Reusing Flowback and Produced Water with Different Salinity to Prepare Guar Fracturing Fluid

Abstract

Economical and environmental concerns have forced the oil and gas industry to consider reusing flowback and produced water for fracturing operations. The major challenge is that the high-salinity of flowback water usually prevents its compatibility with several fracturing fluid additives. In this paper, the authors explored an economic and effective method to prepare guar fracturing fluids with different salinity waters. The main research idea was to use chelating agents to mask metal ions, such as calcium and magnesium, that are harmful to crosslinking. Firstly, a complexometric titration test was conducted to measure the chelating ability of three chelating agents. Secondly, through viscosity, crosslinking, and hanging tests, it was verified that the complex masking method could cope with the problem of high-valence metal ions affecting crosslinking. Thirdly, the preferred chelating agent was mixed with several other additives, including thickeners, crosslinkers, and pH regulators, to prepare the novel guar fracturing fluid. The comprehensive performances of the novel fluid system were tested such as temperature and shear resistance, friction reduction, gel-breaking performance, and core damage rate. The results show that the organophosphate chelating agent (i.e., CA-5) had the greatest ability to chelate calcium and magnesium ions. There was a good linear relationship between the dosage of CA-5 and the total molar concentration of calcium and magnesium ions in brine water. The main mechanism was that the chelating agent formed a complex with calcium and magnesium ions at a chelation ratio of 1:5. The test results of the comprehensive performance evaluation indicate that the prepared guar fracturing fluid met the requirements for field application, and the lower the salinity of the flowback water, the more it is economical and effective.

Synthesis and properties of elevated temperature hydrogels for enhanced oil recovery based on AM/AMPA/NVP copolymer and silica nanoparticles

“…The signal proton peak at chemical shifts of 19.03 ppm belonged to CH 2 CH 2 CH 2 of NVP. There was no chemical shift of C C bonds in the 13 C NMR spectra of TSP. The peaks in Figure 6d contained the characteristic absorption peaks of AM, AMPS, and NVP monomers.…”

“…The structural characterization of TSP was also explored by NMR spectroscopy. The data on the 13 C NMR spectra of the three monomers (AM, AMPS, and NVP) was shown in Figure 6a-c. The chemical shift value at 179.33 ppm was due to the C C C bonds of TSP.…”

“…11,12 On the other hand, an economical crosslinker with heat and salt resistance were selected. 13,14 The 2-acrylamido-2-methylpropane sulfonic acid (AMPS) 15,16 and sodium styrene sulfonate (SSS) 17 monomers contained ion groups (sulfonic acid groups) that were not sensitive to Ca 2+ and Mg 2+ , which could increase the polarity of the polymer chain, making it difficult for the polymer chain to rotate freely and improving the salt resistance of the polymer. It was reported that the AM-co-AMPS copolymer in the 5000 mg/L salt solution revealed a high viscosity retention (35%), which was higher than the conventional polymer HPAM.…”

“…On the one hand, functional monomers with ionic groups, rigid side groups, or hydrophobic groups were introduced into the main chains of the conventional polymer HPAM to synthesize heat‐ and salt‐resistant copolymers 11,12 . On the other hand, an economical crosslinker with heat and salt resistance were selected 13,14 . The 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) 15,16 and sodium styrene sulfonate (SSS) 17 monomers contained ion groups (sulfonic acid groups) that were not sensitive to Ca 2+ and Mg 2+ , which could increase the polarity of the polymer chain, making it difficult for the polymer chain to rotate freely and improving the salt resistance of the polymer.…”

“…Data on the13 C NMR spectra of the three monomers (Legend: AM (a), NVP (b), AMPS (c)) and13 C NMR Spectra (d) of the TSP. [Color figure can be viewed at wileyonlinelibrary.com]…”