Influence of Pressure on Boron Cross-Linked Polymer Gels

Parris, Michael D.; MacKay, Bruce A.; Rathke, J. W.; Klingler, R. J.; Gerald, Rex E.

doi:10.1021/ma801187q

Cited by 53 publications

(30 citation statements)

References 19 publications

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“…Their applications have mainly been in very high temperature reservoirs where borate crosslinked fluids are no longer effective. 20 Parris et al 25 reported pressure dependency of guar crosslinked gels using different sources of borate ions. This viscosity reduction due to pressure was reversible.…”

Section: Reviewmentioning

confidence: 99%

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A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

Barati

Liang

2014

J of Applied Polymer Sci

594

341

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Hydraulic fracturing has been used by the oil and gas industry as a way to boost hydrocarbon production since 1947. Recent advances in fracturing technologies, such as multistage fracturing in horizontal wells, are responsible for the latest hydrocarbon production boom in the US. Linear or crosslinked guars are the most commonly used fluids in traditional fracturing operations. The main functions of these fluids are to open/propagate the fractures and transport proppants into the fractures. Proppants are usually applied to form a thin layer between fracture faces to prop the fractures open at the end of the fracturing process. Chemical breakers are used to break the polymers at the end of the fracturing process so as to provide highly conductive fractures. Concerns over fracture conductivity damage by viscous fluids in ultra-tight formations found in unconventional reservoirs prompted the industry to develop an alternative fracturing fluid called "slickwater". It consists mainly of water with a very low concentration of linear polymer. The low concentration polymer serves primarily to reduce the friction loss along the flow lines. Proppant-carrying capability of this type of fluids is still a subject of debate among industry experts. Constraints on local water availability and the potential for damage to formations have led the industry to develop other types of fracturing fluids such as viscoelastic surfactants and energized fluids. This article reviews both the traditional viscous fluids used in conventional hydraulic fracturing operations as well as the new family of fluids being developed for both traditional and unconventional reservoirs.

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Section: Reviewmentioning

confidence: 99%

“…Parris et al reported pressure dependency of guar crosslinked gels using different sources of borate ions. This viscosity reduction due to pressure was reversible.…”

Section: Introductionmentioning

confidence: 99%

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

Barati

Liang

2014

J of Applied Polymer Sci

594

341

View full text Add to dashboard Cite

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“…It has been reported that viscosity of borate crosslinked guar is a strong function of pressure and viscosity decreases with increasing the pressure. [98] Studying the rheological properties of PEC nanoparticles under typical pressure applied during a fracturing job or after the injection is recommended. This may give some insight about the shear sensitivity of EL2X-loaded nanoparticles mixed with HPG gel while they showed little shear sensitivity when mixed with HPG solution.…”

Section: Rheology Testsmentioning

confidence: 99%

Fracturing fluid cleanup by controlled release of enzymes from polyelectrolyte complex nanoparticles

Ghahfarokhi

Johnson

McCool

et al. 2011

J of Applied Polymer Sci

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Guar-based polymer gels are used in the oil and gas industry to viscosify fluids used in hydraulic fracturing of production wells, in order to reduce leak-off of fluids and pressure, and improve the transport of proppants. After fracturing, the gel and associated filter cake must be degraded to very low viscosities using breakers to recover the hydraulic conductivity of the well. Enzymes are widely used to achieve this but injecting high concentrations of enzyme may result in premature degradation, or failure to gel; denaturation of enzymes at alkaline pH and high temperature conditions can also limit their applicability.In this study, application of polyelectrolyte nanoparticles for entrapping, carrying, releasing and protecting enzymes for fracturing fluids was examined. The objective of this research is to develop nano-sized carriers capable of carrying the enzymes to the filter cake, delaying the release of enzyme and protecting the enzyme against pH and temperature conditions inhospitable to native enzyme.Polyethylenimine-dextran sulfate (PEI-DS) polyelectrolyte complexes (PECs) were used to entrap two enzymes commonly used in the oil industry in order to obtain delayed release and to protect the enzyme from conditions inhospitable to native enzyme. Stability and reproducibility of PEC nanoparticles was assured over time.An activity measurement method was used to measure the entrapment efficiency of enzyme using PEC nanoparticles. This method was confirmed using a concentration measurement method (SDS-PAGE). Entrapment efficiencies of pectinase and a commercial high-temperature enzyme mixture in polyelectrolyte complex nanoparticles were maximized. Degradation, as revealed by reduction in viscoelastic moduli of borate-crosslinked hydroxypropyl guar (HPG) gel by commercial enzyme loaded in polyelectrolyte nanoparticles, was delayed, compared to equivalent systems where the enzyme mixture was not entrapped. This indicates that PEC nanoparticles delay the activity of enzymes by entrapping them. It was also observed that control PEC nanoparticles decreased both viscoelastic moduli, but with a slower rate compared to the PEC nanoparticles loaded with enzyme.Preparation shear and applied shear showed no significant effect on activity of enzyme-loaded PEC nanoparticles mixed with HPG solutions. However, fast addition of chemicals during the iv preparations showed smaller particle size compared to the drop-wise method. PEC nanoparticles (PECNPs) also protected both enzymes from denaturation at elevated temperature and pH.Following preparation, enzyme-loaded PEC nanoparticles were mixed with borate crosslinked HPG and the mixture was injected through a shear loop. Pectinase-loaded nanoparticles mixed with gelled HPG showed no sensitivity to shear applied along the shear loop at 25 °C. However, EL2X-loaded PEC nanoparticles showed sensitivity to shear applied along the shear loop at 40 °C.Filter cake was formed and degraded in a fluid loss cell for borate crosslinked HPG solutions mixed with either enzymes or...

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“…Note that during the shear history testing, the fluid outlet is open to atmospheric pressure and does not have application of back pressure. Recent papers have noted a potential negative impact of high pressure on borate crosslinked fluid rheology (Parris et al 2008 andEngland et al 2011); it is not known to date whether shear profile in combination with high pressure imparts an additional affect on fluid performance. The shear rates, exposure times and temperatures for these tests were taken from the anticipated field conditions for both spotting and fracturing rates and are shown in Figure 2 for Field 1 and Figure 3 for Field 2.…”

Section: Shear History and Rheology Testsmentioning

confidence: 99%

Preemptive Scale Management: Treating with Scale Inhibitor While Frac Packing a Well

2011

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Fracpacks have become the completion of choice for deepwater wells due to concerns over loss of productivity associated with fines and sand production, limited rig availability and high intervention / sidetracking costs. Many deepwater reservoirs also require seawater injection in order to maintain reservoir pressure and increase the ultimate recovery of hydrocarbon reserves. This practice can significantly increase the potential for scaling, particularly the deposition of barium sulphate (BaSO 4 ) scale in reservoirs with high barium concentrations. Mechanical removal of sulphate scale at the reservoir level and / or from a damaged fracpack is not feasible. Chemical dissolution is not always practical, particularly in cases of high scale buildup. In these circumstances, little can be done to restore loss production except for pulling the completion or sidetracking the well. In either case, the consequences of sulphate scale build-up can be detrimental to the economics of the project, especially for high rate producer wells. For these reasons, preemptive scale management, most often in the form of scale squeezes, is a standard operating practice in high value wells susceptible to scaling. Deployment of a scale inhibitor concurrently with well completion operations is very attractive in that it delays the onset of scaling while providing a means for scale inhibition monitoring from the start of production. This not only provides adequate protection in case of early water breakthrough, but it also provides warning to plan and schedule routine well interventions, efficient utilization of resources (rig availability, workover crews, etc.), and better reservoir management. The addition of a phosphonate scale inhibitor into the pre-frac acid and overflush brine stages preceeding the frac operation was previously discussed in SPE 127768. As an extension of the previous work, a liquid pentaphosphonate scale inhibitor has been successfully incorporated into a seawater-based, borate-crosslinked frac fluid for fracpack operations in deepwater environments. Many challenges, including complex shear and temperature profiles, as well as potential incompatibilities arising from the interaction between the SI, crosslining agent / buffer package, and seawater were overcome by adjustments made to the crosslinking package, polymer loading, and fluid pH. The rigorous laboratory testing that led to the development of optimized fluid formulations, the assessment of scale inhibitor efficacy and formation damage potential is described herein.

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Influence of Pressure on Boron Cross-Linked Polymer Gels

Cited by 53 publications

References 19 publications

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

Fracturing fluid cleanup by controlled release of enzymes from polyelectrolyte complex nanoparticles

Preemptive Scale Management: Treating with Scale Inhibitor While Frac Packing a Well

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