Study On Preparation And Properties Of Thermal Resiatant And Salt-tolerant Water Swellable Rubber Plugging Agents

As a new type of rubber functional material,water-swellable rubber(WSR)is mainly composed of a rubber matrix and a hydrophilic component.The hydrophilic component includes anionic,cationic and nonionic hydrophilic agents.The method is divided into two types: physical addition composite type and reaction covalent graft type.The water-swellable rubber has both water swelling performance and excellent mechanical properties of the elastomer.Due to the choice of hydrophilic components and the composite technology used,most of the WSR exhibits low expansion ratio,high expansion rate,easy loss of hydrophilic components,and poor stability in high salinity water,that limits the application of WSR.Therefore,the study of WSR materials with high expansion rate,delayed expansion and high mechanical properties in high salinity water has become the focus,difficulty and development direction of the research.Based on the performance characteristics of WSR materials,it has a good application prospect in the development of oilfields with high water cut period.In view of the characteristics of high reservoir temperature(>130 ?)and high salinity(2.2×105mg/L)in fractured cavern reservoir of Tahe Oilfield in Northwest China,a new rubber plugging agent material,which can resistant temperature and salt,and delay expansion,is studied and developed in this paper.In this thesis,WSR materials were modified by reactive hydrophilic agent to prepare covalently crosslinked WSR rubber plugging agent based on nitrile rubber(NBR)and hydrogenated nitrile rubber(HNBR).We evaluated the blocking behavior of rubber plugging agent.The thesis used physical blending method to prepare WSR materials based onNBR.It were studied that the effect of different WSR types,salinity,temperature,crosslink density and carbon black content on the swelling behavior of water absorption.The results showed that the hydrophilic component of the covalently crosslinked WSR precipitated little,which alleviated the precipitation of water absorbing agent.The material could exhibit excellent water swelling behavior only when the crosslink density was appropriate in the rubber.The content of carbon black determined the mechanical properties and compactness of the rubber.The higher the rubber compactness,the more it could sink in the simulated water of Tahe,but at the same time,the loss of filler also occurs.The delayed expansion time of the covalently crosslinked WSR with NBR as the matrix was about 10 h.However,the WSR processed by this method had a phenomenon that the loss of the filler caused a low expansion ratio,which could not meet the construction requirements of the long-distance transportation of the Tahe reservoir and the pursuit of a higher expansion ratio.Next,the covalent cross-linked WSR materials were prepared by using HNBR as matrix.We studied the effect of temperature,salinity and rubber matrix on the water-absorbing expansion behavior.The results showed that the higher the temperature was,the faster the expansion rate was.The covalently crosslinked WSR with HNBR as matrix had a higher expansion rate in the simulated water of Tahe at130 ?,and could ensure the high density of the material,which could sink and a longer delay behavior in the simulated water of Tahe.However,the rubber test piece was larger and could not be injected into the Tahe reservoir,and needed to be cut into plugging particles.Finally,the vulcanized rubber was cut into plugging agents of 1 mm size,in order to studied the swelling behavior of the plugging particles in Tahe simulated water.We studied the physical simulation plugging experiment of fracture cores and evaluated the plugging performance of plugging agents in fracture-cavity reservoirs.The results showed that the blocker particles with HNBR as the matrix had longer delayed expansion time and higher expansion ratio after being coated with waterborne polyurethane film,and could sink in Tahe simulated water.The rubber plugging agent showed a good sealing effect after being injected into the crack.The experimental simulation of the crack flow channel sealing effect was outstanding,which could wellmeet the requirements of the deep water blocking profile control technology of the Tahe reservoir.