Acid Diversion by Use of Viscoelastic Surfactants: The Effects of Flow Rate and Initial Permeability Contrast

Al-Ghamdi, A.H.; Mahmoud, Mohamed; Wang, Guanqun; Hill, A.D.; Nasr‐El‐Din, Hisham A.

doi:10.2118/142564-pa

Cited by 41 publications

(11 citation statements)

References 9 publications

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“…An experimental study of shear stability of several high-molecular weight polymers used as mobility control agents in EOR projects has been performed in wellcontrolled conditions [149,150]. The shearing device was made of a capillary tube with an internal diameter of 125 μm, through which polymer solution was injected at a controlled rate.…”

Section: Shear Stabilitymentioning

confidence: 99%

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Enhanced oil recovery

2015

Petroleum Engineer's Guide to Oil Field Chemicals and Fluids

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Section: Shear Stabilitymentioning

confidence: 99%

“…Various commercial EOR polymer products were tested with a poly(acrylamide) backbone and different substitution monomer groups [149,150]. All macromolecules behave as flexible coils in solution.…”

Section: Shear Stabilitymentioning

confidence: 99%

Enhanced oil recovery

2015

Petroleum Engineer's Guide to Oil Field Chemicals and Fluids

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“…It was found that the maximum apparent viscosity, which developed during VES-based acids injection, occurred over a narrow window of acid-injection rates [243,244]. The acid-injection rate was found to be a critical parameter to maximize the efficiency of the use of VES-based acids as a diverting chemical in addition to creating wormholes.…”

Section: Matrix Stimulationmentioning

confidence: 99%

“…Both single-and parallel-coreflood experiments were performed in a study [243,244]. Carbonate cores were used with initial permeabilities of 4-150 mD, and the flow rate was varied from 1.5 to 50 cm 3 min 1 .…”

Section: Matrix Stimulationmentioning

confidence: 99%

Fracturing fluids

2015

Petroleum Engineer's Guide to Oil Field Chemicals and Fluids

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Hydraulic fracturing is a technique to stimulate the productivity of a well. A hydraulic fracture is a superimposed structure that remains undisturbed outside the fracture. Thus the effective permeability of a reservoir remains unchanged by this process. The increased productivity results from the increased wellbore radius, because in the course of hydraulic fracturing, a large contact surface between the well and the reservoir is created.The literature from 2004 to 2014, more than 100 references concerning waterbased fracturing fluids for fracturing ultralow-to moderate-permeability reservoirs has been reviewed [1].Guar-based polymers are still used in fracturing at temperatures less than 150 • C. To minimize the damage associated with this class of polymers, several approaches are known. These include the use of a lower polymer concentration in formulating these fluids and the use of different crosslinking agents. Higher viscosities with lower polymer loadings can be achieved. In addition, cleaner guar-based polymers are used now, because commercial guar contains some 5% of residues, which may cause a damage of proppant packs.It has been found that shear and pressure effects on the rheological behavior of borate crosslinked gels are important. Although these fluids recover their viscosity after shear, they have been observed to lose a significant portion of their viscosity under high pressures.When fracturing is done in deeper wells, i.e., in hotter reservoirs, a new class of thermally stable polymers became relevant. These are poly(acrylamide)-based polymers. These synthetic polymers show a sufficient viscosity at temperatures up to 230 • C [1]. Examples are 2-acrylamido-2-methylpropanesulfonic acid and copolymers of partially hydrolyzed acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, and vinyl phosphonate. High-density brines have been used to increase the hydrostatic pressure by 30% for high-pressure pumping.Also, new breaker materials emerged [1]. These breakers destroy the gel by a reaction with the crosslinking agent. They form ligands with the metallic crosslinking agents and displace them from the crosslinking moieties of the guar-based polymers. Examples of these breakers include poly(succinimide) derivates and lignosulfonate derivates.To minimize the environmental impact of using massive amounts of fresh water and to minimize costs associated with treating produced water, the use of produced water in hydraulic fracturing treatments has been reported. Petroleum Engineer's Guide to Oil Field Chemicals and Fluids. http://dx.567 568 CHAPTER 17 Fracturing fluids B HO 17.3 Types of hydraulic fracturing fluids 571 TYPES OF HYDRAULIC FRACTURING FLUIDSGenerally, a hydraulic fracturing treatment involves pumping a proppant-free viscous fluid, or pad, usually water with some fluid additives to generate high viscosity, into a well faster than the fluid can escape into the formation so that the pressure rises and the rock breaks, creating artificial fractures or enlarging existing fractures.After fracturing...

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“…Single and dual coreflood experiments at reservoir conditions can be used to evaluate the efficiency of a certain VES-based fluid for diversion. Al-Ghamdi et al (2014) examined the constraints that limit the success of using VES-based fluids in terms of the initial contrast in permeability of the two zones for which the diversion is intended. The study concluded that the maximum performance of VES acid systems is achieved when the ratio of permeability is initially lower than 10.…”

Section: Introductionmentioning

confidence: 99%

New Viscoelastic Surfactant with Improved Diversion Characteristics for Carbonate Matrix Acidizing Treatments

et al. 2016

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Viscoelastic surfactants (VES) have been used to replace polymer-based fluids as effective, cleaner, and non-damaging viscofying carriers in frac-packing, acid fracturing, and matrix acidizing. However, several limitations challenge the use of VES-based fluids including: thermal instability, incompatibility with alcohol-based corrosion inhibitor, and intolerance to the presence of contaminating iron. This work introduces a new VES-based acid system for diversion in matrix acidizing that exhibits excellent thermal stability and diversion performance in both low-and high-temperature conditions. Rheology measurements were conducted on spent VES-acid system as a function of temperature (77-300°F) at a pH of 4-5. The effect of acidizing additives on the VES viscosity was investigated. The additives included a corrosion inhibitor, non-emulsifier, iron-chelating agent, and iron-reducing agent. Single and dual coreflood experiments were performed using limestone core samples with an initial permeability range of 4-200 md and a permeability contrast of 1.5-55. Post CT-scan imaging was conducted to investigate the wormhole topography. The diversion characteristic of the new VES in the dual coreflood experiments was evaluated by the structure and the extent of wormhole propagation in the low-permeability core.Rheological data for 15 wt% HCl spent VES-solutions showed a maximum viscosity of 200-800 over a temperature range of 150-170°F, depending on the VES concentration in the sample. Without acidizing additives, a minimum of 50 cP was obtained at 195, 230, 250, and 275°F at 4, 5, 6, and 8 vol% of the VES in solution, respectively. None of the tested acidizing additives had a negative impact on the VES viscosity. At 8% VES loading, the acidizing package was optimized such that a minimum of 75 cP was obtained at 300°F.Dual coreflood experiments were conducted at 150 and 250°F, and the results proved the ability of the proposed VES to divert efficiently in limestone formations. Single coreflood experiments also confirmed these results. Coreflood data indicated that a range of permeability contrast of 4-10 is the optimum for diversion ability in terms of the final permeability enhancement of the low-permeability cores. The results revealed 18.6, 45.6, 82%, and infinity when the permeability contrast was 28.3, 14.4, 6. 3, 1.63, respectively. A dual coreflood experiment was conducted for two cores with a permeability contrast of 1.6 at 150°F. The VES-acid system in the presence of all acidizing additives exhibited divergent performance that exceeded the performance of the VES in the absence of additivies. These results prove the stable performance of the VES and the enhancement in viscosity response after addition of both the iron-control agent and the non-emulsfier, which resulted in less acid leakoff and better wormhole structure.

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Acid Diversion by Use of Viscoelastic Surfactants: The Effects of Flow Rate and Initial Permeability Contrast

Cited by 41 publications

References 9 publications

Enhanced oil recovery

Enhanced oil recovery

Fracturing fluids

New Viscoelastic Surfactant with Improved Diversion Characteristics for Carbonate Matrix Acidizing Treatments

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