Fracturing Fluids: Fluid-Loss Measurements Under Dynamic Conditions

Roodhart, Leo

doi:10.2118/11900-pa

Cited by 50 publications

(17 citation statements)

References 4 publications

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“…14 Therefore, the C w data should be obtained with porous material representative of field conditions. Recent laboratory measurements 15 suggest that the filter cake is compressible at low pressure differentials and becomes incompressible at high D.p, contrary to the older data.…”

Section: The General Fluid Loss Modelmentioning

confidence: 61%

A New General Model of Fluid Loss in Hydraulic Fracturing

Settari

1985

Society of Petroleum Engineers Journal

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This paper gives a new fonnulation of fluid loss in hydraulic fracturing that is much more general than the classical theory while retaining its simplicity. The model allows many parameters to vary during filtration and can, therefore, simulate nonlinear effects.The model has been validated against laboratory data for Newtonian fluids and crosslinked gels. The results show that the finite length of the core, viscosity screenout, and shear sensitivity are important parameters that. can be represented by the model. The standard analysis gives values of leakoff coefficients that will give incorrect, considerably higher leakoff when applied to field conditions. IntroductionThe estimate of fluid loss is an important part of a hydraulic fracturing treatment design. Although the control of fluid loss has improved with the use of modem fracturing fluids, the size of the generated fracture areas increases with the size of a job. Consequently, fluid loss can be important even in low-penneability reservoirs for large treatments.For design calculations, fluid loss has been treated in the past by use of the simplified theory proposed by Howard and Fast, 1 which expresses the rate of filtration perpendicular to a fracture wall as a simple function of leakoff coefficients.The advantage of this approach, besides its simplicity, is that it can be directly (if not always correctly) related to experimental data on fluid filtration obtained in a laboratory. Apart from the correction of the derivation of the combined leakoff coefficient, 2,3 very little has been done to improve the classical theory.With the recent development of a simulation approach to fracturing design,4,5 it has been recognized that fluid loss can be computed directly by solving the basic multiphase flow equations in porous media. Such an approach is more general and does not have many of the assumptions that limit the chtssical theory. 6 However, the computational cost is much higher and the data required to describe the process are difficult to measure. This paper presents a generalization of the classical approach that includes the effect of several parameters that are variable in the field. The mathematical fonnulation includes the model of filter-cake behavior developed by the author 6 and the results of the work of Biot et al. , 7 which improves the calculation of flow in the reservoir. The model is then fonnulated numerically, which allows

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Section: The General Fluid Loss Modelmentioning

confidence: 61%

A New General Model of Fluid Loss in Hydraulic Fracturing

Settari

1985

Society of Petroleum Engineers Journal

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“…Roodhart, [70] Navarette et al [59] and McGowen et al [61,62] demonstrated three stages for filter-cake buildup during a fracturing job when fracturing fluid flows perpendicular to the direction in which filter cake forms:…”

Section: Dynamic Fluid Lossmentioning

confidence: 99%

“…[61] Roodhart [70] and McGowen et al [61,62] Figure 39 Schematic picture of dynamic fluid loss process, Vitthal et al [61] Glenn at al. [30] classified the laboratory models designed by different researchers to measure the fluid loss dynamically into four groups:…”

Section: Dynamic Fluid Lossmentioning

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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“…Thus the above description can be used to calculate in situ temperatures of e.g. crosslinked polymer gels, which are known not to follow a square root of time dependency under dynamic conditions(l4, 15). …”

Section: Temperature Recovery After Fracture Closure 'mentioning

confidence: 99%

A New Simulator For the Calculation of the In Situ Temperature Profile During Well Stimulation Fracturing Treatments

Kamphuis¹,

Davies

Roodhart

1993

Journal of Canadian Petroleum Technology

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Many essential parameters in hydraulic fracturing operations such as the viscosity of the fracturing fluid and the effectiveness of certain breakers, are strongly dependent on temperature. A finite-difference computer program has been developed that accurately computes temperature profiles in a propagating fracture. It is based on a rigorous description of the heat transfer processes involved:the heat influx from the fracture wall is computed numerically via a special coordinate transformation of the energy balance equation for the rock,the temperature of the frac fluid and the adjacent rock face are allowed to be different (particularly relevant for wide fractures).local time derivatives in the energy balance are fully accounted for. The code and the underlying model are valid for the full range of conditions encountered in the field, e.g.:high leak-off rates of the fracturing fluid (high permeability rock),low heal conductivity of the rock (certain carbonates) It was found that fractures are often significantly cooler than previously reported results. Consequently, the proppant carrying capacity of the frac fluid will be better and it is possible to carry out successful treatments (good proppant placement and reduced impairment) more cost-effectively. The size of prepad stages for cooling can often be reduced. Further, the temperature recovery profile after proppant placement can aid in the design of resin coated proppant systems. Introduction Many essential parameters in hydraulic fracture simulation operations are strongly dependent on the temperature level prevailing locally in the hydraulically created fracture. In fracturing treatments, the temperature affects:the viscosity of frac fluids and thereby the settling rate of the proppant.The stability of multiphase frac fluid (foams, emulsions).Crosslinker effectiveness.Viscosity breaker effectiveness.Fracture geometry (depending on the fracture propagation model assumed) These will in turn affect the ultimate productivity improvement achieved by the fracture stimulation treatment. Knowledge of the fracture temperature profile is thus requires for optimal design of the frac fluid formation (e.g. type of crosslinker) and/or the treatment stages (e.g. the size of a pre-pad sometimes required to cool the formation). The heat transfer processes taking place during a hydraulic fracture treatment are depicted in Figure q. Cold fluid is pumped into the fracture, where it cools the fracture face and the interior of the rock adjacent to the fracture by conduction and by leak-off. Simultaneously, the fluid heats up as it travels through the fracture because if conduction of heat from reservoir towards the fracture, and, in the case of acid fracturing, by the heat produced by the etching of the rock by the acid. A variety of models have been published in the open literature describing temperature profiles in the fracture for hydraulic fracturing treatments during the pumping stage(1–9), and after the pumping stage prior to closure of the fracture(10, 11) and for acid fracturing treatments(12, 13) In virtually every theory published simplifications had to be made to arrive at a workable semianalystical expression for the temperature. In this work, many restricting assumptions have been avoided. i.e.:

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Fracturing Fluids: Fluid-Loss Measurements Under Dynamic Conditions

Cited by 50 publications

References 4 publications

A New General Model of Fluid Loss in Hydraulic Fracturing

A New General Model of Fluid Loss in Hydraulic Fracturing

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

A New Simulator For the Calculation of the In Situ Temperature Profile During Well Stimulation Fracturing Treatments

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