Thermoreversible Gels and Temperature Triggered Kinetically Controlled Gels for Oilfield Applications

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2000-05

Authors

Nasakul, Siree

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Abstract

Polymer gels have been extensively used in oil and gas wells. In this dissertation we explore the use of novel thennoreversible gels and temperature triggered kinetically controlled gels for application in water shutoff, gravel packing and fracturing. Thermoreversible gels consisting of block copolymer surfactants have the unique property of forming a gel between a certain temperature range. The range of gelation temperatures can be controlled by varying the surfactant concentration, molecular weight, hydrophobicity and functional groups. The gelation is reversible and both the lower and upper gelation temperatures are sharp phase transitions. Gelation and rheological properties of a range of Pluronic and Tetronic surfactants are investigated. Core flow experiments are conducted to show that gels can be used to reversibly reduce the permeability of cores. The gels will find likely applications in fracturing and gravel packing. Temperature triggered kinetically controlled gels have been synthesized primarily from crosslinked functionalized PEGs and Pluronics. The gelation times and gel properties can be varied based on the molecular weight, functional groups, and degree of crosslinking of gels synthesized. Gelation kinetics are controlled by monomer concentration, monomer type, initiator concentration, initiator type, pH and temperature. Some gels formed are found to be hard and swell in the presence of water to several times their weights as well as being stable for extended period of time. Such gels will find applications in water shutoff treatments. Other gel systems have been formulated to degrade rapidly with time. The swelling and degelation of such gels have been investigated in detail. It is found that the use of crosslinked PEGs and Pluronics provide a family of gels that will find likely application in water shutoff treatments. Thermoreversible gels such as those from Pluronics and Tetronics can find applications in fracturing and gravel packing applications. Core flow experiments performed to evaluate these gels at reservoir conditions indicate the suitability of these gel systems for these applications.

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