Study On Influence Factors Of Fracture Proppants Conductivity In Soft Coal Seam

Coalbed methane is one of the clean energies,it is widely distributed in our country.With the increase of unconventional oil and gas exploration degree,CBM development has also received more and more attention in recent years.In the reason of the low permeability characteristic,only by some stimulation measures can the coalbed methane be successfully exploited.Hydraulic fracturing is one of the most commonly used technologies.Proppants conductivity is an important factor affecting the fracture stimulation,which physical meaning is the product of width and permeability of support fracture.Compared to the conventional oil and gas reservoir,the soft coal seam has more complicated fracture morphology,the proppants are more likely to embed and the coal powder is output easily,the factors that affect fracture conductivity are also more complicated.Based on the reasearch of coalbed meathane fracturing,proppants fracture conductivity and evaluation of CBM fractures.This paper has described the rock properties,mechanics properties,microfracture morphology and stress state of target area.The conductivity experiment method has also been improved,the experimental scheme has been conducted which aimed to explore the condutivity change features in the condition of different proppant,different size combinations,different coal powder contend and different fracture morphology.Through the indoor experiment we found that in terms of proppant type combination,the best type is quartz sand and the low density ceramsite,the combination of two different characteristics can provide effective conductivity in both low and high closed pressure;in terms of proppant size composition,the best mixture is 20/40 and 30/50 match,the former can increase the frature width and the latter can help improving loading capacity.Considering the different network influence of conductivity,the best fracture morphology is vertical and horizontal combination model which is more helpful to build and maintain the high conductivtiy.When the closure pressure is low,the fracture conductivity is influenced greatly by the coal powder content and fracture network type.When the closure pressure is high,the fracture conductivity is influenced greatly by the proppant type and different size combination.The closure pressure has a great influence on the fracture conductivity,with the increase of closure pressure,the embeding of the proppant and the occurrence of the crushing condition have been increased,and the fracture width has been decreased in a certain extent,which reduced the fracture conductivity.