Proppant flowback after fracturing coal bed methane (CBM) wells is a very common challenge which results in fracture pinching out, noticeable well productivity decrease, downhole and surface facility damage, etc. In this paper, fibre was studied as a low-cost and environmentally friendly additive to control proppant flowback in CBM well fracturing operation. Two kinds of glass fibre (short fibre and long fibre) are selected. Extensive experimental studies have been conducted to test the effects of fibre concentration and fibre control length exerting on the critical proppant flowback rate. The optimal fibre combination is 1:2 as the mass ratio of long fibre to short fibre. And fibre control length is 225 mm in a 300 mm tube. An optimisation model is also presented to optimise the fibre concentration and fibre control length in the field application. So the in-situ fracturing design can be conducted by repeating fracture propagation and proppant transport simulations and parameters optimisations. The experimental results and the optimisation model were applied in CBM well fracturing in Hancheng area in China. 23 tested wells have achieved a significant increase of gas production and decrease of workover times than the 9 offset ones without fibre-added sand.
Keywords: coal bed methane, hydraulic fracturing, proppant flowback, glass fibre, experiment study, critical flowback rate