bluuebunny/crossref_metadata_2025_split huggingface dataset:
Near Wellbore and Reservoir Effects in In-Situ Combustion
Authors: Chavez Mario-Luis Rodriguez , Glatz Guenther , Clemens Torsten , Kovscek Anthony 
Published: May 2015

Abstract
In addition to the physical processes relevant in conventional oil production, additional physical-chemical processes have to be considered for in-situ combustion. These processes include heat conduction, steam drive and the kinetics and thermodynamics of combustion.
To determine the kinetic and thermodynamic parameters, kinetic cell and combustion tube experiments were performed.
In this study, oil from a commercially producing in-situ combustion field was sampled. A newly developed kinetic cell was used which enabled performing experiments at various heating rates. The large range of heating rates is used for describing the reactions in the combustion tube and near-wellbore as well as for the conditions at the front in a larger distance from the wells.
The near-wellbore during in-situ combustion is characterized by fast movement of the combustion front, large heating rates at a given location and spatial separation of low-and high temperature combustion reactions.
Once the front propagates further away from the wells, the speed of the front reduces to less than 0.05 m/d. At this speed of the front, heat conduction ahead of the front warms the reservoir up without oxygen being present. Oxygen arriving at the front results in Low and High Temperature Oxidation occurring almost simultaneously.
The far-field conditions were mimicked by pre-heating a kinetic cell prior to exposing it to air. These experiments showed that for these conditions, the high and low temperature oxidation reactions cannot be distinguished and could be approximated by a single reaction.
This study shows that a simplified reaction scheme might be used to simulate the reservoir effects of combustion whereas for simulating the early phase of an in-situ combustion project, a more exhaustive set of chemical reactions might be required.
The results of the study can be used to investigate the start-up phase of an in-situ combustion project (near-wellbore effect focus) and the effects during advancement of the combustion front in the reservoir.
Using the example of a Central European field operated using in-situ combustion in a line-drive configuration, the near-wellbore and far field operational aspects are shown.
Application of Multiple Well Deconvolution Method in a North Sea Field
Authors: Thornton Emma J. , Mazloom Jalal , CNOOC Nexen , Gringarten Alain C. , Cumming Jonathan A. 
Published: May 2015

Abstract
Single-well deconvolution is now commonly used in well test analysis. Within a reservoir, the pressure drop as a function of time is equal to the convoluted product of the rate and the reservoir response at that time. To obtain the reservoir response, inverse convolution – or deconvolution - must take place. This technique, until recently, could only be applied to single-well reservoirs since the deconvolution algorithms assumed zero interference from surrounding wells.
A multi-well deconvolution algorithm was recently presented by Cumming et al, (2013), in which a single-well deconvolution algorithm was adapted to account for interference whilst deconvolving a group of communicating wells. This paper provides further evaluation of the algorithm by applying it to two regions of a North Sea oilfield – the first area including three interfering wells, and the second area including eight interfering wells.
The deconvolved derivatives for four individual wells were analysed for permeability and boundary effects, and the results were in agreement with pre-existing seismic interpretation and geological knowledge of the area. The reliability of the deconvolved derivatives produced by the multiwell algorithm was confirmed by using the algorithm to perform single-well deconvolution and then comparing the results to the outputs from a well-trusted single-well deconvolution tool.
The algorithm also outputs an interference response for each pair of deconvolved wells. Interpreting the interference responses allows to identify relative strengths of communication between wells and to obtain storativity and permeability-thickness of the reservoir between a pair of wells.
It was determined that the run-times of the algorithm were reasonable, and a study of computer run-times is found at the end of this paper whereby some typical multiwell deconvolutions have been run on two different specifications of computer.
Comparative Performance of History Matching Algorithms Using Diverse Parameterization Methods: Application to a Synthetic and North Sea Cases
Authors: Al-Shamma Basil R. , Gosselin Olivier , King Peter , Christie Mike , Mendez Maria 
Published: May 2015

Abstract
Extending the life of the Johnston field requires an ability to produce reliable forecasts of the effects of reservoir interventions. Reliable forecasts need an effective, robust and accurate history match. The goal of this paper is to evaluate the relative performance of three different global assisted history-matching algorithms. We describe the implementation of an integrated parameterization and optimization method, which was tested on the Brugge synthetic model (SPE benchmark case study), and the results based on the best selected method are applied to the Johnston gas field in the Southern North Sea.
There are two key components to assisted history matching: (i) choice of the parameterization, and (ii) selection and performance of the optimization algorithm. In this paper, three parameterization methods are tested (including use of gradients) on three global history-matching algorithms: Particle Swarm Optimization (PSO), Evolutionary Algorithm (EA) and Differential Evolution (DE). A combination of two different algorithms was also examined.
We assessed the algorithm efficiency based on the lowest achieved objective function and the time taken to converge to the lowest value; the quality of the parameterization was examined based on the lowest objective value, the best history match (the most geologically consistent models amongst the lowest objective function models) and the consistency of geological parameters used for the history match.
The results show that the effectiveness of each optimization algorithm is dependent on the parameterization method. When comparing parameterization methods, the Around the Median method seems to give the best results in terms of lowest misfit, and best history match when using the same history matching algorithm for the Brugge model example. When comparing across algorithms the DE method performs better than the rest. An iterative combination of algorithms is seen to be the best option and assists in a further minimization of the objective function. The effect of parameterization on match quality is also proved to be important. In some cases, an iterative process can be effective, where the history match is further improved by adding additional parameters or zoning existing parameters.
This paper stresses and illustrates the importance of the choice of parameterization methods, while many papers focus only on the performances of the minimization algorithm. It also combines gradient-based parameterization method with global optimization method.
Addressing Operator Concerns: Will Surfactant's Performance be Compromised Under Harsh Conditions?
Authors: He Kai , Xu Liang 
Published: May 2015

Abstract
Surfactant is typically pumped during hydraulic fracturing to enhance production from unconventional reservoirs. The primary function of surfactant is believed to generate a short-lived oil-in-water (OIW) emulsion, thereby aiding oil solubilization and mobilization. Ideally, the OIW emulsion should be maintained throughout the entire liquid flow path. However, a temperature gradient typically exists from topside to the interior of the matrix, and the matrix temperature can be high. This temperature gradient is compounded by the fact that, upon dilution by the reservoir connate water, anionic surfactants typically used during fracturing, become more lipophilic at the oil-water interface because of its selective partitioning into the aqueous phase upon dilution or at high reservoir temperature. Therefore, the optimum surfactant formulation cannot be well maintained when the fracturing fluids invade the matrix and reservoir fluids begin to produce. Some nonionic surfactants, on the other hand, typically partition into the oil phase at high temperature or upon dilution. By taking those phenomena into account, an optimum surfactant-oil-water system was created by mixing both anionic and nonionic surfactants to help eliminate the effect of dilution and high reservoir temperature. The new system has been widely used in hundreds of wells in the Eagle Ford (EF) and Mississippi Lime (ML) shale, with favorable production results.
Insights into Whether Low Salinity Brine Enhances Oil Production in Liquids-rich Shale Formations
Authors: He Kai , Nguyen Christina , Kothamasu Ramya , Xu Liang 
Published: May 2015

Abstract
Low salinity water (LSW) flooding has been an attractive technique for enhancing oil recovery. Several LSW mechanisms have been proposed to account for the additional oil recovery, such as interfacial tension (IFT) reduction, wettability alteration, clay migration and microdispersion. However, none of the adequate mechanisms can consistently explain different cases because of the nature of heterogeneity in crude oil and formation rock. Because of a gradual shift from using fresh water to produced water, there is a need to investigate the effects of low salinity on oil recovery from shales to understand potential implications of this shift. Additionally, few studies have been documented on low salinity brines (LSBs) as the fracturing fluids for stimulation applications in liquids-rich shale plays with or without surfactant.
This paper discusses a study in which low salinity surfactant solutions were injected into the Muskwa shale rock from Canada. Laboratory results suggest that LSBs ([LSBs], ≤4% KCl) extract more hydrocarbon than high salinity brines ([HSBs], ≥8% KCl). Notably, additional oil recovery was observed when surfactant is used in LSB. To explore the mechanisms, interfacial tension, emulsion tendency, and reservoir on a chip (ROC) were performed. Interfacial tension reduction was not observed for LSB with surfactants. However, short-lived emulsions were observed in LSB in the presence of a surfactant. Additionally, LSB with surfactant were injected into a microfluidic based ROC device, where the pore size was comparable to that of shale rocks, and the oil recovery that was visualized on ROC was consistent with that found in core flooding tests, and shows the benefit of injection of low salinity surfactant solutions. Based on such observations, two-step mechanisms are proposed for improved oil recovery (IOR) for low salinity surfactant injection: (1) destabilized oil layers (oil/rock) and enhanced pair interaction (surfactant/oil) extract more oil globules and (2) a short-lived emulsion formed by surfactants enables a higher tendency to mobilize the oil globules.
The results suggest a potential methodology for optimizing source water prior to fracturing operations. This study strongly suggests that low salinity and surfactant additives optimization are imperative to enhanced well productivity from liquids-rich shale plays.
New Al-based and Dual Cross-linkers to Form a Strong Gel for Hydraulic Fracturing Treatments
Authors: Sokhanvarian Khatere , Nasr-El-Din Hisham A. , Harper Thomas L. 
Published: May 2015

Abstract
Hydraulic fracturing has been a common practice in US. The chemistry of hydraulic fracturing fluids is very complicated, which makes the optimization process challenging. In designing fracturing fluids, one of the major unknowns is the fluid chemistry. Therefore, understanding the chemistry and interactions between chemicals to form a strong gel is a must. A strong gel is a factor of different parameters such as polymer loadings, crosslinker concentrations, buffer systems, and temperatures.
Different crosslinkers such as boron and several metals including titanium, zirconium, and aluminum have been used in the oil and gas industry. Aluminum and boron reside in the same group on the periodic table. The latter means that there are some similarities in their chemistry. Aluminum chemistry is critical in the preparation of highly effective aluminum-based crosslinkers. Therefore, the objective is to 1) investigate the performance of two new Al-based and Al-Zr-based crosslinkers to form a stable gel with Carboxymethyl hydroxypropyl guar (CMHPG) at high temperatures and shear rates, and 2) determine the leakoff rates of the cross-linked gels with the optimized formulations.
New aluminum-based and aluminum-zirconium crosslinkers to form a stable gel with guar derivatives are studied. This study investigates various parameters including polymer loading, crosslinker concentrations, pH, and temperatures to form a high quality gel. High viscosity gels increases fracture width, and also can carry higher concentrations of proppant that leads to fluid loss decrease and enhances the propant transport.
The results of this study indicate that Al-based crosslinkers at pH 10.8 and 3.8 are very effective in forming high quality gels that are stable at temperatures up to 250°F after 140 minutes. Varying shear rate is studied and the results showed that the Al-based crosslinkers in this study are stable at shear rate of 170 s−1 if an optimized formulations is chosen. It is found that forming a stable gel is strongly a function of concentrations of Al crosslinkers as shear rate increases. Time and temperatures delay in forming gels can be achieved through the optimization of pH, crosslinker concentrations, and polymer loadings.
Extensive lab research and understanding the chemistry of crosslinkers help to design a successful field treatment.
Maintaining Well Productivity Through Controlling Fines Migration and Scale Formation
Authors: Stanciu C. , Vo L.K. , Nguyen P.D. , Weaver J.D. 
Published: May 2015

Abstract
The intrusion of formation fines and formation sand grains into the proppant pack drastically reduces the conductivity of propped fractures, which can negatively impact well production. This paper describes the development and field treatments using a new form of surface modification agent (SMA) that is a low-tackiness surface modification agent (LTSMA) that can be applied during primary hydraulic fracturing or remedial treatments of propped fractures. Studies were conducted to demonstrate the mechanisms by which this LTSMA controls migration and intrusion of formation sand and fines into the proppant pack, while inhibiting scale formation in the treated pack.
Molecular modeling data on the LTSMA suggests that both the polymer backbones and the hydrophobic chains on the polymers are responsible for its reduced tackiness to the treatment equipment and significant scale inhibition ability. Once coated on the proppant as part of hydraulic fracturing treatment, or injected into the proppant pack and formation matrix surrounding the fractures, this LTSMA forms a thin film on the particulates, covering and anchoring the particulates in place. This LTSMA coating also forms a hydrophobic film on the particulate surfaces, inhibiting chemical reactions that lead to scale formation in the pack matrix and subsequent productivity losses.
Laboratory experiments using packed beds of proppant, formation sand grains, and various fines were performed to simulate proppant pack conditions and formation fines before and after remedial treatments. Experimental results indicate that treatments with this particular LTSMA effectively control the migration of formation fines into proppant packs and successfully prevent the buildup of scale in various sand packs to maintain the fluid flow paths. No pressure buildup was noticed, opposed to the proppant that was not treated with the LTSMA, for which severe scaling had occurred by 24 hours, leading to an exponential increase in pressure drop across the proppant pack. Examination with scanning electron microscopy analysis clearly demonstrated that no scale was formed in the pore spaces between the treated proppant grains compared to a massive buildup of scale on the proppant particles and in their pore spaces when not coated with the LTSMA.
In addition to remedial treatments, LTSMA treatment fluid can be applied while treating formations following an acidizing treatment, during treatment of formations before a high-rate water pack or frac-pack treatment, or as part of a pad fluid to treat the fracture faces before placement of proppant into a fracture and/or a screen annulus.
The Value of Inter-well and Single Well Tracer Technology for De-Risking and Optimizing a CEOR Process - Caracara Field Case
Authors: Cubillos H. , Yuste E. , Bozorgzadeh M. , Montes J. , Mayorga H. , Bonilla S. , Quintanilla G. , Lezana P. , Panadero A. , Romero P. 
Published: May 2015

Abstract
Recent advances in tracer technology deliver accurate data in a cost-efficient manner. Tracer applications typically aim to improve reservoir description by solving connectivity questions, to evaluate and derisk the potential for secondary and tertiary recovery processes, along with inflow profiling and allocation of injected water or gas.
A previous paper (SPE-164930) presented the strategy and planning of a chemical EOR (CEOR) process for sandstone reservoirs of the Caracara Sur Field, Colombia. The project is moving forward and laboratory studies have been successfully completed to define an optimum alkaline surfactant polymer (ASP) formulation. Along with simulation studies, comprehensive inter-well (IWTT) and single well tracer tests (SWTT) have been carried out to provide valuable input to understand aquifer drift, the reservoir flooding process and to analyse residual oil saturations to waterflood (Sorw). This paper presents these two tracer applications: IWTTs were performed in Caracara Sur sandstone reservoir zones to characterize aquifer drift. Tracer response was used as input for analysing the implications of chemical dilution by the aquifer and also as an input for history matching, resulting in a more reliable reservoir model.The results of the first SWTT in Caracara Sur Field (and - to our knowledge - in Colombia), are presented. By measuring Sorw, the potential for CEOR application has been confirmed.
An ASP one-spot test has subsequently been completed and followed-up by a second SWTT to evaluate the efficiency of the chemical formulation. Results are currently under evaluation but appear favourable. Planning for expanded use of CEOR in Caracara Sur continues. Lessons learnt and best practices for implementing tracer technology in similar fields include: Use of tracer backflow tests (TBFT) to derisk SWTTs; also the use of FBA passive tracers.Planning, operating and analysing the results of tracer-tests in-house rather than sub-contracting to third parties increases flexibility, increases internal knowledge and is cost-effective.
Prediction of the Minimum Onset Time for Convection in a Gravitationally Unstable Diffusive Boundary Layer Using a Finite Difference Pressure Solver
Authors: Taheri Amir , Wessel-Berg Dag , Torsæter Ole 
Published: May 2015

Abstract
CO2 dissolution as one of the most promising mechanisms for trapping of CO2 free phase into brine causes increased density of the brine and initiation of gravitational instability that eventually leads to density-driven natural convection in brine aquifers. The gravitational instability of a diffusive boundary layer in porous media has been studied in several papers in recent years and there are several methods in the literature for prediction of the onset time for convection and the related unstable wavelength.
In this study we present a numerical solution for prediction of the critical time for the onset of convection and the critical unstable wavelength in semi-infinite anisotropic homogeneous brine aquifer models. A finite difference pressure solver is used for solving this numerical problem. The numerical model is initialized by the recent developed approach and the gravitational instability is triggered by a weak wavy perturbation with dimensionless wavenumber of K. The minimum of the calculated time for onset of instability as a function of wavenumber is called the critical time and the associated wavenumber to this critical time is the critical unstable wavenumber. The results of this analysis shows acceptable agreement with previously published ones derived from other methods. By applying this prediction approach in more complex numerical models, their related critical time for the onset of convection and the critical unstable wavelength can be calculated.
Book-Tax Differences and Future Earnings Changes
Authors: Jackson Mark 
Published: May 2015

ABSTRACT
Prior studies suggest that large book-tax differences (BTDs) are associated with future earnings changes or earnings persistence. The literature has explored a number of potential explanations for this relation, without a clear answer emerging. To integrate the various assertions I divide total BTDs into temporary and permanent categories and hypothesize that temporary BTDs (reflected in deferred taxes) predict future changes in pretax earnings, whereas permanent BTDs predict future changes in tax expense. The results are consistent with these hypotheses. Prior studies also suggest that both types of BTDs are associated with earnings management and tax avoidance. I find evidence that tax avoidance firms have a more positive association between their BTDs and both pretax earnings changes and tax expense changes. However, I find only inconsistent evidence on the influence of earnings management on the association of the components of BTDs and future earnings changes, with results dependent on the research design. Overall, the evidence suggests that while tax avoidance and earnings management may contribute to the association between BTDs and future earnings changes, there are also more fundamental drivers of this association.
The Nature and Meaning of Insulin Pump Use in Emerging Adults With Type 1 Diabetes
Authors: Hood Donna G. , Duke Gloria 
Published: May 2015

Objective. The purpose of this study is to investigate the meaning of living with an insulin pump for the management of type 1 diabetes during the period of emerging adulthood. Through a phenomenological narrative, this study contributes to the reflective understanding of the everyday life experiences of this population.
Methods. A hermeneutic phenomenological design was used for this study of nine emerging adults (aged 19–24 years). Data were generated through face-to-face interviews and analyzed using the phenomenological approach of Max van Manen.
Results. Four themes represent the essence of the day-to-day experiences of these emerging adults: seeking control, becoming responsible, staying connected, and accepting me.
Conclusions. An in-depth understanding of the meaning of daily experiences with insulin pump technology has the potential to promote a developmentally appropriate approach to this age-group. The human understanding gained through this study is essential to the development of evidence-based practice guidelines and resources for this vulnerable population.