A Comparative Study of Borate-Crosslinked Gel Rheology Using Laboratory and Field Scale Fracturing Simulations

Goel, Naval; Willingham, J.D.; Shah, Subhash; Lord, David

doi:10.2118/38618-ms

Cited by 5 publications

(8 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, the heat transfer coefficient of the guar slurry is similar to that of the water. 21 This similarity means that the heat transfer characteristics of the fracturing slurry can be satisfactorily estimated from that for the water. Therefore, the current practice of predicting the slurry heat transfer characteristics with water can be successfully continued without compromising the fluid performance under real conditions.…”

Section: -52mentioning

confidence: 95%

“…The results, however, also showed that the viscometer values differ considerably from the HPS viscosities measured after shear conditioning through 3000 ft length of the coiled tubing. 21 This result implies that the crosslinked fluid may exhibit ideal fluid properties under laboratory conditions, but under actual field conditions its behavior may be completely different. 20 Hence the borate crosslinked fluid rheology must be determined under conditions that closely simulate pumping environment through the wellbore and therefore, the laboratory characterization must incorporate shear history simulations prior to the viscometric measurements.…”

Section: -32mentioning

confidence: 99%

“…[20][21] Results: Prior to performing rheological characterization of fracturing fluids, measurements were made to confirm the accuracy and reproducibility of viscosities measured with the HPS slot. The result of this reproducibility test performed over seven days is shown in Figure 7.4.1.…”

Section: Procedurementioning

confidence: 99%

“…However, recent studies have shown that the coefficient of discharge can vary significantly with fluid viscosity and perforation size. 21,22 Thus, a rough estimate for the coefficient of discharge can introduce a serious error in the predicted perforation pressure loss. For instance, an error of 10 % in the coefficient of discharge will result in a 25% error in the predicted pressure loss across the perforations.…”

Section: -63mentioning

confidence: 99%

See 3 more Smart Citations

Fracturing Fluid Characterization Facility

Shah¹

2000

View full text Add to dashboard Cite

Aggressive efforts were also made to effectively transfer the past research results to the industry Abstract (limit 200 words)Hydraulic fracturing technology has been successfully applied for well stimulation of low and high permeability reservoirs for numerous years. Treatment optimization and improved economics have always been the key to the success and it is more so when the reservoirs under consideration are marginal. Fluids are widely used for the stimulation of wells. The Fracturing Fluid Characterization Facility (FFCF) has been established to provide the accurate prediction of the behavior of complex fracturing fluids under downhole conditions. The primary focus of the facility is to provide valuable insight into the various mechanisms that govern the flow of fracturing fluids and slurries through hydraulically created fractures.During the time between September 30, 1992, and March 31, 2000, the research efforts were devoted to the areas of fluid rheology, proppant transport, proppant flowback, dynamic fluid loss, perforation pressure losses, and frictional pressure losses. In this regard, a unique above-the-ground fracture simulator was designed and constructed at the FFCF, labeled "The High Pressure Simulator" (HPS).The FFCF is now available to industry for characterizing and understanding the behavior of complex fluid systems. To better reflect and encompass the broad spectrum of the petroleum industry, the FFCF now operates under a new name of "The Well Construction Technology Center" (WCTC).This report documents the summary of the activities performed during 1992 -2000 at the FFCF Document Analysis a. DescriptionOil and Gas Industry, Natural Gas Production, Hydraulic iii DEPARTMENT OF ENERGY DISCLAIMERThis report was prepared by The University of Oklahoma (OU) as an account of work sponsored, in part, by U.S. Department of Energy (DOE) , Financial Assistance Award DE-FC21-92MC29077. Such support does not constitute an endorsement by DOE of the information contained in this report. UNIVERSITY OF OKLHAOMA DISCLAIMER "LEGAL NOTICE"This report was prepared by The University of Oklahoma as an account of work sponsored by the U.S. Department of Energy (DOE). Neither DOE members of DOE, The Board of Regents of The University of Oklahoma, nor any person acting on behalf of the aforementioned; (a) makes any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or, (b) assumes any liability with respect to the use of, or for damages resulting form the use of any information, apparatus, method, or process disclosed in this report.iv During the contract period, based on consultation received from the Project Advisory Group (PAG) and the Technical Advisory Group (TAG), DOE/GRI periodically modified the statement of work to steer the project toward its goals and objectives....

show abstract

Section: -52mentioning

confidence: 95%

Section: -32mentioning

confidence: 99%

Section: Procedurementioning

confidence: 99%

Section: -63mentioning

confidence: 99%

See 2 more Smart Citations

Fracturing Fluid Characterization Facility

Shah¹

2000

View full text Add to dashboard Cite

show abstract

“…Several papers have been written describing the adverse effect that pumping fracturing fluids at high shear rates has on fluid stability (Goel et al 1997;. Other papers have presented data on the adverse effects on fluid stability caused by pumping fracturing fluids at low rates through coiled tubing (Shah and Subramanian 1997), but little information is available on the adverse effects of pumping at high rates.…”

Section: Introductionmentioning

confidence: 99%

Specific Fluid Requirements for Successful Coiled-Tubing Fracturing Applications

Cawiezel¹,

Wheeler²,

Vaughn³

2007

SPE Production &Amp; Operations

View full text Add to dashboard Cite

The recent success of coiled-tubing fracturing in shallow wells has increased interest in using coiled tubing for fracturing deeper and hotter wells. Industry efforts now need to focus on understanding what properties a fracturing fluid must possess to carry proppant successfully at high rates through coiled tubing, frac ports, and perforations and into these deeper formations. The key performance requirements of a coiled-tubing fracturing fluid for deeper wells are low frictional pressure loss and adequate proppant-carrying capability after exposure to high-shear zones and high temperatures.This paper summarizes the results of pilot-and field-scale testing that led to the development of an optimized coiled-tubing fracturing fluid. Results show that polymer-based fracturing fluids can be controllably delayed to have low frictional pressure loss through the curved coiled-tubing unit and straight tubing. However, results also show that fluid stability can be reduced significantly when the fluid is pumped through small-diameter tubing followed by high-shear zones such as frac ports and then by perforations. Results demonstrate that correct fluid choice and fluid optimization are required to meet proppant-transport requirements. For coiled-tubing fracturing to be successful, the fluid and treatment-design recommendations should balance frictional-pressureloss limitations with fluid-stability limitations.

show abstract

New Empirical Correlation To Predict Apparent Viscosity of Borate-Crosslinked Guar Gel in Fractures

Goel

Shah

Asadi

2000

SPE Production &Amp; Facilities

View full text Add to dashboard Cite

Summary Successful design and completion of hydraulic fracturing treatments depend on accurate estimation of fracturing fluid viscosity. This requires better knowledge of the fluid viscosity under in situ conditions. The viscosity estimation is even more important for borate-crosslinked guar gel because the gel behavior depends on temperature, wellbore shear pre-conditioning, fracture shear rate, and fluid pH. These factors require that the fluid characterization be performed under representative field conditions. Borate-crosslinked gel rheology is currently characterized in the laboratory and there is no theoretical correlation available to describe the gel rheology as a function of its dependent properties. The present study describes a correlation that is developed from data gathered by utilizing a field-scale fracture simulator and is based on the method of reduced variables. The study also extends the method to include the effect of shear history on the rheology of guar crosslinked with borate ions. The correlation relates the apparent viscosity of the crosslinked guar to the fluid temperature, shear history, and shear rate. It is presented in a simple equation, which can be incorporated into fracturing software. The present study also provides master curves of the reduced apparent viscosity-shear rate for the borate-crosslinked guar at three pH values. Introduction Estimation of fluid viscosity is crucial for the success of a hydraulic fracturing treatment. A successful treatment means a wide fracture and proper distribution of proppant in complete length of the fracture; it can be realized with a high-viscosity fracturing fluid. This fact is supported by several case histories which have shown that the viscous fluid system improves the treatment results.1 Prior to a treatment, knowledge of the viscosity is important for proper fracture design. Moreover, the information on the viscosity is necessary for estimation of friction pressure losses down tubular and for prediction of proppant transport in the fracture. Also, reliable predictive viscosity correlations can be integrated into hydraulic fracturing computer simulators. Furthermore, the usefulness of correlations is considerably increased when it is developed from the results of experiments performed using a field-scale fracture simulator. The Fracturing Fluid Characterization Facility (FFCF) has been established to study fluid behavior under representative surface and downhole conditions. The facility characterizes the fluid using field-scale mixing and pumping equipment. The fluid viscosity is measured in a parallel-plate-type device, which has provisions to dynamically vary the fracture gap width. Prior to the viscosity measurements, the fluid is subjected to shear pre-conditioning through various lengths of coiled tubing. This pre-conditioning provides a shear history simulation for the fluid and brings the viscosity measurements under conditions that are closer to the fluid flow in an actual downhole situation. The Importance of Shear History. Shear pre-conditioning of a fluid is important in hydraulic fracturing. This importance arises from the highly sensitive characteristics of crosslinked-based fracturing fluids. Several researchers have shown the effect of pre-shearing on the viscosity of guar crosslinked with different crosslinkers like titanium, zirconium, and borate.2–5 The shear history effects are also well known for other fluid systems;6–10 these effects, however, are not included into the viscosity models used to describe the various systems. The present work is part of a study conducted to include the effect of shear history on the rheological properties of fracturing fluids. The results from experiments performed on the rheology of borate-crosslinked guar-based fracturing fluids were presented earlier.5 In the present paper, these results are utilized to develop an empirical relationship between the fluid viscosity and its controlling parameters. The empirical relationship is based on the method of reduced variables.11 This method is widely used to correlate the rheology of a polymer at different temperatures,12,13 and is also known as the time-temperature superposition.14 The method of reduced variables has been used earlier by other researchers to relate the viscoelastic properties of guar and hydroxypropyl guar (HPG) crosslinked with borate ions.15,16 These studies, however, did not consider the effect of shear history in their measurements. In the present work, the effect of shear history is included in the method of reduced variables and a correlation is developed to relate the nominal shear rate with the borate-crosslinked guar viscosity measured at different temperatures and shear histories. The present study also provides viscosity-shear rate master curves at different fluid pH values. Experimental Procedure A schematic of the experimental setup is shown in Fig. 1. A brief description of the setup is given below; a detailed description of the instruments used in the setup is presented elsewhere.17 A batch of 100 bbl of 35 lbm/Mgal guar polymer solution was prepared in mixing and storage tanks. Upon hydration, the fluid pH was adjusted to a desired level. The adjustment in pH was necessary to initiate a reaction between the borax crosslinker and the polymer. The guar solution was fed to a triplex pump by a centrifugal pump, which was also used to mix the crosslinking agent into the base polymer. The fluid was then pumped through different lengths of coiled tubing. These lengths were varied from 0 to 5,000 ft. The tubings have an internal diameter of 1.188 in. A constant flow rate of 60 gal/min was maintained through the coiled tubing and the pressure drop was measured. A single flow rate was used to maintain uniform shearing prior to characterizing the fluid in the slot flow apparatus. 18,19 The flow through the coiled tubing helped to simulate pre-conditioning of the fluid, and to introduce the effect of shear history into the rheological properties. For the case where fluid viscosity was measured without shearing in coiled tubing, the measurement was termed as "no pre-shear" characterization.

show abstract

A Comparative Study of Borate-Crosslinked Gel Rheology Using Laboratory and Field Scale Fracturing Simulations

Cited by 5 publications

References 0 publications

Fracturing Fluid Characterization Facility

Fracturing Fluid Characterization Facility

Specific Fluid Requirements for Successful Coiled-Tubing Fracturing Applications

New Empirical Correlation To Predict Apparent Viscosity of Borate-Crosslinked Guar Gel in Fractures

Contact Info

Product

Resources

About