Effect of polyacrylamide friction reducer on calcite dissolution rate at 25 °C and implication for hydraulic fracturing

Abstract

Hydraulic fracturing is widely used to create cracks and increase the size and connectivity of existing fractures, leading to higher permeability of shale rocks and production of unconventional hydrocarbon sources. The main chemicals used in hydraulic fracturing fluids can initiate fractures in shale reservoirs by acid induced carbonate dissolution, and minimise energy loss during the pumping process by friction reducer enhanced fluid viscosity. Here, using batch reactor experiments we investigate the effect of non-ionic polyacrylamide polymer (friction reducer) on the dissolution rate of calcite in acidic solutions (0.2 M buffer solution of sodium acetate/acetic acid) at 25 °C. The results demonstrate that polyacrylamide (from 0 to 30 mg) slows down the dissolution rate by a factor of 4. Hydrogen bonding and surface complexation between non-ionic polyacrylamide and calcite potentially trigger an adsorption mechanism that protects calcite from dissolving.This research provides new insights into friction reducer (polyacrylamide) influenced pore generation, enabling engineers to optimise the fracturing fluid design (amount of polyacrylamide) and to consider suitable actions to prevent the polymer from having a negative impact on productivity.

Effect of Anionic Polyacrylamide Polymer on Frost Heave Mitigation and Its Implication for Frost-Susceptible Soil

“…Bridging adsorption which can accumulate two or more soil particles in the presence of APAM polymer should be responsible for the aggregation of soil particles in the solution (Figure 12) [38]. This enables the possibility of attachment of APAM polymer segments to other particles and thus bridges solid particles together [39]. Hence, the bridging adsorption (Figure 12) potentially drives the aggregation of solid particles, and this explains what can be seen in Figure 11.…”

“…The hydrogen atoms (on the amide groups, Figure 13) and oxygen atoms on the soil particle surface can generate hydrogen bonding. It is noted that the carbonyl (C=O) group has a strong electron-withdrawing character, and this allows the migration of non-bonded electrons from nitrogen (N) to the adjacent carbonyl group (C=O) [39]. This can therefore increase the electron density around oxygen and pull the electron away from the hydrogen at the end of amide groups.…”

Zr, N-Co-Doped Carbon Quantum Dot Crosslinking Agents for Use in Fracturing Fluids

“…Water-based polyacrylamide fracturing fluids are widely used in extracting petroleum and natural gas, but it is difficult to complete fracturing only by its viscosity. − Adding crosslinking agents can greatly improve the width generation capacity and cuttings transportation of the fracturing fluid, thereby improving the reservoir conductivity and increasing the oil throughput. , Transition metal and nano-crosslinking agents are commonly used in this fracturing fluid. , Both organozirconium crosslinking agents and organotitanium crosslinking agents are common transition metal crosslinking agents, which are excellent in temperature resistance and delaying crosslinking. However, they have poor shear resistance. , Especially, the nano-crosslinking agents overcome the common defects of traditional crosslinking agents.…”