Evaluating the Chemical Reaction of Chelating Agents with Xanthan Gum

Xanthan gum is a polysaccharide natural polymer that is used heavily as a viscosifier in oil and gas industry especially with fracturing and gravel pack fluids. Numerous additives are required to control the properties of the fracturing and gravel pack fluids such as biocides, clay stabilizers, and some other additives to maintain the viscosity at high temperature during the fracturing operations. These additives have their limitations, and they will increase the cost of the operation. The objective of this research is to evaluate the chemical reaction of xanthan gum with different chelating agents [ethylenediaminetetraacetic acid (EDTA), glutamic acid diacetic acid (GLDA), and diethylenetriaminepentaacetic acid (DTPA)] at different conditions of pH, concentrations, temperature, and time to determine the optimum conditions for removing the polymer filter cake after fracturing and gravel pack operations. The results obtained showed that mixing chelating agents (DTPA, EDTA, and GLDA) with xanthan gum had a big effect of increasing the viscosity of the solution. DTPA and EDTA at different pH and shear rates over long time (36 h) did not break the XC-polymer solution at 200∘F. GLDA (20 wt%, pH 12) increased the viscosity of the xanthan gum solution from 33 to 45 cP for 11 h at 200∘F and a shear rate of 170.3S-1. Under the same conditions, GLDA worked as a breaker after 11 h as the apparent viscosity of the GLDA-XC solution was decreased from 45 cP to 11 and 3 cP after 24 and 36 h, respectively. The optimum concentration of GLDA was found to be 20 wt%, and the optimum pH was found to be 12.