Productivity model of CBM wells considering the stress sensitivity and its application analysis

The stress sensitivity of the coal reservoir is one of the geological factors affecting the productivity of CBM wells, how to reduce or avoid effect of the stress sensitivity on CBM well production is a question worth considering in CBM wells production process. Through the analysis of the stress sensitivity of coal reservoir, the productivity model of CBM wells considering the permeability stress sensitivity was deduced, then the yield reduced the magnitude of value (β) was put forward to describe the influence degree of the stress sensitivity on the productivity of CBM wells, and the impact of the effective stress on the permeability of coal reservoir and the effect law of CBM wells productivity were finally revealed. Research results show that the permeability of coal reservoir reduces with the effective pressure increases by the negative exponential law and coal reservoir shows obvious stress sensitivity during the development of CBM wells. The productivity of CBM wells which consider the stress sensitivity of the coal reservoir is lower than that don't. With the producing differential pressure increases, CBM wells productivity increases significantly, and gradually tend to be stable, and the yield reduced the magnitude of value (β) increases meanwhile. The value (β) should be the overall increased with increasing the stress sensitive coefficient of coal reservoir. The production of CBM well increases to a lesser extent with the pressure difference increases and gradually tend to be stable. Enlarging the production pressure difference can not get the maximum yield. Therefore CBM development need to be draw up a reasonable production pressure difference and strictly control the production intensity.