Production Characteristics And Prevention Measures Of Solid Particles In CBM Wells In Fanzhuang Block Of Qinshui

A certain amount of solid particles will be produced in the coal reservoir in the process of coalbed methane development,which cause certain damage to the reservoir and drainage and greatly restrict the efficient development of coalbed methane wells.This paper takes Fanzhuang development area in southern Qinshui Basin as the research object.On the basis of geological background of coalbed methane,through theoretical analysis,sampling test,production test,data simulation and effect evaluation,the influence of solid particles on coalbed methane well drainage and production is analyzed.The characteristics and influence factors of pulverized coal production,pulverized coal migration and pump jamming are studied emphatically,and the technology of solid particle prevention and control and shaft cleaning in Fanzhuang block is proposed.The results show that the pulverized coal production of coalbed methane well in Fanzhuang area has obvious regularity.The water quality of No.3 coal production well is clear in the process of drainage and production,which changes little after fracturing.The total production of pulverized coal in coal reservoir is small.While the water quality of No.15 coal production well is poor in the process of drainage and production,mainly dark black and black,containing a large number of pulverized coal particles.The total production of pulverized coal in coal reservoir is large.The water quality of the same well varies significantly in different stages.In the early stage of production,the water quality is mainly black and gray.Before desorption,the water quality gradually becomes worse,and after gas release,the water quality gradually becomes better,most of which is gray or colorless.The pore structure characteristics of coal reservoir determine the gas discharge rate of coalbed methane well,and the water quality is affected by the gas discharge rate.In the process of drainage and production,the gas discharge is too fast,which will lead to the increase of gas-water two-phase flow velocity and enhance the carrying capacity of solid particles of the fluid.The coal reservoir in the region has a small porosity,which will lead to the decrease of gas production capacity due to the blockage of pores.The coal body structure of the coal reservoir in the study area is relatively complete,most of which are original structural coals with a fast desorption rate of coalbed methane,so that the critical gas production pressure of the well is slightly lower than the critical desorption pressure on the whole,and the permeability of the coal reservoir is good,which is conducive to the smooth production of pulverized coal.In the fault detection pump of coalbed methane wells in Fanzhuang block,the influence of solid particles has the highest fault proportion,which is the primary factor affecting the production of coalbed methane wells.It is confirmed that pure pulverized coal particles will not cause pump jamming through the jamming test of coalbed methane well,which is caused by the mixture of asphaltene,iso-colloidal coagulant and pulverized coal particles.The solid particle settlement model of coalbed methane well is established,the special solid particle prevention pipe string structure of coalbed methane well is formed,downhole accessories were reduced and screens were removed,which effectively reduce the impact of solids on the string and extend pump inspection cycles.Aiming at the problem that solid particle accumulation in wellbore is easy to cause the failure of coalbed methane wells,the downhole tools such as vacuum recovery sand pump and pulverized coal scraper are applied.Compared with the traditional sand recovery tools,the cycles of pump inspection are greatly shortened and the effect of sand removal are significantly improved,which is conducive to the stable and continuous drainage of coalbed methane wells.The paper has 48 pictures,15 tables,and 70 references.