煤层气多分支水平井井筒压力及入流量分布规律

运用流体力学相关理论,结合质量守恒和动量守恒方程,推导考虑多分支水平井井筒内摩擦压降、加速度压降和混合压降的井筒压降模型,建立煤储层渗流与多分支水平井井筒内变质量流耦合的数学模型,并对其进行求解;在此基础上对煤层气多分支水平井主井筒及分支井筒的井筒压力及入流量分布进行研究。结果表明:开采期间,煤层气多分支水平井主支和分支井筒的压力均随距跟端距离的增大而增大,但主井筒压力增加的幅度越来越小;在开采前期,煤层气多分支水平井主井筒入流量分布曲线呈上凸趋势,在开采后期则呈下凹趋势;各分支井筒入流量在开采前期呈U型分布,在开采后期呈倒U型分布。

Wellbore pressure and inflow rate distribution of multi-lateral horizontal well for coalbed methane

According to corresponding hydrodynamic theory and combined with the principles of mass and momentum conservation, a pressure drop model along a multi-lateral horizontal wellbore was derived, in which the influences of wellbore friction, flow acceleration and mixture on the pressure drop were considered. The mathematical model was coupling with the gas flow in coal-bed with a variable mass flow in multi-lateral horizontal wellbore, and the solving method was given. Based on the model, the distribution characteristics of the wellbore pressure and inflow performance along the main and lateral wellbores were studied. The results show that, during gas production, the pressures in the main and lateral wellbores increase with the increase of the distance to the heel, but the extent of this pressure increasing in the main wellbore reduces gradually. The curve of the main wellbore inflow rate distribution is convex at the early production stage while the curve is concave at the later production stage. The curve of the lateral wellbore inflow rate distribution is the shape of "U" at the early production stage, while at the later production stage, the curve is the shape of reverse "U".