Impact of acid wormhole on the mechanical properties of chalk, limestone, and dolomite: Experimental and modeling studies

Mustafa, Ayyaz; Alzaki, Taqi; Aljawad, Murtada Saleh; Sølling, Theis I.; Dvorkin, Jack

doi:10.1016/j.egyr.2021.11.249

Cited by 23 publications

(10 citation statements)

References 16 publications

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“…However, when the injection rate is substantially greater than the reaction rate, branching wormholes are formed. This was corroborated in the work of Mustafa et al (2022). Thus, the development of a wormhole is maximized at a certain Damkohler number (i.e., the ratio of reaction rate to mass transfer).…”

Section: Resultsmentioning

confidence: 99%

“…• Furthermore, the results also demonstrated that the mechanical properties exhibit rock weakening post-acid treatment. The mechanical properties (i.e., elastic modulus, Poisson's ratio, material index, and the coefficient of lateral earth pressure at rest) showed that the rock weakened after acidizing, and this finding is in line with the work of other researchers (Lai et al 2021;Mustafa et al 2022;Zhang et al 2020a). • Young's modulus for the seven rock samples investigated exhibited a reduction of 26-37%.…”

Section: Discussionmentioning

confidence: 99%

“…In this study, acid core-flooding tests were carried out at various injection rates on different rock samples, causing the wormholes to differ in structure from one rock sample to the other and even within the same rock type. The size and nature of the wormhole may be responsible for the change in mechanical and physical characteristics of the rock (Artyushkova et al 2021;Martyushev et al 2019;Mustafa et al 2022;Song et al 2021;Zhang et al 2020a). Micro-CT images of two of the acidized rock samples were reconstructed using the 3D Slicer software.…”

Section: Computed Tomography (Ct)mentioning

confidence: 99%

“…In radial acid treatment experiments of hollow chalk samples, Walle and Papamichos (2015) demonstrated that acidizing rock samples causes a reduction in the rock's mechanical strength, and this was confirmed by comparing the mechanical properties of the acid-treated rocks and the intact ones. Mustafa et al (2022) studied the impact of acid wormholes on the mechanical properties of carbonates (chalk, limestone, and dolomite), and their findings indicate that acidizing reduces the hardness and elastic modulus of the rocks. The authors noted that dolomite was the least impacted by the acid treatment, while chalk samples were affected the most.…”

Section: Introductionmentioning

confidence: 99%

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Effect of acid treatment on the geomechanical properties of rocks: an experimental investigation in Ahdeb oil field

Alameedy

Alhaleem

Isah

et al. 2022

J Petrol Explor Prod Technol

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Acidizing is one of the most used stimulation techniques in the petroleum industry. Several reports have been issued on the difficulties encountered during the stimulation operation of the Ahdeb oil field, particularly in the development of the Mishrif reservoir, including the following: (1) high injection pressures make it difficult to inject acid into the reservoir formation, and (2) only a few acid jobs have been effective in Ahdeb oil wells, while the bulk of the others has been unsuccessful. The significant failure rate of oil well stimulation in this deposit necessitates more investigations. Thus, we carried out this experimental study to systematically investigate the influence of acid treatment on the geomechanical properties of Mi4 formation of the Mishrif reservoir. The acid core-flood experiments were performed on seven core samples from the oil reservoir in central Iraq. The porosity, permeability, acoustic velocities, rock strength, and dynamic elastic parameters were computed before and after the acidizing treatment. To determine the optimal acid injection rate, different injection flow rates were used in the core-flooding experiments. The propagation of an acid-induced wormhole and its effect on the rock properties were analyzed and compared to that of intact rocks. Computed tomography (CT) scan and a 3D reconstruction technique were also conducted to establish the size and geometry of the generated wormhole. To analyze the influence of mineralogical variation and heterogeneity and confirm the consistency of the outcomes, acidizing experiments on different rock samples were conducted. The results demonstrate that for all the rock samples studied, the mechanical properties exhibit rock weakening post-acid treatment. The Young’s modulus reduced by 26% to 37%, while the Poisson’s ratio, the coefficient of lateral earth pressure at rest, and the material index increased by 13% to 20%, 23% to 32%, and 28% to 125%, respectively. The CT scan visually confirmed that the acid treatment effectively creates a pathway for fluid flow through the core.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Computed Tomography (Ct)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of acid treatment on the geomechanical properties of rocks: an experimental investigation in Ahdeb oil field

Alameedy

Alhaleem

Isah

et al. 2022

J Petrol Explor Prod Technol

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“…The effect of straight fractures and arc fractures on wormholes was defined. Mustafa et al (2022) [ 23 ] established acid efficiency curves which included different rock lithologies (chalk, limestone, and dolomite) that react with gelling acid at different injection rates. The rock surface hardness at ambient pressure was measured by the impulse hammer technique, and the dynamic Young’s modulus and Poisson ratio were measured through acoustic measurements at high confining pressures.…”

Section: Introductionmentioning

confidence: 99%

Simulated Investigation in Wormhole Expansion Law of Gelling Acid Etching and Its Influencing Factors in Deep Carbonate Reservoirs

Wang

Zhou

Li³

et al. 2022

Gels

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Acidizing with gelling acid is the key technology in developing a carbonate reservoir successfully. It is difficult for the laboratory to carry out the radial displacement experiment with a large rock core. It is necessary to establish the gelling acid wormhole expansion model under the radial conditions, simulate the gelling acid wormhole expansion law under the radial conditions, optimize the construction parameters, and provide the basis for the optimal design of carbonate reservoir matrix acidizing. The research objective is to simulate the gelling acid etching wormhole expansion in a deep carbonate reservoir and make clear its influencing factors, which are helpful for reservoir stimulation. The mathematical model of gelling acid wormhole expansion was established, considering the influence of pore microscopic characteristics on acid flow and acid rock reaction. The simulation results indicated that viscosity, surface reaction rate, and hydrogen ion diffusion coefficient have different effects on gelling acid etching wormhole. The spatial distribution of pores determines the trend of gelling acid solution and thus the shape of the armhole. Perforation completion has a significant impact on the expansion of gelling acid etching wormhole. The wormhole extends forward along the perforation hole, and perforation increases the length of the wormhole. This wormhole expansion law is very suitable in situations where a deep carbonate reservoir is needed for gelling acid fracturing.

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Sustaining Wormholes Mechanical Stability in Weak Acidized Carbonates Using Consolidants

et al. 2023

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Impact of acid wormhole on the mechanical properties of chalk, limestone, and dolomite: Experimental and modeling studies

Cited by 23 publications

References 16 publications

Effect of acid treatment on the geomechanical properties of rocks: an experimental investigation in Ahdeb oil field

Effect of acid treatment on the geomechanical properties of rocks: an experimental investigation in Ahdeb oil field

Simulated Investigation in Wormhole Expansion Law of Gelling Acid Etching and Its Influencing Factors in Deep Carbonate Reservoirs

Sustaining Wormholes Mechanical Stability in Weak Acidized Carbonates Using Consolidants

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