Performance Evaluation And Study On The Law Of In-slot Transportation Of Self-suspending Proppant

Increasing the transport efficiency of fracturing proppants and making which orderly into the deep reservoirs is of great significance for improving the fracturing effect.The self-suspending proppant(SSP)is made of quartz sand or ceramsite,and a thin layer of hydrogel polymer is wrapped around it to suspend it in fracture liquid by expansion or adsorption of external hydrogel during transportation.Which is a new type of efficient delivery proppant system.At present,the industry standard for proppant evaluation does not apply to SSP.There did not form a complete system,and there only existed qualitative research of suspension and transport mechanism of SSP.Therefore,it is necessary to improve the performance evaluation system of SSP and its transportation law in complex fractures.In this paper,a systematic test method for the performance evaluation of inflated SSP was eatablished,and the suspension and conductivity performances of three commonly used SSP.Considering the various forces between solid-liquid two phases,the SSP transport model in complex fractures is established by computational fluid dynamics method,and the semi-implicit method for solving the pressure-coupled equations is used to solve the problem.The correctness of the model was verified by comparing the experimental results of the SSP and the conventional proppant.The mechanism and effects of the SSP in fractures were verified based on the previous experimental parameters.The factors have been studied and the following findings have been achieved.(1)The concept of self-suspended critical concentration and the evaluation index for describling the final sand pile volume and settling time of the SSP system are proposed.(2)The SSP has good heat resistance,can be kept stable below 100oC,and has good shear resistance.The SSP system has almost no residue after breaking the glue,and the damage rate is lower than that of the guar fracturing fluid.(3)The Euler-Eluerian method was used to establish a numerical model suitable for the migration of SSP in complex fractures.The experimental results of SSP and conventional proppant were used to verify the correctioness and feasibility of the model.(4)Most of the proppant is suspended in the fracturing fluid during the migration process,and a small amount of proppant settles at the bottom of the fracture to form a thin sand dune,but the sand dune still has fluidity.(5)Factors affecting the migration of SSP in the fracture include proppant density,proppant particle size,injection rate,proppant concentration,and fracturing fliud viscosity.Among them,the proppant concentration and the viscosity of the fracturing have great influence.The higher the proppant concentration,the higher the visicosity of the fracturing fluid,the better the proppant suspension and migration performance.(6)The SSP has a good conveying effect in the branch fractures of complex fractures,which is beneficial to improve the paving efficiency of the proppant in complex fractures.