The Effect of Pore-Scale Heterogeneities on Carbonate Stimulation
Treatments

Ziauddin, Murtaza; Bize, Emmanuel

doi:10.2523/104627-ms

Cited by 14 publications

(7 citation statements)

References 11 publications

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“…Carbonate reservoirs account for around 50% to 60% of the world's total oil and gas reserves (Sha et al, 2019;Zaeri et al, 2018). However, these reservoirs are characterized by heterogeneities on different scales (He et al, 2014;Sha et al, 2019;Wei et al, 2015;Ziauddin and Bize, 2007) and a tendency to oil wetness (Al-Hadhrami and Blunt, 2000;Hirasaki and Zhang, 2004;Wardlaw, 1996;Zaeri et al, 2018). These characteristics difficult the oil recovery in such reservoirs.…”

Section: Introductionmentioning

confidence: 99%

Experimental evaluation of low concentration scleroglucan biopolymer solution for enhanced oil recovery in carbonate

Ferreira

Moreno

2020

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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Injection of polymers is beneficial for Enhanced Oil Recovery (EOR) because it improves the mobility ratio between the displaced oil and the displacing injected water. Because of that benefit, polymer flooding improves sweep and displacing efficiencies when compared to waterflooding. Due to these advantages, polymer flooding has many successful applications in sandstone reservoirs. However, polymer flooding through carbonatic rock formations is challenging because of heterogeneity, high anionic polymer retention, low matrix permeability, and hardness of the formation water. The scleroglucan is a nonionic biopolymer with the potential to overcome some of those challenges, albeit its elevated price. Thus, the objective of this work is to characterize low concentration scleroglucan solutions focusing on EOR for offshore carbonate reservoirs. The laboratory evaluation consisted of rheology, filtration, and core flooding studies, using high salinity multi-ionic brines and light mineral oil. The tests were run at 60 °C, and Indiana limestone was used as a surrogate reservoir rock. A rheological evaluation was done in a rotational rheometer aiming to select a target polymer concentration for the injection fluid. Different filtration procedures were performed using membrane filters to prepare the polymer solution for the displacement process. Core flooding studies were done to characterize the polymer solution and evaluate its oil recovery relative to waterflooding. The polymer was characterized for its retention, inaccessible pore volume, resistance factor, in-situ viscosity, and permeability reduction. Rheology studies for various polymer concentrations indicated a target scleroglucan concentration of 500 ppm for the injection solution. Among the tested filtration methods, the best results were achieved when a multi-stage filtration was performed after an aging period of 24 h at 90 °C temperature. The single-phase core flooding experiment resulted in low polymer retention (20.8 μg/g), inaccessible pore volume (4.4%), and permeability reduction (between 1.7 and 2.4). The polymer solution in-situ viscosity was slightly lower and less shear-thinning than the bulk one. The tested polymer solution was able to enhance the oil recovery relative to waterflooding, even with a small reduction of the mobility ratio (38% relative reduction). The observed advantages consisted of water phase breakthrough delay (172% relative delay), oil recovery anticipation (159% and 10% relative increase at displacing fluid breakthrough and 95% water cut, respectively), ultimate oil recovery increase (6.3%), and water-oil ratio reduction (38% relative decrease at 95% water cut). Our results indicate that the usage of low concentration scleroglucan solutions is promising for EOR in offshore carbonate reservoirs. That was supported mainly by the low polymer retention, injected solution viscosity maintenance under harsh conditions, and oil recovery anticipation.

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Section: Introductionmentioning

confidence: 99%

Experimental evaluation of low concentration scleroglucan biopolymer solution for enhanced oil recovery in carbonate

Ferreira

Moreno

2020

Oil Gas Sci. Technol. – Rev. IFP Energies nouvelles

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“…This would result in enormous computational time, and it practically limits the domain size to a few inches on even the most powerful computers available today. Therefore, it is much more efficient to investigate the influence of pore-scale heterogeneity experimentally and represent it by an average PV bt curve . The approach and data reported in this study can be used for this purpose.…”

Section: Applicationmentioning

confidence: 99%

“…Therefore, it is much more efficient to investigate the influence of pore-scale heterogeneity experimentally and represent it by an average PV bt curve. 24 The approach and data reported in this study can be used for this purpose. A single tracer test can be conducted with nondestructive fluid on a reservoir core sample without significant core-scale heterogeneity, and the flowing fraction can be then measured.…”

Section: ■ Applicationmentioning

confidence: 99%

Flow of Emulsified Acid in Carbonate Rocks

Zakaria

Nasr‐El‐Din

Ziauddin

2015

Ind. Eng. Chem. Res.

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We conducted tracer experiments on core samples from six different carbonates to study the flow of acid fluid through the porous media of carbonate rocks and correlate the carbonate pore classes to the acid response. Pore structures were characterized by section analysis, high pressure mercury injection tests, and nuclear magnetic resonance measurements; mineralogy was determined by X-ray diffraction. Tracer concentration profiles were analyzed to quantify the carbonate pore-scale heterogeneity. The heterogeneity is expressed using a parameter fthe available fraction of pore structure contributing to the flow. From the results, different characterization methods could be connected to the acid fluid flow through the porous media of carbonate rocks. It was also found that the response of the acid depends on the carbonate pore classes. Applications include the design of matrix acid treatments in carbonate rocks. ■ INTRODUCTIONThe goal of acid-stimulation treatments in carbonate reservoirs is to remove or bypass formation damage by creating highconductivity channels known as wormholes. To propagate deeper wormholes in the formation for better productivity enhancement, retarded acids should be used. Emulsified acids are one of the most widely used retarded-acid systems. HCl acid is commonly used as the internal phase of the emulsion. For the external phase, oil and diesel are the most commonly used hydrocarbons. The external hydrocarbon phase acts as a diffusion barrier to reduce the diffusion of the acid droplets to the surface of the rock, 1,2 which helps in the creation of deep wormholes. Several studies 3−5 examined the reaction of emulsified acid with carbonate. Navarrette et al. 4 indicated that the reaction rate of 28 wt % HCl emulsified acid with limestone was 8.5 times less than that of 28 wt % HCl with limestone. Al-Anazi et al. 6 studied the application of the emulsified acid in tight carbonate rocks using coreflood experiments, and the results showed that the emulsified acid can form deep wormholes in tight carbonate cores. Buijse and van Domelen 7 studied the effect of the injection rate, viscosity, and acid volume fraction on the emulsified acid pore volume to breakthrough in carbonate rocks. Sayed et al. 8 studied the performance of the emulsified acid in low and high permeability carbonate formations using coreflood experiments. It was found that the high permeability carbonate cores consumed more acid volume to breakthrough than did the low permeability cores. Also, an optimum injection rate was observed for the highpermeability cores whereas the acid pore volumes to breakthrough decreased with increases in the injection rate for lowpermeability formations.Hoefner and Fogler 9 studied the pore evolution during the flow and the reaction of the acid in porous media. The initiation of wormholes occurs when the live acid penetrates into pores present in carbonate rocks, and then, pore structure evolution occurs. The process is more efficient when only the large pores in the matrix lead to wormholes. 10 C...

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“…Ziauddin and Bize studied core samples from eight different carbonate rocks and classified them into a Reservoir Rock Types (RRT) based on type of porosity [14]. They observed that connected heterogeneous porosities were favorable to faster wormhole growth.…”

Section: Literature Reviewmentioning

confidence: 99%

Digital Rock Technology for Quantitative Prediction of Acid Stimulation Efficiency in Carbonates

Klemin

Nadeev

Ziauddin

2015

SPE Annual Technical Conference and Exhibition

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The complex pore structure and porosity in carbonate rocks have a strong influence on the stimulation efficiency of the acid. Recently, it was shown that nondestructive tracers can be used to predict pore volume of acid to breakthrough (PVBT) for both plain and emulsified acids [1,2]. The present study explores the use of digital rock technology to simulate tracer injection in carbonate rocks. The accuracy of the digital rock method is compared to the laboratory measured values for five carbonate rocks of different porosity types and heterogeneity scales. The digital rock simulations are performed by an industry-unique direct hydrodynamic pore flow simulator that operates on pore geometries from digital rock models obtained from 3D scanning electron microscope images. The pressure-volume-temperature and rheological models used in the simulator represent real treatment and reservoir fluids. Fluid-solid interactions are introduced using distributed microscale wetting properties. The simulator uses the density functional approach applied to the hydrodynamics of complex systems. The simulations are used to calculate a measure of the accessible rock volume which is then used to predict the acid response.Conventional laboratory testing methods require large volumes of formation rocks for optimization of acid type and volume and it often prohibitively expensive. The digital rock methodology has the potential of significantly reducing the required volume of formation cores, which could be an enabler for more frequent carbonate porosity specific stimulation optimization. The present study explores the limits of its applicability.

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The Effect of Pore-Scale Heterogeneities on Carbonate Stimulation Treatments

Cited by 14 publications

References 11 publications

Experimental evaluation of low concentration scleroglucan biopolymer solution for enhanced oil recovery in carbonate

Experimental evaluation of low concentration scleroglucan biopolymer solution for enhanced oil recovery in carbonate

Flow of Emulsified Acid in Carbonate Rocks

Digital Rock Technology for Quantitative Prediction of Acid Stimulation Efficiency in Carbonates

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