powder and water,coal powder sediment,fracture flow and matrix flow models,which can describe the coal powder generation,start,migration and sediment process.Then the parameter experiments are designed with the coal powder maximum flow capability experiments,coal powder generation,flow difference between water and coal powder liquid,coal powder sediment and velocity sensitivity experiments.4.The facility is developed which can evaluates coal powder generation,migration,sediment and plug.The facility is composed of vacuum modular,core flow modular,visualization modular,bottom water modular,confining pressure modular,back pressure,calculation modular,and temperature and data collection modular.The coal powder maximum flow capability experiments,coal powder generation,flow difference between water and coal powder liquid,coal powder sediment and velocity sensitivity experiments are conducted.The relation of flow velocity and coal powder migration capability,the coal powder concentration and water velocity,displacement velocity and generation volume,permeability performance in fractures and velocity sensitivity are achieved5.The numerical model is established to solve the model combining the flow velocity,permeability and conductivity relation from experiments.The coal powder simulation is performed by SZ block case to test our model.The results indicate that the coal powder migration has a dramatic influence on well production.The water production need to produce the coal powder based on no coal powder sediment.The optimized production schedule is 5.5m3/day. |
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