bluuebunny/crossref_metadata_2025 huggingface dataset:
Groundwater Monitoring in the Eagle Ford: Evaluating Baseline Conditions in a Risk Management Context
Authors: Zimmerman M. , Patterson K. , Hedgcoxe H. R. , Houghton J. , Berger K.
Published: June 2014

Unconventional Resource (UCR) development requires a robust understanding of baseline conditions and potential for environmental impacts due to its dependence on water and other shared resources, geographic overlap of target locations and the presence of potential receptors. While many operators have committed to monitor groundwater as part of their Environmental Management programs, the value of a monitoring program depends on having a coherent strategy for identifying critical data and implementing program elements in the correct stage of the project lifecycle. Increasingly, operators are also recognizing that implementing a sound groundwater monitoring plan is a key component of their strategy to manage business risk in the rapidly developing shale plays.

Using the Eagle Ford shale as a case study, this paper evaluates the emerging industry standard of baseline and on-going groundwater monitoring to assess the potential for impacts to water resources from drilling and hydraulic fracturing. Data sources for this study include publicly-available state and federal agency data, interviews with major operators, and groundwater data collected as part of early lifecycle baseline assessments.

Water management programs in UCR development are complicated by factors such as population density, land use, depth and availability of potable or non-potable groundwater, and competition between water users. The challenge for operators has been to develop a monitoring program that is robust enough to manage current and potential future risk, while remaining efficient and flexible enough to accommodate changing development schedules. The monitoring program must be readily modified in response to new data.

Recent work in this area has been focused on using risk-based assessments to identify critical areas where monitoring will provide key information on the potential impacts of drilling and hydraulic fracturing operations. Major components of a water monitoring program include developing the risk basis for sample locations, agreeing on the suite of analytes to be monitored, and incorporating the program into the development schedule. This approach helps operators design a "fit-for-purpose" program based on local and regional hydrogeology, surrounding land use and potential sources of contamination, the presence of historical oil and gas operations, current groundwater use, and the presence of receptors. Such a program provides operators with the critical groundwater data and risk management information necessary to address stakeholder concerns, maintain schedule, transfer water resource infrastructure for future use later in the development lifecycle, and, ultimately, maintain this component of their social license to operate.
Process Safety Management: Taking PSM to Next Level
Authors: Al Abdul Salam Abdulla , Al-Qallaf Yousef , Pichery Leslie Anthony , Adivi Bala Siva
Published: June 2014

Process Safety Management (PSM), though not a relatively new concept, has been implemented by many organizations to eliminate incidents like tragic Bhopal catastrophe; however, even after more than 25 years has been passed; still we are encountering disasters which occurred in different parts of the world. The BP Texas City incident and consequent Baker Panel Report have made it explicitly clear that PSM had to be established and administered as a distinct management system having its own management tools. Though every organization has its own metrics to manage Process Safety Management, however, the importance lies exactly whether those metrics (performance indicators) are rightly chosen or not. This paper presents holistic review of various process safety metrics suggested and developed by well-known international bodies.
Building Energy Efficiency Into the Design and Retrofit of Facilities
Authors: Rowbottom R. A. , Kuykendall D.
Published: June 2014

Energy efficiency in building design is an ongoing and continuously evolving process as state-of-the-art technology and standards develop over time. To maintain best-in-class facilities, energy efficiency must be incorporated into the design of new construction, and based on the principle of continuous improvement for building standards and specifications. In addition to design principles for new construction, companies need to routinely review existing facilities to incorporate retrofits based on criteria such as return on investment, energy costs and reliability, life cycle replacement of existing equipment and structures, and greenhouse gas emissions along with other environmental impacts.

This paper describes the integration of sustainable building specifications and energy efficiency programs into both new construction standards and guidelines for facility retrofits. Critical aspects include:Developing sustainable building specifications to meet internal company requirements for new construction.Identifying energy improvement opportunities through energy audits and use of best management practices for facility retrofits.Conducting equipment life cycle analysis to calculate return on investment (ROIs) based on amortized annual cash flow projections.

The process is based on internationally recognized standards such as the ASTM International E60 standard "Specification for Minimum Environmental, Social and Economic requirements for Building and Promoting Sustainability".

Case studies are presented to illustrate how a company’s energy reduction program began and evolved during a two-year period. An additional case study will highlight the application of retrofits at 67 facilities reducing annual energy consumption by 9.5 million kilowatt hours (KWh), eliminating 6,534 metric tons of greenhouse gas emissions, and reducing annual energy costs by USD $817,000.

The use of measurement and tracking tools is critical for determining energy reduction results and effects on carbon footprints. This paper also describes the company’s tracking system and how the data is used for internal and external sustainability reporting.
Automatic Tank Cleaning: A Shining Example
Authors: Massam Karen , Hunter Martin , Eriksen Frank , Stolen Geir
Published: June 2014

Manual cleaning methods can vary from man entry into the tanks, using shovels and pressure washers, to the use of more sophisticated automated systems. The risks associated with confined-space entry are well documented and any cleaning system that reduces or eliminates the need to go inside tanks significantly improves the safety of a cleaning operation.

This paper presents a case study of a tank cleaning operation on board a supply vessel that transports drilling fluids and their constituent products. The automated system installed enabled 20 to 30 tanks to be cleaned every month with exceptional results and no operational downtime. The system was safe, simple and reliable, and resulted in significant reductions in confined space entry. The volume of waste generated was only 20 m3 in 12 months of operation, achieved by using a physical separation and water recycling process. This significantly reduced the cost and improved the safety of the operation.

The case study highlights the need for optimal equipment selection and installation based on the unique features of the tank system, methods to eliminate confined space entry, achievable cleaning performance and techniques for waste minimization. The principles presented are widely applicable to tanks and vessels common throughout industry.
Wetland Restoration Using Mangroves in Southern Louisiana
Authors: Madison Maxine J. , Mack Sarah K. , Lane Robert R. , Day John W.
Published: June 2014

Wetland restoration is essential in addressing wetland loss along the coasts of Southern Louisiana. Wetland restoration techniques, such as planting mangroves, provide a wealth of benefits such as storm surge reduction, fish and wildlife habitat, carbon sequestration, recreation, job creation, and economic development that are vital to the sustainability of coastal Louisiana. The Louisiana Land & Exploration Company, a wholly owned subsidiary of ConocoPhillips, is one of the largest private owners of coastal marsh in the nation, owning approximately 640,000 acres located in the coastal zone of southeast Louisiana. A pilot project was recently initiated by ConocoPhillips and Tierra Resources to apply the latest scientific approaches to measure the benefits of mangrove plantings for restoration purposes and viability of carbon sequestration on ConocoPhillips’ property in Southern Louisiana. This paper discusses the pilot project as well as the application of the first certified methodology for quantifying the carbon sequestration benefits of this wetland restoration project. Results from this three-year (2012–2015) pilot project will address science gaps, determine costs, benefits, and barriers to implementation.
Phytoremediation of Chlorinated Solvents in Fractured Rock
Authors: Kuykendall Dina , Snow Brad , Gatliff Edward
Published: June 2014

Over a 21 year period, several remediation methods were used for the cleanup of chlorinated solvents dissolved in groundwater at an oilfield pump manufacturing facility in Claremore, Oklahoma. These methods included soil excavation and off-site disposal, air sparging/soil vapor extraction, groundwater circulation wells, high vacuum multiphase extraction, carbohydrate injection and throughout the project’s history, the current pump-and-treat system. The primary chemicals of concern (COCs) include trichloroethene (TCE); 1,1,1 trichloroethane (TCA); and associated degradation products. Due to challenging hydrogeologic conditions and the nature of the contaminants, only a modest improvement in groundwater quality has been achieved. Even with the significant historical remediation efforts and considerable expenditures, there was no foreseeable end point. The company objective is to reduce the contaminant concentrations and to assure that no off-site contaminant migration can occur which might impact sensitive receptors. The company sought a sustainable solution that would not involve continued expensive remediation system operations and maintenance.

The remediation strategy was evaluated and revised to include engineered phytoremediation as a primary component. In March 2012, 52 trees were installed within large diameter boreholes for groundwater hydraulic control and in situ treatment.

This paper presents the challenges and solutions for drilling and completing the tree installations in highly variable fractured shale and sandstone within the constraints of tight spaces at a busy operating plant. Preliminary data concerning tree health, growth and hydrologic effects are presented. This evaluation includes the varying mortality of bare root versus potted trees and the importance of staking the trees in the strong Oklahoma winds. During the first growing season, the tree roots reached and began using groundwater, enabling them to survive an unusually hot and dry summer.

Once the trees are more fully established, phytoremediation is expected to provide a sustainable and cost effective remedial alternative to the long-term groundwater pump-and-treat system. Its successful application at this site opens up the possibility for using phytoremediation at other challenging fractured rock sites.
Brine Contaminated Soil Remediation Field Tests Using a Novel New Product
Authors: Burns Lyle D.
Published: June 2014

Salt contamination of soils is a serious environmental issue facing the oil and gas industry today according to many stripper well operators and state regulators. Salts such as sodium chloride from produced oilfield brine spills can completely devastate surrounding vegetation. The most common response is the application of gypsum and straw or manure. This ineffective, time consuming technique may take several remediation applications over a period of years making it very expensive when all costs, loss of soil use, and damages are considered. The problem lacks a suitable solution with the benefits of being rapid, simple, economical, dependable and environmentally safe. Today, there is much more emphasis on operating in an environmentally conscious manner than ever before.

The Phase I Stripper Well Consortium project developed a solution that offers a rapid and economical way to remediate salt damaged soils and enhance oil field aesthetics for new and old brine contaminated sites. The project involved a laboratory effort to evaluate the hypothesis which questioned whether a soil remediation product could be formulated to quickly remediate the sodium contamination from brine spills. The result was an affirmative response to the hypothesis. This SPE paper is about the Phase II field testing effort to verify the lab work, simplify field application for the customer’s benefit, and verify formulation dependability. Field testing was very successful with 10 out of 11 field tests or 91% showing positive results with rapid grass growth within 2 – 6 weeks after remediation. All sites had2 – 5 cm of rainfall during that period.

The major formulation constituents are a highly soluble calcium source, a proprietary multi-basic amendment and fertilizer that were mixed into the soil, all environmentally safe components. Native grass seed is planted and raked into the soil immediately after remediation. The field tests occurred in Oklahoma, Kansas and New York.
Design for HSE: Improving Equipment and Product Safety by Reducing Risk through the Integration of HSE into the Design Life Cycle
Authors: Jee V. J. , Kubala G.. , Mayes J. C.
Published: June 2014

Well site operations utilize many types of equipment which can involve health, safety and environment (HSE) aspects. Changes in equipment design in the industry have often been made in reaction to incidents or in reaction to changes in legislation and regulatory standards.

This reactive approach can reduce the safety margin of the equipment when engineering teams become focused on minimum standard compliance rather than overall safety. This can be an increasing concern where the equipment is new and novel as the speed of design changes may outpace changes in regulation, and there is less in-use experience on which to base the risk analysis. It can also increase overall cost if changes in design are made at later stages in development.

In order to move to a more proactive approach for HSE in engineering, an oilfield services company formally implemented a program to integrate HSE aspects into the equipment design cycle. The program not only considers the operational risk of the equipment but also considers the risks in the verification and testing phases, and during manufacturing. Key elements to this implementation are:HSE competency and training of engineers, designers and project managers.Documented standards and best practices that can foster intelligent reuse.Project management framework that guides development teams in identifying risk in all areas, including HSE.Integrating HSE personnel with design teams to understand the functional and business requirements and constraints.

Proactively introducing HSE requirements early, and continuously, during engineering projects can positively affect design, making the resulting equipment safer to use and reducing costs due to non-compliance and design re-work.
Application of Computers to the Interpretation of Well Logs
Authors: Tuman Vladimir S. , Bollman Dorothy
Published: June 2014

Available digital computers can be effectively used for the interpretation of well logs by the following procedure:digitizing the well log data,preparing the programs to process the data, andanalysis and evaluation of the results.

Types of available digitizing units are discussed. At present, the cost of digitization is greater than the cost of processing the same data by a computer. Consequently, further developments will be required to reduce the cost of getting the data in digital form.

An effort is made to indicate how to write a program for a digital computer, and a step-by-step example is worked out. Some examples processed on the computer for the formations in the Illinois basin are also included. Five programs prepared at the U. of Illinois are discussed. Detailed flow charts for four of these programs, including the "Discriminating Routine Program", are given. This program discriminates sands or porous beds from shales. It is the basic program for the automatic processing of the well logs which will control the over-all operation of the computer. It also can be used by geologists who are interested in sand/shale counts.

A rough economic study of the problem indicates that it will be advantageous to encourage service companies in the future to offer digitized well logs.

Introduction

High-speed computers are useful in handling two types of problems:a group of complex problems which have a very large number of operations; andone or more problems where there is a need for varying the parameters and, consequently, for repeating the operations a large number of times.

The thorough evaluation of well logs embraces both groups of problems.
Creating a Culture of Safety and Reliability in the Offshore World
Authors: Spigener Jim
Published: June 2014

Most organizations in the offshore oil industry have squeezed all of the performance they can get from traditional approaches to procedures, rules, and other administrative controls. Adding more programs to an already overtaxed workforce is not only undesirable and costly but can actually be detrimental to safety, environmental, and cost performance. Operators don’t need more things to do but a way to get more out of what they are already doing. Operational reliability and execution are the keys to effective performance. And this means developing a safety culture that engages people at all levels to fully commit to doing the right thing at the right time in the right way. This paper will discuss research findings that demonstrate how a strong safety culture leads to operational reliability and is the leading factor that sets the very best performers in offshore drilling apart from their counterparts.
Aeration and Microfiltration for Solids Removal of Produced Waters from the Barnett Shale
Authors: Palmgren Tor H. , Fajt James R. , Danilov Alexander G. , Burnett David B.
Published: June 2014

Suspended solids are typically removed by mechanical and or chemical methods. Microfiltration commonly requires some treatment to remove large particles, and oil and organics that can affect filter production rates. The extent of total water treatment required depends on quality of the raw water and the disposition of the treated water. Total suspended solids (TSS) removal may often be sufficient treatment to meet a given target and satisfy key chemical performance criteria for water re-use for the formulation of hydraulic fluids.

This study explored the use of aeration and settling to reduce iron content of produced water prior to filtration with a 10-µm bag filter and with hollow fiber, stainless steel and ceramic filters of submicron porosity. It was determined that aeration with compressed air for sufficient time to oxidize the iron was an effective treatment to convert ionic iron to particulate iron oxide in a produced water sampled from an unconventional gas well in the Barnett Shale near Dallas in Arlington TX.

The 10-µm bag filtration proved inadequate for achieving any significant reduction of turbidity, particle count or iron reduction. However, the filters rated to remove particles smaller than one micron proved useful. A comparison of different submicron-rated filters, comprising hollow fiber, stainless steel and ceramic membranes, all capable of removing particles greater than 1 µm when used in the treatment of mixed aerated water and settled aerated water, showed no major difference in their gross performance of TSS reduction or their ability to remove iron oxide particles. All the submicron filters reduced the water turbidity and particle count by more than 90% and reduced total iron to a concentration that was below detection limit.
Addressing Well and Field Infrastructure Siting Challenges in the Wetlands and Streams of the Haynesville, Marcellus, Utica, and Eagle Ford Shale Plays
Authors: Krauss Russell F
Published: June 2014

Abstract

As U.S. shale play activities move from appraisal to production phase, it is increasingly difficult for surface operations to avoid impacts to environmentally sensitive wetlands and streams. Many shale plays are located in areas more visible to the general public than ever before in the history of domestic onshore oil and gas field development. Shale play development for oil, natural gas and natural gas liquids, has therefore resulted in increased scrutiny by agencies causing successful operators to be more proactive in the siting of wells and associated field infrastructure including access roads, flowlines, and gathering systems. Complex regulatory regimes must be navigated by producers and operators in each shale play and, although operating under standardized Federal regulations, are required to address the preferences of each regulatory agency, and in many cases, individual regulators themselves.

Working under new rules since 2008, regulatory agencies require offsets for unavoidable impacts to wetlands and streams to occur in the watershed where the impacts will occur. With limited mitigation acreage available in areas where surface rights are locked up by landowners and operators, and the increased visibility of environmental risk and liability from field operations, the need for proactive, creative wetland and stream mitigation solutions is self-evident.

In the Pennsylvania Marcellus Shale, streams need to be crossed every 2,000 feet, often needing both a state and Federal permit. In the Louisiana Haynesvlle Shale, every fifth well pad typically requires a permit under Section 404 of the Clean Water Act. In the Eagle Ford shale, what is now an access road was once a dry streambed, which potentially should have been permitted, if indeed it was not.

A multitude of functional assessment methodologies are employed by regulatory agencies to assess project-related impacts on habitat functions and values. Even within a single shale play, these methods abound. Only through proactive understanding of complex regulatory regimes in each shale play can operators, producers and infrastructure providers plan for solutions early in their project life cycle, to eliminate operational risk and control their own destiny with regard to managing risk and operational liability in these environmentally sensitive areas.
Unique System for Managing Data From Oil and Gas Operations
Authors: Veil J. A. , Jehn P. , Fine M. J. , Griffith B. G.
Published: June 2014

State agencies have the primary responsibility for overseeing and regulating oil and gas operations. Those operations generate a large amount of data. Managing the data in an effective and coordinated way presents challenges to federal, state, and local agencies and to other interested users. In 1992, the U.S. Department of Energy (DOE) provided initial funding to the Ground Water Protection Council (GWPC), a national association of state agencies, to develop the Risk Based Data Management System (RBDMS), a family of software applications that allows management of data associated with oil and gas operations. The RBDMS software is used for a variety of purposes including: managing operator and bonding information; the permitting processes; tracking well locations and construction details; tracking production data; assessing the impacts of injection wells on underground sources of drinking water; and tracking inspections, compliance, and other enforcement activities. Since its inception, RBDMS has relied on a combination of DOE’s financial support and matching funds and feedback from the 21 states that use the system to keep it updated and to incorporate new features. RBDMS has recently added a variety of new features that are discussed in the full paper. The paper and presentation will show many of the features and capabilities of RBDMS that can be useful to oil and gas companies, researchers, and other interested persons.
Prediction of Stimulated Reservoir Volume and Optimization of Fracturing in Tight Gas and Shale With a Fully Elasto-Plastic Coupled Geomechanical Model
Authors: Nassir M.. , Settari A.. , Wan R..
Published: June 2014

Hydraulic fracturing is essential for the economic development of tight gas reservoirs and shale-gas reservoirs. Current techniques are unable to predict the stimulated-reservoir-volume (SRV) dependence on fracturing-job and rock-mechanics parameters, which precludes any meaningful optimization. In the authors' previous work on the SRV-propagation prediction, the combined tensile/shear fracturing model applied to the fracturing of tight gas formations has shown the creation of a relatively narrow, focused SRV that resembled behavior dominated by a single fracture. In this work, the model has been significantly improved by the implementation of a rigorous full Newton elasto-plastic solution of the geomechanics of rock containing induced fractures. The results reveal interesting features of complex-fracture propagation in tight formations, which are in broad agreement with the shapes of SRVs obtained from microseismic imaging.

The developed code is flexible enough to allow either tensile or shear fracturing or the occurrence of both to be examined on the basis of initial reservoir conditions. Different cases of 2D and 3D simulations will be presented that demonstrate some important features of the process. First, it is found that a wide SRV can result in cases in which initial reservoir conditions are close to the shear-fracturing point, such as in formations with microfractures, partially cemented natural fractures, and abnormally high initial pore pressure. Second, the SRV width is found to depend on the horizontal stress contrast, as expected. Third, wide SRV growth is associated with constant or increasing pumping pressure necessary for further failed-zone growth as a result of the loss of elastic coupling by off-planar failure propagation. Further, under high injection pressure, an efficient fracture elasto-plastic constitutive model developed can drive both maximal and minimal effective stresses to zero or tensile, and, therefore, the creation of tensile fracturing can be predicted simultaneously with shear fracturing. This will then provide a means of modeling proppant transport. The new model is a significant step toward the development of an integrated predictive tool for the optimization of shale-gas development.
Evolution of Drilling and Completions in the Slave Point To Optimize Economics
Authors: Lerner Nolan , Schaab Brent , Garcia Juan , Bianco Dan , Thomas Scott , Thompson Jason , Hollan Jeremy
Published: June 2014

This paper will detail the technological evolution of drilling and completion practices used to optimize the economic development of the Slave Point carbonate platform, specifically in the Evi and Otter fields in northern Alberta, Canada. The Slave Point platform was initially targeted for conventional production by means of vertical wells in the early 1980s. Success was marginal because of the unpredictability of localized porosity development. As a result, the full-scale commercial development of this resource was deemed uneconomic because of poor reservoir quality. More recently, however, horizontal-drilling and multistage-fracturing technology has allowed operators to open up lower-porosity horizons to improve flow capacity, to improve recoveries, and to allow for commercial development from zones previously deemed uneconomic.

The Slave Point has a greater thickness and is less permeable than other tight-rock plays in Alberta, such as the Cardium and Viking. It produces high-quality, light oil with low water- and solution-gas-production rates. Despite high estimates of original oil in place (OIP) of approximately 3 to 10 million bbl per section, horizontal-well rates are still challenged because of the lower permeability through the pay section. In this regard, the continued deployment of innovation and technology has been critical in improving well-production performance, compressing project costs, and ultimately optimizing project economics.

The focus of this paper is solely on one of the major Slave Point operators who has drilled 49 horizontal wells that account for 200 000 m (656,000 ft) drilled and 1,350 fracture stages in the Evi and Otter Slave Point fields since 2008. This operator has continually deployed advancing technologies to improve project economics. The information will be presented in terms of the influence of technology on well design, the optimization and deployment of the various technologies, and the demonstrated improvement on productivity and reserves recovery. The discussion will focus on three development phases that highlight the progression from vertical to horizontal technology:

Vertical Appraisal Single-Lateral (SL) Development Dual-Lateral (DL) Development

The case studies presented will demonstrate clearly the production impact from the use and application of these technologies. The methods and lessons learned through the use of DLs, openhole junctures, and openhole multistage systems can be applied to other unconventional formations.
Enhanced Jetting Tool Integrated with Sand/Well Vacuuming Technology Optimizes Cleaning and Stimulation for Heavy-Oil Wells
Authors: Duque E. D. , Diaz J. D. , Pineda R. , Marin C. , Núñez M.
Published: June 2014

The Orinoco Oil Belt (OOB) is located in the southern strip of the eastern Orinoco River basin in Venezuela, with a total area of 55,314 km2. This formation represents the largest heavy-oil reserves from unconsolidated sandstones in the world. Unfortunately, sand production is a common problem associated with this type of formation. In addition, it is very challenging to successfully remove solids and stimulate large, highly deviated wells with low bottomhole pressures.

Since 1999, a technology combining concentric coiled tubing (CCT) with a jet pump has been used in the OOB to remove solids and fluids (stimulation treatments, drilling fluids, etc.) from the wellbore. Due to the characteristics of these heavy-oil wells, with their unconsolidated sands and highly deviated well paths, sand/well vacuuming technology (SWVT) has become the main alternative for intervention operations such as sand cleanouts, stimulations, drilling fluid removal, and any kind of job requiring the use of coiled tubing.

Conventional SWVT permits changing the configuration of the tool into two modes: sand vacuuming for solids removal, and well vacuuming for fluids recovery. During SWVT operations, two main scenarios exists where it is necessary to change the bottomhole assembly (BHA) used with SWVT for a regular BHA with enhanced jetting, thereby requiring extra runs to finish the jobs.Breaking through hard bridges formed by sand and oil or by solid materials as elastomers from progressive cavity pumps.Pumping down chemical stimulations treatments.

To overcome the issues resulting from cleaning and increasing efficiency with stimulations jobs in a single run (avoiding extra running of different BHAs), an improved SWVT with a jetting switch has been developed, incorporating a third mode: high jetting. In this mode the SWVT BHA can handle higher fluid rates and achieve the necessary impact pressure to break solids bridges or to perform stimulations jobs efficiently. This paper discusses the implementation of this tool in the OOB and explains the results in terms of efficiency increase and best practices for this type of intervention.
The Use of Inhibition Kinetics and NMR Spectroscopy in Thermal Stability Study of Scale Inhibitors
Authors: Wang Wei , Kan Amy T. , Yan Chao , Tomson Mason B.
Published: June 2014

As the oil and gas industry is making firm stride in deepwater exploration and development, possible thermal degradation of scale inhibitor molecules poses a great challenge for scaling control and flow assurance for high temperature reservoirs. Although extensive research has been conducted to test thermal stability of scale inhibitors, little work has been devoted to study the thermodynamics/kinetics of thermal degradation of scale inhibitors. In this work a novel and efficient testing approach based on inhibition kinetics has been developed and successfully applied to determine the fraction of the initial inhibitor molecules in preheated samples of scale inhibitors with various generic chemistries. Moreover, for the first time, we have modeled the kinetics of inhibitor thermal degradation based on the integrated first-order rate equation and Arrhenius equation, with good agreements between the model predictions and experimental data. The preheated scale inhibitors have been analyzed by nuclear magnetic resonance (NMR) spectroscopy for organic compound characterization. Our results and predictions based on inhibition testing assay are consistent with the 31P/1H NMR analyses. This work has enabled an in-depth understanding of the time and temperature dependence of thermal degradation of scale inhibitors, and facilitates the rational selection and deployment of scale inhibitors for high temperature oil and gas production.
Measurement and Prediction of Thermal Degradation of Scale Inhibitors
Authors: Wang Wei , Kan Amy T. , Zhang Fangfu , Yan Chao , Tomson Mason B.
Published: June 2014

As the oil and gas industry is making firm strides in deepwater and shale exploration and development, possible thermal degradation of scale-inhibitor molecules poses a great challenge for scaling control and flow assurance for high-temperature reservoirs. Although extensive research has been conducted to test thermal stability of scale inhibitors, little work has been devoted to study the thermodynamics/kinetics of thermal degradation of scale inhibitors. In this work, a novel and efficient testing approach based on inhibition kinetics has been developed and successfully applied to determine the fraction of the active inhibitor molecules in preheated samples of scale inhibitors with various generic chemistries. Moreover, for the first time, we have modeled the kinetics of inhibitor thermal degradation on the basis of the integrated first-order rate equation and Arrhenius equation, with good agreements between the model predictions and experimental data. The preheated scale inhibitors have been analyzed by nuclear-magnetic-resonance (NMR) spectroscopy for organic-compound characterization. Our results and predictions based on inhibition testing assay are consistent with the 31P/1H NMR analyses. This work has enabled an in-depth understanding of the time and temperature dependence of thermal degradation of scale inhibitors, and facilitates the rational selection and deployment of scale inhibitors for high-temperature oil and gas production.
Novel Scale Remediation for Steam Assisted Gravity Drainage (SAGD) Operations
Authors: Cheung Timothy , Scheck Michael
Published: June 2014

Shell runs a Steam Assisted Gravity Drainage (SAGD) operation at the Orion field in Alberta, Canada. Pressure drops during bitumen and water recovery can lead to precipitation and buildup of scales which can plug up well equipment and lead to an increase in differential pressure and lower production. Early attempts to remove such blockages with high pressure steam or salinity-altering brine injections resulted in transient returns to normal operations but with diminishing returns. Acid treatments to dissolve the scale encountered problems with corrosion and an inability to handle the discovery of the presence of acid insoluble scales. Alterations to the operating conditions such as pH along with the addition of a chelating agent, EDTA, were successful in treating both types of scales. As a result, differential pressures and steam to oil ratios decreased while oil production grew. This treatment was extremely cost-effective and payout was on the order of a few days.
Scale Inhibitor Consumption in Long-Term Static Barium Sulphate Inhibition Efficiency Tests
Authors: Shaw S. S. , Sorbie K. S.
Published: June 2014

In typical bulk barite inhibition efficiency (IE) experiments testing scale inhibitors (SI), the IE is determined by comparing the concentrations of the barium ion in the mix to that in an uninhibited "blank" solution. That is, [Ba2+] vs. time is monitored for both a blank and an inhibited solution. The fate of the scale inhibitor itself over this test time period is rarely monitored although this can give some important insights into the inhibition mechanism. This paper presents a series of long-term (up to 96 hour) barium sulphate static inhibition efficiency (IE) experiments in which both the supernatant scale inhibitor concentration, [SI], and [Ba2+] are assayed at multiple sampling times after initial mixing of sea water (SW) and formation water (FW) brines. In standard IE tests to determine SI minimum inhibitor concentration (MIC), sampling is normally carried out at 2 hours and 22 hours only. The long-term IE experiments described in this paper involve up to eleven sampling times, typically at t = 0.5, 1, 2, 3, 4, 5, 6, 22, 48, 72 and 96 hours after mixing.

The aim of this type of experiment is to determine the fate of the SI over time, and secondly, to determine whether the IE and %SI in solution versus time profiles correlate with each other. Clearly, SI removed from solution is consumed into the forming barium sulphate lattice in the barite precipitate. IE and solution SI often continue to decline beyond 22 hours, up to 96 hours after the mixing stage. In these experiments, the SI concentration is set at a pre-2 hour MIC threshold concentration, such that the IE and %SI consumption profiles will both decline sufficiently over time, possibly even as early as 0.5 hour after mixing. The SI consumption profiles obtained testing an extensive range of phosphonate and polymeric SIs are compared and discussed. Normally a phosphorus-containing SI is selected for evaluation, to facilitate assay of SI by means of inductively coupled plasma (ICP) spectroscopy. However, intriguing results are also presented where selected polymeric SIs were assayed by non-ICP analytical techniques. We interpret this extensive series of SI lattice consumption experiments in terms of the mechanisms of barite inhibition and Type 1 / Type 2 SI classifications presented in previous papers (Shaw et al., 2012a, 2012b).
Inorganic Scaling and Chemical Inhibition Challenges Associated with Production of Reservoir Equilibrated Spent Acid Stimulation Fluids
Authors: Morrow Timothy , Farooqui Mohammad , Morshidi Leozarin , VanNuis Russell , Graham Gordon , Kidd Sam , Dyer Sarah , Simpson Caroline
Published: June 2014

Hydrochloric acid (HCl) is commonly used to remove wellbore damage and to enhance near-wellbore formation permeability in carbonate formations. Although in most cases the spent acid is recovered rapidly during well flow back after the treatment, in heterogeneous reservoirs some of the spent acid can remain trapped for long periods becoming fully saturated with CaCO3 under downhole conditions. These reservoir-saturated spent acids then lead to scaling when eventually unloaded into the production system.

This paper describes a modelling and laboratory study to replicate the system, to allow selection of inhibitors which are effective against carbonate scales in spent acid solutions containing extremely high levels of Ca2+/Mg2+, and also remain stable at elevated temperatures in the spent acids. The work also examined chemical retention and release via coreflood testing followed by field application modelling to select effective scale inhibitors (SI) which possess poor retention properties on the carbonate substrate thereby remaining present in the "spent acid".

One significant challenge associated with this study was the ability to reproduce the mildly oversaturated field scaling environment in the laboratory. When using these fully saturated (with respect to CaCO3) partially acidic brines, very small changes in the brine chemistry or preparation procedures had a significant impact on scaling. A detailed evaluation of brine preparation, stabilisation and buffering was therefore required prior to evaluating generic scale inhibitors for performance under these extreme conditions leading to selection of appropriate species. The second stage of the work then involved core test procedures to determine those chemicals that offered minimal retention properties on the reservoir along with performance.

This paper will present the field scaling challenges observed due to unloading of trapped spent acids; describe challenges faced within the laboratory in reproducing these conditions and present results from generic chemical types which are effective at preventing scale under these extreme conditions. From the shortlisted products further results are presented demonstrating those which offer poor retention, which is generally the opposite of what is required for conventional scale inhibitor squeeze treatments, allowing selection for upcoming field trials in the selected field system.
The Impact of Dissolved Organic-Carbon Type on the Extent of Reservoir Souring
Authors: Burger E. D. , Jenneman G. E. , Gao X.
Published: June 2014

A reservoir souring forecasting model was presented previously. This model utilized a generic algorithm to determine, via history match, the extent of H2S biogeneration by sulfate-reducing bacteria (SRB) within the waterflooded reservoir such that the production to the surface could be forecasted. The generic algorithm assumed a decline in SRB-usable organic nutrients as a function of water flow within the reservoir. However, nutrient utilization by non-SRB (e.g., nitrate-reducing bacteria) could not be differentiated from the SRB with this model. The current study has incorporated stoichiometry of microbial sulfate and nitrate reduction utilizing both volatile fatty acids (VFA) and BTEX components as dissolved organic carbon (DOC) substrates. This paper presents the updated algorithms and discusses partitioning of the DOC components between oil and water within the reservoir. VFAs such as acetate have historically been assumed to be the favored nutrient source by SRB, but recent field experience has suggested that other DOC sources are contributors. BTEX components, especially toluene, are shown with the model to potentially have a large impact on souring in spite of their limited solubility in the reservoir water. While nitrate usage to control reservoir souring is becoming a "standard" practice, H2S generation in reservoirs with conditions that support BTEX as an SRB nutrient might not be sufficiently inhibited with nitrate.
Calcium Naphthenate Mitigation at Sonangol's Gimboa Field
Authors: Junior Jorge , Borges Luis , Carmelino Carlos , Hango Pedro , Milliken John Duncan , Asomaning Sam
Published: June 2014

Sonangol's Gimboa production is located in deepwater block 4 offshore Angola. Early in the life of the field and with the advent of water cut, it experienced solids production that fouled processing equipment and that were later identified as calcium naphthenates. The paper describes in detail Gimboa's calcium naphthenate deposition including its history and progression. Detailed characteristics of the crude and produced water are provided. The mechanisms of solids formation are elucidated and the remedial measures adopted to solve the problem are examined in detail. The impact of water cut and the role of system parameters like temperature and pressure in the resolution of the naphthenate problem are outlined and the use of field filtration and bottle testing methods in designing the eventual solution are highlighted. As with most oilfield problems calcium naphthenate deposition at Gimboa was brought under control through the conscientious efforts of Sonangol, Nalco Energy Services and Saipem personnel working as a team.
Prevention of Acid Induced Asphaltene Precipitation: A Comparison of Anionic vs. Cationic Surfactants
Authors: O'Neil Bill , Maley Darren , Lalchan Chris
Published: June 2014

With the recent proliferation of horizontal drilling specifically targeting oil bearing reservoirs, high strength acid fracturing treatments in the Beaverhill Lake formation in northern Alberta have dramatically increased in both product volume and number of treatments. The Beaverhill Lake formation is a limestone/calcareous shale that produces a desirable mid to high API sweet crude oil. Although the crude oil typically has a low concentration of asphaltenes, the oil is very sensitive to acid and/or iron induced asphaltene precipitation. As the acid strength increases and ferric iron is dissolved into solution, it becomes increasingly difficult to chemically prevent the asphaltenes from precipitating. Acid blends designed to prevent asphaltene precipitation also tend to be very emulsifying with the crude oil, therefore a careful balance between anti-sludge additives and non-emulsifiers must be found.

This paper will describe the chemistry of surfactants that can be used to prevent asphaltene precipitation as a result of acid/oil contact. Specifically, a comparison of anionic versus cationic surfactants will be given, describing both the benefits and detriments of using these in acid blends. A discussion of the change from vertical well completions in the Beaverhill Lake formation to horizontal multi-zone completions will be presented. As a result of this change in completions, the desired properties of the acid blends have changed noteably. The final results of a comprehensive laboratory study to optimize cost and performance of the acid blends will be presented. A review of field case studies comparing formation response to anionic and cationic acid blends will also be presented.
Simultaneous Well Stimulation and Scale Squeeze Treatments in Carbonate Reservoirs
Authors: Jordan M. M.
Published: June 2014

In many oilfields the relatively small number of high-cost, highly productive wells, coupled with a carbonate and or sulfate scaling tendency (upon waterflood breakthrough of injected seawater) requires effective scale management along with removal of near-wellbore damage in order to achieve high hydrocarbon recovery.

The nature of the well completion strategy in new fields such as frac packs for sand control and acid stimulation for carbonate reservoirs has resulted in some wells with higher than expected skin values due to drilling fluid losses, residual frac gel, fluid loss agents, and fines mobilization within the frac packs where applied.

This paper presents how the challenges of managing impaired completions and inorganic scale forced innovation in terms of when to apply both stimulation and scale inhibitor packages to carbonate reservoirs. The combined treatment has the potential to provide cost savings with a single mobilization for the combined treatment. The paper will describe the laboratory testing that was performed to qualify the treatments for two carbonate reservoirs (black oil and HT gas/condensate). In the test program assessment was made of oil, brine and gas permeability prior to and following application of the stimulation packages. The chemical packages assessed included classic HCl formulation and chelant stimulation chemicals on their own and with inclusion of scale inhibitor chemicals to provide simultaneous stimulation/squeeze treatments. These formation damage results and chemical return profiles were then compared to coreflood test results with scale inhibitor applied as a typical squeeze treatment. Results for these studies show that under matrix flow conditions inclusion of even highly compatible scale inhibitor resulted in formation damage due to chemical/rock/brine incompatibility during the stimulation process. Details of the solution to this problem are outlined within this document.