Mechanism And Application Of Biodegradable Fibers In Coalbed Methane Fracturing

At present,the active water fracturing fluid is generally preferred when the CBM reservoir is reformed.However,the active water fracturing fluid has the problems of weak sand carrying capacity,strong filtration loss,and high sand plugging risk in the CBM reservoir fracturing.In addition,China's CBM reservoir geology is relatively brittle.When coal-bed gas development is carried out,large amounts of coal powder will be produced.At present,methods for controlling the movement of coal powder such as active agents and screw pumps are relatively expensive,and the active agent has strong adsorption and is not easily broken at low temperatures.According to the investigation,the fiber fracturing fluid has many advantages such as: solve proppant flow back problem,improve the sand carrying capacity of the sand-carrying liquid,easy to flow back quickly,improve the fracture conductivity,and the low damage of the fracturing fluid to the fracture.There is few researches on controlling the movement of pulverized coal.Therefore,fiber fracturing fluid technology is proposed for coal powder treatment.This paper mainly studies the performance of fiber fracturing fluids and the influence of degradable fibers on the movement of pulverized coal,and analyzes the mechanical action mechanism of fibers on pulverized coal.Firstly,based on the properties of coal samples,KTL1 fibers are formulated into fiber fracturing fluids in terms of fiber and proppant compatibility,static suspension experiments,reservoir damage,etc.,and then the rheological properties of the configured fiber fracturing fluids are tested.The optimum fiber addition amount is 1% according to the sand-carrying performance of the fracturing fluid,then a suitable fiber fracturing fluid is preferably selected and applied to the development of the coal bed gas.Based on the force analysis of coal powder in the fracture and the microstructure of fiber-proppant,a critical particle size model of coal powder is built,and the model is mainly related to fiber properties,proppant particle size and flow velocity.To verify the critical coal particle size model,the FCES-100 fracture deflector is used to study the influence of fibers on the transportation of pulverized coal in the proppant pack.Five groups of comparative experiments are set up,namely,no fiber,0.25 g undegraded fiber.,0.25 g degradable fiber,0.5g undegraded fiber,0.5g degraded fiber,change flow rate and closure pressure,and conduct particle size analysis of discharged pulverized coal.The experimental results show that fiber and proppant can form a space network structure that can effectively intercept coal powder,which decreases the probability of pulverized coal migration and agglomerating,and thus it is beneficial to improve the fracture conductivity;With the increase of the flow velocity,coal particle size shows an increasing trend.By comparing the particle size of the pulverized coal with the model calculation results,the average error is 19.6%,and the maximum error is 28.9%.The fracturing optimization design of LX-2S well is carried out by applying the fracturing design software Meyer.The results show that the fiber fracturing fluid has good sand carrying ability and can carry the proppant to the depth of the fracture to form an effective support fracture.Fiber fracturing fluid technology is bound to promote new progress in CBM exploration and development.