Control and Modeling of Fluid Leakoff During Hydraulic Fracturing

Penny, Glenn S.; Conway, M.W.; Lee, Wellington

doi:10.2118/12486-pa

Cited by 56 publications

(21 citation statements)

References 15 publications

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“…[30] Not only can bacteria reduce the molecular weight of polymers, some of them can also sour the reservoir fluid by reducing sulfate ions to hydrogen sulfide. [30] Adding bactericides to the polymer kills the bacteria but it is not able to inactivate the enzymes already produced by the bacteria. That is why it is always recommended to add bactericides to fracture tanks before adding water.…”

Section: 2-5 Bactericidesmentioning

confidence: 99%

“…Williams [65] and Settari [66] Filter Cake: At a constant pressure, the rate of filtration is proportional to the square root of time assuming that: [1,30] • The amount of cake deposited is proportional to the volume of fluid V L passed through a unit surface area (…”

Section: Equation 24mentioning

confidence: 99%

“…Pressurizing the polymer solution against a porous media one might be able to measure the wall building coefficient (C w ) by plotting the filtrate volume vs. t using Equation 30.…”

Section: Equation 24mentioning

confidence: 99%

“…Figure 32 Classical Carter filtration model (Glenn, and Penny) [30] Filtrate Zone: Is the zone invaded by the filtrate from fracturing fluids assuming that: [1,64,65] • Pressure drop across the zone is constant Where fil k is the permeability related to the filtrate and L v is the length of the invaded zone.…”

Section: Equation 24mentioning

confidence: 99%

“…However, longer times can be applied for treatments with long pump times. [30] In order to minimize the variations in results Glenn and Penny [30] recommended to pay enough attention to mix the fluids based on a correct and repeatable procedure, apply the differential pressure after the temperature is stable and just before opening the leakoff valve and keeping the core length constant for different tests. A schematic picture of a static fluid loss cell, published by Constien et al , [1] is shown in Figure 33.…”

Section: Static Fluid Loss Testsmentioning

confidence: 99%

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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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Section: 2-5 Bactericidesmentioning

confidence: 99%

Section: Equation 24mentioning

confidence: 99%

“…Pressurizing the polymer solution against a porous media one might be able to measure the wall building coefficient (C w ) by plotting the filtrate volume vs. t using Equation 30.…”

Section: Equation 24mentioning

confidence: 99%

Section: Equation 24mentioning

confidence: 99%

Section: Static Fluid Loss Testsmentioning

confidence: 99%

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