Optimization of an in-situ polymerized and crosslinked hydrogel formulation for lost circulation control: Dataset and Analysis

Lost circulation is a recurring problem during well drilling. This work proposed a new gel formulation, and optimizes its composition using a fractional design of experiments. The gel was analyzed using rheology and nuclear magnetic resonance (NMR). The responses were the maximum elastic modulus (G'max), plateau G', gelation time according to the Hill5 model, gel stability (%), gelation time obtained from NMR and the presence of syneresis, also obtained from NMR. Models were created considering the main effects and first order interactions, and showed a very high coefficient of determination, over 0.95. A more detailed ANOVA can be found in the paper. In general, pH and amount of acrylic acid are the most significant effects, but the amount of ammonium persulfate (APS), chromium (III) salt and carboxymethylcellulose are also relevant. The rheological properties match or are higher than those from the literature, showing this formulation is a good candidate for lost circulation control. A set of optimal gel compositions can be obtained from the data, depending on the desired characteristics of the gel, such as its gelation time and viscoelastic properties. These can be used for further tests under high temperatures and pressures, such as a breakthrough pressure test.