Vikas Mahto

Preformed particle gels (PPGs) have been introduced as an efficacious chemical technology to alleviate or reduce unwanted water production from heterogeneous mature oil fields. However, there are some limitations to the existing developed PPGs, such as mechanical robustness, temperature stability, and formation fluid resistance. To address these limitations, a nanomaterial-reinforced preformed particle gel was introduced. In this current research work, the authors have reported a new type of novel nanomaterial-reinforced PPG using the reinforcement of zinc oxide (ZnO) nanomaterial, methacrylic acid, N,N-dimethyl acrylamide as a monomer, and N,N-methylene bis acrylamide as a cross-linker. The newly developed reinforced PPG, termed RF-PPG, shows high mechanical strength and exceptional long-term thermal resistance, salinity tolerance, and pH resistance. The resulting PPG (RF-PPG) exhibited superior performance compared to conventional PPG (without nanomaterial), i.e., WRF-PPG. Preformed particle gel with reinforcement (RF-PPG) has shown the equilibrium swelling of 119 and 32 in distilled water and 30,000 ppm of NaCl brine solution, respectively. The elastic modulus of RF-PPG is up to 2100 Pa, which is significantly higher than the particle gel without reinforcement (WRF-PPG), i.e., 600 Pa. Moreover, the swelling characteristics of RF-PPG, in high salinity and pH, show less variation, although the swelling capacity of RF-PPG is less in different solvents as compared to WRF-PPG. The nanomaterial reinforcement significantly improved the long-term thermal resistance for more than 185 days in 30,000 ppm of NaCl brine solution at 100 °C and shows an increment in swelling at higher temperatures. Laboratory sandpack flooding study demonstrated that RF-PPG provides exceptional plugging capacity of more than 90% and residual resistance factor of 11.92 and 15.03 for high permeable sandpacks at 100 °C. Considering the unique characteristics of the engineered preformed particle gel, RF-PPG is ideally suited for water shutoff jobs in heterogeneous reservoirs.

Hydrated shale formations often lead to severe drilling problems and may lead to wellbore instability. These instabilities can result in issues such as bit balling, borehole collapse, formation damage, stuck pipe, and low drilling rates. Keeping these fundamental issues with drilling in shale formation in mind, this study is aimed at designing a water-based drilling fluid system for effective shale inhibition, ensuring enhanced wellbore stability and drilling efficiency. The designed mud system comprises a typical base fluid along with newly synthesized chitosan derivative chitosan-N-(2-hydroxyl)-propyl trimethylammonium chloride (HACC) as an additive. This additive was found to be soluble in water and conducive for shale inhibition. The derived product was characterized by field emission scanning electron microscopy, thermogravimetric analysis, and Fourier-transform infrared spectroscopy (FTIR). Various drilling fluid tests, including filtration and rheological experiments, were conducted to evaluate its proficiency as a drilling mud additive. The results showed improvement in rheological and filtration properties after hot rolling at 100 °C in comparison to a conventional shale inhibitor, polyethylenimine. As we increase the concentration of synthesized chitosan derivative from 0.3 to 1.5 w/v%, the filtration loss is reduced from 40% to 65% as compared to the base fluids. Shale recovery tests were also conducted using shale samples from an Indian field to assess its viability for field application. The addition of 0.3 to 1.5 w/v% chitosan derivative resulted in high shale recovery above 88% to 96% at 100 °C compared to polyethylenimine, which showed a change in recovery from 62% to 73%. HACC intercalates into clay platelets, reducing the interlayer spacing between particles and preventing clay from hydrating and swelling. This mechanism of inhibition is evaluated by X-ray diffraction, FTIR, and zeta potential analysis. This bolsters the hypothesis of using the synthesized chitosan derivative as a shale inhibitor.