A three components thixotropic agent to enhance the thixotropic property of natural gas well cement at high temperatures

Abstract

This paper investigated the suitability of xanthan gum as a thixotropic agent utilized in high-temperature natural gas well cementation. The konjac gum and KCl are used to synthesize a novel thixotropic agent and keep the thixotropic property of xanthan gum at high temperatures. The increment of consistency method are used to evaluate the thixotropic performance of the cement. Compressive strength tests, scanning electron microscope, and X-ray diffraction analysis are performed to study the effects of the thixotropic agent on the properties of cement at high temperatures. Moreover, the thixotropic mechanism is revealed, as well. Test results show that the high-temperature resistance property of xanthan gum is limited. The konjac gum and KCl should be used to enhance the thermal stability of xanthan gum to achieve better thixotropic property at high temperatures. The thixotropic agent does not influence the hydration products but slows down the hydration process of cement. Even though the thixotropic agent influences the microstructure of cement, the compressive strength still meets the sealing requirements of natural gas wells. The K+ ions in KCl connect the molecular chains in xanthan gum through the salt bridge effect, which inhibits the transformation of xanthan gum's double helix structure and enhances the thermal stability of the molecular structure. Furthermore, the acetyl groups in konjac gum generate hydrogen bonds with pyruvate groups in xanthan gum. This effect makes the composite structure more stable and finally results in a thermal stable thixotropic agent. The proposed novel three components thixotropic agent is an effective solution to solve the gas migration issue in high-temperature natural gas wells.