Simulation of Dissolution Front Propagation During Acid Injection Into Porous Media: A CFD Approach

2018 ◽  
Author(s):  
Elsayed Abdelfatah ◽  
Maysam Pournik ◽  
David Craig
Keyword(s):  
Porous Media ◽  
Reaction Rate ◽  
Surface Reaction ◽  
Injection Pressure ◽  
Fluid Temperature ◽  
Thermal Interaction ◽  
Acid Dissolution ◽  
Acid Rock ◽  
Rock Interaction ◽  
Dissolution Front

Acid is often injected into porous media to dissolve rock material and enhance flow capability of the rock. Most simulation studies on the propagation of the dissolution front are based on constant injection rate (CIR). Therefore, the objective of this work is to develop numerical model to study acid dissolution front under constant injection pressure (CIP) and also incorporate the effect of fluid temperature on acid–rock interaction. Commercial computational Fluid Dynamics (CFD) software (ANSYS Fluent) is used to solve three-dimensional acid-rock interaction model in cylindrical coordinates. In this work, correlated porosity and permeability distributions are generated. Effect of heat transfer between the injected fluid and the formation on fluid properties and surface reaction rate are accounted for in the model. The study confirmed that all types of acid dissolution patterns exist during constant injection pressure. CIP technique requires lower acid volume to achieve breakthrough in the conical and branched dissolution regimes, than that is required for CIR technique. In dominant wormhole pattern, both techniques require nearly the same acid volume to breakthrough. Thermal interaction between the injected fluid and the formation leads to change of surface reaction rate and physical properties of the fluid, such as viscosity, density, and diffusivity. Injection of cold fluid into heated formation leads to a higher wormhole density as found from experimental studies due to retardation of surface reaction rate. The model developed in this work accurately captures different dissolution patterns. The model shows that the acid volume required for wormhole breakthrough depends on the inlet conditions (CIR or CIP) and the thermal interaction between the injected fluid and formation. This modeling study attempts to answer the critical questions pertaining to the effect of temperature and injection conditions on acid-rock interaction.

Effect of Heat of Reaction on Temperature Distribution and Acid Penetration in a Fracture

1980 ◽  
Vol 20 (06) ◽  
pp. 501-507 ◽  
Author(s):  
M.H. Lee ◽  
L.D. Roberts
Keyword(s):  
Temperature Distribution ◽  
Thermal Energy ◽  
Balance Equation ◽  
Reaction Rate ◽  
Energy Equation ◽  
Fluid Temperature ◽  
Heat Of Reaction ◽  
Mass Balance Equation ◽  
Acid Rock ◽  
First Time

Abstract In a fracture acidizing treatment the acid reacts with the fracture faces. This acid/rock reaction generates heat that causes the acid temperature itself to increase. To predict accurately the temperature profile and acid spending rate of acid traveling down a hydraulically created fracture, this heat must be considered.Since the heat generated by reaction depends on the reaction rate, the thermal energy equation must be coupled with the acid spending equation. A model has been developed that, for the first time, examines the effect of the heat of reaction on fluid temperature and acid penetration in a fracture. Some sample calculations have also been made to illustrate the effects of the most important parameters on acid penetration in a fracture. Introduction Acid hydraulic fracturing is a common method of stimulating a reservoir. Acid selectively reacts with, and dissolves, portions of the fracture wall so that a finite fluid conductivity remains when the well is returned to production. An important aim in designing such fracturing treatments is determining the distance that live acid will penetrate down the hydraulically induced fracture. This distance is usually called the acid penetration distance and is essential to estimate the production improvement from a given treatment.Because of its importance in predicting stimulation ratio, acid penetration in fractures has been studied by numerous investigators. They assumed the temperature in the fracture was uniform. In real fractures, however, the temperature will vary from the wellbore to the tip of the fracture. Therefore, the assumption of constant temperature seems to be an oversimplification.Whitsitt and Dysart were among the first to study the temperature distribution in a fracture. They constructed a model but it could be applied only to a nonreacting fluid flowing in a fracture because the heat generated by an acid/rock reaction was not considered. In a fracture acidizing treatment, the acid is reacting with the rock walls. This acid/rock reaction generates heat, which causes the acid temperature itself to increase. To predict accurately the temperature profile along the fracture, this heat also must be considered. A model has been developed that, for the first time, examines the effect of the heat of reaction on fluid temperature and acid penetration distance. Mathematical Development The mathematical model is a modification of that introduced by Whitsitt and Dysart to allow for the heat of reaction in the energy-balance equation. Since the heat generated by the acid reaction also depends on the reaction rate, the thermal-energy equation is coupled with the mass-balance equation. These two equations must be solved simultaneously .The model for acid spending in a fractures is illustrated in Fig. 1. The fluid leakoff velocity Vw is assumed constant over the fracture length. Assuming steady-state flow in a vertical fracture and constant fluid properties, the mass-balance equation for acid flowing in a fracture is ................(1) SPEJ P. 501＾

scholarly journals The Single-Blow Problem Including the Effects of Longitudinal Conduction

1964 ◽  
Author(s):  
C. P. Howard
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Heat Conduction ◽  
Transient Behavior ◽  
Step Change ◽  
Graphical Form ◽  
Compact Heat Exchanger ◽  
Fluid Temperature ◽  
Transfer Data ◽  
Method Of Calculation

The results are presented from a numerical finite-difference method of calculation for the transient behavior of porous media when subjected to a step change in fluid temperature considering the case where the longitudinal thermal heat conduction cannot be neglected. These results, given in tabular and graphical form, provide a useful means for evaluating the heat-transfer data obtained from the transient testing of compact heat-exchanger surfaces.

Semi-analytical finite element method for simulating chemical dissolution-front instability problems in fluid-saturated porous media

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chongbin Zhao ◽  
B.E. Hobbs ◽  
Alison Ord
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Porous Media ◽  
Chemical Dissolution ◽  
Saturated Porous Media ◽  
Content Type ◽  
Front Instability ◽  
Fluid Saturated Porous Media ◽  
Dissolution Front ◽  
Element Method

PurposeThe objective of this paper is to develop a semi-analytical finite element method for solving chemical dissolution-front instability problems in fluid-saturated porous media.Design/methodology/approachThe porosity, horizontal and vertical components of the pore-fluid velocity and solute concentration are selected as four fundamental unknown variables for describing chemical dissolution-front instability problems in fluid-saturated porous media. To avoid the use of numerical integration, analytical solutions for the property matrices of a rectangular element are precisely derived in a purely mathematical manner. This means that the proposed finite element method is a kind of semi-analytical method. The column pivot element solver is used to solve the resulting finite element equations of the chemical dissolution-front instability problem.FindingsThe direct use of horizontal and vertical components of the pore-fluid velocity as fundamental unknown variables can improve the accuracy of the related numerical solution. The column pivot element solver is useful for solving the finite element equations of a chemical dissolution-front instability problem. The proposed semi-analytical finite element method can produce highly accurate numerical solutions for simulating chemical dissolution-front instability problems in fluid-saturated porous media.Originality/valueAnalytical solutions for the property matrices of a rectangular element are precisely derived for solving chemical dissolution-front instability problems in fluid-saturated porous media. The proposed semi-analytical finite element method provides a useful way for understanding the underlying dynamic mechanisms of the washing land method involved in the contaminated land remediation.

Feedback mechanisms in mineral replacement networks: an experimental investigation of the ultramafic model system

2021 ◽  
Author(s):  
Ingvild Aarrestad ◽  
Oliver Plümper ◽  
Desiree Roerdink ◽  
Andreas Beinlich
Keyword(s):  
Reaction Rate ◽  
Energy Transport ◽  
Kinetic Modelling ◽  
Indirect Evidence ◽  
Reaction Network ◽  
Reaction Networks ◽  
Silicate System ◽  
Rock Interaction ◽  
Feedback Mechanisms ◽  
Salinity Effect

<p>The overall rates of multi-component reaction networks are known to be controlled by feedback mechanisms. Feedback mechanisms represent loop systems where the output of the system is conveyed back as input and the system is either accelerated or regulated (positive and negative feedback respectively). In other words, feedback mechanisms control the rate of a reaction network without external influences. Feedback mechanisms are well-studied in a variety of reaction networks (e.g. bio-chemical, atmospheric); however, in fluid-rock interaction systems they are not researched as such. Still, indirect evidence, theoretical considerations and direct observations attest to their existence [e.g. 1, 2, 3]. It remains unknown how mass and energy transport between distinct reaction sites affect the overall reaction rate and outcome through feedback mechanisms. We propose that feedback mechanisms are a missing critical ingredient to understand reaction progress and timescales of fluid-rock interactions. We apply the serpentinization of ultramafic silicates as a relatively simple reaction network to investigate feedback mechanisms during fluid-rock interactions. Recent studies show that theoretical timescale-predictions appear inconsistent with natural observations [e.g. 4, 5]. The ultramafic silicate system is ideal for investigating feedback mechanisms as it is relevant to natural processes, is reactive on timescales that can be explored in the laboratory, and natural peridotite typically consists of less than four phases. Our preliminary observations indicate a feedback between pyroxene dissolution and olivine serpentinization. Olivine serpentinization appears to proceed faster in the presence of pyroxene. Furthermore, the bulk system reaction rate increases with increasing fluid salinity, which is opposite to the salinity effect on the monomineralic olivine system. Dunite (>90% olivine) is rare, which is why it is crucial to explore the more common pyroxene-bearing systems. The salinity effect is important to investigate due to the inevitable increase in fluid salinity from the boiling-induced phase separation and OH-uptake in the formation of serpentine. Here we present preliminary textural and chemical observations, which will subsequently be used for kinetic modelling of feedback.</p><p>[1] Ortoleva P., Merino, E., Moore, C. & Chadam, J. (1987). American Journal of Science <strong>287</strong>, 997-1007.</p><p>[2] Centrella, S., Austrheim, H., & Putnis, A. (2015). Lithos <strong>236–237</strong>, 245–255.</p><p>[3] Nakatani, T. & Nakamura, M. (2016). Geochemistry, Geophysics, Geosystems <strong>17</strong>, 3393-3419.</p><p>[4] Ingebritsen, S. E. & Manning, C. E. (2010). Geofluids <strong>10</strong>, 193-205.</p><p>[5] Beinlich, A., John, T., Vrijmoed, J.C., Tominaga, M., Magna, T. & Podladchikov, Y.Y. (2020). Nature Geoscience <strong>13</strong>, 307–311.</p>

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