bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Oil-Based Chemical Gel System for Wellbore Stabilization
Authors: Scorsone Jason T. , Sanders Mark W. , Patel Arvind D.
Published: April 2009

Historically, water-based chemistries, such as epoxy resins, latex polymers and transition metal crosslinked polymers have been used to mitigate many of the operational problems associated with formation fractures. However, these approaches have found limited success for various reasons such as temperature limitations, complicated mixing and placement issues, weak gel strengths, health & safety concerns, and compatibility with various types of drilling fluids. A new oil-based chemical gel system which addresses many of the issues associated with current systems has been developed. The thermal stability, curing time, compressive strength, and adhesion properties of the new system depend on the manipulation of the composition and chemistry of the components. This newly developed chemical gel is more controllable over a wide range of temperature and time, and is compatible with many invert-emulsion drilling fluids.

This paper will detail the innovative chemistry of this oil-based gel system. The gel is formed by the crosslinking reaction of a modified polyurethane resin and a uniquely modified siloxane mechanism. Systematic development and evaluation, including temperature stability, controllable curing times, compressive strength and adhesion strength to formation of the system will be included.
pH Sensitive Polymers for Novel Conformance Control and Polymerflood Applications
Authors: Choi Suk Kyoon , Sharma Mukul M. , Bryant Steven L. , Huh Chun
Published: April 2009

Novel conformance control and polymerflood applications that exploit the pH-sensitivity of partially hydrolyzed polyacrylamide (HPAM) are proposed. The key feature of this process is the injection of the HPAM solution under acidic conditions. The low pH makes polymer molecules coil tightly, resulting in a very low polymer solution viscosity. This allows the polymer solution to be injected into the reservoir at a substantially reduced injection pressure. Once injected, the acid reacts with the formation minerals to cause a spontaneous pH increase, uncoiling the polymer chains and causing a large increase in solution viscosity. Such a viscosity control scheme can be exploited for placement of a concentrated polymer solution in high-permeability zones, where it later viscosifies to divert subsequently injected fluids (in-depth conformance control), or to reduce the high pressure drop near the wellbore during polymer injection (injectivity improvement). Extensive rheological measurements and coreflood experiments (for different polymer molecular weights and degree of hydrolysis, and at different pH, salinity, and polymer concentration), are performed and interpretated.

Rheological measurements show that both shear and oscillatory viscosities of HPAM solution have a pronounced, but reversible, dependence on pH. Coreflood results show that the HPAM solution under acidic conditions can be propagated through cores with much higher mobility than at neutral pH. The use of a weak acid is the key. The peak pH's observed in several shut-ins guarantee that spontaneous geochemical reactions can return the polymer solution to its original high viscosity. However, low-pH conditions increase adsorption (polymer-loss) and require additional chemical cost (for acid). The optimum injection formulation (polymer concentration, injection pH) will depend on the specific reservoir mineralogy, permeability, salinity and injection conditions.
Laboratory Measurement of pH of Live Waters at High Temperatures and Pressures
Authors: Mathews S. G. , Raghuraman B. , Rosiere D. W. , Wei W. , Colacelli S. , Rehman H. A.
Published: April 2009

This paper describes a new technique for measuring pH on live formation water samples in the laboratory at high temperature and pressure. The technique involves adding pH sensitive dyes to pressurized single phase water samples collected using a formation tester and spectroscopically determining the pH in the laboratory at reservoir conditions. Water chemistry and pH are important inputs for scale and corrosion modeling. Due to the lack of standard laboratory techniques for such measurements at high temperatures and pressures, current practice involves flashing the single phase water sample, analyzing the flashed water and gas phases, and then using water chemistry models to predict pH at reservoir conditions. Uncertainties in the thermodynamic models for formation waters at high temperature and pressure, as well as uncertainties associated with the flash process and possible precipitation of salts, can propagate as errors into scale and corrosion models. It is proposed that the direct pH measurement on live water samples described here be used as an additional input for the water chemistry models to improve confidence in their predictions. This will allow for more efficient selection of completion materials and planning for scale treatment and mitigation.

In this paper, we present results of laboratory pH measurements on formation water samples from two offshore Gulf of Mexico wells for pressures to 20,000 psi and temperatures to 242°F. Results are compared to predictions from two commercial thermodynamic models that use the flashed gas and water analysis data as inputs. The setup can also measure the sensitivity of pH to pressure and temperature. Comparison of the laboratory pH measurement to real-time in situ downhole pH measurements made on the same formation water with a formation tester showed good agreement. This is an example of the implementation of the chain of custody concept, which compares a measurement made downhole with that made in the laboratory on the same sample using the same technique, to validate the representativeness of the sample as it is transported from downhole to the laboratory.
Evaluation of H2S Scavengers for Matrix-Acidizing Treatment
Authors: Xiao Z. , Morgenthaler L. N. , Cowan M. K. , Aremu K. , Adams J. G.
Published: April 2009

Operational reports indicate that a spike of H2S is sometimes evolved while flowing back the acidizing treatment. H2S is produced by the reactions between acid and sulfide scales. We investigate in this paper the performance of various H2S scavengers and deliver guidelines for field application of H2S scavengers in acid treatment of wells.

Five commercial H2S scavengers from chemical suppliers and service companies are evaluated under various conditions such as temperatures, acid-mineral ratios, and scavenger concentrations. Scavenger effects on reaction kinetics, acid dissolution capacity and scavenging capacity are investigated. Core flow tests, sequential spending tests, scavenger performance tests under field conditions, and compatibility tests were also performed to study scavenger effectiveness at various operation conditions and potential formation damage caused by spent scavengers.

In the tests reported here we identify one product that meets all our performance criteria, several that meet most performance criteria and several that meet few of our performance criteria for potential application to scavenge H2S in well acidizing fluids.
Reacting Ions Method to Identify Injected Water Fraction in Produced Brine
Authors: Ishkov Oleg , Mackay Eric , Sorbie Ken
Published: April 2009

Waterflooding is a very common method of oil displacement and pressure support. One particular problem that may arise after injection water (IW) breakthrough at the production well is the formation of sulphate scale. One of the main parameters that determines the severity of this type of scale formation is the amount of injection water/formation water (IW/FW) mixing that has taken place. Thus, the injected water fraction in the produced brine mix is an important value to determine. Our ability to model scale precipitation in situ and in the well is linked to our ability to accurately determine the IW fraction at production wells. Current industry practice is to work on an analytic approach for determining the fraction of IW in the produced brine stream in general, and for identifying IW breakthrough in particular.

A robust and accurate method for determining IW fraction in field produced water analysis is required to match the modelled IW fractions. When this is achieved, it is possible to use various modelling techniques with a higher degree of confidence to predict future scaling tendencies, and to help implement an appropriate scale management strategy to economically mitigate the potential effects of scale damage.

In this paper, the "Reacting Ions" method is introduced for determining the fraction of IW (and FW) in produced waters. This method is then applied to a synthetic produced water case where the "correct" answer is known, and a very good match is achieved, even when significant noise is applied to the synthetic data. The method is then applied in the analysis of produced brines for several wells in a North Sea field. Results of the study presented here show that the method is more effective in detecting IW fractions than conventional ion tracking techniques, especially at low IW fractions close to when breakthrough occurs. The significant new development presented in this work is that this approach may be used accurately even in situations where scale deposition deep in the reservoir impacts the concentrations of the ions used in this method.
Nonaggressive Matrix Stimulation Fluids for Simultaneous Stimulation of Heterogeneous Carbonate Formations
Authors: Wang Xiaolan , Qu Qi , Cutler Jennifer , Boles Joel L.
Published: April 2009

Two major challenges associated with conventional stimulation fluids are the corrosive nature of the fluids and their inability to treat the entire productive interval of heterogeneous formations without employing diversion techniques. It is often difficult to prevent corrosion on oilfield tubular from the conventional acid stimulation fluids, especially in high temperature wells. Additionally, when conventional acid is injected into a long heterogeneous formation, it preferentially enters intervals of least resistance or highest permeability. The injected acid continues reacting with formation material to further increase formation permeability thus ensuring acid intake into the same high perm zone. This thief-like behavior leads to inadequate stimulation of target low permeability or damaged zones. This is especially true for matrix treatments of long open-hole horizontal wells. Various diverting techniques such as ball sealers, foams, and polymer pills, have been used to ensure stimulation focusing on the areas requiring most treatment. Without proper removal mechanisms after stimulation treatment, however, diverting agents may even cause formation damage.

This paper highlights the development of a nonaggressive matrix stimulation fluid. The non-reactive nature of this fluid at ambient temperature allows it to penetrate both high and low perm zones proportionally in a long heterogeneous reservoir. The strong acid generated in-situ during shut-in can stimulate both zones simultaneously. With this new system, not only the diverting agents can be eliminated, but also the procedures become simplified and cost is reduced. Laboratory testing demonstrates that this new stimulation fluid system can treat the heterogeneous productive intervals with significant permeability contrast without using damaging diverting agents under various conditions. Laboratory corrosion tests validate the fluid's low corrosion on oilfield tubular at elevated temperatures. Stimulation efficiency of the new fluid over conventional acids on carbonate formations will be discussed to illustrate that the new fluid provides a better alternative in many situations.
Diversion and Propagation of Viscoelastic Surfactant Based Acid in Carbonate Cores
Authors: Al-Ghamdi Abdulwahab H. , Mahmoud Mohamed A. , Hill A. D. , Nasr-El-Din Hisham A.
Published: April 2009

Surfactants have been used over the past few years as a diverting material when mixed with acid solutions. Several papers are aimed to understand the overall process and the diversion capability. However, most of the coreflood experiments, if not all, used relatively short cores usually ranging between 2 to 6 inches in length and 1 to 1.5 inches in diameter. In this paper and for the first time, 20 inches long cores were used in conducting the acidizing experiments. The lithology of the rock type used was calcite, which has permeability of 50 to 120 md. In addition to the appropriate surfactant concentration, 15 wt% HCl was used. A key parameter such as flow rate, affects the behavior of the gelling material significantly. Therefore to capture that effect, flow rates chosen to be representative ranged between 5 and 15 cm3/min. A further analysis included is the effluent concentration for the mineral composition mainly Ca++. In addition, the acid concentration in the effluent was measured and validated with an analytical model to address the acid profile along the wormhole, which becomes an important aspect in understanding the flow of VES fluids in carbonate cores.

Part of this study is to characterize the wormhole propagation expected from the acidizing process. To accomplish this task, computerized tomography (CT) was used to generate 3-D images to describe the shape of the wormhole. There is a major difference in the shape of the wormhole when using the diverting material compared to conventional acids. The wormhole path observed in the first case tended to have several changes in direction as the acid tried to find its way to propagate further and avoid any possible blockage caused by the diverting material. This phenomenon would not be captured with short cores that were used in the previous studies.
Quantitative Analysis of an Amphoteric Surfactant in Acidizing Fluids and Coreflood Effluent
Authors: Yu M. , Mahmoud Mohamed A. , Nasr-El-Din H. A.
Published: April 2009

Viscoelastic surfactants (VES) exhibit remarkable viscoelastic character due to their ability of forming wormlike micelles and entangled structures, which can greatly increase the viscosity of the fluid. The VES fluids can be used to improve the proppant suspension ability and fluid diverting ability in well acidizing treatments. As a result, VES have been found numerous application in the oil fields as fracturing fluids and matrix acidizing fluids in the recent years.

According to previous studies, the concentration of VES in the fluids has profound effects on their performance downhole. Additionally, the loss of VES is also a very important indicator of the downhole events. Therefore, being able to analyze the concentration of VES surfactants in both live and spent acids is of great importance for production engineers who apply VES in the oil fields.

In the present work, a two-phase titration method was optimized for the quantitative analysis of a carboxybetaine viscoelastic surfactant, and the interference by typical additives in the acidizing fluids on this method was determined. This method was used in the determination of coreflood effluent, and it was found that tremendous amount of the viscoelastic surfactant is trapped in the core.
ab initio and Molecular Simulation Studies of Organic and Inorganic Counterions' Effect on Anionic Viscoelastic Surfactant
Authors: Sultan A. S. , Balbuena P. B. , Hill A. D. , Nasr-El-Din H. A.
Published: April 2009

Viscoelastic surfactants have a wide range of applications in the oilfield industry, including acid fracturing and matrix acidizing. A problem associated with acidizing is the tendency of the live acid or spend acid to form sludge which can reduce the effectiveness of the treatment or plug the formation or production equipments. Formation of sludge results from precipitation of insoluble materials upon interaction with acid. Presence of cations such as ferric will enhance the aggregation process. Emulsion and corrosion are other problems associated with well acidizing and it can impact flow to the wellbore. It has been reported that anionic surfactants can address some of the problems associated with well stimulation and align themselves due to intermolecular attraction or non-covalent bonds to form wormlike micelles. The micelles can be absorbed on the formation or further interact to form a network exhibiting elastic behavior dependent on type of rocks. This increase in viscoelasticity helps in many cases to control fluid placement while acidizing multiple zones with variation in permeability and it also has sufficient properties to suspend and carry the proppant into the fractured zone. Several previous experimental studies highlighted the significant role of counterions in determining the apparent properties of aqueous solutions that contained viscoelastic surfactants. Wormlike micelles are formed by aggregation of amphiphiles. Presence of co-surfactant, additives, salts or appropriate counterions helps promote growth of such micelles. The effect of counterions can be detrimental on the properties of the whole system. Understanding how macroscopic properties depend on intermolecular interactions for complex fluids is the main focus of this study.

Density functional theory and molecular dynamics simulations are employed to better understand how organic and inorganic counterions can impact physical properties of viscoelastic surfactants and hence their functionality in carbonate reservoirs. Anionic surfactants with different head groups include acetic acid (AA), potassium butanoate (PB) and sodium butane-1-sulfonate (S1BS), together with their counterions are simulated over a wide range of parameters. Competition between mono-, di- and trivalent counterions was studied in the gas phase of three anionic surfactant head groups with organic counterions (sodium salicylate, NaSal, and sodium hydroxynaphthalene carboxylate, NaHNC) and inorganic counterions (Na+, Mg2+, Ca2+, Fe2+ and Fe3+). Binding energy and thermodynamic properties show that trivalent counterions are more strongly bonded than di- and monovalent ones. The results give important insight into the links between molecular structure of surfactant and ions present in solution, which will help in developing more systematic procedures for treatment optimization, and better design of more efficient/effective viscoelastic diverting systems.
Biodegradable Alternatives for Scale Control in Oilfield Applications
Authors: Holt Stuart , Sanders Jannifer , Rodrigues Klin , Vanderhoof Matthew
Published: April 2009

Environmental legislation has significantly reduced the variety of scale inhibitor chemistries that can be used to prevent inorganic scale formation during the production and separation of crude oil from produced water. Poor ecotoxicity has severely impeded the use of phosphonates, while many polymers, the other traditional approach to scale control, fail to meet minimum biodegradation requirements.

We have developed biopolymers based on synthetic/natural polymer hybrids that show enhanced biodegradation, are environmentally benign and are much less reliant on non-renewable monomer feedstocks than classical polymer scale inhibitors. As well as being more sustainable, this novel technology allows the inclusion of a broad range of functional groups that can be designed to meet the varying technical demands of oilfield scale inhibitor application environments.

Various hybrid polymers have shown excellent performance under standard oilfield performance testing conditions versus a range of currently used chemistries. Some distinct benefits of hybrid technologies pertaining to oilfield scale control will also be expanded upon.
Effect of Salinity on Wettability Alteration of Porous Media From Liquid Wetting to Intermediate Gas Wetting
Authors: Wu Stanley , Firoozabadi Abbas
Published: April 2009

The synergetic effect of salinity and fluorochemicals on the alteration of wettability from water-wetting to intermediate gas-wetting is studied in this work. We find that NaCl salinity increases water-wetting when a core is saturated with brine. NaCl also reduces absolute gas permeability as reported in the literature. CaCl2 salinity is drastically different from NaCl brine, and has a minor effect on permeability. The NaCl, KCl and CaCl2 brines have an adverse effect on wettability alteration. To alleviate the effect of salt on treatment, we suggest pre-treatment by displacement of brine with water and subsequent drainage by nitrogen.
Review and Evaluation of Corrosion Inhibitors Used in Well Stimulation
Authors: Rostami A. , Nasr-El-Din H. A.
Published: April 2009

Corrosion inhibitors are an indispensable part of the fluid mix pumped downhole when a well is acidized. Of the various approaches to mitigate corrosion, the best way to reduce corrosion problems in the petroleum industry is to use corrosion inhibitors. Determining the most effective corrosion inhibitor for a given environment is essential.

There are enormous examples of chemical inhibitors, which are propriety mixtures of several chemicals to induce synergistic effect. But basic function of corrosion inhibitors is by using some organic compounds containing oxygen, sulfur and nitrogen. This paper gives a complete vision of what the corrosion inhibitor is. How the structure of corrosion inhibitor molecule can affect the functionality of these molecules. This work discusses the effect of factors like chain length, degree of branching, substitution of multiple for single bond, using sulfur instead of nitrogen and other factors that affect the efficiency of corrosion inhibitor molecules. Depending on the mechanism of corrosion mitigation, corrosion inhibitors are classified as cathodic inhibitors, anodic inhibitors and mixed inhibitors which are explained in the paper.

Corrosion inhibitors used in well stimulation acidizing are organic molecules, usually film-forming amines. They are classified as mixed inhibitors that affect both cathodic and anodic reactions and will decrease corrosion rates. Their effectiveness is largely a function of their ability to adsorb at the metal/metal-oxide surface. Adsorption occurs due to the polar or charge nature of organic molecules/ionic species first establishing a physisorbed surface film (through Vander walls forces), which may further stabilize through chemisorption to form a donor-type bond. This paper discusses and compares the performance of various corrosion inhibitors and intensifiers, addresses limitations of each inhibitor and give recommendations for field application.
New Insights into the Viscosity of Polymer-Based In-Situ Gelled Acids
Authors: Gomaa A. M. , Nasr-El-Din H. A.
Published: April 2009

Diversion techniques must be employed to remove all the damage from the entire producing interval. Diversion in carbonates is more difficult than in sandstones because of the ability of acid to significantly increase the permeability in carbonates as it reacts in the pore spaces and flow channels of matrix. The apparent viscosity of the in situ gelled acid based on polymer plays a key role in diversion because it creates a viscosity differential in treated and untreated zones. An extensive literature survey and field data, there is no agreement on the effectiveness of this acid system. Therefore , this study was conducted to better understand this acid system and determine factors that impact its viscosity build-up. Three commercially available in-situ acids were examined.

The effect of salts, iron contamination on the apparent viscosity of these acids was examined. Several new findings were identified, including: Polymer and other additives were separated out of the acid when these acids were prepared in high salinity water. Preparing the in-situ gelled acid with saline water decreased the viscosity of the acid in live and neutralized conditions. Concentrated HCl solutions produced high concentrations of calcium chloride that reduced the viscosity of the acid system. Therefore, in-situ gelled acids that are based on the polymer should be used at low HCl concentrations (3-5 wt% HCl). Sodium, calcium or ferric chlorides reduced the apparent viscosity of live acids. A brown precipitate was noted during the neutralization of acid systems that contained Fe(III) even in the presence of the recommend concentration of iron control agents.
Design and Development of Quaternary Amine Compounds: Shale Inhibition With Improved Environmental Profile
Authors: Patel Arvind D.
Published: April 2009

Novel cationic-based drilling fluid additives that provide excellent shale inhibition with improved environmental profile have been developed and tested. Low-molecular-weight bis-quaternary amines that contain structures similar to naturally occurring cationic compounds provide low toxicity and excellent shale-inhibition properties. This paper describes both the laboratory development and chemistry of such shale inhibitors.

Cationic shale inhibitors provide more effective shale inhibition by anchoring to the negatively charged shale surfaces as compared to traditional anionic products. However, cationic shale inhibitors are perceived to be more toxic in both onshore and offshore drilling applications than commonly used anionic drilling fluid additives. The toxic nature of many cationic amine compounds has limited their application as shale inhibitors in offshore and other environmentally sensitive areas. Along with toxicity-related issues of cationic compounds, these types of chemical additives are not compatible with conventional anionic drilling fluid additives such as polyanionic cellulose (PAC), polyacrylates, bentonite and various biopolymer additives. Thus, the utilization of cationic additives, specifically cationic shale inhibitors has been limited; yet, there is a need to develop such shale inhibitors which mitigate these limitations making them usable for environmentally sensitive areas.

Extensions of the latest amine-shale inhibitor chemistries have enabled the design and development of cationic amine shale inhibitors, which provide efficient shale inhibition to water sensitive shale without the adverse environmental impact. The paper describes the chemistry and development of such modified cationic shale inhibitors, resolving the inherent environmental toxicity limitations and providing excellent shale inhibition to a variety of water-sensitive clays. The paper also includes various drilling fluid formulations containing these innovative shale inhibitors and compares their performance with state-of-the-art inhibitive water-based drilling fluids currently used in the field for similar applications.
Foams and Emulsions Stabilized With Nanoparticles for Potential Conformance Control Applications
Authors: Zhang Tiantian , Roberts Matthew R. , Bryant Steven L. , Huh Chun
Published: April 2009

While emulsions stabilized by colloidal solid particles have been widely used for industrial and consumer applications, their use for enhanced oil recovery purposes has been very limited. This is because the colloidal solids generally cannot be transported long distances within oil reservoirs, e.g. from injection well to production well. Nanoparticles are two orders of magnitude smaller than colloids and thus can migrate through the pore throats in sedimentary rocks. Emulsions stabilized with nanoparticles can withstand the high-temperature reservoir conditions for extended periods. This can substantially expand the range of reservoirs to which EOR can be applied. Finally, nanoparticles can carry additional functionalities such as super-paramagnetism and reaction catalysis. The former could enable transport to be controlled by application of magnetic field. The latter could enable in situ reduction of oil viscosity.

We have employed aqueous suspensions of surface-modified silica nanoparticles (5- & 20-nm diam.) in a set of laboratory experiments. We report the phase behavior of nanoparticle-stabilized oil/water emulsions and the transport of these emulsions in porous media. Very stable oil/water emulsions were generated, with average droplet size between 2 and 4 microns, at ambient and at elevated temperature. The emulsion stability was not strongly dependent on nanoparticle concentration or on salinity. The transport in glass-bead packs (ca. 20 Darcy) of the silica-stabilized oil/water emulsions showed a sharp emulsion-bank front, with no visible loss of their integrity, and high apparent viscosity (30 cp). Permeability to the aqueous phase post-flush was significantly reduced. It was not possible to determine whether emulsion droplets were retained in pores during emulsion injection, or whether the post-flush fingered through the emulsion and failed to displace all of it. An on-going modeling effort to characterize the equilibrium and stability of the emulsions suggests formation of relatively compact interfacial layer of nanoparticles at the droplet surface.
A New Shear-Tolerant High-Temperature Fracturing Fluid
Authors: Parris Mike , Mirakyan Andrey , Abad Carlos , Chen Yiyan , Mueller Fred
Published: April 2009

The extent of crosslinking a polymeric fracturing gel can significantly contribute to the success or failure of a hydraulic fracturing treatment. In certain cases, excessive crosslinking while the fluid is in the tubulars can result in friction pressures that are too high, and may prohibit the treatment from achieving the design goals. With titanium (Ti) or zirconium (Zr) crosslinked gels, which are known to be prone to irreversible shear degradation, early crosslinking in the tubulars can substantially reduce the final gel strength, even to the degree that near wellbore proppant transport is compromised, and the treatment may screenout. On the other hand, a Ti or Zr crosslinked gel which crosslinks substantially after exiting the perforations may not have sufficient proppant transport capability to complete the treatment successfully.

Varying treatment conditions such as mixwater composition and temperature, tubular shear rate and transit time, and reservoir temperature pose difficult challenges to routinely achieving the optimal crosslinking state. Conditions such as offshore wellbore temperature profiles and viscous heating in smaller diameter tubing can further complicate the task. Various chemical means have been employed to tune the crosslinking temperature for specific treating conditions. These methods involve addition of chemicals to control the crosslinking kinetics, such as pH buffers, crosslinker concentration, and competing ligands to temporarily bind the metal crosslinker. Blended crosslinkers containing a single Group 4 (Ti, Zr) metal with different organic ligands with different binding strengths have been employed to achieve crosslinking at two temperature ranges so that early viscosity for proppant transport can be developed. Mixed metal crosslinkers, such as aluminum and Zr have also been formulated for this same purpose.

This paper examines the disadvantages of these strategies, and describes the development and deployment of a high-temperature fracturing fluid system that has shown to overcome those issues.
Incremental Oil Success From Waterflood Sweep Improvement in Alaska
Authors: Ohms Danielle , McLeod Jennifer , Graff Craig J. , Frampton Harry , Morgan Jim C. , Cheung Stephen , Yancey Katrina , Chang K. T.
Published: April 2009

Waterflood thief zones in communication with the rest of the reservoir are a severe and previously challenging problem. This paper gives an introduction to the nature of a novel, heat-activated polymer particulate. Details of a trial of this in–depth diversion system, resulting in commercially significant incremental oil from a BP Alaskan field are presented. The system of one injector and two producers was selected because of a high water oil ratio and low recovery factor, which was recognized as an indicator of the presence of an injection water thief zone and confirmed by study of a previous injection survey. The area around the wells is bounded by faults so the system can be considered to be isolated from surrounding wells and operations. The position of the thermal front in the reservoir, tracer transit times, injection rates and inter-well separations indicated that the slowest reacting of the three commercial grades available was most appropriate for the trial.

The treatment was designed using laboratory tests, and numerical simulation informed by pressure and chemical tracer tests. Long sandpack tests indicated permeability reduction factors of 11 to 350 for concentrations of 1500 to 3500 ppm active particles in sand of 560 to 670 mD permeability at 149°F. 15,587 gallons of particulate product was dispersed, using 8,060 gallons of dispersing surfactant, into 38,000 barrels of injected water and pumped over 3 weeks at a concentration of 3300 ppm active particles.

Placement deep in the reservoir between injector and producer was confirmed by pressure fall off analysis and injectivity tests. The incremental oil predicted from the simulation was 50,000 to 250,000 bbl over 10 years. In fact over 60,000 barrels of oil was recovered in the first 4 years at a cost comparable with traditional well work and less than sidetracking.
Environmentally Friendly Water-Based Fluid for HPHT Drilling
Authors: Tehrani A. , Gerrard D. , Young S. , Fernandez J.
Published: April 2009

In Europe where environmental regulations prohibit the use of oil-based mud, high-temperature wells are drilled with HPHT water-based fluids. Chrome-lignosulfonates are a common component in high-temperature water-based fluids, acting as effective dispersants and conferring excellent fluid-loss control and rheological properties. However, tightening of regulations signals the emergence of restrictions on the use of chrome-based products in water-based fluids. Elsewhere in land operations where currently oil-based fluids are used for high-temperature applications, a move towards HPHT water-based fluids, and ultimately to chrome-free fluid systems is thought to be inevitable. Thus, alternative chrome-free products are desired that will perform at least as well as the current products in high-temperature, high-density water-based fluid systems.

Fluid-loss control in high-temperature environments can become problematic due to the degradation of many polymers at high temperature. A main challenge is to use a high-temperature synthetic polymer that can control fluid loss without a significant impact on rheology. High-temperature gelling is another problem that may confront high-density fluid systems and lead to significant problems during the drilling operation. This must be prevented by using effective, temperature-stable dispersants.

This paper describes the development of a new chrome-free, high-density HPHT water-based fluid system. The new fluid uses a combination of clay and synthetic polymers to provide excellent fluid-loss control and to generate thermally stable rheology. The paper presents the results of extensive testing to show that the use of highly efficient dispersants prevents high-temperature gelling and improves fluid resistance to drill solids contamination. The authors will also present results from an initial field testing of the fluid system.
Development of compact UASB/trickling filter systems for treating domestic wastewater in small communities in Brazil
Authors: De Almeida P. G. S. , Chernicharo C. A. L. , Souza C. L.
Published: April 2009

The paper analyses the concept and performance of compact UASB/TF systems in relation to configuration, use of innovative packing media and operational conditions. For the conditions tested, the UASB/TF systems had consistently complied with the Brazilian discharge standard regarding to COD, BOD and TSS parameters. However, some enhancements are still necessary in order to increase nitrification in the process. The conditions to promote nitrification in shallow TF (packed bed up to 2.50 m height) seem to be compatible with the proposed simplification in the flowsheet, which is to operate the system without secondary clarifiers.
On-line microwave total solids sensoring in sewage characterization
Authors: Poutiainen H. , Laitinen S. , Juntunen P. , Heinonen-Tanski H.
Published: April 2009

We describe a novel application for a microwave on-line sensor to measure the total solids (TS) load entering a municipal wastewater treatment plant (WWTP) from slaughterhouse sewage and some sanitary wastewaters. Measuring this kind of wastewater stream is very challenging, because it contains a high, but varying organic load with nitrogen, phosphorus and microorganisms. The reliability of the measured signal was studied by comparison with laboratory analyses and a correlation is presented of TS-value with other parameters that are typically followed in a wastewater treatment process. The results suggest that on-line microwave sensoring could be used to monitor total solids in wastewater influent. Our results show that the on-line microwave sensor and laboratory reference analyses give similar results with a good correlation between the two techniques. Furthermore, we demonstrate that the total solids values correlate well with conductivity, total nitrogen and BOD7 values but not with phosphorus, pH and temperature.
Removal of hydrogen sulfide and ammonia from gas mixtures by co-immobilized cells using a new configuration of two biotrickling filters
Authors: Ramirez M. , Gómez J. M. , Aroca G. , Cantero D.
Published: April 2009

The simultaneous removal of H2S and NH3 was investigated using two biotrickling filters packed with polyurethane foam cubes. One biotrickling filter was inoculated with Thiobacillus thioparus ATCC 23645 for the removal of H2S (BTT) and the other filter with Nitrosomonas europaea ATCC 19718 for the removal of NH3 (BNE). Three different configurations were studied by modification of the gas line and recirculation medium line. The best results were obtained with the BNE biotrickling filter after the co-immobilization of the two bacteria. A removal efficiency of 100% for 230 ppmv of NH3 and 129 ppmv of H2S was reached at an EBRT of 60 seconds. The results obtained show that it is possible to co-immobilize both microorganisms using the same recirculation medium and remove successfully H2S and NH3 from a gas mixture.
Shock loading in biofilters: impact on biodegradation activity distribution and resilience capacity
Authors: Cabrol L. , Malhautier L. , Poly F. , Lepeuple A. S. , Fanlo J. L.
Published: April 2009

A synthetic contaminated gas was generated, representative of gaseous emissions from sludge composting. It was composed of six volatile organic compounds (aldehyde, ketones, esters, sulphur compound) in an ammoniacal matrix. The gaseous stream was purified by biofiltration, in pilot scale biofilters filled with pine bark woodchips as organic carrier for biomass colonization. After reaching a constant high efficiency, with complete removal, the system was disturbed by transient loading shocks. The impact of perturbations was assessed by both performance evaluation (i.e. contaminant removal) and microbial behaviour. The microbial community was analysed in terms of density. The resilience of functional component following a perturbation was evaluated. This work highlighted the longitudinal distribution of both biodegradation activities and biomass density.
Measuring odour emission and biofilter efficiency in composting plants by proton transfer reaction-mass spectrometry
Authors: Biasioli F. , Aprea E. , Gasperi F. , Märk T. D.
Published: April 2009

PTR-MS (Proton Transfer Reaction-Mass Spectrometry) is an innovative technique that allows the rapid detection of most volatile organic compounds (VOCs) with high sensitivity (sub-ppb) and by direct injection. We describe here the possible use of PTR-MS in waste managements and composting plants both for the real time monitoring of volatile emissions and, after calibration with olfactometric assessments, for the instrumental determination of odour concentration. Beside a short description of the technique, we will report on the calibration of PTR-MS data with olfactometric assessment of odour concentration showing the possibility of a relatively good estimation of odour concentration by instrumental data. We will also show how the rapid PTR-MS fingerprint can be used to visualise the overall effect of a biofilter on the VOCs concentration and to calculate the reduction of the concentration of single masses and, finally, we will provide examples of the performances of a new implementation of this technique based on a time of flight (TOF) analyser. Instead of the usual quadrupole mass filter, the TOF provides an increase of analytical information and the possibility to separate important compounds that in the quadrupole version were not or only indirectly quantifiable. In conclusion we suggest that PTR-MS analysis can be a valuable tool for the rapid and on site monitoring of odour emission and plant operation.
Development of a kinetic model for elemental sulfur and sulfate formation from the autotrophic sulfide oxidation using respirometric techniques
Authors: Gonzalez-Sanchez Armando , Tomas Maria , Dorado Antoni David , Gamisans Xavier , Guisasola Albert , Lafuente Javier , Gabriel David
Published: April 2009

A kinetic model for the elemental sulfur and sulfate production from the autotrophic sulfide oxidation has been proposed. It is based on two kinetic equations able to describe the simultaneous microbial consumption of oxygen and sulfide (OUR and SUR) as a function of a particular sulfide-oxidizing microorganism or its physiological state, these can be characterized by the assessment of their kinetic constants. The respirometric technique allowed to estimate the dynamic experimental OUR and SUR profiles, which were used to calibrate the kinetic model. The ratio OUR/SUR was proposed to predict the sulfide oxidation extent and then the fate of sulfide to elemental sulfur and sulfate.
Characterization of the bacterial community in a biotrickling filter treating high loads of H2S by molecular biology tools
Authors: Maestre Juan P. , Rovira Roger , Gamisans Xavier , Kinney Kerry A. , Kirisits Mary Jo , Lafuente Javier , Gabriel David
Published: April 2009

The diversity and spatial distribution of bacteria in a lab-scale biotrickling filter treating high loads of hydrogen sulfide (H2S) were investigated. Diversity and community structure were studied by terminal-restriction fragment length polymorphism (T-RFLP). A 16S rRNA gene clone library was established. Near Full-length 16S rRNA gene sequences were obtained, and clones were clustered into 24 operational taxonomic units (OTUs). Nearly 74% and 26% of the clones were affiliated with the phyla Proteobacteria and Bacteroidetes, respectively. Beta-, epsilon- and gamma-proteobacteria accounted for 15, 9 and 48%, respectively. Around 45% of the sequences retrieved were affiliated to bacteria of the sulfur cycle including Thiothrix spp., Thiobacillus spp. and Sulfurimonas denitrificans. Sequences related to Thiothrix lacustris accounted for a 38%. Rarefaction curve demonstrated that clone library constructed can be sufficient to describe the vast majority of the bacterial diversity of this reactor operating under strict conditions (2,000 ppmv of H2S). A spatial distribution of bacteria was found along the length of the reactor by means of the T-RFLP technique. Although aerobic species were predominant along the reactor, facultative anaerobes had a major relative abundance in the inlet part of the reactor, where the sulfide to oxygen ratio is higher.
Difference in the odor concentrations measured by the triangle odor bag method and dynamic olfactometry
Authors: Ueno H. , Amano S. , Merecka B. , Kośmider J.
Published: April 2009

‘The triangle odor bag method’, which has been adopted for the offensive odor control law in Japan, and the dynamic olfactometry defined by EN 13725 have been compared. The odor concentration measured by the triangle odor bag method tends to be higher than that of the dynamic olfactometry in the forced choice mode, while well agreed in the Yes/No mode olfactometry when the panel is the same. The difference can be minimized by applying the panel selection criterion of EN13725 to the triangle odor bag method. The European panel selection test is useful to negate the difference in the measurement equipments although the criteria seem to be strict considering the individual threshold data of n-butanol.
Review of adverse health effects of odours in field studies
Authors: Sucker K. , Both R. , Winneke G.
Published: April 2009

Exposure to environmental odours from industrial and agricultural premises, in addition to inducing annoyance responses in a dose-dependent manner, have been shown to be either directly associated with gastric symptoms as well as general health-related complaints under extreme exposure conditions, or indirectly mediated through odour annoyance under moderate odour exposure conditions. Objective: In order to examine the influence of hedonic tone (pleasantness-unpleasantness) and perceived odour strength (intensity) on symptom reporting the results of two pertinent field studies were analysed. Methods: In the vicinity of six industrial plants (sweets, rusk, textile, seed-oil, fat, cast iron) and eleven livestock operations (poultry, pig, cattle) assessment of odour exposure was done by means of systematic field inspections. Effect assessment was done by means of direct interviews (industrial: N=1456, agricultural: N=1053) using questionnaires covering odour annoyance, symptom reporting and relevant covariates. Data analysis: Multiple logistic regression analysis was used to establish dose-response associations between odour frequency, intensity and hedonic tone as independent variables and symptom reporting as dependent variable. Results: Exposure-symptom associations are strongly influenced by hedonic tone, whereas intensity has no additional predictive value. Adding odour annoyance to the regression model shows that symptom reporting is exclusively mediated by annoyance.
Multifactorial optimization of the decolorisation parameters of wastewaters resulting from dyeing flowers
Authors: Pavas Edison Gil , Gómez-García Miguel Ángel
Published: April 2009

This work deals with the treatment of the wastewaters resulting from the process of dyeing flowers. In some local cases for growing flowers near to Medellín (Colombia), wastewater color was found to be one of the main problems in meeting local effluent standards. Wastewaters were treated by photodegradation process (which includes photocatalysis) to achieve the degradation of dyes mixture and organic matter in the wastewater. A multifactorial experimental design was proposed, including as experimental factors the following variables: pH, and the concentration of both catalyst (TiO2) and hydrogen peroxide (H2O2). According to the obtained results, at the optimized variables values, it is possible to reach a 99% reduction of dyes, a 76.9% of mineralization (TOC) and a final biodegradability of 0.834. Kinetic analysis allows proposing a pseudo first order reaction for the reduction, the mineralization, and the biodegradation processes.
The land use plan and water quality prediction for the Saemangeum reclamation project
Authors: Hwang D. H. , Choi J. Y. , Yi S. M. , Han D. H. , Jang S. H.
Published: April 2009

As the final closure of the world's longest sea dike of 33 km, the use of the Saemangeum reclaimed land becomes an issue in Korea. The Korean government has proclaimed that the Saemangeum Reclamation Project will be handled in an environmentally friendly manner but its effect on the water quality of reservoirs has always been controversial. This study was conducted to estimate the water quality of the Saemangeum reservoir using WASP5 according to the new land use plan adopted in 2007. Predictions on water quality shows that Dongjin reservoir would meet the standards for COD, T-P, and Chl-a if the wastewater from the Dongjin region was properly managed. However, T-P and Chl-a in Mangyeong reservoir would exceed the standards even without releasing the treated wastewater into the reservoir. With further reductions of 20% for T-P and Chl-a from the mouth of Mangyeong river, the water quality standards in the reservoir were achieved. This means that additional schemes, as well as water quality management programs established in the Government Master Plan in 2001, should be considered. Although the Saemangeum reservoir would manage to achieve the standards, it will enter a eutrophic state due to the high concentration of nutrients.