Quantifying Acid Placement: The Key to Understanding Damage Removal in Horizontal Wells

Jones, A.T.; Davies, David Roland

doi:10.2118/50975-pa

Cited by 19 publications

(6 citation statements)

References 29 publications

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“…Polymer can adsorb at the interface and crosslink physically on a large scale at the interface. The organized structure formed at the interface increases the interfacial elasticity and prevents the droplet coalescence during the emulsion composition (Kang et al 2011). It is theorized that the elastic droplets resist the deformation or the change in the structure of the droplets or the coalescence of the droplets upon collision during the emulsion composition (Saiki et al 2006).…”

Section: Experimental Studiesmentioning

confidence: 99%

A Novel Polymer-Assisted Emulsified-Acid System Improves the Efficiency of Carbonate Matrix Acidizing

Zakaria

Nasr‐El‐Din

2016

SPE Journal

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In highly heterogeneous carbonate reservoirs, several acid systems were used to enhance acid diversion during matrix-acidizing treatments. Viscosified acid with polymer increases the viscosity of the acid system to improve the wellbore coverage. However, the injection of such acid at low rates had a negative effect on the spending rate and starts filter-cake formation, which inhibits the wormhole growth. On the other hand, relatively low-viscosity emulsified acid is diffusion-retarded, which makes it an effective wormholing agent at the low injection rates that occur, for example, in low-permeability or damaged formations. None of the studies in the literature addresses an acid system that uses both advantages.The objective of this work was to investigate the behavior and the performance of a new acid system, polymer-assisted emulsified acid, as a self-diverting acid by conducting viscosity measurements through coreflood study and acid-diversion experiments. The system was 15 wt% hydrochloric acid (HCl)-gelled acid emulsified in diesel with a 70:30 acid/diesel volume ratio.Coreflood experiments with Indiana limestone were conducted at 230 F at different injection rates, and the core samples were imaged with a computed-tomography (CT) scan technique after each coreflood experiment. Also, 0.5 pore volumes (PV) of the polymer-assisted emulsified acid was injected to assess the effect of the acid on the permeability of the cores before breakthrough. Finally, two acid-diversion experiments at 1 cm 3 /min were conducted into pairs of low-and high-permeability cores to test the effect of polymer concentration in the acid internal phase on diversion.The viscosity measurements and acid-diffusivity measurements showed that increasing the polymer concentration in the acid internal phase of the emulsified acid from 0 to 1.5 vol% significantly enhanced the viscosity of the emulsified acid and reduced the diffusion coefficient by one order of magnitude. Coreflood results showed that the polymer-assisted emulsified acid was an effective wormholing fluid at low injection rates while maintaining the high viscosity of the acid system for zonal coverage.Also, it was shown that the emulsion/polymer retention was the main source for permeability damage. However, flowback with mutual solvent removed any remaining damage, and permeability enhancement was achieved.Acid-diversion experiments are presented that show the selfdiverting ability of the polymer-assisted emulsified acid into the low-permeability cores.

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Section: Experimental Studiesmentioning

confidence: 99%

A Novel Polymer-Assisted Emulsified-Acid System Improves the Efficiency of Carbonate Matrix Acidizing

Zakaria

Nasr‐El‐Din

2016

SPE Journal

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“…Another advantage of emulsified acid over conventional acid is that when used in a heterogeneous reservoir, emulsified acid can enhance the acid diversion and wellbore coverage across the targeted thickness of the reservoir (Jones and Davies 1998;Jones and Dovle 1996). On the other hand, plain acid has a viscosity similar to water.…”

Section: Introductionmentioning

confidence: 99%

Application of emulsified acids on sandstone formation at elevated temperature conditions: an experimental study

Shafiq

Chong

Mahmud

et al. 2018

J Petrol Explor Prod Technol

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Emulsified acid has attracted considerable attention of the oil and gas industry due to its delayed nature that allows deeper penetration of acid into the formation which essentially facilitate further enhancing the well productivity, and at the same time minimizes the corrosion issues. However, emulsified acid has only been extensively studied and applied on carbonate formations. Considering more than half of the reservoirs worldwide are sandstone reservoirs, studying the effects of emulsified acid on sandstone under high-temperature conditions would unlock the potential of emulsified acid and help generate more value for the oil and gas industry by improving the well productivity from sandstone reservoirs. To ensure the applicability of the emulsified acid on the real sandstone reservoir, which usually has a temperature higher than ambient conditions, the stability of emulsified acids is investigated under 300 °F. Then, the stable emulsified acid samples are developed and their impact on the properties of Berea sandstone core samples, including porosity, pore-size distribution, permeability and wettability, are investigated. The core samples have undergone pre-flush (10% HCl:5% CH 3 COOH) before the main flush (emulsified acid). The emulsified acids are prepared using hydrofluoric acid, hydrochloric acid, phosphoric acid, cationic surfactant and chelating agent. Fourteen core samples are saturated with different emulsified acids under vacuum conditions for 3 days to ensure maximum saturation. The porosity, permeability and wettability of each core sample are measured before and after the reaction with acid. Nuclear magnetic resonance analysis has been applied to evaluate the change in pore size distribution. This study has demonstrated that the emulsified acids are capable of improving the porosity and permeability of Berea sandstone core sample. The pore size distribution has also been affected by the application of emulsified acid, where more large pores have been evolved to the core samples due to the reaction of acids with the sandstone which ultimately helps in improving the productivity of hydrocarbons. This indicates less precipitation of the secondary reaction products resulting better enhancement in sandstone flow properties. These results demonstrate the potential of emulsified acid during sandstone acidizing as emulsified acid significantly improved the sandstone properties which can essentially enhance the well productivity.

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“…Without proper design, the treatment will lead to a non-uniform coverage of interest zones and an unsuccessful acid treatment. The increase in acid viscosity can improve the acid diversion in the formation (Jones and Dole 1996;Jones and Davies 1998). In-situ gelled acids are crosslinked polymer based acids.…”

Section: Introductionmentioning

confidence: 99%

Application of Novel Polymer Assisted Emulsified Acid System Improves the Efficiency of Carbonate Acidizing

Zakaria

Nasr‐El‐Din

2015

SPE International Symposium on Oilfield Chemistry

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In highly heterogeneous carbonate reservoirs, several acid systems have been used to enhance acid diversion during matrix acidizing treatments. Viscosified acid with polymer increases the viscosity of the acid system to improve the wellbore coverage. However, the injection of such acid at low rates had a negative effect on the spending rate and it initiates filter cake formation which inhibits the wormhole growth. On other hand, relatively low viscosity emulsified acid is diffusion retarded which makes it an effective wormholing agent at the low injection rates that occur, for example in low permeability, or damaged formations. None of the studies in the literature address an acid system that uses both advantages.The objective of this work was to investigate the behavior and the performance of a new acid system, polymer assisted emulsified acid, as a self-diverting acid by conducting viscosity measurements thorough coreflood study and acid diversion experiments. The system was 15 wt% gelled acid emulsified in diesel with a 70:30 acid/diesel volume ratio.Coreflood experiments using Indiana limestone were conducted at 230°F at different injection rates and the core samples were imaged using a computed-tomography (CT) scan technique after each coreflood experiment. Also, a 0.5 PV of the polymer assisted emulsified acid was injected to assess the effect of the acid on the permeability of the cores before breakthrough. Finally, two acid diversion experiments at 1 cm 3 /min were conducted into pairs of low and high permeability cores to test the effect of polymer concentration in the acid internal phase on diversion.The viscosity measurements and acid diffusivity measurements showed that increasing the polymer concentration in the acid internal phase of the emulsified acid from 0 to 1.5 vol% significantly enhanced the viscosity of the emulsified acid and reduced the diffusion coefficient by one order of magnitude. Coreflood results showed that the polymer assisted emulsified acid was an effective wormholing fluid at low injection rates while maintaining the high viscosity of the acid system for zonal coverage.Also, it was shown that the emulsion/polymer retention was the main source for permeability damage. However, flowback with mutual solvent removed any remaining damage and permeability enhancement was achieved.Acid diversion experiments are presented that show the self-diverting ability of the polymer assisted emulsified acid into the low permeability cores.

show abstract

Quantifying Acid Placement: The Key to Understanding Damage Removal in Horizontal Wells

Cited by 19 publications

References 29 publications

A Novel Polymer-Assisted Emulsified-Acid System Improves the Efficiency of Carbonate Matrix Acidizing

A Novel Polymer-Assisted Emulsified-Acid System Improves the Efficiency of Carbonate Matrix Acidizing

Application of emulsified acids on sandstone formation at elevated temperature conditions: an experimental study

Application of Novel Polymer Assisted Emulsified Acid System Improves the Efficiency of Carbonate Acidizing

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