Pushing the Thermal Stability Limits of Hydraulic Fracturing Fluids

Abstract

In order to satisfy the demand for oil and gas, it becomes increasingly necessary to produce from formations that are deeper, have low permeability, and higher temperature. Conventionally, hydraulic fracturing fluids make use of viscosifiers such as guar and its derivatives to generate the rheological properties required during the fracturing process. However, to withstand the high-temperature environments, higher loadings of polymer is required. This leads to an increase in polymer and additive concentrations. Most importantly, these higher loading fluids do not break completely, and generate residual polymer fragments that can plug the formation and reduce fracture conductivity significantly. This work builds on previous work which introduced a new hybrid dual polymer hydraulic fracturing fluid that was developed for high-temperature applications. The fluid consists of a guar derivative and a polyacrylamide-based synthetic polymer. Compared to conventional fracturing fluids, this new system is easily hydrated, requires less additives, can be mixed on the fly, and is capable of maintaining excellent rheological performance at low polymer loadings. In this work, the fluid is further optimized to withstand even higher temperatures up to 400°F. Total polymer loadings of 30 lb/1,000 gal and 40 lb/1,000 gal dual polymer fracturing fluid were tested in this work and were prepared in the ratio of 1:1 and 1:2 (CMHPG: Synthetic). They were then crosslinked with a metallic crosslinker and placed in a HPHT rheometer to measure the viscosity between 200 and 400°F. After observing the failure temperature of the mixtures, additives such as buffers, crosslinking delayers, and oxygen scavengers were added and tested at temperatures above that point. The type of crosslinker used was also varied to observe the effects of the rate of release of the metallic crosslinker on thermal stability. The results indicate that the 1:2 (CMHPG: Synthetic) mixture performed better at temperatures exceeding 330°F than the 1:1 mixture. The failure point of both mixtures was observed to be 350°F for the latter while the former failed at 370°F. The addition of a crosslinker that allowed a more controllable release was observed to improve the thermal stability of the fluid mixture above 370°F by increasing the polymer's shear tolerance. The addition of additives to the mixture was shown to improve the thermal stability of the solution to varying degrees. Of the three additives, the most significant enhancement came from the addition of oxygen scavengers while the least was from the buffer solution.

Seawater-Based Fracturing Fluid: A Review

“…It is also important to keep a close eye on the fluid’s thermal stability. Maintaining stability at high temperatures requires that the surroundings have a high pH. ,,− In comparison, Na + and K + are commonly employed in fracturing fluid systems due to their low cost and minimal formation damage. In addition, K + is widely used as an antiswelling additive in the oil industry …”

“…Low fluid loss, minimal pressure losses during transport via the tubing and fractures, and the ability to continue the flow after proppant placement are all necessary. , In addition, it needs to be suitable for use with formation fluids . In order to prevent any screenout during the treatment, it is also crucial that the fluid is resistant to shear and heat . There are a variety of water-based fracturing fluids available, including viscoelastic surfactants (VESs), cross-linked fluids, and slick water fluids.…”

“… 6 In order to prevent any screenout during the treatment, it is also crucial that the fluid is resistant to shear and heat. 7 There are a variety of water-based fracturing fluids available, including viscoelastic surfactants (VESs), cross-linked fluids, and slick water fluids. Cross-linking and emulsification are both possible with oil-based fracturing fluids.…”

Investigation on the influence of sulfonic substitution in polyacrylamides for minimizing drag in turbulent flow of slickwater fluids

“…4,5 Linear gels were enhanced by crosslinkers stabilized for high-temperature and high-salinity conditions and were termed as crosslinked gels. [6][7][8][9] Techniques were modified for lowpermeability unconventional wells where fluids consisting of drag-reducing polymers in produced waters, termed as slickwater fluids, were pumped at highflowrates to achieve turbulent conditions for proppant suspension 10,11 to mitigate frictional losses. Standard commercial drag reducers were synthesized using acrylamide-based polymers.…”