Browsing by Subject "GLDA"
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Item Formation Damage due to Iron Precipitation in Acidizing Operations and Evaluating GLDA as a Chelating Agent(2012-02-14) Mittal, RohitIron control during acidizing plays a key role in the success of matrix treatment. Ferric ion precipitates in the formation once the acid is spent and the pH exceeds 1-2. Precipitation of iron (III) within the formation can cause formation damage. Chelating agents such as EDTA and NTA are usually added to acids to minimize iron precipitation. Drawbacks of these chelating agents include limited solubility in strong acids and poor environmental profile. Hydroxy EDTA was introduced because of its higher solubility in 15 wt% HCl. However, its solubility in 28 wt% HCl is low and it is not readily biodegradable. In this study we studied the formation damage caused by iron precipitation in acidizing operations and tested the chelate L-glutamic acid, N,N-diacetic acid (GLDA). This chelant is soluble in higher concentrations of HCl. It is readily biodegradable, and is an effective iron control agent. A study was conducted to study the concentration of iron at different pHs ranging from 1-4 without the presence of any chelating agent at room temperature. A similar study was conducted in the presence of a chelating agent. To simulate field conditions, coreflood tests were conducted on Indiana Limestone, Austin Chalk and Pink Desert. Tests were conducted with and without the chelant. Samples of core effluent were collected and iron and calcium concentrations were measured using atomic absorption spectroscopy (AA). The cores were scanned using X-ray before and after acid injection. Results indicated that precipitation of iron can cause serious reduction in core permeability. The chelate was found to be very effective in chelating iron upto 300 degrees F. No permeability reduction was noted when GLDA was added to the acid. Material balance calculations show that significant amount of the iron that was added to the injected acid was produced when GLDA was used. This chelant is effective, environmentally friendly and can used up to 300 degrees F.Item Investigating the Use of Chelating Agents for Clay Dissolution and Sandstone Acidizing Purposes(2014-08-06) Andotra, GautamMud acid, a mixture of HCl and HF, has been frequently used for stimulating sandstone reservoirs. However, using HCl in such environments can be problematic, especially at higher temperatures. Some of the most common problems are the following: clay sensitivity, secondary/tertiary reactions, and precipitation of salts and corrosion. To combat these problems mixtures of HF have been developed along with organic acids and chelating agents such as citric acid, acetic acid, EDTA, HEDTA, GLDA etc. Compared to HCl, these chelating agents offer lower corrosion, no mineral sensitivity issues, stability at high temperatures (? 200 ?F) and bio-degradability. This thesis explores the use of two chelating agents, citric acid and a newly developed sodium salt of L-Glutamic acid N,N-Di Acetic Acid (Na-GLDA). Experiments were conducted to find out the aluminosilicates dissolution and chelation capabilities of these chelating agents. The first set of experiments were clay dissolution experiments, conducted using different concentrations of citric acid (1 wt%, 3 wt%, and 5 wt%) added to regular 9:1 mud acid. This was done to study and analyze its clay dissolution properties, as well as its chelation abilities to reduce precipitation. For comparison purposes, experiments were also completed using regular 9:1 mud acid to compare its results to that of using citric acid along with 9:1 mud acid. The results suggest that using 1 wt% citric acid along with 9:1 mud acid provided the best results, both in terms of clay dissolution as well as reducing precipitate formation. The next set of experiments investigated the use of Na-GLDA along with HF for sandstone acidizing purposes. First, compatibility experiments were conducted to find out the optimum acid mixture between Na-GLDA and HF that causes no incompatibilities. Following the compatibility test, coreflood experiments were run on Bandera and Berea cores using the optimum acid mixture formulation found in the preceding experiment. Coreflood results showed the good chelation ability of Na-GLDA to iron, calcium and magnesium. But very low concentrations of any aluminosilicates were found in the ICP samples indicating either the lack of dissolution of aluminosilicates or the precipitation of aluminosilicates within the core. In conclusion, the experimental results suggest that adding 1 wt% citric acid to 9:1 mud acid provides better dissolution and precipitation results. But factoring in the cost of citric acid makes it a financially unfavorable formulation, especially since regular 9:1 mud acid performed almost as well as 9:1 mud acid with 1 wt% citric acid added to it. Also, the newly developed Na-GLDA is compatible with HF at certain concentrations of both. The optimum acid mixture formulation was found to be 20 wt% Na-GLDA + 1 wt% HF. Coreflood results show that Na-GLDA added to HF is able to keep cations such as iron, calcium and magnesium in solution at higher temperatures, but it is unable to properly dissolve and chelate to aluminosilicates and its damaging salts.Item Reaction of Calcite and Dolomite with In-Situ Gelled Acids, Organic Acids, and Environmentally Friendly Chelating Agent (GLDA)(2012-11-16) Rabie, Ahmed 1978-Well stimulation is the treatment remedy when oil/gas productivity decreases to unacceptable economical limits. Well stimulation can be carried out through either "Matrix Acidizing" or fracturing with both "Hydraulic Fracturing" and "Acid Fracturing" techniques. "Matrix Acidizing" and "Acid Fracturing" applications involve injecting an acid to react with the formation and dissolve some of the minerals present and recover or increase the permeability. The permeability enhancement is achieved by creating conductive channels "wormholes" in case of "Matrix Acidizing" or creating uneven etching pattern in case of "Acid Fracturing" treatments. In both cases, and to design a treatment successfully, it is necessary to determine the distance that the live acid will be able to penetrate inside the formation, which in turn, determines the volume of the acid needed to carry out the treatment. This distance can be obtained through lab experiments, if formation cores are available, or estimated by modeling the treatment. The successful model will depend on several chemical and physical processes that take place including: the acid transport to the surface of the rock, the speed of the reaction of the acid with the rock, which is often referred to as "Reaction Rate", and the acid leak-off. The parameters describing these processes such as acid diffusion coefficient and reaction kinetics have to be determined experimentally to ensure accurate and reliable modeling. Hydrochloric acid and simple organic acids such as acetic and citric acids have been used extensively for stimulation treatments. The diffusion and reaction kinetics of these acids, in a straight form, were investigated thoroughly in literature. However, solely these acids are used in a simple form in the field. Acid systems such as gelled, crosslinked gelled, surfactant-based, foam-based, or emulsified acids are used to either retard the reaction rate or to enhance acid diversion. Literature review shows that additional work is needed to understand the reaction and report the diffusion and kinetics of these systems with carbonate. In addition, a new chelating agent (GLDA) was recently introduced as a stand-alone stimulating fluid. The kinetics and the mass transfer properties of this acid were not studied before. Therefore, the objective of this work is to study the reaction of different acid systems with calcite and dolomite and report the mass transport and kinetic data experimentally. Lactic acid, a chelating agent (GLDA), and in-situ gelled HCl-formic acids were investigated in this study. In some cases, rheology measurements and core flood experiments were conducted. The data were combined with the reaction study to understand the behavior of these acids and examine their efficiency if injected in the formation.Item Sandstone Acidizing Using Chelating Agents and their Interaction with Clays(2013-01-09) George, Noble Thekkemelathethil 1987-Sandstone acidizing has been carried out with mud acid which combines hydrochloric acid and hydrofluoric acid at various ratios. The application of mud acid in sandstone formations has presented quite a large number of difficulties like corrosion, precipitation of reaction products, matrix deconsolidation, decomposition of clays by HCl, and fast spending of the acids. There has been a recent trend to use chelating agents for stimulation in place of mud acid which are used in oil industry widely for iron control operations. In this study, two chelates, L-glutamic-N, N-diacetic acid (GLDA) and hydroxyethylethylene-diaminetriacetic acid (HEDTA) have been studied as an alternative to mud acid for acidizing. In order to analyze their performance in the application of acidizing, coreflood tests were performed on Berea and Bandera sandstone cores. Another disadvantage of mud acid has been the fast spending at clay mineral surfaces leading to depletion of acid strength, migration of fines, and formation of colloidal silica gel residue. Hence, compatibility of chelates with clay minerals was investigated through the static solubility tests. GLDA and HEDTA were analyzed for their permeability enhancement properties in Berea and Bandera cores. In the coreflood experiments conducted, it was found out that chelating agents can successfully stimulate sandstone formations. The final permeability of the Berea and Bandera cores were enhanced significantly. GLDA performed better than HEDTA in all applications. The substitution of seawater in place of deionized water for mixing purposes also led to an increased conductivity of the core implying GLDA is compatible with seawater. In the static solubility tests, chelates were mixed with HF acid at various concentrations. GLDA fluids kept more amounts of minerals in the solution when compared with HEDTA fluids. Sodium-based chelates when mixed with HF acid showed inhibited performance due to the formation of sodium fluorosilicates precipitates which are insoluble damage creating compounds. The application of ammonium-based chelate with HF acid was able to bring a large amount of aluminosilciates into the solution. The study recommends the use of ammonium-based GLDA in acidizing operations involving HF acid and sodium-based GLDA in the absence of the acid.Item Well Productivity Enhancement of High Temperature Heterogeneous Carbonate Reservoirs(2014-05-08) Wang, GuanqunAcidizing is one of the most popular techniques for well productivity enhancement during oil and gas production. However, the treatment method is not very effective when the wellbore penetrates through multiple layers of heterogeneous reservoirs. Uneven acid distribution always results in productivity enhancement under expectation. When such a well is drilled, the temperature of the well could be too high to keep the acid reaction under control. The acid used in the treatment fluid, most commonly HCl, would react with the tubular and the formation at a very high rate. Rather than creating long wormholes to bypass the damaged area, face dissolution, loss of pipelines, and potential damage are the outcomes after the treatment. Thus, several new techniques were proposed in this study to solve the issues discussed above. To address the heterogeneity of the reservoir, viscoelastic surfactants (VES) were used as diverting agents during acidizing treatments. A recently developed chelating agent, L-glutamic acid-N,N-diacetic acid (GLDA), was evaluated as a possible alternative for the traditional HCl. Coreflood tests and measurements of rheology properties of the treatment fluids were used to investigate the performance of the treatment fluids based on the two new systems. In total, two VES were evaluated for their diverting abilities. The first VES was based on amine oxide. It was found that the live VES-based acids had the highest apparent viscosity when the concentration of HCl was 5 wt%. During the coreflood tests, the VES-based acid was only able to build up pressure drop across the core at injection rates less than 1 cm_(3)/min. A significant amount of the VES was left inside the core after the treatment, which reduced the efficiency of production enhancement. The other VES, based on carboxysulfobetaine, can tolerate high temperatures up to 325?F. According to the viscosity measurements of the spent VES-based acid, the addition of various corrosion inhibitors lowered the fluid viscosity at temperatures above 150?F. Mutual solvent was able to break the wormlike micelles formed by the VES in the presence of calcium chloride. The diverting ability of the VES was proved through coreflood tests. For the GLDA-based treatment fluids, two additives were added into the system in effort to improve the efficiency of the treatments. Polymers and VES were added into the GLDA to achieve even fluid distribution during treatment. A significant viscosity increment was observed with the help of the viscosifier, which could expand the application of the GLDA.