bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zero Wellsite Personnel. The First Truly Man-Less Operation for Directional Drilling Services
Authors: Chatar Crispin , Stepnov Alexey , Mardyashov Anton , Fedotov Viacheslav 
Published: October 2018

Abstract
Years of effort, knowledge, innovation, and process integration resulted in the first unmanned remote operation where the drilling services company completed the directional drilling contract without any physical presence of personnel on the rig. In addition, the company has successfully run these remote operations across multiple continents. An opportunity presented itself to the global drilling community to drill a well where it was deemed unsafe for human operations. Building on prior successes in remote operations, a relevant solution was provided that could be executed anywhere on the Earth remotely from any other location. The evolution of remote drilling operations began in 2009, the most significant result of which occurred in 2016 when for the first time, a well was drilled without any directional services staff even visiting the drilling rig. This operation was the result of more than 8 years of foundation work.
This paper will present three main concepts for any future efforts in this drilling area. Due to the need for maintaining the drilling company's strategic advantage, not all of the details will be explored. The process and procedures used to accomplish the remote operations will be summarized, followed by a brief update on the history of remote operations. Secondly, a description if remote operations in directional drilling, intercontinental remote operations, and unmanned directional drilling operations will be presented. Finally, tools and technologies to accomplish these goals will be summarized in a suitable manner for the industry to build on to take remote operations to the next level. The main goal of this paper will be to highlight what was achieved with current technology and predict the future of area of the industry. This paper will divulge many industry firsts; unmanned directional drilling jobs, unmanned logging-while-drilling (LWD) jobs, intercontinental remote operations, and finally, for the first time, operations where the service company never visited the rig.
Enhanced Flux Management for Sand Control Completions
Authors: Cameron John , Zaki Karim , Jones Colin , Lazo Antonio 
Published: October 2018

Abstract
A probabilistic flux and erosion model and workflow has been constructed to estimate the inflow through sand screen on a foot by foot basis along the wellbore using the completion details, production rate, and reservoir and bottom hole flowing pressures. The model is then calibrated & history matched using well data from pressure transient analyses, well test and production logs as available. Extensive laboratory testing coupled with computational flow dynamics modelling provided the algorithms for a number of different screen types to relate flux and sand production to the expected service life for any given future production profile. This allows the well's planned production profile to be optimized by balancing risk, rate and reserves recovery.
Osmosis and Clay Swelling Effects in Gas Shale Formations under Stress
Authors: Eveline Vena F. , Akkutlu I. Yucel 
Published: October 2018

Abstract
Water-shale interactions are traditionally perceived as complex phenomena due to reactive nature of shale with water. However, the current trends in shale gas industry requires an advanced-level of understanding of these interactions and their impact on gas production. In this paper we investigate the invasion of fracturing water into the formation and the subsequent water-shale interactions. Objective of this work is to study osmosis and clay swelling effects of the invasion on the formation permeability.
For this purpose, a new geomechanically-coupled reservoir flow simulator is developed, which accounts for water imbibition, osmosis and clay swelling effects on the formation permeability under stress. The simulation model considers the formation has a multi-scale pores consisting of microcracks, clay pores and organic pores. Water imbibition occurs in the water-wet inorganic part of the matrix in the microcracks. Osmosis and clay swelling effects develop in the clay pores acting as semi-permeable membrane to the imbibed water and changing the local stress in the formation. The simulation model includes aqueous and gaseous phases with three components: water, gas and salt.
The simulation results show that the formation permeability is dynamically affected during the shut-in period by a combination of mechanisms including imbibition, capillarity, diffusion/osmosis, and total stress. Notably, a permeability impairment zone, rather a fracture skin, develops near the fracture. The permeability alteration is due to osmosis-related clay swelling and changing stresses in the formation. The magnitude of the permeability alteration is controlled mainly by the salt concentration difference between the fracturing fluid and the clay-bound water, the clay-membrane efficiency, the clay cation exchange capacity (CEC), the clay porosity, the stress and the duration of the shut-in time. We develop a fracture skin factor that can be used with the single-phase (gas) shale reservoir flow simulators that are typically run in the absence of water invasion at the scale of the stimulated reservoir volume (SRV) and in multidimensional geometries.
Currently there is a clear need in the unconventional industry to better-understand and control the hydraulic fracturing fluid-shale interactions. This work is an important milestone considering the complexity of the problem and suggesting that the water chemistry and the formation lithology plays a significant role after the fracturing operations.
Evaluation of New Viscoelastic Surfactant Systems in High-Temperatures Carbonates Acidizing
Authors: Ibrahim Ahmed Farid , Nasr-El-Din Hisham , Paulo Jaqueline de , Ewbank Conrado , Poltronieri Olívia Cueva 
Published: October 2018

Abstract
Viscoelastic surfactants (VES) have been introduced as acid divergent agents for easier cleaning and mixing advantage over in-situ gelled acid systems. Thermal stability and compatibility with the other additives, such as corrosion inhibitors, are the main problems with conventional VES. This work introduces five VES-based acid systems for diversion in matrix acidizing.
A series of VES samples were developed, hereinafter named samples A, A1, B, C and C1 according to their chemical composition, and evaluated for various applications. The initial screening was conducted by viscosity measurements of the spent acid system at 150°F and shear rates of 10 and 100 s−1. The effects of different corrosion inhibitors on the viscosity of the selected VES were then examined. The viscosity of the VES system was then measured as a function of temperature (77 to 300°F) and shear rate (10 and 100 s−1) to evaluate thermal stability. The diversion characteristic of the VES systems was evaluated with single core flood experiments on Indiana limestone cores with a permeability range of 10-200 md. CT-scan imaging of the cores after the acid treatment was used to evaluate the structure and the propagation of the wormhole. Dual coreflood experiments were conducted on Indiana limestone cores with permeability contrast of 1.5-50 to examine the ability of the VES to divert the acid system on heterogeneous limestone formations.
Phase separation was observed during the preparation of the systems with a samples C and C1 VES samples. High viscosity was found in the case of A and B VES systems with the viscosity of 2,500, and 350 cP at 10 and 100 s−1, respectively, at 150°F. The viscosity of the Sample A1 and B VES systems were not affected by the tested corrosion inhibitor. The single coreflood experiments revealed the ability of the VES to divert the acid system. The breakthrough injected acid volumes were 0.7 and 0.6 in the case of Sample A1 and Sample B, respectively. The wormhole tortuosity was 1.8 in sample A, compared to 1.4 in Sample B.
This work introduces VES systems with superior divergent ability and viscosity measurements at high temperature even when in contact with the other acid additives, which leads to less acid spending and better wormhole structure.
Activating Shale to Form Well Barriers: Theory and Field Examples
Authors: Kristiansen Tron Golder , Dyngeland Torill , Kinn Sigurd , Flatebø Roar , Aarseth Nils Andre 
Published: October 2018

Abstract
Shale is a general term used for argillaceous (clay-rich) rocks which are the most abundant sediment on the earth. It is believed that clay rich rocks comprise more than 50-75% of the geologic column. Shale has very varying petrophysical and mechanical properties. Shale is in the most cases acting as a trap or seal for hydrocarbon migration, but has also in more recent years been targeted as a reservoir target in some basins. In some wells it has been observed on cement bond logs that shales in uncemented intervals have moved in and closed the annulus. Pressure communication testing has been performed on these sections and the sections has been qualified as well barrier elements (Williams et al., 2009) for plug and abandonment (P&A) purposes. The main mechanism behind the deformation process is believed to be shale creep.
In this paper we will discuss shale creep and other shale deformation mechanisms and how an understanding of these can be used to activate shale that has not contacted the casing yet to form a well barrier. We have developed a numerical model based on first order principles to better understand the mechanical deformation process. We are also supporting the modeling results with laboratory experiments, before we discuss a couple of field cases where shale intervals have been activated and verified to have formed a well barrier as part of the well construction process in new wells.
An Assessment of the Physical and Mechanical Properties of Foamed Cement Generated at a Field Site vs. Laboratory
Authors: Spaulding Richard , Kutchko Barbara , Haljasmaa Igor , Fazio Jim 
Published: October 2018

Abstract
The objective of this paper is to evaluate the physical and dynamic mechanical properties of foamed cement generated at a field site and compare them to similar cements fabricated within the laboratory. Physical and mechanical properties such as porosity, permeability, Young's modulus, Poisson's ratio, bulk modulus, shear modulus, etc. will be discussed. Mechanical properties were obtained under cyclic confining pressures ranging from 12 – 52 MPa. This paper will document the final results of a long-term project that examined the differences between foamed cements generated with laboratory equipment and field foamed cementing equipment. The cement samples in this study were generated at pressure using field foamed cementing equipment as part of a joint effort between the API Sub-Committee 10 and the National Energy Technology Laboratory (NETL). The samples were characterized using helium porosimetry, ultrasonic velocity, and permeability measurements after they were depressurized. To test the variation in permeability and strength parameters of various foam cements, stepwise loading and unloading experiments were conducted. Effective pressures varied between ≈6.8 MPa to ≈46 MPa in ≈4 MPa increments. Permeability was measured at each effective pressure step to determine the change in flow pathways due to cyclic confining pressures. Dynamic moduli including Poisson's ratio and Young's modulus were calculated to determine the impact of effective pressures on the flexibility of the cement. The data shows that the cement's physical and mechanical behavior varied along the length of the sampling containers. During the initial loading of some of the samples, permeability decreased to a point lower than the initial permeability and stayed constant for the remainder of the pressure cycle, which was observed in previous experiments. However, some of the permeability values increased suggesting that the pressure cycles had permanently reconfigured the internal structure of the samples. Our approach to evaluating foamed cement is somewhat novel in that we have collaborated with the API, operators, and service companies, to obtain foamed cement generated at pressure using field equipment enabling a robust comparison to those generated in a laboratory per the API's RP 10-4B. Not only will the information provided by these comparisons help to facilitate the better design and implementation of foam cement generation processes but it will also help improve the understanding of the physical and mechanical behavior of foam cement.
Look-Ahead Vertical Seismic Profiling VSP Inversion Approach for Density and Velocity in Bayesian Framework
Authors: Daoud Ahmed M. , Abd El Dayem Muhammad A. 
Published: October 2018

Abstract
To reduce drilling uncertainties, zero-offset VSPs can be inverted to quantify acoustic properties ahead of the bit. In this work, we propose an approach to invert VSP corridor stacks in Bayesian framework for look-ahead prediction. The implemented approach helps to successfully predict density and velocity using prior knowledge from drilled interval. Hence, this information can be used to monitor reservoir depth as well as quantifying high-pressure zones, which enables taking the correct decision during drilling.
The inversion algorithm uses Gauss-Newton as an optimization tool, which requires the calculation of the sensitivity matrix of trace samples with respect to model parameters. Gauss-Newton has quadratic rate of convergence thus ensure speeding up the inversion process. Moreover, geo-statistical analysis has been used to efficiently utilizes prior information supplied to the inversion process. The algorithm has been tested on synthetic and field cases. For the field case, a zero-offset VSP data taken from an offshore well was used as input to the inversion algorithm. Well logs acquired after drilling the prediction section was used to validate the inversion results.
The results from the synthetic case applications were encouraging to accurately predict velocity and density from just a constant prior model. The field case application shows the high strength of our proposed approach in inverting VSP data to obtain density and velocity ahead of a bit with reasonable accuracy.
Unlike the commonly used VSP inversion approach for acoustic impedance using simple error to represent the prior covariance matrix, this work shows the importance of inverting for both density and velocity with using geo-statistical knowledge of density and velocity from the drilled section to quantify the prior covariance matrix required during Bayesian inversion.
Collaborative Real-Time Analysis to Reduce Non-Productive Time
Authors: Guidry Garrett , Spezia Kyle , Salmon Graeme 
Published: October 2018

Abstract
Operators often use real-time operation centers (RTOC) as a funnel point for data streams transmitted from multiple rigs during the well construction process. A RTOC is typically staffed by subject matter experts (SMEs), with the primary goals of interpreting real-time wellbore conditions and relaying actionable recommendations to help reduce nonproductive time (NPT) and well control incidents.
Automation is a strong industry trend. Autonomous systems are being developed to flag potential NPT events before they occur; however, these systems are not yet widely used. In the absence of these systems, workflows among complementary disciplines have been developed to identify potential NPT events in large data streams transmitted to a RTOC. This paper presents example scenarios from deepwater prospects with potential actionable recommendations.
Robust data streams transmitted to a RTOC can be received by the overlapping disciplines of hydraulics optimization, drilling optimization, and geomechanics. Staff from each discipline filter through the raw data to capture incoming information relevant to their respective output analysis. A key goal of each discipline is to mitigate the risk of NPT through real-time identification of warning trends observed during deepwater drilling in narrow pressure window situations. The multidisciplinary overlapping efforts produce a process that is much more effective than is possible with each discipline operating independently. Because real-time geomechanics seeks to update the bounding conditions of the downhole pressure operating windows, collaborative workflows are structured around validation and calibration of the real-time geomechanical model.
Collaborative workflows are presented for specific operations during the well construction process in which NPT events are likely to occur, such as tripping out of the hole and drilling. In the examples, real-time calculated equivalent circulating density (ECD) models, hole cleaning parameters, swab pressure models, and torque/drag plots provide input to the real-time geomechanical model. Outputs of this analysis are actionable recommendations, such as an extended flow check, check trip, or mud weight increase. The workflows were developed based on lessons learned from information in a central database and the resulting best practices from multiple deepwater wells.
Decision makers are provided with data-supported recommendations at crucial junctures; these recommendations typically involve costly rig time. The trade-off between increased rig time and benefits gained from the recommendation is difficult to quantify. The workflows derived from a library of NPT events address the perception of wasted rig time and provide context to real-time interpretations. Combined plots supporting the recommendation provide confidence for the driller that the increased rig time is time justified.
Mechanistic Modeling of Electrical Submersible Pump ESP Boosting Pressure Under Gassy Flow Conditions and Experimental Validation
Authors: Zhu Jianjun , Wang Zhihua , Zhu Haiwen , Cuamatzi-Melendez Ruben , Martinez-Farfan Jose Alberto , Jiecheng Zhang , Zhang Hong-Quan 
Published: October 2018

Abstract
As an artificial lift method for high-flow-rate oil production, electrical submersible pumps’ (ESP) performance surfers from gas entrainment, a frequently encountered phenomenon in ESPs. When it occurs, ESPs can experience moderate or severe head degradation accompanied with production rate reduction, gas locking and flow instabilities. For the design and operation of an ESP-based production system, the accurate model is needed to predict ESP boosting pressure under gassy flow conditions. In this paper, a simplified mechanistic model is proposed to model gas-liquid flow inside a rotating ESP. The model not only maps flow patterns in ESPs but also captures the multiphase flow characteristics in terms of in-situ gas void fraction, boosting pressure, bubble size, etc.
The experimental facility for testing ESP gas-liquid performance comprises of a 3″ stainless steel fully closed liquid flow loop and ½″ semi-open gas flow loop. A radial-type ESP with 14 stages, assembled in series, was horizontally mounted on the testing rig. Pressure ports were drilled at each stage to measure stage-by-stage pressure increment. The mixture of gas and liquid is separated in a horizontal separator, where excessive gas was vented and the liquid continues circulation. Experimental data were acquired with two types of tests (mapping tests and surging tests) to completely evaluate the pump behaviors at different operational conditions. The water/gas flow rates, ESP rotational speeds, intake pressure etc. were controlled in the experiments.
The new model starts form from Euler equations, and introduces a best-match flowrate at which the flow direction at ESP impeller outlet matches the designed flow direction. The mismatch of velocity triangle in a rotating impeller results from the varying liquid flow rates. Losses due to flow direction change, friction, and leakage etc., were incorporated in the model. Based on the force balance on a stable gas bubble in a centrifugal flow field, the in-situ gas void fraction inside a rotating ESP impeller can be estimated, from which the gas-liquid mixture density is calculated. The predicted ESP boosting pressures match the corresponding experimental measurements with acceptable accuracy.
An Efficient Probabilistic Assisted History Matching Tool Using Gaussian Processes Proxy Models: Application to Coalbed Methane Reservoir
Authors: Rana Sachin , Ertekin Turgay , King Gregory R. 
Published: October 2018

Abstract
Currently used assisted history matching algorithms such as differential evolution, particle swarm optimization etc. usually requires a large number of numerical simulation runs in order to converge to acceptable solutions. If each numerical simulation takes a long time to complete, these algorithms become inefficient. In this research, a new assisted history matching tool is presented that can provide multiple solutions of history matching in much less number of numerical simulations. The proposed tool uses Gaussian process based proxy models to provide fast approximate forward solutions which are used in Bayesian optimization to find history match solutions in an iterative manner. The uncertainty in history match solutions is quantified via MCMC sampling on trained forward GP model. In order to check for independence and convergence of the collected MCMC samples, auto-correlation plots and Geweke z-score diagnostic tests are also performed. The converged MCMC samples are then used to quantify uncertainty in EUR of gas reserves via a forecasting GP model. The proposed methodology is successfully applied to a synthetic heterogeneous coalbed methane reservoir. The code and data for this case study is also available online for future studies. The results show that history matching can be performed in approximately four times less number of numerical simulation runs as compared to state of the art differential evolution algorithm. Besides, the P50 estimate of EUR is shown to be in close agreement with truth values for the presented case study.