Research On Flexible Proppant Fracturing Transmission Technology

Hydraulic fracturing is one of the main techniques to improve oil recovery at home and abroad,in which fracturing fluid and proppant is an important part.The water base fracturing fluid has gone through from the active hydraulic fracturing fluid to the thickened hydraulic fracturing fluid and then to the water gel fracturing fluid.Although many types of fracturing fluid,but they are more or less some problems,such as active water fracturing fluid with water,low viscosity,high cost;thickening water fracturing fluid viscosity,sand carrying performance;water gel fracturing fluid gel breaking is not complete,high residue content,reduced filling permeability etc..The traditional quartz sand proppant has the advantages of small compressive strength,high cost of preparation of ceramic proppant,short shelf life of coated proppant and so on.Based on the above problems,this paper proposes a kind of flexible proppant fracturing transmission technology,which provides a new research direction.The flexible supporting agent coated by a layer of polymer above the outer-surface could be swelled quickly when soaked in water,and it can be suspended when the buoyancy is greater than gravity,and so that it could expand the transmission radius,avoid the accumulation of proppant,then the filtration loss get reduced and proppant would be transmitted to the edge to the fracture branch,and reduce the damage to the stratum.Based on the analysis of the feasibility of the preparation of the self suspending proppant,the monomers of acrylic acid and acrylamide were synthesized,and the crosslinking agent was N,N'-methylene-bis-acrylamide.The coating layer of the support was synthesized by aqueous solution polymerization.Through the comparison of the preparation process,the preparation of the flexible proppant by the fluid bed process.In this paper,the optimum conditions for the synthesis of the coating layer are obtained by selecting the formula of the expansion ratio,the expansion rate,the suspension factor and the strength of the coating.The microstructure of the coating was characterized by IR and SEM.The results show that the microstructure of the coating is consistent with the molecular structure.At last,the performance of the hydraulic fracturing fluid was evaluated,and the evaluation criteria were as follows:the expansion ratio,the expansion rate,the strength and the suspending factor.The flexible proppant fracturing fluid was formulated into different temperature,salt concentration,Ca2+,Mg2+ concentration,suspension,filtration,gel breaking and other related performance evaluation when using.In addition,the gel was characterized by IR spectrum and gel chromatography,and the core damage test was carried out.The research shows that the flexible support agent can meet the demand of construction of fracturing fluid,such as the temperature,expansion ratio of flexible support agent can reach the requirements of the suspension,suspension factor greater than 1,the suspension performance can be satisfied;the content of NaCl in saline solution below 40000 mg/L,the flexible support agent can be suspended,and in the formation of Ca2+ and Mg2+ with almost no influence on the suspension.Therefore,the fracturing fluid can be prepared by formation water or sea water to solve the problem of oil field water consumption.In addition,the flexible support agent showed that the gel breaking under each temperature the viscosity of the gel breaking liquid can almost meet emission requirements,almost no damage to the formation.