Modeling, analysis and simulation of wormhole formation in carbonate rocks with in situ cross-linked acids

Ratnakar, Ram R.; Kalia, Nitika; Balakotaiah, Vemuri

doi:10.1016/j.ces.2012.12.019

Cited by 82 publications

(34 citation statements)

References 21 publications

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“…Therefore, we need 3D numerical simulations to predict quantitatively the experimentally observed results. In the literature, a few 3D numerical studies (Cohen et al 2008;De Oliveira et al 2012;Ratnakar et al 2012Ratnakar et al , 2013Maheshwari et al 2013) have been performed recently to understand the dissolution process. However, these studies deal with slow-reacting acids and may not predict the results quantitatively for fast-reacting acids such as HCl.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Carbonate HCl Acidizing Experiments With 3D Simulations

Maheshwari

Balakotaiah

2013

SPE Production &Amp; Operations

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Acidization of carbonate rocks is a common practice to reduce formation damage near the wellbore. In this process, an acidic solution is injected to dissolve some of the rock, creating conductive channels called wormholes. These wormholes facilitate the flow of hydrocarbons to the wellbore. In the literature, there are several theoretical and experimental studies performed to understand this process. Recent work by Maheshwari et al. 2013 focused on a qualitative comparison of 3D numerical results for slow-reacting acids with experimental data and presented a sensitivity analysis of the acidization process with respect to various transport, reaction, and rock properties. There are very few 3D numerical studies that can predict the experimental results quantitatively, such as the optimum injection rate for fast-reacting acids such as hydrochloric acid (HCl). Therefore, the main objective of this study is to quantitatively predict the experimentally observed acidization curve and dissolution patterns in carbonates with HCl.We present 3D numerical simulations of carbonate acidization with HCl using a two-scale continuum (TSC) model. The model describes the reactive transport at Darcy scale and retains all porescale physics through structure-property relations. Unlike previous studies, we use a new two-parameter (pore-broadening and poreconnectivity) structure-property relation to describe the change in permeability, pore radius, and interfacial area per unit volume with porosity. We predict quantitatively the experimentally observed acidization curve for an HCl/limestone system and show the existence of a critical heterogeneity (that corresponds to the minimum amount of acid required to breakthrough). We also present scaling criteria to estimate the wormhole-tip diameter and optimum acidinjection rate for vuggy and nonvuggy carbonates. Finally, we present the flow dynamics of acid inside the wormhole.

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Section: Introductionmentioning

confidence: 99%

Comparison of Carbonate HCl Acidizing Experiments With 3D Simulations

Maheshwari

Balakotaiah

2013

SPE Production &Amp; Operations

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“…For Indiana limestone, the tracer-concentration profile was found to be symmetrical (C=C 0 ¼ 0:5Þ at 1 pore volume (PV) injected. These results are expected because carbonates of wellconnected intergranular pores exhibit a symmetrical profile approximately 1 PV injection at C=C 0 ¼ 0:5 (Skauge et al 2006). The tracer profile is dominated by a low fraction of inaccessible pores, and no capacitance effect (no dead-end pores) was present.…”

Section: Resultsmentioning

confidence: 57%

Predicting the Performance of the Acid-Stimulation Treatments in Carbonate Reservoirs With Nondestructive Tracer Tests

2015

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Carbonate formations are very complex in their pore structure and exhibit a wide variety of pore classes, such as interparticle porosity, moldic porosity, vuggy porosity, and microporosity. Geologists have defined carbonate pore classes on the basis of sedimentology, thin sections, and porosity/permeability relationships, but the question remains concerning how these pore classes govern the acid flow through porous media.Core samples from six different carbonates, mainly limestone, were selected for the study. The samples were first investigated with thin-section analysis, high-pressure mercury-injection tests, and nuclear-magnetic-resonance measurements for pore-structure characterization, and X-ray diffraction for mineralogy examination. Next, tracer experiments were conducted, and the tracer-concentration profiles were analyzed to quantify the carbonate porescale heterogeneity. The heterogeneity is expressed with a parameter f-the available fraction of pore structure contributing to the flow. The data were used to study the flow of acid through carbonate rocks and correlate the pore classes to the acid response.More than 30 acid-coreflood experiments were conducted at 150 F and a hydrochloric acid concentration of 15 wt% on 1.5 Â 6-in. core samples at different injection rates on each carbonate rock type. The objective of these sets of experiments is to determine the acid pore volume to breakthrough for each carbonate pore class.The findings of this study help us to connect the results from different characterization methods to the acid flow through the porous media of carbonate rocks. It was also found that the response of the acid depends on the carbonate pore classes. Application to the design of matrix acid treatments in carbonate rocks is discussed. IntroductionThe goal of acid-stimulation treatments in carbonate reservoirs is to bypass the formation damage by creating high-conductivity channels known as wormholes. The shape and structure of these wormholes depend on the acid injection rate, among other factors. Hoeffner and Fogler (1988) conducted a set of linear core experiments to study the effect of the injection rate on the wormhole pattern, and the results are very similar to those obtained by Daccord and Lenormand (1987). The wormhole pattern is governed by a competition of axial convection, transverse diffusion, and reaction mechanisms. At low injection rates, the movement of the reaction front is suppressed by the transverse dispersion, and face dissolution occurs (Panga et al. 2005). As the injection rate increases, the dissolution pattern changes from face dissolution to wormhole. Uniform dissolution pattern occurs at high injection rates. Hoefner and Fogler (1989) showed that the transition from one pattern to another depended on the Damköhler number: the ratio of acid reaction rate to acid transport by convection.The beginning 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 on...

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“…And in the acid system, most of the studies focus on diverting acid because of extensive applying in both sandstone and carbonate heterogeneous reservoirs. The simulation results of diverting effects achieved a high agreement with experimental results [18] [19] [20] [21] [22]. The acid types (HAc, CDTA, EDTA and HCl acid system) affecting wormhole patterns, pressure drops, PVBT and wormhole density also achieved an extensively discussion through both laboratory experiments and numerical simulations [15] [18] [22] [23].…”

Section: Introductionmentioning

confidence: 59%

Wormholing Influenced by Injection Temperature in Carbonate Rocks

Xue¹,

Huang²,

Zhao³

et al. 2019

OJOGas

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This paper presented empirical models of describing reaction rate vs. hydrochloric acid temperature and concentration by regressing experimental data. And this paper also introduced the dependent reaction heat model into the thermal non-equilibrium models and coupled with two-scale continuum model to obtain governing equations for describing wormholing under non-isothermal conditions. The governing equations were discretized by implicit difference method and solved by programing. The effects of temperature on wormholing have been investigated based on the simulation results on 2-D vision. A significant difference of the effluent temperature between the dependent reaction heat model in present work and the constant reaction heat model in available literatures was observed, especially in high injection rate and strong acid concentration. In addition, the tendencies of optimum injection capacity vs. injection temperature under isothermal and non-isothermal conditions were almost different. Finally, an optimum injection temperature was found by changing the injection temperature under non-isothermal conditions. 13Open Journal of Yangtze Gas and Oil the production of carbonate reservoirs were based on investigations of the initiation and propagation of wormholes or unstable dissolution fronts. Many mathematical models were developed to describe the wormhole patterns observed in experiment results [1] [2] [3] [4]: the capillary tube model [5] [6] [7]; the network model [8]; the averaged model [4] [9]; the fractal model [1] [2]. Pangaet al. (2005) coupled Darcy-scale dissolution model with the pore-scale model to summarize the governing equations which is called the two-scale continuum model [10]. In this model, the macroscopic properties such as mass transfer coefficients and dispersion properties were properly considered. Since the results calculated from the two-scale continuum model matched experiment results very well, most of the extension simulation studies were based on them. Kalia and Balakotaiah (2007) studied dissolution patterns in radial flow by extending the linear model to radial model [11]. Maheshwari et al. (2013) analyzed the 3-D dissolution patterns [12]. Smith et al. (2013) simulated core CO 2 flooding of low permeability carbonates coupled with X-ray computed microtomography (XCMT) [13]. The wormholing process is very complicated since there are many known factors influencing convection, dispersion and reaction properties, such as acid system, concentration of acid, porosity or permeability distribution, fracture or vug medium, injection conditions, acid flow types and temperature. In the physical heterogeneities, Kalia and Balakotaiah (2009) used a unique heterogeneity parameter to characterize porosity heterogeneity, and found that the dissolution depended on the orientation of fractures [14]; Liu et al. (2012) introduced a The designate parameters f γ , m Cl , B HCl , E and C HCl in Equation (8) are given by Alkattan et al. (1998) [28]. Pore Scale ModelThe dissolution process determined local qua...

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Modeling, analysis and simulation of wormhole formation in carbonate rocks with in situ cross-linked acids

Cited by 82 publications

References 21 publications

Comparison of Carbonate HCl Acidizing Experiments With 3D Simulations

Comparison of Carbonate HCl Acidizing Experiments With 3D Simulations

Predicting the Performance of the Acid-Stimulation Treatments in Carbonate Reservoirs With Nondestructive Tracer Tests

Wormholing Influenced by Injection Temperature in Carbonate Rocks

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