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The Effects Of Initial Condition Of Fracture Surfaces Acid Spending And Type On Conductivity Of Acid Fracture
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Book Synopsis The Effects of Initial Condition of Fracture Surfaces, Acid Spending, and Type on Conductivity of Acid Fracture by : Ali Mansour A. Almomen
Download or read book The Effects of Initial Condition of Fracture Surfaces, Acid Spending, and Type on Conductivity of Acid Fracture written by Ali Mansour A. Almomen and published by . This book was released on 2013 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fracture conductivity and the effects of treatment variables can be studied in the laboratory. We conducted experiments based on scaling down the field conditions to laboratory scale by matching Reynold's and Peclet numbers. Experiments conducted were comprised of three stages: dynamic etching, surface characterization of etched cores, and conductivity measurement. The effect of initial condition of fracture surfaces on the etching pattern and conductivity were investigated in this study. Another area of interest is the variation of conductivity along the fracture due to acid spending. We also investigated the contact time, acid system type, and treatment temperature effects on conductivity using San Andres dolomite cores. The results from these studies showed that rough-surface fractures generate higher conductivity by an order of magnitude compared with a smooth-surface fracture at low-closure stress. Also, conductivity generated on rough-surface fractures by smoothing peaks and deepening valleys which widen the gap between the fracture surfaces after closure and acid creates conductivity on smooth-surface fractures by differential etching that creates asperities. The results suggest that an increase in acid spending does not automatically result in lower conductivity; and etched volume alone is not adequate to predicate the conductivity. Conductivity results from a combination of etching pattern, etched volume, and rock compressive strength after etching. In-situ crosslinked acid was found to be more effective in etching rock and controlling acid leakoff compared with linear-gelled acid. Also, crosslinked acid reduces the number of pits and the pit diameters. Based on conductivity tests, linear-gelled acid is more favorable at higher temperatures while in-situ crosslinked acid showed higher conductivity at lower temperatures. For a rough-surface fracture, shorter contact time created high conductivity compared to longer contact while injecting the same volume of acid, suggesting the existence of an optimum contact time. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151186
Book Synopsis Experimental Study of Acid Fracture Conductivity of Austin Chalk Formation by : Andrea Nino Penaloza
Download or read book Experimental Study of Acid Fracture Conductivity of Austin Chalk Formation written by Andrea Nino Penaloza and published by . This book was released on 2013 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid fracture conductivity and the effect of key variables in the etching process during acid fracturing can be assessed at the laboratory scale. This is accomplished by using an experimental apparatus that simulates acid injection fluxes comparable to those in actual acid fracture treatments. After acid etching, fracture conductivity is measured at different closure stresses. This research work presents a systematic study to investigate the effect of temperature, rock-acid contact time and initial condition of the fracture surfaces on acid fracture conductivity in the Austin Chalk formation. While temperature and rock-acid contact are variables normally studied in fracture conductivity tests, the effect of the initial condition of the fracture surface has not been extensively investigated. The experimental results showed that there is no significant difference in acid fracture conductivity at high closure stress using smooth or rough fracture surfaces. In addition, we analyzed the mechanisms of acid etching and resulting conductivity creation in the two types of fracture surfaces studied by using surface profiles. For smooth surfaces, the mechanism of conductivity creation seems connected to uneven etching of the rock and roughness generation. For rough surfaces, acid conductivity is related to smoothing and deepening of the initial features on the sample surface than by creating more roughness. Finally, we compared the experimental results with Nirode-Kruk correlation for acid fracture conductivity. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/149578
Book Synopsis The Effects of Acid Contact Time and Rock Surfaces on Acid Fracture Conductivity by : Maria Georgina Melendez Castillo
Download or read book The Effects of Acid Contact Time and Rock Surfaces on Acid Fracture Conductivity written by Maria Georgina Melendez Castillo and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The conductivity created in acid fracturing is a competition between two phenomena: etching of the rock surface and weakening of the rock. This study presents experimental results of acid fracturing conductivity experiments with polymer gelled acid, while varying contact time and rock type. The experiments were conducted in a laboratory facility properly scaled from field to laboratory conditions to account for the hydrodynamic effects that take place in the field. The rocks of study were Indiana limestone, San Andres dolomite and Texas Cream chalk. Our results illustrate that acid fracturing conductivity is governed by the etching pattern of the rock surface and influenced by the hardness of the rock. If channels are created, the fracture is more likely to retain conductivity after closure. The hardness of the rock is the dominating factor to determine the conductivity response when no channeling is present. Among the rocks tested, Texas Cream chalk had the lowest hardness measurement before and after acidizing and the fracture closed at a much lower stress compared with limestone and dolomite. Dolomite had the highest conductivity under all closure stresses even without a channeling pattern. Additionally, it was observed that a higher reduction in rock strength at the contact points for dolomite yielded lower conductivity after closure. The effects of hardness variation on conductivity are higher in dolomite than in limestone and chalk. It is apparent that longer contact times do not always provide higher conductivity after closure.
Book Synopsis Acid Fracture and Fracture Conductivity Study of Field Rock Samples by : Jarrod Thomas Underwood
Download or read book Acid Fracture and Fracture Conductivity Study of Field Rock Samples written by Jarrod Thomas Underwood and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid fracturing is a well stimulation strategy designed to increase the productivity of a producing well. The parameters of acid fracturing and the effects of acid interaction on specific rock samples can be studied experimentally. Acid injection data and fracture conductivity measurements obtained in the research presented in this thesis yielded results that qualified and quantified the impact of a specific acid system on rock samples of varying acid solubility. Six rock samples from a carbonate reservoir were labeled A through F to protect proprietary information included in this research. A 2% potassium chloride solution was used for the acid system and fracture conductivity measurements to prevent clay swelling. Injection temperature, contact time, and injection rate were designed to simulate field treatment conditions. The effects of a chelating agent on fracture conductivity were also studied. Before and after images of the rock samples indicated that the effect of 15% hydrochloric acid on the samples was limited but correlated with the rock acid solubility. Samples E and F had a greater value of acid solubility and showed noticeable surface etching. Samples A, B, and C had lower values of acid solubility and did not show signs of surface etching. Sample D was of moderate acid solubility and showed minimal signs of surface etching. Fracture conductivity did not correlate directly with acid solubility, but likely was a function of inherent matrix permeability based on leak-off measurements and fracture conductivity measurements. Finally, the fracture conductivity of Sample D increased after exposure to a chelating agent. Commonly, acid fracture experimental studies are carried out with outcrop rock samples. The samples have more homogenous properties and without hydrocarbon content. In this study, cores from downhole formation were used. The original condition was preserved as much as possible to simulate real field situations. However, using field rock samples does present challenges not generally associated with outcrop rock samples. Based on the information gathered from the work presented in this thesis, conclusions were drawn concerning the effectiveness of a 15% hydrochloric acid treatment in this formation and the challenges of using field rock samples. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151691
Book Synopsis Laboratory-scale Fracture Conductivity Created by Acid Etching by : Maysam Pournik
Download or read book Laboratory-scale Fracture Conductivity Created by Acid Etching written by Maysam Pournik and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Success of acid fracturing treatment depends greatly on the created conductivity under closure stress. In order to have sufficient conductivity, the fracture face must be non-uniformly etched while the fracture strength maintained to withstand the closure stress. While there have been several experimental studies conducted on acid fracturing, most of these have not scaled experiments to field conditions and did not account for the effect of rock weakening and etching pattern. Hence, acid fracture conductivity predictions based on the above works have not been able to match actual results. In order to develop a more appropriate and accurate prediction of acid fracturing treatment outcome, a laboratory facility was developed that is properly scaled to field conditions and enables analysis of etching pattern and rock strength. A systematic experimental study that covered a variety of formations, acid types, and acid contact times was conducted. An acid fracture conductivity correlation was developed based on etched volume, etched pattern, and fracture strength under closure stress. Results suggested that there is an optimal time of acid exposure resulting in maximum fracture conductivity. There were large differences in the conductivity created with the different acid systems tested due to different etching patterns and degree of rock strength weakening. There was an optimal acid system depending on formation type, contact time and overburden stress. The acid fracture conductivities measured did not agree with the predictions of the Nierode-Kruk correlation. The newly developed correlation predicts conductivity much closer as it includes the effect of rock strength and surface etching pattern on resulting conductivity.
Book Synopsis An Innovative Closed Fracture Acidizing Technique for Deep Carbonate Reservoirs Using GLDA by : Jia He
Download or read book An Innovative Closed Fracture Acidizing Technique for Deep Carbonate Reservoirs Using GLDA written by Jia He and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The closed fracture acidizing (CFA) technique is designed to overcome inadequate conductivity development in traditional acid fracturing treatments. However, achieving adequate fracture length is challenging due to the fast acid spending rates and the high corrosion rate to well tubular, especially at high temperatures. This study developed a new closed fracture acidizing (CFA) technique using glutamic acid-N,N-diacetic acid (GLDA) to overcome the limitations of conventional acid fracturing systems and achieve significant length and final fracture conductivity. In this study, a tensile fracture was created across a low permeability Indiana limestone core of 6 in. in length and 1.5 in. in diameter, using an Instron electric compression test machine. The rough fracture surfaces created were scanned using a profilometer to characterize the etched fracture faces before and after the CFA tests. CFA tests were then conducted using a specially designed coreflood setup with the injection of 20 wt% GLDA and 15 wt% HCl at various temperature conditions. CT scans were used to characterize the grooves or channels developed in the CFA tests. The concentrations of the dissolved calcium ions were measured using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), and the effluent samples were titrated to determine the acid concentration. Results show that closed fractures substantially increased the core permeability under low closure stress, with limited increase under high closure stress (>1,500 psi). Surface topography of natural tensile fractures was highly correlated with initial permeability of tensile fractures and had little correlation with the changing rate of fracture permeability with closure stress; while rock embedment strength was found to be mostly associated with permeability change. 20 wt% GLDA was effective in creating a sufficient amount of flow channels to obtain substantial fracture conductivity at various closure stress conditions. Rock embedment strength measurements showed that 15% HCl tends to weaken the rock embedment strength by more than 20%, while 20 wt% GLDA weakens the rock embedment strengthen by no more than 13% on average. Under all circumstances, most of the HCl was consumed after being injected across the cores, thus resulting in limited fracture length in field conditions. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155672
Book Synopsis Modeling Acid Transport and Non-uniform Etching in a Stochastic Domain in Acid Fracturing by : Jianye Mou
Download or read book Modeling Acid Transport and Non-uniform Etching in a Stochastic Domain in Acid Fracturing written by Jianye Mou and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Success of acid fracturing depends on uneven etching along the fracture surfaces caused by heterogeneities such as variations in local mineralogy and variations in leakoff behavior. The heterogeneities tend to create channeling characteristics, which provide lasting conductivity after fracture closure, and occur on a scale that is neither used in laboratory measurements of acid fracture conductivity, which use core samples that are too small to observe such a feature, nor in typical acid fracture simulations in which the grid block size is much larger than the scale of local heterogeneities. Acid fracture conductivity depends on fracture surface etching patterns. Existing acid fracture conductivity correlations are for random asperity distributions and do not consider the contribution of channels to the conductivity. An acid fracture conductivity correlation needs the average fracture width at zero closure stress. Existing correlations calculate average fracture width using dissolved rock equivalent width without considering the effect of reservoir characteristics. The purpose of this work is to develop an intermediate-scale acid fracture model with grid size small enough and the whole dimension big enough to capture local and macro heterogeneity effects and channeling characteristics in acid fracturing. The model predicts pressure field, flow field, acid concentration profiles, and fracture surface profiles as a function of acid contact time. By extensive numerical experiments with the model, we develop correlations of fracture conductivity and average fracture width at zero closure stress as a function of statistical parameters of permeability and mineralogy distributions. With the model, we analyzed the relationships among fracture surface etching patterns, conductivities, and the distributions of permeability and mineralogy. From result analysis, we found that a fracture with channels extending from the inlet to the outlet of the fracture has a high conductivity because fluid flow in deep channels needs a very small pressure drop. Such long and highly conductive channels can be created by acids if the formation has heterogeneities in either permeability or mineralogy, or both, with high correlation length in the direction of the fracture, which is the case in laminated formations.
Book Synopsis Mechanical Behavior of Small-scale Channels in Acid-etched Fractures by : Jiayao Deng
Download or read book Mechanical Behavior of Small-scale Channels in Acid-etched Fractures written by Jiayao Deng and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The conductivity of acid-etched fractures highly depends on spaces along the fracture created by uneven etching of the fracture walls remaining open after fracture closure. Formation heterogeneities such as variations of mineralogy and permeability result in channels that contribute significantly to the fracture conductivity. Current numerical simulators or empirical correlations do not account for this channeling characteristic because of the scale limitations. The purpose of this study is to develop new correlations for conductivity of acid-etched fracturing at the intermediate scale. The new correlations close the gap between laboratory scale measurements and macro scale acid fracture models. Beginning with acid-etched fracture width profiles and conductivity at zero closure stress obtained by the previous work, I modeled the deformation of the fracture surfaces as closure stress is applied to the fracture. At any cross-section along the fracture, I approximated the fracture shape as being a series of elliptical openings. With the assumption of elastic behavior for the rock, the numerical simulation presents how many elliptical openings remain open and their sizes as a function of the applied stress. The sections of the fracture that are closed are assigned a conductivity because of small-scale roughness features using a correlation obtained from laboratory measurements of acid fracture conductivity as a function of closure stress. The overall conductivity of the fracture is then obtained by numerically modeling the flow through this heterogeneous system. The statistical parameters of permeability distribution and the mineralogy distribution, and Young's modulus are the primary aspects that affect the overall conductivity in acid-etched fracturing. A large number of deep, narrow channels through the entire fracture leads to high conductivity when the rock is strong enough to resist closure stress effectively. Based on extensive numerical experiments, I developed the new correlations in three categories to predict the fracture conductivity after closure. Essentially, they are the exponential functions that incorporate the influential parameters. Combined with the correlations for conductivity at zero closure stress from previous work, the new correlations are applicable to a wide range of situations.
Download or read book NBS Special Publication written by and published by . This book was released on 1968 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Acid Fracturing Feasibility Study for Heterogeneous Carbonate Formation by : Assiya Suleimenova
Download or read book Acid Fracturing Feasibility Study for Heterogeneous Carbonate Formation written by Assiya Suleimenova and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid fracturing is a stimulation technique that is commonly used by the industry to increase productivity or injectivity of wells in carbonate reservoirs. To determine a feasibility of acid fracturing treatment for a heterogeneous formation, the effect of rock properties on the created fracture conductivity needs to be investigated experimentally. In this study, the influence of rock lithology, porosity, and permeability on the resultant fracture conductivity was investigated for the Middle Canyon formation. Six carbonate cores collected from different depths of Middle Canyon interval were selected for this study. The cores had the permeability ranging from 0.07 to 28 md and the porosity ranging from 1.7 to 15.4%. The acid etching experimental conditions, such as injection rate, reaction temperature, and acid type, were selected to simulate field treatment conditions. The fracture surface of each sample was scanned before and after the acid treatment to characterize the change in surface profile and to calculate the etched volume of rock. The results of the study indicated that the final conductivity values under the maximum closure stress of 4000 psi were similar to each other (6.4 - 13.5 md-ft) for all the cores, regardless the variation in cores' porosity and permeability. It was also observed that the cores with a lower porosity had a lower decline rate of acid fracture conductivity with increasing closure stress. Based on the results of this study, it was concluded that acid fracturing stimulation of the Middle Canyon formation may not be effective to achieve the goals defined by the operator. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/155028
Book Synopsis Publications of the National Bureau of Standards ... Catalog by : United States. National Bureau of Standards
Download or read book Publications of the National Bureau of Standards ... Catalog written by United States. National Bureau of Standards and published by . This book was released on 1983 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Three-dimensional Modeling of Acid Transport and Etching in a Fracture by : Cassandra Vonne Oeth
Download or read book Three-dimensional Modeling of Acid Transport and Etching in a Fracture written by Cassandra Vonne Oeth and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid fracture stimulation generates higher well production but requires engineering design for treatment optimization. To quantify the cost and benefit of a particular acid fracture treatment an engineer must predict the resulting fracture's conductivity, which is based on the etched width created by the injected acid. Etching occurs along the fracture surface but is based on acid flowing through the fracture, so an evaluation tool should describe three-dimensional physics and chemistry. Current practice is to estimate conductivity utilizing two-dimensional models. Unfortunately, these models necessarily assume how acid is distributed in the fracture and often misrepresent the amount of acid etching upon which the conductivity is based. A fully three-dimensional modeling tool to evaluate and predict acid fracture performance across the wide range of carbonate field properties has been developed. The model simulates acid transport and fracture face dissolution. The acid transport model includes the solution of the three-dimensional velocity and pressure fields, the non-Newtonian characteristics of most acid fracturing fluids, and diffusion of acid toward the fracture surface. The model numerically solves the equations describing the three-dimensional acid transport and reaction within a fracture to yield the etched width created by acid along the fracture. The conductivity is calculated with the simulator derived acid-etched width, using correlations recently developed that reflect the small scale heterogeneity of carbonate rock as it creates etching along the fracture surface. The performance of an acid fracture treatment is quantified with conductivity, which is strongly dependent on the etched width created by the acid. This robust new tool more accurately models the impact of design decisions on the acid-etched width and provides a rational path for treatment optimization. Cases typical of industry practice are presented that demonstrate the model capabilities. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/151892
Book Synopsis Standard Handbook of Petroleum and Natural Gas Engineering by : William Lyons
Download or read book Standard Handbook of Petroleum and Natural Gas Engineering written by William Lyons and published by Gulf Professional Publishing. This book was released on 2015-12-08 with total page 1823 pages. Available in PDF, EPUB and Kindle. Book excerpt: Standard Handbook of Petroleum and Natural Gas Engineering, Third Edition, provides you with the best, state-of-the-art coverage for every aspect of petroleum and natural gas engineering. With thousands of illustrations and 1,600 information-packed pages, this handbook is a handy and valuable reference. Written by dozens of leading industry experts and academics, the book provides the best, most comprehensive source of petroleum engineering information available. Now in an easy-to-use single volume format, this classic is one of the true "must haves" in any petroleum or natural gas engineer's library. A classic for over 65 years, this book is the most comprehensive source for the newest developments, advances, and procedures in the oil and gas industry. New to this edition are materials covering everything from drilling and production to the economics of the oil patch. Updated sections include: underbalanced drilling; integrated reservoir management; and environmental health and safety. The sections on natural gas have been updated with new sections on natural gas liquefaction processing, natural gas distribution, and transport. Additionally there are updated and new sections on offshore equipment and operations, subsea connection systems, production control systems, and subsea control systems. Standard Handbook of Petroleum and Natural Gas Engineering, Third Edition, is a one-stop training tool for any new petroleum engineer or veteran looking for a daily practical reference. - Presents new and updated sections in drilling and production - Covers all calculations, tables, and equations for every day petroleum engineers - Features new sections on today's unconventional resources and reservoirs
Download or read book SPE Production & Facilities written by and published by . This book was released on 2003 with total page 594 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Evaluation of Acid Fracturing Using the Method of Distributed Volumetric Sources by : Jaehun Lee
Download or read book Evaluation of Acid Fracturing Using the Method of Distributed Volumetric Sources written by Jaehun Lee and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acid fracturing stimulation is one of the preferred methods to improve well productivity in carbonate reservoirs. Acid is injected into the fractured zone after a starter fracture is created in the near wellbore area by viscous fluid (pad). This results in propagation of a two-wing crack away from the perforations with simultaneous dissolution etching of the created surfaces. If the created etched surface is non-uniform, then after the treatment ends and the fracture face closes, a high conductivity path may remain in the formation, connected to the well. The important factors controlling the effectiveness of acid fracturing are the etched-fracture penetration and conductivity. In this research, I use the distributed volumetric sources (DVS) method to calculate gas production from a well stimulated by acid fracturing. The novel concept realized in this research is that, during the production process, the conductivity of the acid created fracture changes. I use the Nierode - Kruk correlation to describe this effect as a function of effective closure stress that in turn is determined from the flowing bottomhole pressure and minimum horizontal stress. By combining the well productivity calculation from the DVS method taking into account varying fracture conductivity with gas material balance, I obtain an improved model of gas production. The model is then used to not only forecast production from acid fractured wells but also to evaluate the known production history of such wells. Based on the concepts discussed above, I have developed a program called "Gas Acid" which is useful to optimize acid fracturing treatments and also suitable to infer created fracture parameters from known production history. The "Gas Acid" program has been validated with data from two Saudi Aramco gas wells. It was found that the production forecast obtained from the "Gas Acid" program matches the actual production history with reasonable accuracy and the remaining discrepancy could be resolved by taking into account refinement of the material balance. The refinement became necessary, because the "Gas Acid" program was developed for dry gas but the reservoir fluids in the field examples were classified as retrograde gas and wet gas. When accounting for the additional mass of gas "hidden" in the produced condensate, the match of forecast and actual data was improved considerably.
Book Synopsis Unified Fracture Design by : Michael J. Economides
Download or read book Unified Fracture Design written by Michael J. Economides and published by . This book was released on 2002 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Acid fracture conductivity of the Clearfork Formation by : Mirza Shoaib Beg
Download or read book Acid fracture conductivity of the Clearfork Formation written by Mirza Shoaib Beg and published by . This book was released on 1993 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt:
