Research On Negative Pressure Drainage Of CBM Wells

The two major coalbed methane industrial bases in Qinshui and the eastern margin of the Ordos Basin face an average single-well production that is generally low,and when the reservoir pressure is reduced to abandonment pressure,there will still be a large amount of adsorbed gas that is not desorbed and free gas not produced in the coal reservoir Therefore,new technologies for increasing production are urgently needed.Negative pressure drainage technology is conducive to reducing downhole flow pressure to promote further desorption of coal bed gas,and pressurized conveyance of gas from the wellhead to the pipe network,which provides new ideas for increasing coal bed gas production.Although the coalbed gas well negative pressure drainage production has achieved good results in field experiments,no systematic research on negative pressure drainage production has been formed.In this paper,laboratory tests of negative pressure desorption of different watercontaining coal samples were carried out.It was found that the negative pressure desorption curve can be regarded as an extension of the atmospheric pressure desorption curve;and around the negative pressure drainage and extraction,the coal bed gas desorption amount,reservoir seepage rate,and reservoir damage,etc.In terms of the impact,the potential production increase factors of negative pressure drainage are discussed in detail.Based on the negative pressure gas production process,a negative pressure drainage production process was formed,and the negative pressure drainage selection well conditions and negative pressure drainage intensity control ideas were determined.Based on the block desorption curve and the coalbed methane production status,negative pressures were formulated respectively.Timing of equipment on the well.Pilot tests of negative pressure drainage and production stimulation were carried out in the J19 well group and B4 well group in the Bao De test area,which effectively solved the problem that the output of the production well casing was lower than the pressure of the pipe network system,which could not be transported outside,the low-production and low-efficiency wells,and the decline in wells near the coal mine The problem is too fast,and it is found that the use of reciprocating compressor skids for negative pressure equipment will obtain greater economic benefits.Finally,the B8-X2 well in the Baode test block has been put into production as an example to illustrate the optimization of negative pressure drainage and production of coalbed methane wells.This paper makes up for the gaps in the negative pressure desorption of coalbed methane and the theory of negative pressure drainage production and production stimulation.It has certain guiding significance for negative pressure drainage production and selection wells,timing of negative pressure equipment uptime and negative pressure drainage production intensity control.The application of large-scale negative pressure drainage to increase production has laid the foundation.