bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Higher-Resolution Flow-Oriented Scheme With an Adaptive Correction Strategy for Distorted Meshes Coupled With a Robust MPFA-D Method for the Numerical Simulation of Two-Phase Flow in Heterogeneous and Anisotropic Petroleum Reservoirs
Authors: Souza M. R. , Contreras F. R. , Lyra P. R. , Carvalho D. K. 
Published: October 2018

Summary
In this paper, we propose a full-cell-centered finite-volume approach to simulate two-phase flow in heterogeneous and anisotropic petroleum reservoirs. We adopt a segregated formulation where the pressure equation is discretized by a multipoint flux approximation with a diamond-type support (MPFA-D). To solve the saturation equation, we propose a higher-order modified flow-oriented scheme (M-FOS). In this scheme, adaptive weights tune the formulation multidimensionality according to the grid distortion. Also, we adopt a multidimensional limiting process (MLP) and an efficient entropy fix to produce convergent solutions. We evaluate the performance of our numerical schemes by solving some relevant benchmark problems.
Analysis of Well-Completion Performance and Production Optimization of a Gas Well Using Computational Fluid Dynamics
Authors: Molina Oscar M. , Tyagi Mayank 
Published: October 2018

SummaryThis paper investigates the effects of high production rates on well performance for a casedhole gas well using two types of completion schemes: frac pack and gravel pack. We model fluid dynamics in the near-wellbore region, where the most dramatic changes in pressure and velocity are expected to occur, using computational fluid dynamics (CFD). The fluid-flow model is dependent on the Navier-Stokes equations augmented with the Forchheimer equation to study inertial and turbulence effects in regions where the velocity increases and decreases sharply over a relatively small length scale. Real-gas properties are incorporated into the momentum-balance equation using the Soave-Redlich-Kwong (SRK) equation of state (EOS) (SRK-EOS). The near-wellbore model is pressure-driven under steady-state and isothermal conditions. Well-performance curves are generated depending on simulation results for both completion schemes. Furthermore, we introduce the concept of rate-dependent pseudoskin factor to assess inertial and turbulence kinetic energy (TKE) losses under various pressure differential. Analysis of the simulation results suggests that the rate-dependent pseudoskin changes from negative at low gas-production rates to positive at medium-to-high gas-production rates. This is primarily because of the inertial and turbulence effects being triggered at a certain flow rate, which we define as the optimal operating point. We demonstrate that the gas-deliverability curve plotted along with the pseudoskin-factor curve allows us to estimate the optimal operating condition as the point where the rate-dependent pseudoskin is zero. An analytical model to estimate the optimal production rate is proposed as an extension to typical multirate tests.
Low-IFT Foaming System for Enhanced Oil Recovery in Highly Heterogeneous/Fractured Oil-Wet Carbonate Reservoirs
Authors: Dong Pengfei , Puerto Maura , Jian Guoqing , Ma Kun , Mateen Khalid , Ren Guangwei , Bourdarot Gilles , Morel Danielle , Bourrel Maurice , Biswal Sibani Lisa , Hirasaki George 
Published: October 2018

Summary
Oil recovery in heterogeneous carbonate reservoirs is typically inefficient because of the presence of high-permeability fracture networks and unfavorable capillary forces within the oil-wet matrix. Foam, as a mobility-control agent, has been proposed to mitigate the effect of reservoir heterogeneity by diverting injected fluids from the high-permeability fractured zones into the low-permeability unswept rock matrix, hence improving the sweep efficiency. This paper describes the use of a low-interfacial-tension (low-IFT) foaming formulation to improve oil recovery in highly heterogeneous/fractured oil-wet carbonate reservoirs. This formulation provides both mobility control and oil/water IFT reduction to overcome the unfavorable capillary forces preventing invading fluids from entering an oil-filled matrix. Thus, as expected, the combination of mobility control and low-IFT significantly improves oil recovery compared with either foam or surfactant flooding.
A three-component surfactant formulation was tailored using phase-behavior tests with seawater and crude oil from a targeted reservoir. The optimized formulation simultaneously can generate IFT of 10−2 mN/m and strong foam in porous media when oil is present. Foam flooding was investigated in a representative fractured core system, in which a well-defined fracture was created by splitting the core lengthwise and precisely controlling the fracture aperture by applying a specific confining pressure. The foam-flooding experiments reveal that, in an oil-wet fractured Edward Brown dolomite, our low-IFT foaming formulation recovers approximately 72% original oil in place (OOIP), whereas waterflooding recovers only less than 2% OOIP; moreover, the residual oil saturation in the matrix was lowered by more than 20% compared with a foaming formulation lacking a low-IFT property. Coreflood results also indicate that the low-IFT foam diverts primarily the aqueous surfactant solution into the matrix because of (1) mobility reduction caused by foam in the fracture, (2) significantly lower capillary entry pressure for surfactant solution compared with gas, and (3) increasing the water relative permeability in the matrix by decreasing the residual oil. The selective diversion effect of this low-IFT foaming system effectively recovers the trapped oil, which cannot be recovered with single surfactant or high-IFT foaming formulations applied to highly heterogeneous or fractured reservoirs.
Evaluation of Software-Based Early Leak-Warning System in Gulf of Mexico Subsea Flowlines
Authors: Thiberville C. J. , Wang Y.. , Waltrich P.. , Williams W. C. , Kam S. I. 
Published: October 2018

SummaryEarly detection of subsea pipeline leaks is a very serious and ongoing issue for the oil and gas industry with limited successful cases reported. For example, aerial surveillance of pipelines can be applied only for relatively shallow and concentrated areas, and an advanced technology such as fiber-optic cable can be considered at the significant expense of time and cost for installation and equipment. The objective of this study is to evaluate a software-based leak-detection technique through complex multiphase flow mechanics. More specifically, this study investigates (i) how leak-detection problems can be formulated from a fluid-mechanics viewpoint and (ii) how reliable such a technique can be under conditions resembling the deepwater Gulf of Mexico (GOM). In examining a wide range of scenarios, this study proves that software-based techniques have a potential for playing a key role in the future.First, this study defines a base case selected from the literature review of deepwater GOM flowlines in terms of pressure and temperature conditions, fluid properties, reservoir properties, and flowline characteristics that allows a steady-state flow in pipeline to be determined with no leak present. Next, leaks with certain opening sizes (dleak) at different longitudinal locations (xD = x/L) are positioned, and new steady states in the presence of leaks are calculated. By comparing the two steady-state responses (with and without leak), finally, the changes in two leak-detection indicators [i.e., change in upstream pressure (ΔPin) and change in downstream total flow rate (Δqt out)] can be calculated in a wide range of input parameters. This study presents the results in the form of contour plots for pressure and flow responses.The major finding of this study is that, theoretically, it is possible to estimate both size and longitudinal location of the leak with the two leak-detection indicators in the software-based leak-detection method. The results from various subsea flowline conditions [such as different gas/oil ratios (GORs) and fluid types, water depths, pressures at the receiving facilities, inclination angles, pipe diameters, water cuts, and so on] show that the reliability of this technique is improved when the sink term (i.e., amount of leaking fluid) is more dominant, which, in turn, means that leaks positioned farther upstream, with larger opening size, and occurring at higher pressure inside pipe are relatively easier to detect. In many of the scenarios considered, Δqt out as a leak-detection indicator shows more than a 10% change in the presence of a leak with dleak&gt;1 in., allowing relatively easier activation of a leak-warning system, which demonstrates the robustness of this technique. Other scenarios in which the indicators are less than a few percent changes, however, may be challenging—in those cases, additional responses from other methods (hardware-based or transient simulation) will be helpful.
Improved Method of Moment To Determine Mobile-Phase Saturations Using a Single-Well Chemical-Tracer Test
Authors: Tian Wei , Wu Xingru , Shen Tong 
Published: October 2018

Summary
The single-well chemical-tracer test (SWCTT) has been applied for decades with much success in estimating residual oil saturation in near-wellbore locations. The information obtained from an SWCTT is critical for designing a method for enhanced oil recovery (EOR). However, a key assumption in the conventional SWCTT is that only single-phase (water) is mobile. In reality, this is often not the case, and significant error can occur if the conventional SWCTT analysis method is used when multiple phases flow at the same time. The objective of this study is to improve the accuracy and precision of SWCTT interpretation in a multiphase-flow condition.
In this paper, we propose an innovative procedure of SWCTT and modify the method of moment (MOM), aiming at the two-mobile-phase condition. In the development of the algorithm, a ratio parameter is introduced to adjust the calculated swept-volume difference between the conservative tracer and the partitioning tracer. In addition, a mixture injection of oil and water is required, instead of the pure-water injection in an SWCTT.
The proposed approach is verified through numerical simulation on synthetic cases with known input parameters. The model being simulated consists of a radial-flow regime with a single vertical well in the center. The input oil saturation varies from 0.1 (immobile oil saturation) to 0.9. Our results show that the saturation estimated from the modified MOM matched the simulation input data, indicating that our approach is able to capture the saturations under two-mobile-phase condition. Moreover, the modified MOM can also be applied in single-mobile-phase condition and can improve the accuracy of conventional MOM.
Downhole-Gauge-Data Analysis of Openhole Gravel-Packing Treatments: Method and Examples
Authors: Kumar A.. , Beldongar M.. , Agee D.. , Gadiyar B. R. , Parlar M.. 
Published: October 2018

Summary
Two key benefits of downhole-gauge (DHG)-data analysis are identifying and minimizing the root causes of any failures that might occur during gravel packing and calibrating or verifying friction-pressure data for gravel-placement simulations. Although downhole pressure and temperature gauges are used often in openhole gravel packing, and expertise in analyzing the data certainly exists in companies that routinely use DHGs, to our knowledge, there is no publication that comprehensively discusses the method of analysis. DHG-data analysis, in general, requires more information than the gauge data themselves. This includes logs, wellbore schematic, pumping schedule, fluid properties, return-flow measurements, daily rig reports, and data relevant to displacements.
The objective of this paper is to provide guidelines for DHG-data analysis to completion engineers, who are not routinely involved and thus are not experts in such analysis, by detailing the factors that must be kept in mind, offering a method, and demonstrating this method with several examples.
Estimating Unpropped-Fracture Conductivity and Fracture Compliance From Diagnostic Fracture-Injection Tests
Authors: Wang HanYi , Sharma Mukul M. 
Published: October 2018

Summary
A new method is proposed to estimate the compliance and conductivity of induced unpropped fractures as a function of the effective stress acting on the fracture from diagnostic-fracture-injection-test (DFIT) data. A hydraulic-fracture resistance to displacement and closure is described by its compliance (or stiffness). Fracture compliance is closely related to the elastic, failure, and hydraulic properties of the rock. Quantifying fracture compliance and fracture conductivity under in-situ conditions is crucial in many Earth-science and engineering applications but is very difficult to achieve. Even though laboratory experiments are used often to measure fracture compliance and conductivity, the measurement results are influenced strongly by how the fracture is created, the specific rock sample obtained, and the degree to which it is preserved. As such, the results may not be representative of field-scale fractures.
During the past 2 decades, the DFIT has evolved into a commonly used and reliable technique to obtain in-situ stresses, fluid-leakoff parameters, and formation permeability. The pressure-decline response across the entire duration of a DFIT reflects the process of fracture closure and reservoir-flow capacity. As such, it is possible to use these data to quantify changes in fracture conductivity as a function of stress. In this paper, we present a single, coherent mathematical framework to accomplish this. We show how each factor affects the pressure-decline response, and the effects of previously overlooked coupled mechanisms are examined and discussed. Synthetic and field-case studies are presented to illustrate the method. Most importantly, a new specialized plot (normalized system-stiffness plot) is proposed, which not only provides clear evidence of the existence of a residual fracture width as a fracture is closing during a DFIT, but also allows us to estimate fracture-compliance (or stiffness) evolution, and infer unpropped fracture conductivity using only DFIT pressure and time data alone. It is recommended that the normalized system-stiffness plot (NS plot) be used as a standard practice to complement the G-function or square-root-of-time plot and log-log plot because it provides very valuable information on fracture-closure behavior and the properties of fracture-surface roughness at a field-scale, information that cannot be obtained by any other means.
Modeling of Low-Frequency Downhole Electrical Measurements for Mapping Proppant Distribution in Hydraulic Fractures in Casedhole Wells
Authors: Zhang Peng , Sen Mrinal K. , Sharma Mukul M. , Gabelmann Jeff , Glowka David 
Published: October 2018

Summary
A tool concept using downhole electrical measurements for mapping electrically conductive proppant in hydraulic fractures is presented in this paper. The method relies on direct excitation of the casing, which is expected to overcome the severe limitations of induction tools in casedhole wells. An array of insulating gaps is installed and cemented in place as a permanent part of the casing string. The envisioned electrical measurements are performed by imposing a voltage across each insulating gap, one at a time, before and after hydraulic-fracture operations. The voltages across other insulating gaps near the transmitter gap are recorded.
The proposed tool's response to the geometry of a single fracture was modeled by solving for the electrical potential with a finite-volume method. Previous simulation results have shown that the electrically conductive proppant alters the path of the electrical current in the formation, and this is recorded as differential signals by the string of insulating gaps surrounding the source gap. The simulated differential signals are highly sensitive to a fracture's location, length, and orientation, and less sensitive to the fracture's aspect ratio. However, to enable the implementation of such a practical system, various aspects of the tool concept must be investigated further through simulations. Following our previous work, this paper focuses on the forward modeling of the tool's response to multiple fractures, which demonstrates the influence of these fractures on the signals, and provides important guidance for inverse modeling. Parametric inversion of fractures from synthetic data, generated by exciting various insulating gaps, is solved with very fast simulated annealing (VFSA).
Simulation results show that, when multiple hydraulic fractures are present, the voltages measured at the receiver gaps are determined primarily by the fracture that is in direct contact with the excited section of casing. When two fractures touch the same casing section, they induce voltages very similar to those from a single fracture with the same conductivity and volume. Preliminary inversion results that use synthetic data computed from circular fractures indicate that the proposed VFSA can solve for the multiple fractures’ widths and radii at the same time, without requiring numerous forward simulations. Even with noisy synthetic data, VFSA can make good estimates of the fractures’ parameters. This indicates that the VFSA technique is a proper and robust inversion technique for the measured voltages at various receiver gaps.
Modeling Transient Inflow Performance Relationship in Artificial-Lift Systems
Authors: Xiang Z.. , Kabir C. S. 
Published: October 2018

Abstract
This study presents a transient inflow-performance relationship (IPR) model using the steady-state solution to the diffusivity equation on a periodic varying well-flowing pressure. A wellbore model can be coupled to accurately depict the deliverability from wells with an artificial-lift system (ALS), such as gas lift and plunger lift. The commercial simulators allowed verification of model results and field data validated the solution approach.
For verification of this simplified IPR modeling approach, we first attempted to replicate two-step rate flow and shut-in periods, such as those associated with a transient flow test. Our model successfully reproduced those transient pressure profiles obtained from a rigorous superposition approach, generated with an analytical model using a commercial software package. Thereafter, we replicated the results of a coupled wellbore/reservoir model for a gas-lift well, using a numerical simulator. The difference between the results of rigorous simulators and our simplified transient-IPR model turned out to be well within engineering accuracy.
Field data from two plunger lift operations validated the transient-IPR model presented in this study. One important aspect to note is that a smaller period of oscillation translates into a more significant error between the traditional steady-state IPR model and the actual transient-IPR model. This finding suggested the need for the accuracy of the transient-IPR model in ALS to express the realistic rates and pressures. By capturing the essence of transient behavior, it is possible to combat downhole tool failures due to large pressure fluctuations or issues with surface metering due to higher than expected rates.
Surfactant Batch Treatment Efficiency as an Artificial Lift Method for Horizontal Gas Wells
Authors: Gcali Cikida , Karami Hamidreza , Pereyra Eduardo , Sarica Cem 
Published: October 2018

Abstract
Liquid accumulation in deviated gas wells is a major challenge in production systems. Limitations with the use of gas lift, pumping or plunger lift methods add to this challenge. Recently, surfactants have been injected continuously or as batch to help with the well deliquification by foam generation. The batch treatment is done by intermittent application of soap sticks or liquid surfactants.
This study is an effort to characterize surfactant batch treatment as an artificial lift method in horizontal gas wells. Given the practical potential and yet limited number of studies on this topic, the results can provide an experimental source to optimize surfactant application in mature production systems.
The experimental study is performed in a 2-in ID facility consisting of a 64-ft lateral section with 1° downward inclination followed by a 41-ft vertical section. Water and compressed air are the liquid and gas phases, and an anionic surfactant is applied in batches at the heel of the well. First, static tests are conducted to analyze surfactant efficiency in well start-up conditions. The surfactant concentration, initial liquid loading level and gas rate are varied, and the final liquid loading volume is measured as the target parameter. Then, dynamic tests are conducted to mimic the flowing well conditions. Surfactant concentration, liquid and gas flow rates are varied, and pressure fluctuations at the toe are monitored with time. The surfactant batch is delivered after air-water flow stabilization to investigate the surfactant efficiency. In addition, a high speed camera is used to record the flow conditions.
For well startup conditions, surfactant batch treatment is most effective for lower gas flow rates. Furthermore, the efficacy of surfactants is more pronounced at lesser-loaded wells. The effect of increasing surfactant concentration is eminent below the critical micelle concentration (CMC) with no further improvement beyond CMC. Generally, surfactant batch treatment does not significantly improve well cleanup time.
During well production, surfactant batch treatment is most efficient in low liquid and gas flow rate systems. At increased liquid and gas flow rates, with increasing surfactant concentration, its use can be inefficient due to adverse effects caused by foam frictional pressure losses. When the surfactant batch treatment is efficient, its effect increases with increasing concentration until CMC is reached. During severe slugging, surfactant batch treatment eliminates the slug production phase and partially or fully eradicates the severe slugging depending on the severity of the slugs. Generally, no significant trends can be observed between the period of effectiveness and concentration of surfactant.
Visualizing Rod Design and Analysis Through the Wave Equation
Authors: Phillips Walter 
Published: October 2018

Abstract
Rodstring dynamics are complex and difficult to understand. This work presents a multi-dimensional, interactive visual depiction of the full and intermediate wave equation results for rod design and analysis. Because rod motion exists in both time and space, one can build detailed virtual representations through a series of snapshots on different dimensions. Traditional dynamometer cards are an example of visualizing complex data, through time, in a 2-dimensional context. Extending this into 3-dimensions results in a virtual object generated through time (i.e. a single stroke) and depth (i.e. the rod-string). These visuals can expose a deeper understanding wave dynamics as they travel through the entire length of the rod-string. Further dimensions can be represented by coloring the rendered surface. There are a multitude of such views that can be constructed, all of which stem from the basic 2-dimensional dynamometer cards and time plots familiar to rod pump analysis.