煤层气多分支水平井井身结构优化

摘要

Multi-lateral horizontal CBM wells can effectively increase the drainage area, reduce the skin factor and remarkably increase production capacity. In order to obtain the most cost-effective production capacity, the optimization of such wells’ wellbore structure is essential. This paper investigates the effects of coal seam dip angle, reservoir protection and wellbore structure on the pro-ductivity of horizontal CBM well. Taking a multi-lateral horizontal CBM well in 3# coal seam for block of the southern Qinshui basin, as an example, numerical simulation is conducted to optimize the parameters of the wellbore structure. It turned out that, the orientation of main hole had great impact on production capacity, with the most preferable orientation as perpendicular to the direction of main permeability;the production capacity increased with the lengths of main hole and laterals, which taking the economy and enhancement effecs should be controlled in 900~1 300 m and 250~400 m respectively;the spacing between laterals and the angle between main hold and lateral also impair the production capacity to some extent, which should be controlled in 200~300 m and 36°~53° respectively. The research results will provide reference for designing the wellbore structure of CBM multi-lateral horizontal well.%煤层气多分支水平井能有效增加控制面积，降低表皮因数，其井身结构优化对获得最经济有效的产能至关重要。为此，分析了煤层倾角、储层保护和井身结构对煤层气水平井产能的影响。采用数值模拟的方法，以沁水盆地南部某区块3#煤层为例，对多分支水平井的井身结构参数进行优化。优化结果表明：主支走向对产能影响较大，适宜的方向为垂直主渗透率方向；产能随着主支长度和分支长度的增加而增加，结合经济性和增产效果，主支长度宜控制在900~1300 m之间，分支长度宜控制在250~400 m之间；分支间距和主分支夹角在一定程度上影响产能，分支间距宜控制在200~300 m之间，主支和分支夹角宜控制在36°~53°之间。研究结果可为煤层气多分支水平井的井身结构设计提供参考。