Download or read book Matrix Acidizing of Heterogeneous Carbonates written by Ryan Keys and published by LAP Lambert Academic Publishing. This book was released on 2011-03-01 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: In matrix acidizing, the goal is to dissolve minerals in the rock to increase well productivity. This is accomplished by injecting an application-specific solution of acid into the formation at a pressure between the pore pressure and fracture pressure. A hydrochloric acid solution is used in carbonate reservoirs, which actually dissolves the calcite rock matrix in the form of conductive channels called wormholes. These wormholes propagate from the wellbore out into the reservoir, bypassing the damaged zone. In matrix acidizing of carbonates, there are four parameters that affect performance: the concentration of calcite present, injection rate of the acid, reaction type, and heterogeneity. Of these parameters, this paper will focus on how rock heterogeneity affects performance. To do this, a coreflood and acidizing apparatus was used to acidize heterogeneous limestone core samples. Rock characterizations and volumetric measurements were considered with the results from these experiments, which made it possible to correlate and quantify the results with rock and volume parameters.

Download or read book The Effect of Heterogeneity on Matrix Acidizing of Carbonate Rocks written by Ryan Scott Keys and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In matrix acidizing, the goal is to dissolve minerals in the rock to increase well productivity. This is accomplished by injecting an application-specific solution of acid into the formation at a pressure between the pore pressure and fracture pressure. A hydrochloric acid solution is used in carbonate reservoirs, which actually dissolves the calcite rock matrix in the form of conductive channels called wormholes. These wormholes propagate from the wellbore out into the reservoir, bypassing the damaged zone. In matrix acidizing of carbonates, there are four parameters that affect performance: the concentration of calcite present, injection rate of the acid, reaction type, and heterogeneity. Of these parameters, this paper will focus on how rock heterogeneity affects performance. To do this, a coreflood and acidizing apparatus was used to acidize heterogeneous limestone core samples. Rock characterizations and volumetric measurements were considered with the results from these experiments, which made it possible to correlate and quantify the results with rock and volume parameters. It was found that the core samples with more and larger heterogeneities generally required less acid (measured in pore volumes) to achieve breakthrough, that is, a wormhole created axially from one end of the core to the other. This value for pore volumes to breakthrough was one to two orders of magnitude less than more homogeneous samples. The general procedure and best practices for acidizing the core samples is also detailed in this thesis. This procedure was followed for preparation, coreflooding, and acidizing for all core samples.

Download or read book A Model for Matrix Acidizing of Long Horizontal Well in Carbonate Reservoirs written by Varun Mishra and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Horizontal wells are drilled to achieve improved reservoir coverage, high production rates, and to overcome water coning problems, etc. Many of these wells often produce at rates much below the expected production rates. Low productivity of horizontal wells is attributed to various factors such as drilling induced formation damage, high completion skins, and variable formation properties along the length of the wellbore as in the case of heterogeneous carbonate reservoirs. Matrix acidizing is used to overcome the formation damage by injecting the acid into the carbonate rock to improve well performance. Designing the matrix acidizing treatments for horizontal wells is a challenging task because of the complex process. The estimation of acid distribution along wellbore is required to analyze that the zones needing stimulation are receiving enough acid. It is even more important in cases where the reservoir properties are varying along the length of the wellbore. A model is developed in this study to simulate the placement of injected acid in a long horizontal well and to predict the subsequent effect of the acid in creating wormholes, overcoming damage effects, and stimulating productivity. The model tracks the interface between the acid and the completion fluid in the wellbore, models transient flow in the reservoir during acid injection, considers frictional effects in the tubulars, and predicts the depth of penetration of acid as a function of the acid volume and injection rate at all locations along the completion. A computer program is developed implementing the developed model. The program is used to simulate hypothetical examples of acid placement in a long horizontal section. A real field example of using the model to history match actual treatment data from a North Sea chalk well is demonstrated. The model will help to optimize acid stimulation in horizontal wells.

Download or read book Applied Matrix Acidizing of Carbonate Reservoir written by Ehsan Khamehchi and published by Springer Nature. This book was released on with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Numerical Modeling of Matrix Acidizing in Carbonate and Sandstone Reservoirs written by Wan Wei and published by . This book was released on 2020 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt: Matrix acidizing is a stimulation technique to improve productivity/injectivity in the near-wellbore region in carbonate and sandstone reservoirs. Carbonate reservoir is heterogeneous in mineralogy, primary porosity, and secondary porosity such as fractures. Optimally through acidizing treatment, wormholes are generated in carbonate reservoirs to improve the permeability and bypass the damaged zone. A two-scale continuum model is implemented in a radial coordinate system to simulate acidizing process in the near-wellbore geometry. The model is extended from single-phase to two-phase by considering mobility change due to water-oil displacement and defining a new criterion for acidizing breakthrough applicable to two-phase flow. The requirement of acid consumption is lower with the existence of oil prior to acidizing treatment. This indicates that for field treatment, maintaining a higher oil saturation can enhance acidizing efficiency. To consider varying mineral compositions in carbonates, the acidizing model is implemented in the UTCOMP-IPhreeqc coupled software to model homogeneous and heterogeneous reactions among acid and minerals. Different acid pore volumes are predicted for limestone, dolostone, and partially dolomitized formation due to the difference in reaction rate and dissolution structures generated. To consider fracture effect in carbonates, the acidizing model in UTCOMP-IPhreeqc is extended to consider reactions on the fracture surface with the aid of EDFM (Embedded Discrete Fracture Model). The fracture with a high conductivity will receive most acid and slow down the wormhole propagation in the matrix. To improve computational efficiency, the acidizing model is also implemented in the semi-parallel version of UTCOMP-IPhreeqc, with the parallelized geochemical calculation. Besides, speedup techniques through defining a tolerance on the relative amount change of geochemical elements to reduce IPhreeqc calls are also applied. Parallel computing saves up to 85% of the total computational time when using 16 processors. And speedup techniques obtain about 50% improvement for the wormhole pattern. The acidizing model in UTCOMP-IPhreeqc is also extended to simulate acidizing process in sandstone reservoirs through modifying IPhreeqc database to include primary and secondary reactions. A largest possible injection rate is recommended to achieve best performance mitigating formation damage caused by precipitation

Download or read book Modeling and Optimization of Matrix Acidizing in Horizontal Wells in Carbonate Reservoirs written by Hậu Trần and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, the optimum conditions for wormhole propagation in horizontal well carbonate acidizing was investigated numerically using a horizontal well acidizing simulator. The factors that affect the optimum conditions are rock mineralogy, acid concentration, temperature and acid flux in the formation. The work concentrated on the investigation of the acid flux. Analytical equations for injection rate schedule for different wormhole models. In carbonate acidizing, the existence of the optimum injection rate for wormhole propagation has been confirmed by many researchers for highly reactive acid/rock systems in linear core-flood experiments. There is, however, no reliable technique to translate the laboratory results to the field applications. It has also been observed that for radial flow regime in field acidizing treatments, there is no single value of acid injection rate for the optimum wormhole propagation. In addition, the optimum conditions are more difficult to achieve in matrix acidizing long horizontal wells. Therefore, the most efficient acid stimulation is only achieved with continuously increasing acid injection rates to always maintain the wormhole generation at the tip of the wormhole at its optimum conditions. Examples of acid treatments with the increasing rate schedules were compared to those of the single optimum injection rate and the maximum allowable rate. The comparison study showed that the increasing rate treatments had the longest wormhole penetration and, therefore, the least negative skin factor for the same amount of acid injected into the formations. A parametric study was conducted for the parameters that have the most significant effects on the wormhole propagation conditions such as injected acid volume, horizontal well length, acid concentration, and reservoir heterogeneity. The results showed that the optimum injection rate per unit length increases with increasing injected acid volume. And it was constant for scenarios with different lateral lengths for a given system of rock/ acid and injected volume. The study also indicated that for higher acid concentration the optimum injection rate was lower. It does exist for heterogeneous permeability formations. Field treatment data for horizontal wells in Middle East carbonate reservoirs were also analyzed for the validation of the numerical acidizing simulator. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149428

Download or read book MATRIX ACIDIZING IN CARBONATES USING MICROEMULSIONS THE STUDY OF FLOW DISSOLUTION AND CHANNELING IN POROUS MEDIA written by MARK LAWRENCE HOEFNER and published by . This book was released on 1987 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: technique.

Download or read book Reservoir Stimulation written by Michael J. Economides and published by . This book was released on 2000-06-23 with total page 932 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sets forth a rationalisation of stimulation using reservoir engineering concepts, and addresses topics such as formation characterisation, hydraulic fracturing and matrix acidizing. Formation damage, which refers to a loss in reservoir productivity, is also examined comprehensively.

Download or read book Numerical Simulation of Acid Stimulation Treatments in Carbonate Reservoirs written by Rencheng Dong and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Matrix acidizing and acid fracturing are two main types of acid stimulation treatments that are extensively employed by industry in carbonate reservoirs to improve permeability and enhance production. Matrix acidizing involves injecting acid to dissolve minerals in order to create long highly conductive channels (wormholes) whereas acid fracturing is used to etch fracture surfaces and create fracture conductivity. Numerical modeling of acid stimulation treatments couples processes of fluid flow, reactive transport, and rock dissolution, which imposes great computational challenges. The purpose of this dissertation is to develop efficient and accurate numerical models for acidizing process and acid fracturing process respectively. In most of matrix acidizing simulations, acid transport is generally solved by a single-point upwinding (SPU) scheme based on finite volume method. Simulation results of wormhole growth may have large numerical errors due to grid orientation effect of SPU scheme. In this work, we apply adaptive enriched Galerkin (EG) methods for solving coupled flow and reactive transport equations of acidizing model. EG is constructed by enriching the standard continuous Galerkin (CG) finite element method with piecewise constant functions. Since EG is a higher-order method compared with standard finite volume method, EG reduces non-physical numerical errors caused by grid orientation effect. Wormhole growth usually exhibits fingering patterns, which requires very fine mesh to resolve. Instead of global mesh refinement, we apply adaptive mesh refinement technique to dynamically refine the mesh in the vicinity of wormhole interfaces and coarsen the mesh after dissolution fronts pass. The simulation runtime using adaptive mesh is only about 30% of the runtime using globally refined mesh in our numerical examples. The key to success in acid fracturing treatments is to achieve non-uniform acid etching on fracture surfaces. Carbonate reservoir heterogeneity such as heterogeneous mineral distribution can lead to non-uniform acid etching. In addition, the non-uniform acid etching can be enhanced by the viscous fingering mechanism. By injecting a low-viscosity acid into a high-viscosity polymer pad fluid, acid tends to form viscous fingers and etch fracture surfaces non-uniformly. Acid fracturing simulations rarely modeled the effect of acid viscous fingering. In this work, a 3D acid fracturing model is developed to simulate acid etching process with acid viscous fingering. Our acid fracturing model considers fluid flow inside the fracture, acid and polymer transport, and change of fracture geometry due to mineral dissolution. A numerical simulator is developed to solve the acid fracturing model and compute the rough acid fracture geometry induced by non-uniform acid etching. We investigate the effects of viscous fingering, perforation design, and alternating injection of pad and acid fluids on the acid etching process. Our model is capable of simulating growth of acid-etched channels caused by acid viscous fingering. According to our simulation results, properly increasing the number of perforations can restrain the height of acid-etched channels and help sustain acid fracture conductivity under the reservoir closure stress. Compared with single-stage acid injection, multi-stage alternating injection of pad and acid fluids leads to narrower and longer acid-etched channels, which improves the effectiveness of acid fracturing treatments

Download or read book Reactive Flow in Vuggy Carbonates written by Omer Izgec and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbonates invariably have small (micron) to large (centimeter) scale heterogeneities in flow properties that may cause the effects of injected acids to differ greatly from what is predicted by a model based on a homogenous formation. To the best of our knowledge, there are neither theoretical nor experimental studies on the effect of large scale heterogeneities (vugs) on matrix acidizing. The abundance of carbonate reservoirs (60% of the world?s oil reserves) and the lack of a detailed study on the effect of multi-scale heterogeneities in carbonate acidizing are the main motivations behind this study. In this work, we first present a methodology to characterize the carbonate cores prior to the core-flood acidizing experiments. Our approach consists of characterization of the fine-scale (millimeter) heterogeneities using computerized tomography (CT) and geostatistics, and the larger-scale (millimeter to centimeter) heterogeneities using connected component labeling algorithm and numerical simulation. In order to understand the connectivity of vugs and thus their contribution to flow, a well-known 2D visualization algorithm, connected component labeling (CCL), was implemented in 3D domain. Another tool used in this study to understand the connectivity of the vugs and its effect on fluid flow is numerical simulation. A 3D finite difference numerical model is developed based on Darcy-Brinkman formulation (DBF). Using the developed simulator a flow-based inversion approach is implemented to understand the connectivity of the vugs in the samples studied. After multi-scale characterization of the cores, acid core-flood experiments are conducted. Cores measuring four inches in diameter by twenty inches in length are used to decrease the geometry effects on the wormhole path. The post acid injection porosity distribution and wormhole paths are visualized after the experiments. The experimental results demonstrate that acid follows not only the high permeability paths but also the spatially correlated ones. While the connectivity between the vugs, total amount of vuggy pore space and size of the cores are the predominant factors, spatial correlation of the petro-physical properties has less pronounced effect on wormhole propagation in acidiziation of carbonates. The fact that acid channeled through the vugular cores, following the path of the vug system, was underlined with computerized tomography scans of the cores before and after acid injection. This observation proposes that local pressure drops created by vugs are more dominant in determining the wormhole flow path than the chemical reactions occurring at the pore level. Following this idea, we present a modeling study in order to understand flow in porous media in the presence of vugs. Use of coupled Darcy and Stokes flow principles, known as Darcy-Brinkman formulation (DBF), underpins the proposed approach. Several synthetic simulation scenarios are created to study the effect of vugs on flow and transport. The results demonstrate that total injection volume to breakthrough is affected by spatial distribution, amount and connectivity of vuggy pore space. An interesting finding is that although the presence and amount of vugs does not change the effective permeability of the formation, it could highly effect fluid diversion. We think this is a very important observation for designing of multi layer stimulation.

Download or read book Study Towards Improving the Efficiency of Matrix Acidizing in Oil bearing Carbonate Formations written by Mohamed Mustafa Elmabruk Elsafih and published by . This book was released on 2021 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Viscoelastic Surfactants Used in Carbonate Matrix Acidizing on Wettability written by Oladapo Adejare and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbonate reservoirs are heterogeneous; therefore, proper acid placement/diversion is required to make matrix acid treatments effective. Viscoelastic surfactants (VES) are used as diverting agents in carbonate matrix acidizing. However, these surfactants can adversely affect wettability around the wellbore area. Lab and field studies show that significant amounts of VES are retained in the reservoir, even after an EGMBE postflush. Optimizing acid treatments requires a study of the effect of VES on wettability. In a previous study using contact angle experiments, it was reported that spent acid solutions with VES only, and with VES and EGMBE are water-wetting. In this thesis, we studied the effect of two amphoteric amine-oxide VES', designated as "A" and "B" on the wettability of Austin cream chalk using contact angle experiments. We extended the previous study by using outcrop rocks prepared to simulate reservoir conditions, by demonstrating that VES adsorbs on the rock using two-phase titration experiments, by studying the effect of temperature on wettability and adsorption, and by developing a detailed procedure for contact angle experiments. We found that for initially oil-wet rocks, simulated acid treatments with VES "A" and "B" diversion stages and an EGMBE preflush and postflush made rocks water-wet at 25, 80, and 110 degrees C. Simulated acid treatments with a VES "A" diversion stage only made rocks water-wet at 25 degrees C. Our results suggest that both VES formulations cause a favorable wettability change for producing oil. The two-phase titration experiments show that both VES "A" and "B" adsorb on the rock surface. From our literature review, many surfactant wettability studies use contact angle measurements that represent advancing contact angles. However, wettability during stimulation is represented by receding contact angles. Results of static receding contact angles may be misinterpreted if low oil-acid IFT's cause oil droplets to spread. Spreading could be a reflection of the effect of the surfactants on the fluid-fluid interface rather than the rock-fluid interface. The new procedure shows the effect of VES and EGMBE on the rock-fluid interface only, and so represents the actual wettability.

Download or read book Petroleum Production Systems written by Michael J. Economides and published by Pearson Education. This book was released on 2013 with total page 752 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by four leading experts, this edition thoroughly introduces today's modern principles of petroleum production systems development and operation, considering the combined behaviour of reservoirs, surface equipment, pipeline systems, and storage facilities. The authors address key issues including artificial lift, well diagnosis, matrix stimulation, hydraulic fracturing and sand control. They show how to optimise systems for diverse production schedules using queuing theory, as well as linear and dynamic programming. Throughout, they provide both best practices and rationales, fully illuminating the exploitation of unconventional oil and gas reservoirs. Updates include: Extensive new coverage of hydraulic fracturing, including high permeability fracturing New sand and water management techniques * An all-new chapter on Production Analysis New coverage of digital reservoirs and self-learning techniques New skin correlations and HW flow techniques

Download or read book Proceedings of the International Field Exploration and Development Conference 2020 written by Jia'en Lin and published by Springer Nature. This book was released on 2021-06-17 with total page 3487 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a compilation of selected papers from the 10th International Field Exploration and Development Conference (IFEDC 2020). The proceedings focuses on Reservoir Surveillance and Management, Reservoir Evaluation and Dynamic Description, Reservoir Production Stimulation and EOR, Ultra-Tight Reservoir, Unconventional Oil and Gas Resources Technology, Oil and Gas Well Production Testing, Geomechanics. The conference not only provides a platform to exchanges experience, but also promotes the development of scientific research in oil & gas exploration and production. The main audience for the work includes reservoir engineer, geological engineer, enterprise managers senior engineers as well as professional students.

Download or read book Experimental Investigation on the Effect of Permeability on the Optimum Acid Flux in Carbonate Matrix Acidizing written by Jordan Ruby Etten and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Determination of optimal acidizing conditions through laboratory experimental study is crucial for designing matrix acid stimulation jobs in the field. Optimum interstitial velocity, v[subscript i-opt] (the velocity of injected fluid that yields the minimum volume of acid needed to propagate wormholes) can be determined though curve fitting of experimental data. This optimum interstitial velocity coincides with the minimum volume of acid required for wormhole breakthrough, and therefore, the most efficient stimulation design. Optimum interstitial velocity determines the injection rate for a treatment, and the optimum pore volume to breakthrough, PV[subscript bt-opt], suggests the total volume of acid needed. Studies of carbonate matrix acidizing have focused on the role of many parameters, such as acid concentration, acid type, temperature, and core dimensions. However, under the same experimental conditions, different limestone rocks exhibit different optimal conditions. It is important to explore how changes in rock properties, such as permeability and pore structure, can also impact the efficacy of matrix acidizing techniques. In this work, a series of linear coreflood experiments on relatively homogenous Indiana limestone and Desert Pink limestone cores were performed at ambient temperature. Cores of 1.5-in. diameter by 8-in. long were acidized using 15% hydrochloric acid. The average permeabilities of the cores tested were 6, 11, 33 and 239 mD with varied porosity. The effects of permeability and porosity were isolated using thin section analysis to study pore structure. Based on experimental results, a detailed explanation of the pore structure and permeability effects on optimum interstitial velocity is presented. The coreflood acidizing results show that at low permeabilities, optimum interstitial velocity increases with permeability. When permeability of the rock reaches a certain value, the effect of permeability on the optimum injection condition diminishes. In addition, the optimum pore volume to breakthrough increases across the entire range of permeabilities tested. This work also briefly quantifies the differences in pore structure of the samples, leading to recommendations for future work. The implications and applications of this work are far-reaching; better understanding of optimal acidizing conditions based on the studied rock properties has significant potential economic and operational impact. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155227

Download or read book Challenges and Innovations in Geomechanics written by Marco Barla and published by Springer Nature. This book was released on 2021-01-14 with total page 1124 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the latest advances, innovations, and applications in the field of computational geomechanics, as presented by international researchers and engineers at the 16th International Conference of the International Association for Computer Methods and Advances in Geomechanics (IACMAG 2020/21). Contributions include a wide range of topics in geomechanics such as: monitoring and remote sensing, multiphase modelling, reliability and risk analysis, surface structures, deep structures, dams and earth structures, coastal engineering, mining engineering, earthquake and dynamics, soil-atmosphere interaction, ice mechanics, landfills and waste disposal, gas and petroleum engineering, geothermal energy, offshore technology, energy geostructures, geomechanical numerical models and computational rail geotechnics.

Download or read book Carbonate Reservoir Characterization A Geologic Engineering Analysis Part I written by G.C. Dominguez and published by Elsevier. This book was released on 1992-01-17 with total page 659 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book integrates those critical geologic aspects of reservoir formation and occurrence with engineering aspects of reservoirs, and presents a comprehensive treatment of the geometry, porosity and permeability evolution, and producing characteristics of carbonate reservoirs. The three major themes discussed are: • the geometry of carbonate reservoirs and relationship to original depositional facies distributions • the origin and types of porosity and permeability systems in carbonate reservoirs and their relationship to post-depositional diagenesis • the relationship between depositional and diagenetic facies and producing characteristics of carbonate reservoirs, and the synergistic geologic-engineering approach to the exploitation of carbonate reservoirs. The intention of the volume is to fully aquaint professional petroleum geologists and engineers with an integrated geologic and engineering approach to the subject. As such, it presents a unique critical appraisal of the complex parameters that affect the recovery of hydrocarbon resources from carbonate rocks. The book may also be used as a text in petroleum geology and engineering courses at the advanced undergraduate and graduate levels.