bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature Transient Analysis During Boundary Dominated Flow Period
Authors: Mao Yilin , Zeidouni Mehdi
Published: April 2018

Temperature transient analysis is emerging as a reservoir characterization and production analysis approach partly due to the progress in the downhole temperature monitoring system. Among different flow regimes encountered during reservoir exploration, the long-lasting boundary dominated flow is a major focus since most of the hydrocarbon is recovered during this period. In this work, we derive a novel temperature transient analytical solution to model arriving temperature signals under boundary dominated flow, which is validated in multiple cases with numerical results. This solution can be incorporated with previous temperature transient analytical solutions to model the temperature signals during the entire life cycle of the production well. Compared to the heating Joule-Thomson effect in the transient period near the production well, a temporal cooling effect is observed throughout the entire volumetric reservoir after pressure transient reaches the reservoir boundary. This finding enables the thermal surveillance from monitoring wells away from the production well during boundary dominated flow. Among all the parameters involved, total compressibility and production drainage area are sensitive to this cooling effect only. From the thermal modeling, we extend existing reservoir characterization procedures to incorporate the boundary dominated flow period. Drainage area can be estimated from the measured temperature signals acquired in both production and monitoring wells. Decent accuracies of the estimations (more than 93%) are achieved from the examples presented in this work. The estimations from the monitoring wells are more accurate (more than 99% accuracy) compared to those from production wells. We find that monitoring well temperature transient analysis is promising for field application during the boundary dominate flow period. Another implication of this work is to develop variable rate temperature transient analysis (rate-temperature transient analysis) and temperature based decline curve analysis for reservoir characterization.
Injection Well Rate and Pressure Analyses Suggest Practical Waterflood Improvements
Authors: Swanson G. S.
Published: April 2018

Waterflood injection wells operate at maximum efficiency when delivering maximum, non-fracturing matrix rates to highest oil water ratio (OWR) subzones. Decreasing OWR observed during the later years of a mature waterflood intensifies need for analysis and optimization of injection efficiency. Analyses of injection rates, pressures and distribution profiles, especially when combined with recently more available step rate test (SRT) data allow injector efficiencies to be quantified in terms of estimated resulting BOPD.

The Los Angeles basin is home to many mature, low OWR waterfloods and a large, steadily increasing number of injection wells. In order to analyze injection efficiency over time, a prototype injection well, designed to include features common to LA basin injectors, was evaluated at key times of design, SRT, startup, profile deterioration, and finally, 100% point exit.

Local DOGGR injector permitting practices were incorporated into determination of "Maximum Allowable Surface Pressure" (MASP) for the prototype well. Estimated losses of injection capacity resulting from conservative "safety" practices of frac gradient discounting and ignoring friction pressure were significant, suggesting consideration of alternative uses of SRT data.

Damage/stim cycling, an unfortunately common LA basin injector operational practice, was analyzed in detail, focusing on inefficiencies resulting from damage accumulation followed by unintentional selective stimulation of lowest priority subzones. Since the industry's common goals would be advanced by a basin wide decrease of damage/stim cycling, improvements are suggested for the consideration of both operators and regulators.

Operators with best record for maximizing injection efficiency reduce damage/stim cycling by maintaining appropriate water quality standards and optimized injection profiles. When coupled with aggressive production well management policies which minimize low OWR production, e.g., shutting in highest water cut wells, even very mature waterfloods have been shown to perform without rapid BOPD declines.

Paper concludes with practical suggestions to accomplish DOGGR/UIC fracture-prevention goals utilizing traditional and/or modified SRT designs to generate a permitted "Maximum Allowable Rate" (MAR). In addition to avoiding unintended consequences of the traditional MASP permitting approach, waterflood management and regulation by MAR would encourage development of new technologies and operational practices.
Dynamic Layered Pressure Map Generation in a Mature Waterflooding Reservoir Using Artificial Intelligence Approach
Authors: Li Yuanjun , Popa Andrei , Johnson Andrew , Ershaghi Iraj , Cassidy Steve
Published: April 2018

In this paper, we present an Artificial Neural Network (ANN) solution approach to estimate average reservoir pressure from partial data recorded from fall-off tests. The methodology, while relatively simple, is entirely based on calibrating data from well tests with full fall-off information. Compared with conventional reservoir pressure estimation models, which usually require a long shut-in time and manual analysis for an individual well, this approach provides an efficient way of processing large data sets. Using data from injection well fall-off tests can avoid cost from non-producing periods of production wells. Also, utilizing injection profile tracers with shut-in pressure trends at the surface, we can infer the sand face pressure trends assuming a hydrostatic column during a shut-in period, greatly reducing instrumentation costs and downhole jewelry requirements.

This methodology is extremely helpful for mapping average pressure around injection wells in a reservoir with hundreds of injection wells with multiple flow units. In principle, maps generated from fall-off tests can be used as diagnostic tools to assist in formulating water flooding plans, ameliorating oil production capability, arranging well pattern density and preserving reservoir stability by providing an overview of internal oilfield conditions. Because of its practical simplicity and maneuverability, this new methodology can rapidly offer actionable data and generate remarkable business value.
Applying a Combined Hydraulic Fracturing, Reservoir, and Wellbore Simulator: Staged Field Experiment #3, Cluster Spacing, and Stacked Parent/Child Frac Hits
Authors: McClure Mark W. , Kang Charles A.
Published: April 2018

This paper describes three applications of a fully integrated hydraulic fracturing, reservoir, and wellbore simulator. The simulator describes hydraulic fracturing, shut-in, and production in a single continuous simulation. It describes multiphase effects (using either the black oil model or a compositional fluid model), thermal effects, transport of tracers and/or non-Newtonian fluid additives, stress shadowing from fracture propagation, and poroelastic stress effects from depletion, and uses a detailed proppant transport algorithm. It uses constitutive relations that smoothly transition from equations for flow through an open crack to equations for flow through a closed crack (with or without proppant). In the first example, we build a simulation model of Staged Field Experiment #3, a well-known historical dataset. Our result is compared with other published simulations and is matched to 15 years of production data. The simulation shows how the transport and settling of proppant in the fracture during injection and shut-in are impacted by processes such as clustered and hindered settling. Gel crosslinking and breaking are described with first-order reaction rate constants. In the second example, we perform a sensitivity analysis on cluster spacing in a generic slickwater fracturing treatment in a horizontal well. The simulations show complex interactions between stress shadowing, fracture propagation, proppant transport, and multiphase flow. The sensitivity analysis indicates that minimizing near-wellbore pressure drop is critical for improving production. Closer cluster spacing decreases near-wellbore pressure drop by providing more conduits for flow. In the third example, we simulate a vertically stacked parent/child scenario. Depletion of the overlying parent well leads to upward propagation from the child well and direct frac hits. The frac hits remobilize proppant as water sweeps into the parent well fractures, displacing gas. In the appendix, we summarize a suite of validation simulations that confirm the numerical accuracy of the simulator.
Remediation Solutions for Lost Circulation Using Case Based Reasoning
Authors: Reedy K. , Popa A. S. , Cassidy S. D.
Published: April 2018

Lost circulation represents a very costly, time consuming challenge to drilling through depleted geological zones that has proven difficult to accurately predict and manage. The standard approach relies on the driller's experience with the field to know how best to treat lost circulation when it occurs, or better yet, avoid it altogether, usually by enforcing maximums and minimums to various drilling parameters. This approach, however, ignores the key interplays between all of the variables involved, geological and reservoir performance information in addition to drilling data, where a change in one variable may affect the safe operating range of another. Taking all variables into account can be a prohibitively arduous task, particularly while managing the many other demands of drilling operations. Fortunately, a computer can quickly make all of the necessary calculations, and with programs designed to mimic human decision-making, can even make recommendations. The aim of this project was to create a program that would take into account all of the key variables related to lost circulation and provide drillers in the field on-the-spot recommendations as to the most successful method of remediation, and to provide proof of concept that a such programs could be created to help prevent lost circulation in the first place. The objective was achieved by creating a system using Case-Based Reasoning, which reviews a database of past incidents, determines those most similar in nature, and provides recommendations based on previous successes and failures. This program, when run on test cases, was able to accurately recommend the proper lost circulation remedial method. This paper will cover details on the types of data used, the operating mechanics of this system, example cases, and a detailed breakdown of the results.
Modeling Coupled Nonisothermal Reservoir/Wellbore Flow Behavior in Gas Reservoir Systems
Authors: Xu B. , Kabir S. , Hasan A. R.
Published: April 2018

Most analytical and numerical flow modelling presuppose isothermal flow behavior in the reservoir. However, for high rates and large consequent drawdown gas reservoirs, the nonisothermal behavior becomes the norm due to the Joule-Thomson (J-T) effect. Other factors, such as a fluid's adiabatic expansion (AE), heat convection, and the heat exchange with surrounding formations may also make contributions. Accounting for this nonisothermal flow behavior becomes a necessity for accurately estimating a wells's performance due to changes in fluid properties and also from the standpoints of wellbore flow assurance and its mechanical integrity.

This paper starts with the general energy balance in the reservoir and presents a semianalytical solution to estimate the nonisothermal, single-phase gas temperature in the reservoir during production. This solution considers the J-T effect, adiabatic expansion effect, transient temperature behavior, heat convection, and heat exchange of fluid with over and under-burden formtions. The variations of gas viscosity, density, J-T coefficient as a function of temperature and pressure are taken into consideration by making a small spatial step at each computional node. A field case study validates the time-variant wellbore temperature profiles with the coupled reservoir heat transfer model. Distributed temperature measurements during a drill stem test (DST) made this validation feasible.

The J-T effect dominates in the near wellbore region due to dramatic pressure change. The J-T induced cooling effect is usually happened for gas in the reservoir. However, for high-pressure systems, the gas behaves like a liquid and gets heated up. For some intermediate pressure intervals, the gas temperature slightly increases with expansion, reach a plateau, and then gradually decreases as the gas moves toward the wellbore with declining pressure. By coupling the reservoir heat transfer model with the wellbore heat transfer model, one can monitor both production and flow assurance related issures that may arise either from thermodynamic solids or tubular mechanical integrity.
Sensitivity Analysis for Solar-Generated Steam for Enhanced Oil Recovery
Authors: Roig R. , Agarwal A. , Kovscek A. R.
Published: April 2018

Increasing regulations on greenhouse gas emissions (GHG) and fluctuations in the price of natural gas are driving innovation for crude-oil production methods. Solar-generated steam has the promise to reduce by up to 80% of GHG emissions in areas of abundant solar insolation. There are cyclic fluctuations in the steam injection rate associated with sunlight hours and seasonal variations that create the risk of temperature and pressure fluctuations along the wellbore. This paper analyzes the recovery efficiency of the steam injection process for solar-generated steam supplemented with conventional steam.

The viability of solar thermal enhanced oil recovery (TEOR) was evaluated using data from the San Joaquin Valley in California as input to a commercial reservoir simulator. The efficiency was quantified through reservoir simulation using a layered homogeneous 3D grid and corresponding economic analysis. Reservoir simulations with variable steam rate, quality, and temperature of diurnal and nocturnal steam injection were conducted. Various injection schedules and reservoir responses were analyzed, including the geomechanical response for continuous variable rate injection. The economic analysis was based on the operating expenses, mainly heating, lifting, and maintenance costs per unit of oil extracted.

This research shows that reducing the dependency on conventional steam using a minimum nocturnal steam rate contributes to better energy efficiency. Also, reducing the steam quality by up to 50% percent in both diurnal and nocturnal injection presented a promising cost-effective solution despite reducing somewhat the amount of oil recovered. We also discovered that reducing the nocturnal steam temperature provided substantial economic benefits with only a minor impact on the cumulative oil recovered. The geomechanical reservoir deformation triggered by steam pressure and temperature variations was within reasonable limits and did not present causes for concern. This economic analysis was done assuming an already paid out capital expense, both for solar and conventional steam. We compute the Net Present Value (NPV) of the profits using multiple price scenarios to compare the different cases. The maintenance cost and efficiency degradation for the solar generated steam is not considered in the absence of any available long term industry data. An optimal injection schedule and conventional steam contribution can be engineered based on the field operating and economic requirements.
An Improved Probability Conditioning Method for Constraining Multiple-Point Statistical Facies Simulation on Nonlinear Flow Data
Authors: Ma W. , Jafarpour B.
Published: April 2018

We evaluate the use of facies probability maps for conditioning discrete multiple-point statistical (MPS) facies simulation on dynamic production data. In MPS simulation, conditional probabilities are estimated from a training image (TI), a conceptual model of geologic connectivity, and used to draw samples of facies distributions that are statistically consistent with those encoded in the TI. Whereas conditioning MPS simulation on both static hard data (e.g., well logs) and soft data (e.g., seismic) is straightforward, calibration of facies against nonlinear flow data is nontrivial. The use of facies probability maps for conditioning MPS simulation on dynamic production data presents a promising approach for calibration of complex facies models. We present an overview of MPS-based conditional simulation with probability maps and discuss some of the important properties and implementation issues of this approach. The paper presents two important contributions: (1) improvement of the original probability conditioning method (PCM) by constructing the facies probability maps based on the first and second order statistical moments of the updated permeabilities at each cell; (2) generalization of the "tau" model to include pixel-based τ values that can assign different confidence levels to the facies probabilities at different grid blocks. Results from numerical examples demonstrate that the proposed approach outperforms the original PCM by incorporating additional information from the observed dynamic data into MPS-based facies simulation.
Agile-Scrum for Facility Design Project Management
Authors: Sljivar I. , Gunasekaran A.
Published: April 2018

Agile-Scrum (AS) Project Management, which originated in the IT industry, has unlimited potential to benefit both operating and service companies in oil and gas industry and many others. This paper will show how it could be applied to facility design work as a framework to improve the quality, timeliness and overall value of delivering construction drawings. The outcome that could be expected from this is less change orders and delays during the construction and much more satisfied operation teams. The design and construction of facilities is a complex work that requires close collaboration between multidisciplinary teams. AS framework enables this collaboration by creating a safe engaging environment in which self-organizing teams can find the best ways to achieve project requirements through incremental and prioritized value delivery. The goal of AS is to first focus on critical work to minimize the project risk and then maximize the benefit to the customer, in this case construction and operation teams, through continuous feedback loops. There are three main team roles that will be described in this paper: Scrum Master, Product Owner, and Development (Design) Team.
Effect of Stress Shock and Pressurization/Depressurization Hysteresis on Petrophysical Properties of Naturally-Fractured Reservoir Formations
Authors: Civan F.
Published: April 2018

This paper presents a theoretically rigorous formulation and correlation of the effect of poroelasticity on stress-dependent petrophysical properties of naturally-fractured reservoirs, including porosity, permeability, relative permeability, and capillary pressure, by consideration of the stress shock effect across a critical effective stress and the pressurization/depressurization hysteresis. This model accounts for the deformation, transformation, deterioration, and collapse of the pore structure during pressurization and depressurization processes and their effects on the properties of naturally-fractured reservoir formations. A stress shock is shown to occur in naturally-fractured reservoir formations at a critical stress during transition between open and closed natural fractures in loading and unloading applications. The effect of the stress shock and pressurization/depressurization hysteresis on petrophysical properties of reservoir formations is formulated by means of a modified power-law equation derived from a phenomenological model referred to as a rate equation. The modified power-law equation is shown to alleviate the shortcomings of the ordinary power-law equation applied in many studies.

The comprehensive model developed in this study is validated by means of various experimental data gathered by testing of samples from sandstone, carbonate, and shale reservoirs. The phenomenological parameters of the rock samples are determined for best match of experimental data. The scenarios examined in this study indicate that pressurization/depressurization hysteresis has a significant effect on the stress-dependent porosity and permeability of reservoirs. The model developed in this paper can describe the stress-dependent porosity and permeability of the fractured rock formations much more accurately than the commonly used empirical correlations. The accurate methodology presented for proper correlation of stress-dependent properties of reservoir formation rocks honors the slope discontinuity at a yield or critical effective stress. The stress-dependency of rock properties are described by the modified power-law expressions separately over the low stress region below the critical stress and the high stress region above the critical stress. The proposed data correlation methodology is proven to be highly effective in the analyses and correlations of the experimental data of various types of reservoir rock formations as indicated by the correlations achieved with significantly high coefficients of regressions very close to the unity.
Unsupervised Statistical Learning with Integrated Pattern-Based Geostatistical Simulation
Authors: Li Q. , Aguilera R.
Published: April 2018

This study presents a new geostatistics modeling methodology for the purpose of achieving the following three objectives. (1) Connecting geostatistics and machine learning methodologies, (2) Using non-linear topological mapping to reduce the original high dimensional data space to low dimensional subspace, as well as clustering for identifying and extracting meaningful patterns for both visualization and efficiency purposes, and (3) Using unsupervised learning algorithms to bypass potential problems encountered while using supervised learning algorithms.

Past observations have indicated that due to lack of labeled input data, artificial neural network (ANN) architecture, based on feedforward and backpropagation supervised learning, is difficult to apply.

To eliminate this difficulty and accomplish the 3 aforementioned objectives we introduce in this paper TopoSim, a neural topology-preserving based geostatistical simulation algorithm, which integrates (1) Self-Organizing Map (SOM) and its updated version, Growing Self-Organizing Map (GSOM), and (2) ANN with an unsupervised competitive learning structure. The proposed simulation integrates in a single step dimensionality reduction and extraction of input data structure pattern. Connectivity between geostatistical simulation problems and machine learning tasks are explained and constructed for the first time.

We perform TopoSim unconditioned geostatistical realizations, which show improvements in continuity and pattern reproduction when compared with previously developed single normal equation simulation (SNESIM) algorithms.

We conclude that the geostatistical simulation task is essentially a machine learning problem, i.e., getting the model to learn from available data and subsequently using the model for prediction purposes.
High Resolution Hydraulic Fracture Network Modeling Using Flexible Dual Porosity Dual Permeability Framework
Authors: Yang D. , Xue X. , Chen J.
Published: April 2018

Advancement of multistage hydraulic fracturing technology made unconventional reservoirs (UCR) development economically very attractive. Accurate and efficient production forecasts from UCR are challenging because of the complexity of the fracture network. Abstractions inherent in the traditional dual porosity dual permeability (DPDK) model makes it inadequate to simulate UCR. Discrete Fracture Model (DFM) provides better resolution of fracture geometry but it is not widely used in the industry because it is computationally expensive and history matching is difficult to perform.

This paper presents a new option which utilizes the dual medium framework from traditional DPDK modeling and incorporates effects of each fracture explicitly as it is done in the DFM approach. Single medium is used to model the matrix where there is no fracture present, and dual medium is used to model the fracture network and matrix. This method takes advantage of the optimized DPDK feature in existing commercial simulators. In the near wellbore areas where fractures exist, matrix-fracture coupling is calculated using the same equation as the Embedded Discrete Fracture Model (EDFM). Additionally, to increase accuracy, high resolution local grid refinements (LGRs) are adopted at fracture locations. The new option is benchmarked with the existing EDFM tool using synthetic and field cases.

The results of the benchmark studies indicate that high resolution LGR can minimize sensitivity to the resolution of matrix grid. Flexible DPDK framework allow us to utilize existing reservoir simulation workflow for grid property modification with clear and detailed 3D visualization of matrix and fracture through comerically available visualization packages.

The new option provides a precise and efficient method to simulate complex fracture networks. Implementation and integration with other simulation workflows are straightforward since it makes use of existing functionalities and frameworks in a commercial simulator. Potential applications to improve the efficiency of UCR factory operations include automatic probabilistic forecasting, history matching, and optimization.
Is the U.S. Fuels Infrastructure Resilient? An Examination of Natural Disaster Vulnerabilities
Authors: Mohan H. , Crawford P. M. , Carolus M. J. , Kuczma G.
Published: April 2018

Objective/scope

The U.S. fuels infrastructure has undergone significant changes in the last several years. These changes are in response to shifts in domestic production, imports and exports, processing and distribution. The objective of this analysis is to define and model the U.S. fuels infrastructure, from production, transportation, and processing of crude oil to the distribution, storage, and consumption of refined products, and assess resiliency to natural disasters. This has become a pressing concern in the wake of Hurricane Harvey's impacts on U.S. infrastructure and fuels markets.

Methods, procedures, process

The analysis was conducted through a detailed assessment of the petroleum infrastructure, including wells, pipelines, refineries, crude and product terminals, import and export facilities, natural gas storage and processing facilities, and other key components. Interdependencies between petroleum and other types of infrastructure were also evaluated. As part of this analysis, a wide range of natural disasters, including earthquakes, hurricanes, tsunamis, and wildfires, were considered. For each of these natural threats, the geographic risks, the severity and type of damage, the likelihood of that damage, and the time required for recovery were all established using the latest available research.

To complete the analysis several tools were developed and applied. These include a comprehensive geospatial system used to identify major markets and submarkets and to determine dependencies and vulnerabilities; models of the market supply/demand requirements; a national disruption model which details the major crude and product markets; and disruption models to predict the impact on crude and refined products from hurricanes, earthquakes, and tsunamis.

Results, observations, conclusions

The analysis showed that the U.S. fuels infrastructure is vulnerable to being impaired by natural disasters. Furthermore, the interdependencies of the infrastructure, in terms of both type of infrastructure and geographic location, leave the U.S. vulnerable to cascading risks. As part of the study, potential mitigation efforts were determined to address regional and national vulnerabilities. The proposed mitigation efforts have been incorporated into the Department of Energy's recent Quadrennial Energy Review. This study provides an update and extension of work performed earlier.

Novel/additive information

The paper provides a detailed assessment of the U.S. fuels infrastructure and its vulnerabilities to natural threats. These include earthquakes, hurricanes, and other disasters. For each of these threats, the geographic risks, as well as the type, probability, and severity of damage, are discussed. Finally, case studies of recent disasters, including the impact of Harvey on the Gulf Coast, Midcontinent, and East Coast, are used to illustrate the fuels infrastructure vulnerabilities and the need for mitigation.
Laboratory Tests Conducted to Perforate and Displace Viscous Oil from Saturated Formation Core to Help Optimize Steam Flood Completion
Authors: Haggerty Dennis J.
Published: April 2018

API 19B Section 4 Flow Laboratory tests were conductedto test and optimizethe perforation strategy of wells in a shallow, viscous oil reservoir. Cored sand formation samples sealed inaluminum tubes wereremovedwith care and prepared to allow stressing for simulated perforation and displacement testing.

The first challengewas to extract the viscous crude oil-saturated, unconsolidated cores taken from the zone of interestandpermittheir use with minimal disturbance. Once the cores were prepared such that stress and pore pressure could be appliedin an API RP 19B Section 4 configuration, shaped-charge perforators were shot to determine penetration depth and casing-entrance hole size. The central parameter investigated was casing-hole size, which regulates the flow-velocity/drawdown-pressure relationship important for sand control. The effectof solvent versus heat displacement of the viscous crude oil was also observed.

Tests using heat to assess its effectiveness on promoting crude oil flow of a specific composition throughits associated sand causedminimal sand movement. The focus began with the perforation behavior in the stressed, viscous crude oil-saturated sand, followed by the flow of viscous crude oil through the sand, and then finally on how viscous crude oil-flow behavior was affected by viscosity reduction with heat. Results demonstratedthat even the smaller-shaped charges were capable of sufficient penetration, and the primary attribute was the resulting casing-entrance hole diameter. The desired hole size in a specific shots-per-foot perforator is a compromise betweenoptimal steam delivery for uniform injection across the targeted sand body and the maximum hole size for optimal production while minimizing sand production.

When this abstract was written, multiple wells had been perforated and are currently under field evaluation and data gathering, which will be compared to laboratory findings. This paper includes discussions on the testing process used and the effect of perforating the viscous crude oil sand. Additionally, it offers insight into the effects of increasing the temperature of the viscous crude oil and selecting a perforating strategy.
Surfactant Versus Solvent Co-Injection to Improve Efficiency of Steam Assisted Bitumen and Heavy Oil Recovery Processes
Authors: Ozum Baki
Published: April 2018

In Canada, daily steam assisted bitumen and heavy oil production is about 1.5×106 barrels per day, which is predicted to increase steadily. Oil industry has spent significant effort on solvent, mostly light hydrocarbons co-injection with steam to boost bitumen mobility, therefore, production efficiency; which resulted limited commercial success. In most solvent co-injection with steam studies further reduction of already reduced bitumen viscosity by steam injection was focused, while its effect on bitumen-water interfacial tension was ignored. At our laboratory effects of surfactant (such as biodiesel) and solvent (such as pentane) on bitumen viscosity, bitumen-water interfacial tension and steam assisted gravity drainage were evaluated. Experimental data showed that bitumen recovery efficiency was reduced by solvent co-injection with steam; which is attributed that solvent addition increases bitumen-water interfacial tension, causes slip of water on bitumen and suppresses bitumen mobility, which result in counterbalancing benefits of viscosity reduction. In the present study creeping flow of two immiscible fluids, such as oil and water (condensed steam) in a capillary with no-slip and slip boundary conditions at oil-water interface is discussed to provide technical support for better understanding of solvent versus surfactant co-injection with steam for bitumen and heavy oil recovery, as well as water flooding and CHOPS and Post CHOPS processes.
Slug Dissipation in a Horizontal Enlarged Impacting Tee-Junction
Authors: Mohammadikharkeshi M. , Dabirian R. , Cole T. , Shoham O. , Mohan R. S.
Published: April 2018

Enlarged Impacting Tee-junctions (EIT) are the building blocks of multiphase manifolds, which are large diameter pipe sections fed by several smaller diameter inlet pipelines. The goal of this study is to conduct an experimental and theoretical study on slug dissipation in an enlarged impacting tee-junction (EIT). Experimental data are acquired and a mechanistic model is developed for the prediction of the length required for slugs to dissipate in the EIT, namely, the "slug dissipation length". The developed model is validated with the acquired data.

An EIT test section is designed and installed in a multiphase flow loop to investigate slug dissipation length at an EIT junction. The EIT inlet is a 0.05 m diameter, 4.6 m long pipe, which is connected to the center of an enlarged 0.074 m diameter 5.5 m long pipe forming the EIT section. Air and water are used as the test fluids, with superficial gas and liquid velocities in the ranges of 1-5 m/s and 0.3-1.2 m/s, respectively, to ensure slug flow at the EIT inlet. The slug dissipation process in the branches of the EIT is observed visually and recorded by a set of cameras.

A slug dissipates as it enters from the reduced diameter inlet section into the EIT section. The dissipation of the slug in the EIT is due mainly to liquid drainage from the slug front and penetration of "bubble turning" into the slug body as it moves along the branches of the EIT. Thus, the length of the slug body is continuously reduced until it completely dissipates. The experimental results show that the slug dissipation length increases with increasing superficial gas velocity. The results also confirm that the dissipation length is more sensitive to the superficial gas velocity, as compared to the superficial liquid velocity. The developed mechanistic model is based on the physical slug dissipation mechanism, namely penetration of turning bubble into the slug body. The predictions of the proposed mechanistic model are in good agreement with the experimental data, showing discrepancies less than 15%. The results of this study will enable to properly design a multiphase manifold by providing a criterion for slug dissipation length in EIT.
An Efficient Compositional Model for Unconventional Reservoirs: Eagle Ford Formation Case Study
Authors: Uzun Ilkay , Eker Erdinc , Kazemi Hossein
Published: April 2018

The main complexity of the multi-component, multi-phase simulation in unconventional reservoirs arises because of the thermodynamic phase behavior and component transport in such small pores. To manage these issues, a computationally cost-effective implicit model is needed. This paper presents a new multi-component, multi-phase, dual-porosity numerical model including molecular diffusion for simulating fluid flow for the field applications in Eagle Ford formation, Texas. The model, which is based on the mass transport equations for each component, solves for the pressures and overall compositions simultaneously, then it solves for crossing phase boundaries and saturations sequentially. This new model, which determines the effect of molecular diffusion on production, is computationally robust and efficient. The vapor-liquid equilibrium calculation is performed using Peng-Robinson equation of state including the phase shifts and the capillary pressure effects on phase behavior. The rock and fluid data from Eagle Ford wells are used as an input for the simulation model to evaluate the accuracy and computational efficacy compared to the classic volume balance technique for unconventional reservoirs.

The compositional mass transport equations can be solved using several variants of the fully implicit method in addition to a less stringent sequential volume balance technique. The latter is of interest because one can generate a simple compositional pressure diffusivity equation and sequentially solve for the composition. However, the volume balance technique is sensitive to the grid and time-step size. We compared our results with the volume balance method to examine the accuracy of both solution techniques. The degree of implicitness in our model not only provides better accuracy for the simulation but also eliminates the material balance errors occurring in explicit solutions. Therefore, our method provides a better understanding of the physical phenomena of fluid flow processes at the matrix-fracture interface in unconventional reservoirs.
Production Loss by Scale Formation in Unconventional Reservoirs
Authors: Abouie A. , Tagavifar M. , Sanaei A. , Sepehrnoori K.
Published: April 2018

Scale deposition is a common problem during oil production resulting in equipment corrosion, wellbore plugging, and production rate reduction. In unconventional reservoirs, the negative effect of scale formation and deposition becomes more pronounced as it severely damages the conductivity of hydraulic fractures. However, how and to what extent the scaling changes the gas production is unclear. In this work, a robust and integrated tool is developed to model scale deposition under dynamic flow conditions in unconventional reservoirs considering the damages to fracture and shale matrix. In doing so, a comprehensive compositional reservoir simulator (UTCOMP) coupled with IPhreeqc is utilized to predict carbonate and sulfate scales formation in the Marcellus shale formations. This integrated approach allows to adequately resolve the multiphase flow in the fracture network and near-wellbore region and to determine the associated geochemical behavior. Our results show that scale formation mainly results from changes in the physicochemical properties of brine (pH, temperature, and pressure) and/or mixing with incompatible brine compositions (e.g. mixing of fracturing fluid and formation brine). Precipitations of barite and calcite due to the incompatibility of fracturing fluid with formation water was identified to be the main cause of hydraulic fracture plugging, which resulted in fracture conductivity reduction. Based on the fracturing fluid composition and its invasion depth, fracture conductivity can decrease up to 10%. Due to the complex flowback of the fracturing fluid, we observed a time-dependent fracture plugging. Specifically, a moderate plugging of the fracture face occurs early in Marcellus formation causing a reduction in production peak rate while the fracture tip is severely plugged at later times and further reduces the gas production rate.
A Diagnostic Approach to Predict Asphaltene Deposition in Reservoir and Wellbore
Authors: Davudov Davud , Moghanloo Rouzbeh G. , Akita Emmanuel , Karami Hamidreza
Published: April 2018

Despite the myriad of published literature on asphaltene, true understanding of its characterization, and deposition is still lacking. There have been many proposed models based on principles in thermodynamics, hydrodynamics, and many empirical equations proposed, however, further work still needs to be done to have a better grasp of the asphaltene deposition. In this study, we examine an integrated approach to evaluate asphaletene deposition in both the reservoir and wellbore as a function of fluid velocity.

We discuss the effect of permeability reduction as a function of combined effects of surface deposition and interconnectivity loss due to pore blockage in the reservoir. The effects of pore surface deposition and pore blockage are evaluated based on published experimental data on sandstone and carbonate rock samples. Next, based on different wellbore/tubing configurations (uniform and tapered) and fluid types, the asphlatene deposition is evaluated within the wellbore considering both favorable and non-favorable regions. Simulated values obtained from OLGATM are used to define these regions and critical particle sizes where there is a shift from Region I to Region II.

Results indicate that in terms of asphaletene deposition in the reservoir, for sandstone samples, both surface deposition and pore throat plugging seem to contribute fairly equally to permeability reduction. In the case of carbonate however, pore blockage seems to be mainly dominant, which results in an almost instantaneous sharp decrease in sample permeability. Moreover, increasing fluid velocity, positively contributes to diminishing permeability reduction in sandstone samples, whereas it has no effect in case of carbonate samples.

In case of deposition in the wellbore, asphaltene deposition rate is inversely related to fluid velocity in Region I whereas in Region II, it is directly proportional. More importantly however, this study determines particle size cutoff values for the two regions and does a systematic study of the impact that uniform and tapered wellbore configurations have on asphaltene deposition.

Results of this study may change the industry's predictions of asphaltene deposition in both reservoir and wellbore. Improved understanding of asphaletene deposition leads to better production and far more accurate economic predictions.
Successful Water Shut-Off Treatment Specially Designed for High Temperature: Vizcacheras Experience
Authors: Vega Isabel N. , Campomenosi Álvaro , Hernández María Isabel , Moglia Diego , Peltier José
Published: April 2018

Injection of blocking gels in the near wellbore of producer wells is a technique employed for water production control. A proven and effective alternative to control this water excess is the application of crosslinked gels.

Water shut-off (WSO) treatments efficiency depends on several aspects such as reservoir fluid flow patterns, rock petrophysics, formation heterogeneities and gel characteristics. Although experimental laboratory tests previous field implementation, are many times underestimated, they provide valuable information that increases the chances of success. Integrating lab results with reservoir and field data creates a proper scenario that diminishes the uncertainties during field implementation. It is also crucial the support of a multidisciplinary team work while injecting the WSO tretament.

This paper presents a successful water shut-off treatment specially designed for high temperature, applied in a production well located in Vizcacheras field, Mendoza Agentina.
Costa Norte Project: Enhancing Environmental Protection Against Oil Spills in the Northern Brazilian Coast Through the Combination of Data Collection, Numerical Forecasts and Impact Assessment
Authors: Pessoa M. C. , Guedes A. , Queiroz D. S. , Pellegrini J. D. , Fragoso M. , Cabral M. M. , Soares M. L. , Sabino C. M. , Chaves F. O. , Assad L. D. , Vasconcelos A. , Bock C. S. , Toste R. , Faller D. G. , Rollnic M.
Published: April 2018

The oil and gas industry is continuously improving its standards and procedures in order to operate safely. Risk management and process safety approaches are used to minimize the likelihood of major accidents. However, offshore exploration and production is not, by definition, inherently safe, and therefore the industry also has to enhance its emergency response techniques. When working in remote areas this becomes extremely important.

Offshore oil spills are one of the major accidents that may bring harm not only to the company itself or to its employees, but to the local communities, to the coastal systems, to the marine life, to the food chain, among several others not mentioned in this abstract. An efficient oil spill response is therefore increasingly necessary, and understanding pollutant's transportation in the coastal zones can assist in this response and minimize the impacts of a spill.

The objective of this paper is to describe a research project currently taking place in the Brazilian Equatorial Margin with the collaboration of different institutions. The Costa Norte project considers the development of an integrated marine hydrodynamic and oil dispersion simulation model, in order to enhance the oil dispersion and impact forecast in the coastal areas of the Pará-Maranhão and Foz do Amazonas basins. The integration of these technologies will be made using a simulation environment based on a web portal, remotely accessible to the user. This remotely accessible environment will receive in situ collected environmental data and, together with ocean circulation model, will effectively represent thelocal meteoceanographic conditions. The project will also evaluate the vulnerability level of the coastal environments, notedly the mangroves, considering their environmental sensitivity, contamination susceptibility and resilience aspects in the equatorial margin.
Assessment of ecological and economic efficiency of agricultural lands preservation
Authors: Semenda Dmytro , Semenda Olga
Published: April 2018

The article substantiates the necessity to define and generalize the criteria for assessing the ecological and economic efficiency of using agricultural lands. Due to the transition of the agro-industrial complex to private forms of management, the problems of forming a strategy of rational, ecologically safe and sustainable development of land use in Ukrainian agriculture became of paramount importance. Therefore, systematic studies on the assessment of the ecological and economic efficiency of the agricultural land use need to be conducted. Harmonization of ecological and economic interests is of particular importance in the context of ensuring the conservation, resource-saving and reproductive nature of the agricultural land exploitation.A scientific study found that in Ukraine, the agrarian sector of the economy provides about 47% of GDP, but the question arises: At what price are these achievements given to us? Agricultural land development exceeds environmentally sound standards. Excessive cultivation of the territory leads to an annual increase of eroded lands by 80-90 thousand hectares. Land use is recognized as environmentally unstable, and there is a steady tendency to deteriorate the quality of soil. Each second hectare of cultivated land is erosion-hazardous, that is, these soils are subject to water and wind erosion. In this regard, it is recommended to introduce the world-wide experience of Climate Smart Agriculture (CSA), which provides an opportunity to provide food security to the country and to limit the negative impact of the environment, based on the introduction of organic production.It is proved that regardless of the size of farms and forms of management using resource-saving no-till technologies, enterprises received low cost of grown products, providing profitable activities. Ecological compatibility of the technology provides energy savings of at least 30% in comparison with traditional farming systems, the accumulation of not less than 30-40% of plant residues on the soil surface after harvesting of the predecessor, provides protection of the soil from wind and water erosion by minimizing the amount and depth of technological operations.It is confirmed that the most widespread evaluation of the agricultural lands use is the evaluation of the results of their use through volumes of gross and commodity products, income, and production profitability. The criteria for the environmental effectiveness of agricultural land use should be: the degree of functional use of land resources, ecological stability, the level of anthropogenic loading, the degree of erosional feature of land, etc.According to the study results, it was established that one of the main areas of agriculture is the application of minimal tillage in crop rotation, i.e. resource-saving no-till technology.The economic feasibility of technologies based on the use of different soil tillage systems has been confirmed.