Development of Polyglycolic- and Polylactic-Acid Fluid-Loss-Control Materials for Fracturing Fluids

Abstract

Summary Fluid loss is significant for the standard fracturing fluids without adding solid materials. One method to reduce fluid loss is to add silica flour, although it reduces fracture conductivity. Other methods are to use wall-building polymers. However, the fluid loss is still significant, and complete removal of wall-building materials is not possible, even with breakers. We found that powder, granular, and fibrous materials made of polyglycolic acid (PGA) or polylactic acid (PLA) are very suitable for fluid-loss agents because PGA is stronger than steel and PLA is as strong as rock, although they dissolve as liquid acids after applications. Fluid-loss tests are conducted with the standard American Petroleum Institute slot tester and filtrate-loss tester, mixing powders, grains, and fiber, all made of PGA or PLA in fracturing polymer fluids. The ratio of grains, powder, and fiber is optimized to minimize fluid loss for porous media and fractured porous media. Then, the changes of particle size are measured under heated conditions. Fracture-simulation studies are also conducted with a 3D fracture-boundary element model to compare the fluid efficiency of the fracturing fluids with and without the PLA and PGA particles. The results show that the capability of preventing fluid loss and plugging microcracks is maintained for the porous filters and small slots within a reasonable time period. For short-term applications less than 3 hours, both PGA and PLA fluid-loss agents are stable when the temperature is less than 212°F. Mixing these materials often provides more-efficient properties to reduce fluid loss and to bridge microcracks. No residues are left after experiments if the fracturing fluid is kept heated for 24 hours. The amount of the PGA and PLA fluid-loss agents required to reduce the fluid loss is not significant. Hence, their field applications are feasible, judging the cost and the benefit. The advantage in using these materials is that they turn from solid to liquid after applications so that no formation damage and no proppant-conductivity damage occur. The fluid loss is also significantly reduced with the powder particles. In addition, because the PGA and PLA materials are degradable, solids with arbitrary sizes and shapes may be used as long as they control fluid loss and plug fine fractures. Their applications are not only limited to reducing fluid loss, but one may also use them for engineering fracture design to enhance the fracture conductivity.

Effect of Crosslinker Types on Temporary Plugging Performance of Degradable Preformed Particle Gels for Unconventional Petroleum Reservoir Development

“…In recent years, silicon powder, magnesium carbonate powder, rock salt, and so forth are also used as TPAs. − The second is an oil-soluble resin. , The third type is polylactic acid, but polylactic acid needs to be added with a degradation accelerator (such as ethylenediamine, ethanolamine, polyamines, etc.) to shorten the degradation time. , The fourth is a crosslinked gel. It can be divided into the preformed particle-type crosslinked gel and the in situ crosslinked gel.…”

“…to shorten the degradation time. 16,17 The fourth is a crosslinked gel. It can be divided into the preformed particle-type crosslinked gel and the in situ crosslinked gel.…”

Supramolecular-Structure-Associating Weak Gel of Wormlike Micelles of Erucoylamidopropyl Hydroxy Sulfobetaine and Hydrophobically Modified Polymers

“…9−11 The fluid used to generate the desired viscosity must be safe to handle, thermally stable, resistant to shearing, low-damaging to the reservoir permeability, environmentally friendly, and easy to prepare for field operation. 12,13 Traditionally, guar and its modified derivatives are widely used as thickeners in hydraulic fracturing because of their high viscosity. 14 However, guar has a fatal defect in that it leaves insoluble residues in the formation that extensively plug pore throats and cause formation damage.…”

“…They carry the proppant from the wellbore to the fracture tip and generate the desired net pressure to control the height growth. These processes directly and substantially affect the post-fracture production response in tight reservoirs. − The fluid used to generate the desired viscosity must be safe to handle, thermally stable, resistant to shearing, low-damaging to the reservoir permeability, environmentally friendly, and easy to prepare for field operation. , …”