Optimization Of Deep Coal Seam Fracturing Process In Linxing-Shenfu Block

The coal seams in the Linxing-Shenfu block are deep and there are significant differences from shallow coal seams.Conventional active water fracturing is difficult to effectively fracture coal seams,and sand blocking problems exist due to low sand carrying capacity.The clean fracturing fluid has strong sand-carrying and fractureforming capabilities,but there is controversy and high cost for coal seam adsorption.It is necessary to optimize the fracturing process by combining active water and viscoelastic clean fracturing fluid.The purpose of coal seam fracturing is to form a sand-filling crack with fracture conductivity,and the conductivity of fractures is usually related to the proppant placement in the fracture,so the study of proppant placement is very important.In this paper,the visual cracking device is first used to comprehensively analyze the laying rule of proppant in active water and clean fracturing fluid from the aspects of sand dike formation process,displacement,sand ratio and proppant particle size.Then on this basis,the use of digital simulation software to carry out the study of the proppant placement law of viscous and non-viscous fracturing fluid alternately pumped,and optimize the relevant parameters of alternate injection.The results of the study show that there are large differences in the laying rules of proppant in viscous fracturing fluid and non-viscous fracturing fluid,the sand dike formed in the viscous fracturing fluid is relatively long but the proppant at the entrance of the crack is laid less,and the sand dike formed in the active water is shorter but the height of the sand dike is higher.The two combined liquids are used to carry sand,the viscous fracturing fluid lays the depth of the crack,and the non-viscous fracturing fluid lays the front end of the crack,which can improve the overall proppant lay-out form in the crack.Based on the optimized parameters,a field test of alternating fracturing fluids of viscous and non-viscous fracturing fluids was conducted on the LX-W well.The construction process was smooth and the drainage effect was remarkable.This study provides some guidance for fracturing and increasing production of deep coal seams in this block.