Analysis of factors influencing the productivity of horizontal wells in Gujiao coalbed methane block of Qinshui basin
In recent years,horizontal wells have gradually become the main well type for coalbed methane development in China,achieving significant gas production results in multiple blocks.However,there is a large difference in production between wells,and the overall production rate is relatively low.To understand the factors affecting the production capacity of coalbed methane horizontal wells,research is conducted from the aspects of geological factors,engineering processes,and drainage management.Selecting 20 L-shaped coalbed methane horizontal wells in the Gujiao block of the northern Qinshui basin,based on geological conditions and production performance analysis,10 key parameters were selected,including gas content,well controlled geological reserves,drilling quality,reservoir transformation,and production performance parameters.The impact of these parameters on the production capacity of coalbed methane horizontal wells was discussed,and targeted technical countermeasures suitable for the geological conditions of the study area were proposed.Research has shown that coalbed methane horizontal wells located in structurally high positions,gas content,gas saturation,and well controlled geological reserves are the resource foundation for achieving high production rates.In the case of simple structure and undeveloped faults,the horizontal section length should be above 600 m,with a coal seam drilling rate should be ensured to be over 80％.When the horizontal section length is between 600 and 800 meters,the number of fracturing stages should be controlled below 10,and the optimal fracturing length of each fracturing stage is 60-80 m.Efforts should be made to reduce the number of interruptions during drainage,improve the continuity of mining and drainage.Different reasonable pressure drop rates should be set during the drainage and production periods,respectively,to increase the drainage area and achieve maximum production capacity release of coalbed methane horizontal wells.
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