Reaction of Chelating Agents with Guar Gum Polymer for Completion Fluid

Guar gum polymer is used extensively in the upstream applications such as hydraulic fracturing and gravel pack operations in unconsolidated sandstones. Guar gum will form a filter cake either on the fracture face or on the gravel, and this will affect the well productivity. There is an essential need to remove the filter cake formed by guar gum to enhance the well performance and enhance the oil and gas production rate. The reaction of guar gum with different chelating agents was assessed in this paper. Chelating agents like diethylenetriaminepentaacetic acid (DTPA), ethylenediaminetetraacetic acid (EDTA), and glutamic acid diacetic acid (GLDA) were used at different concentrations, temperature, time, and pH. An optimum formulation was developed to remove guar gum filter cake formed after gravel packing and hydraulic fracturing operations. Fourier transform infrared was used to explain the mechanism of the reaction between guar gum and chelating agents. It is the first time to assess the reaction between chelating agents and guar gum. The results obtained showed that the DTPA, EDTA, and GLDA highly affect the apparent viscosity of the guar gum solution (GG solution). Based on the experimental work, 20 wt% GLDA at pH 7 decreased the apparent viscosity of GG solution from 51 to 9 cP at a shear rate of 170.3 S^{- 1} after mixing for 24 h at 200∘F. The apparent viscosity of the GG solution decreased by 27% after mixing with 20 wt % EDTA (pH 12) at a shear rate of 170.3 S^{- 1} for 24 h at 200∘F. On the other hand, 20% DTPA at pH 4 and 7 at 170.3 S^{- 1}and 200∘F did not reduce the GG solution apparent viscosity and based on that DTPA is not recommended for GG filter cake removal. The results of this research are very important for hydraulic fracturing operations to restore the fracture face permeability after filter cake removal. It will also open a research trend in the oil industry, especially in the fracturing and gravel packing operations.