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

Key words:  coalbed methane(CBM)  multi-lateral horizontal well  wellbore variable mass flow  wellbore pressure  wellbore inflow rate

Abstract:

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".