bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effective Practices in the Abandonment of Canada's Deep Sour Gas Wells
Authors: Wilkie Arugha , Baldree Dusty , Pratt Heidi 
Published: October 2014

Abstract
To meet rising global energy demand, the oil and gas industry is growing at an unprecedented rate. As mature oil and gas fields reach end-of-life, safe and cost effective abandonment techniques are now and will continue to be a critical part of the industry. Ineffective abandonment methods are a serious economic and environmental liability to an operator, particularly one having wells with surface casing vent flows.
The operator's Foothills fields, located in central Alberta, Canada, are home to some of the harshest downhole producing environments in the country. Foothills wells are deep (&gt;3500 m true vertical depth), sour (5% to 90% H2S) and mature (1947 to present) with average well reserves of over 80 million standard cubic meters of gas. They experience sulfur, iron sulfide, calcium carbonate and sodium chloride deposition. Saline water influx causes corrosion of the production tubing strings. Most of the wells have low casing cement tops leaving multiple porous geologic formations uncemented. These factors present many challenges during well abandonment operations.
A well abandonment campaign for these fields began in 2011 and will continue for many years. To date over 40 wells have been abandoned. This paper will describe best practices learned, as well as "game changing" strategies that have led to significant cost savings and reduced operational risk. These include bullheading foamed cement to abandon the producing zone prior to moving in a service rig. This is followed by a "one-trip" abandonment utilizing through-tubing perforating and bradenhead cement squeezes with high pressure, slow-rate pumpers.
The percentage of total well abandonment cost savings will be presented for each strategy. The principles for choosing cement squeeze intervals for the isolation of porous zones, and the success rates of surface casing vent flow shutoff will be discussed. This paper will also present data from cement plug drillouts which show that cement platforms are not required beneath a balanced cement plug in near vertical wellbores. These practical applications will reduce costs, lower risk exposure and lead to improved results in downhole abandonments.
Use of the DREAM Model for Control and Prediction of Concentrations and Environmental Risks Associated with Regular Discharges to Sea: Experiences and Challenges.
Authors: Rye H. , Brönner U. , Ditlevsen M. K. , Frost T. K. , Furuholt E. , Kjeilen-Eilertsen G. , Nepstad R. , Page P. , Paulsen J. E. , Ramos R. , Rønningen P. , Sørstrøm S. E. 
Published: October 2014

Abstract
A numerical model has been developed and applied to serve the offshore industry to predict and report environmental risks associated with offshore discharges. The development has taken place over a time period of about 20 years, and is fully financed by the offshore operators. The model is fully four-dimensional (time and 3D space variations included) and covers the water column and sediment compartments.
The model was first developed and applied to produced water discharges. Later, drilling discharges and coastal discharges (terminal releases) were included. At present, the "DREAM Charter" project focuses on revisions of the risk approach according to recent literature, validation of the numerical model by comparing with laboratory and field data, and also addresses the uncertainties in the predictions. Present participants are BP, ConocoPhillips, Det Norske, ENI, Statoil and Total.
The model tool has been applied to predict and report environmental risks associated with discharges to sea (mostly produced water and drilling discharges). A parameter, EIF (Environmental Impact Factor), has been developed and used as a measure for size of potential environmental impact. This parameter has also been used as a basis for selection of chemicals used, and to give priority to the most cost efficient measures to reduce environmental impact.
The model tool makes it possible to select the best option to reduce environmental impact in a cost efficient manner, weighting reduction of the size of the EIF against costs. The introduction of new OSPAR regulations (OSPAR, 2012) allows for an alternative approach (Whole Effluent Approach) which is discussed as well.
Completion Optimization of an Unconventional Shale Play: Implementation of a Successful Completion Design Optimization Plan and the Results
Authors: Jaripatke Omkar , Samandarli Orkhan , McDonald Beth , Richmond Perry 
Published: October 2014

Abstract
Success of any unconventional shale development depends heavily on the effectiveness of the completion design. Geology, lithology, and production mechanism are the key drivers that determine how prolific a shale play can be. Identification of the geological and reservoir characteristics of the shale play needs to be performed prior to optimizing the completion design. A comprehensive completion design optimization plan is then needed to effectively harness the resource-in-place. The plan needs to account for the variations in the geology, hydrocarbon types, yield, true vertical depths, etc. within the asset. An optimum completion design will be different for rocks with various geologic and reservoir properties. It is equally important to realize that different completion parameters have varying effect on the well performance and the well economics. It is a challenge for an asset team to develop an optimized completion plan by testing different completion parameters in different geological regions within an asset. Rigorous reservoir modeling and economic analysis are needed to determine the actual effect of a completion parameter on well performance. A change of a completion parameter may result in better well performance, but the net incremental cost associated with making that change might not be the best economic decision.
This paper presents the workflow, the analysis, the results and implementation of the Eagle Ford shale completion design optimization plan. It also includes the details of the reservoir and economic analysis associated with each completion parameter test. Information presented in this paper will help completion engineers and asset teams design a workflow for selecting appropriate completion design solutions of an unconventional shale reservoir.
Closed-Loop Feedback Control of Smart Wells for Production Optimization Using Downhole Measurements of Self-Potential
Authors: Ijioma Amadi , Jackson Matthew 
Published: October 2014

Abstract
We present a new closed-loop feedback inflow control strategy, based on downhole measurements of self-potential (SP), and quantify the benefit of this approach in preventing or minimizing water production. Previous studies have demonstrated that downhole measurements of SP in production wells, using permanently installed electrodes, can be used to monitor and image encroaching waterfronts that are tens to hundreds of meters away from an instrumented well; field trials have demonstrated that SP data acquisition is technically feasible. However, no previous studies have investigated the use of SP measurements for closed-loop inflow control of smart wells. SP signals arise naturally during production to preserve electrical neutrality when charge separation occurs due to gradients in pressure, temperature and composition (salinity) of the formation or injected brine. We use numerical modelling as a cheap alternative to field experiments, to develop a closed-loop feedback control strategy triggered by downhole measurements of SP at a production well and compare the performance with feedback inflow control strategies based on downhole watercut measurements. Inflow control is facilitated by ‘variable’ ICVs. Our results show that closed-loop, feedback control using downhole SP measurements can yield gains in well NPV when compared to inflow control based on conventional in-well data in a single smart horizontal well. Moreover, SP-based feedback control can be used to improve well NPV over uncontrolled well production when the reservoir does not behave as predicted. Gains in NPV are close to optimal. These results are significant because they suggest a new reservoir technology that can provide a simple but effective approach to production optimization using smart wells.
Designing Downhole Chemical Injection Systems
Authors: Guerra L. A. , Oliveira G. H. 
Published: October 2014

Abstract
The growing demand for downhole chemical injection, in addition to deeper offshore wells, brings new challenges in controlling chemical injection flow rates. The best way of facing these challenges and avoiding the known problems that spoil the efficiency of chemical injection is a proper design of injection systems.
A good design requires the modelling of the fluids physical properties, a fair estimate of the fluid temperature profile, the assessment of equipment performance and the evaluation of transient effects. Tubing pressure oscillations (caused by well production instability or natural production fluctuations) are the cause of variability in the chemical flow rate delivered downhole. On top of that, column separation, which is liquid-vapor interface established inside the chemical injection line due to very low pressures, cannot be always avoided. This phenomenon intensifies flow rate oscillations and requires additional precautions during the design phase.
Analytical models are proposed for steady-state and for transient flow of chemicals. The first, built on top of well-established models from literature, allows for an easy assessment of the fluid physical properties and the equipment design. This model highlighted a number of important points, for example, a large dependence of the fluid physical properties on pressure and temperature, in contrast to the lack of laboratory data. It has also been found that column separation may occur in more than one point, what leads to additional risk of failure. Field data have been used to illustrate the pitfalls of the injection system design and also the model accuracy. The second model allows for estimating the effects of bottom hole pressure oscillations over the chemical injection flow rate stability. It is shown that flow rate oscillations at the delivery point, if sufficiently large, may spoil all the benefits expected from chemical injection due to the alternating under and overdose.
Experimental and Numerical Studies of Reduced Fracture Conductivity due to Proppant Embedment in Shale Reservoirs
Authors: Zhang Junjing , Ouyang Liangchen , Hill A. D. , Zhu D. 
Published: October 2014

Abstract
Artificially created fracture networks with sufficient fracture conductivities are essential for economic production from shale reservoirs. Fracture conductivity can be significantly reduced in shale formations due to severe proppant embedment. In addition, proppant embedment induces shale flakes that migrate and clog fracture networks.
A laboratory investigation was performed to understand how excessive proppant embedment caused by the shale-water interaction impairs shale fracture conductivity. The experiments were conducted using Barnett shale samples with representative rock properties. The asperities on the fracture surface were carefully preserved. The damage process was simulated in the laboratory by flowing water through the shale fracture packed with proppants. The water used in the experiments had a similar chemical composition to flowback water in the field. The laboratory results were benchmarked with the results from an experimental study conducted with Berea sandstone samples. Post experimental analysis included microscopic imaging of the fracture surfaces and measurement of the proppant embedment depth.
A computational fluid dynamics study was conducted to quantify the conductivity loss due to proppant embedment on a theoretical basis. We developed pore-scale physical models of the proppant pack and calculated the fracture conductivity loss at different proppant embedment depths. The computation was repeated for a variety of proppant layers. The worst case assumed a 40% proppant grain volume embedment.
The experimental study showed up to 88% reduction in fracture conductivity after water flow under 4,000 psi closure stress. The conductivity loss was due to severe proppant embedment as the shale fracture face was softened after its exposure to water. Direct measurement of embedment depths indicated that for fractures that were exposed to water, the average embedment depth was about 50% of the proppant median diameter, while for fractures that were only exposed to gas, the average embedment depth was just 15% of the proppant median diameter. It was also observed that pore space of the sand grains at the outlet of the fracture was clogged by shale flakes and fragments. The computational fluid dynamics study proved that even a 10% proppant grain volume embedment can cause 45%~80% conductivity loss. With the same proppant volume loss due to embedment, the conductivity reduction was less in fractures containing multiple proppant layers than the fracture containing only one layer of proppants.
Performance Testing of a Two-stage Produced Water De-oiling System for Subsea Applications
Authors: Gul Kamran , Grave Ed , van Wingaarden Hubert , Tienhaara Mika 
Published: October 2014

Abstract
ExxonMobil Upstream Research Company (EMURC) conducted a comprehensive laboratory testing program of a produced water de-oiling system primarily targeted for subsea applications. The test program included performance evaluation as well as durability testing of a two-stage mixed-flow de-oiling hydrocyclone technology. The objectives of the test program were to evaluate the separation performance of two system configurations i.e. decoupled and integrated hydrocyclones stages, to understand the overall system integration effects on the performance, and to determine system sustainability to sand loading.
Subsea produced water treatment in deeper water applications requires robust, reliable and compact separation equipment. The performance testing confirmed the feasibility of a multi-stage mixed-flow hydrocyclone system for subsea applications and demonstrated that, within a given operating envelope, the system can treat challenging produced water streams with high oil-in-water (OIW) content of up to 5%, reducing it to a few hundred ppm level. In addition, the issue of turndown can be addressed by designing the de-oiling system with multiple parallel banks of liners.
The de-oiling system testing was conducted with light and heavy crude oils, of gravities of 36 °API and 19 °API respectively, to map performance characteristics of a two-stage system with the first hydrocyclone stage of bulk oil removal and the second stage of water polishing. Variations in test conditions such as the flow rate, temperature, inlet oil concentration and the reject ratios were introduced to establish optimal operating ranges for each stage as well as for the system. The performance of the decoupled and the integrated system was evaluated by determining separation efficiency break-points at different operating conditions. Accelerated sand erosion tests were performed on a dedicated sand erosion test loop to evaluate different erosion resistant coatings for hydrocyclone liners. The erosion tests helped identify a promising coating solution that can withstand continuous sand loads for long-term operations. The test program demonstrated that a two-stage mixed-flow hydrocyclone de-oiling system can meet challenging subsea produced water treatment and reinjection requirements over a wide range of operating conditions. The paper presents the key results of the overall performance tests as well as the results of sand erosion testing of the hydrocylone liners with different coatings.
Novel Processing of Electromagnetic Logging Measurements Through Metallic Casing
Authors: Gao Guozhong 
Published: October 2014

Abstract
This paper presents a novel method to remove the casing effects from electromagnetic (EM) logging measurements through metallic casing. After the removal of the casing effects, the measurements are exactly the same as those measured in the borehole without the casing. As a result, the data can be processed (or inverted) in the same manner as openhole EM logging data, such as the array induction and tri-axial induction measurements. The method converts data with casing effects to casing-free data via simple but efficient correction algorithms based on the measurements of the impedance of the transmitters and receivers, from which the casing effects around the transmitters and receivers can be determined. In addition, the method can be used to determine the magnetic and electric properties of the casing. In addition to single well logging, the method could be particular useful for crosswell EM survey between two cased holes which the industry has not been able to solve. One such benefit is that it could make it possible to see resistivity differences due to ongoing processes (i.e. water flooding) in a producing field. The algorithms and the physics underlying them are discussed in details. Both non-magnetic casing and magnetic casing are considered in the paper.
High-Resolution Mapping of the Distribution and Connectivity of Organic Matter in Shales
Authors: Curtis Mark E. , Goergen Eric. T. , Jernigen Jeremy D. , Sondergeld Carl H. , Rai Chandra S. 
Published: October 2014

Abstract
Organic matter is an important component of shale oil and gas resource plays and can have a profound effect on the properties of shale. Porosity in the organic matter provides potential storage for hydrocarbons, and depending on the connectivity of the organic matter, possible connected pathways for hydrocarbon flow. In addition, from a completions and seismic mapping perspective, the distribution of organic matter will affect the elastic properties of shale as well as the elastic anisotropy. Because of the heterogeneity of shales and micron to sub- micron size of the organic matter, mapping changes in organic distribution with sufficient resolution to capture a statistically meaningful sample of the organic matter has proven difficult. Previous work has used a combination of scanning electron microscopy (SEM) with scanning acoustic microscopy (SAM), x-ray computed tomography (XCT), or optical thin sections to map the distribution of organic matter. All these techniques have limitations in the sense that they either provide large area mapping at low resolution or small area mapping at high resolution but not large areas with high resolution. With the advent of large area ion beam milling and automated high-resolution SEM imaging and stitching, a seven order of magnitude size range can now be spanned allowing the distribution of organic matter over centimeter square areas to be mapped with nanometer resolution. Utilizing this technique, the distribution and connectivity of organic matter over extended contiguous sections of core from the Barnett and Wolfcamp Shales were mapped at one inch intervals. Variations in total organic content between cores and within the same core were measured in the lab, and these variations are compared to the SEM results. In addition, the shape and orientation of the organic matter was analyzed. These measurements aid in placing limits on the scale of variation in organic matter distribution in shale and represent the first crucial step in attempting to upscale SEM data to core petrophysical measurements and potentially to log-scale measurements.
The Use of a "Type Well" Concept Approach for Design, Feasibility, and Creation of a Technology Plan for Well Construction in a New Gulf of Mexico Deepwater Development
Authors: Grant Lisa , Japar Nor Janiah , Van Den Haak Arno 
Published: October 2014

Abstract
The deepwater Mars/Deimos field is located in the central region of the Gulf of Mexico (GoM) at ~3000′ water depth. Mars was discovered in 1989 and production began in 1996 from Mars A, a 24 slot tension leg platform (TLP). The deeper Deimos, with significant hydrocarbon volumes, was later discovered below the original Mars production intervals. After years of development, the shallow target horizons have been severely depleted, whereas new discovery is still at significantly higher virgin pressures.
Mars B Olympus DVA, a new 24 slot TLP, was justified following a holistic evaluation of the deeper discovery. This TLP represents the first brownfield development of a deepwater field in the GoM. The field life is ~50 years, with a development plan requiring +/- 80 independent completions across ~60 hydrocarbon horizons, extending from 10,500′ to 23,000′ true vertical depth (TVD). Due to the limited number of slots and required number of completions, each of the boreholes has to consider future utility (i.e., slot recoveries, slim-hole sidetracks, big-hole sidetracks and up-hole recompletions) as a fundamental design requirement.
The detailed well development concept design was kicked off in 2011, considering extreme design load scenarios due to more stringent regulatory and internal design mandates put in place. Previously used concept design was neither robust nor satisfy long term life requirements.
A representative "Type Well" design concept approach was developed to holistically evaluate existing technologies and equipment feasibility against the new design mandates and to identify gaps. The type wells were analyzed in extreme detail to ensure there were no design oversights and so design limit envelopes could be established. Subsequently, ~20 new technology developments ranging from a high-pressure NACE tieback system to a reverse cementing tool were identified as critical to project delivery, and a multitude of unintended consequences resulting from the new extreme well design were also identified in the process.
The following paper describes the methodology used to create these type wells and examples of technology gaps identified. It also describes the key technologies developed and the domino effect as a result of their implementation.