bluuebunny/crossref_metadata_2025_split huggingface dataset:
Understanding Wormholes in Carbonates: Unprecedented Experimental Scale and 3D Visualization
Authors: McDuff Darren , Jackson Shalawn , Shuchart Chris , Postl Dieter 
Published: June 2014

Technology Today Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering.
Abstract
Matrix acidizing experiments combined with visualization techniques commonly are used to study the details of wormhole networks formed during matrix acidizing of carbonate reservoir rock. Previous experimental studies of wormhole growth focused mainly on small linear core plugs, with only a limited number of radial-flow studies published in the literature. Results from these conventional experiments provided extensive information on linear 1D wormhole growth along with some basic insights into 2D radial growth mechanisms. However, larger-scale test systems must be considered if 3D wormhole characteristics are to be understood. Toward that end, a new method was developed that integrates acidizing experiments on carbonate rock samples up to 14 ft3 in volume, high-resolution nondestructive imaging and analysis, and computational modeling to extend the results of experiments to field applications. This article highlights the experimental and imaging components.
Introduction
Substantial hydrocarbon volumes have been and will continue to be produced from carbonate formations, which hold nearly half of the world's reserves. Because these formations are highly soluble in acid, matrix acid stimulation provides a cost-effective means to enhance well productivity. Effective acid stimulation can be critical to achieving the desired longterm production rates from targeted reservoir layers.
Interaction of acids with carbonate rock has been studied extensively using quarried, outcrop, and formation core samples. Linear flow tests on core plugs are conducted to determine the optimum conditions to generate wormholes (i.e., highly conductive flow channels that connect the nearwell region to the completion). At a given temperature, the ability of a particular acid to generate wormholes is largely dependent on the acid injection rate or ’acid flux,?? as illustrated in Fig. 1. The figure shows an example of a ’wormhole efficiency curve?? developed for core plugs of quarried limestone. As the curve indicates, there is a certain optimal acid flux for which wormholes will most efficiently propagate along the main axis of the core plug.
The Next Generation Top Drive and Lessons Learned from the TDX-1250
Authors: Pickett Jay , Saski Justin , Luher Robert , Cantrell Andre , Wallihan Brett 
Published: June 2014

Abstract
With all the emphasis today on the economics of improving well costs, the industry is faced with finding a way to provide marketable technology to drill more challenging wells even cheaper. The top drive stands out as one of a few key pieces of equipment in the critical path. As a result Top Drive failures have accounted for a large portion of down time, thereby increasing costs to drill a well, and the top drive is in essence "the drill" needed to reach reservoirs that are farther and deeper than once thought possible.
ExxonMobil needed to upgrade its drilling platform in the Yastreb field in order to reach reservoirs with very long, extended reach. Drilling these wells necessitated a need for more torque and speed. Typically these parameters are supplemented with downhole motors. However, in extended reach wells, failure 5,000 – 6,000 feet downhole costs up to a full day to retrieve the equipment and another full day to re-deploy the tool. With performance improvements to today's modern top drive, we have been able to increase torque and speed on the top drive and move that associated risk to the rig floor.
Today's ultra-deepwater drilling necessitates durable, maintenance friendly top drives to off-set the high day rate and spread costs associated with these wells. For that, top drives in this environment have taken a step-change to increase durability with larger main thrust bearings, larger main shaft connections, heavy-duty link tilt function, etc. In addition to this increased focus on durability, these machines also need to be repaired quickly to get them running again. This has created a new generation focused on maintainability, and modularity.
Anatomy of a Coalbed Fire: From Characterization to CO2 Pilot Injection Design at a Coal Fire Near Durango, CO
Authors: Ide S. Taku 
Published: June 2014

Abstract
Underground coal fires pose environmental, social, health, and economic hazards. Many coal fires burn persistently over time scales of many years to decades, despite efforts to control them. Results of research performed at a subsurface coal fire near Durango, CO, are used to delineate the life cycle of a natural coal fire. Methods to identify oxygen influx points (mapping of surface fissures), how these fissures are created (numerical simulations), combustion zone boundaries (subsurface temperature, surface snowmelt, and magnetometer data), and coal consumption rates (combustion product gas flux estimates) are described. Based on the locations of the mapped subsurface combustion zone, a CO2 pilot injection test was designed and conducted at this site. Results of this pilot project demonstrate that (1) air required to support continued combustion flows through a zone of fractured rocks that forms where coal has burned previously, (2) the primary driving force for air flow is the density-driven flow of hot combustion product gases through surface fissures that form as a result of subsidence as the coal burns, and (3) CO2 injected into the air flow zone is drawn by the density-driven flow into the combustion zone, replacing a portion of the air flow that sustains combustion. The pilot test results suggest that a CO2 injection scheme can be designed to control these fires if sufficient CO2 (or other inert gas) is available to reduce the oxygen flow to the combustion zone below levels required to support continued combustion, and if the combustion region can be cooled sufficiently to prevent resumption of the air flow when injection ceases.
Experimental Investigation of Spontaneous Imbibition in Fractured Reservoirs
Authors: Lee Chung-Hao 
Published: June 2014

Abstract
Spontaneous imbibition is the mechanism that allows oil recovery from the porous matrix due to the capillary migration of water into the water-wet rock. This mechanism is of particular importance to oil recovery from fractured reservoirs. The present work is one component of a multi-variable, experimental analysis of fracture matrix flow focus on the influence of injection rate and viscous forces in a rock sample with a single tensile fracture. Displacement of a non-wetting phase (gas or liquid) by sopntaneous imbibition was monitored using X-ray computed tomography. The impact of two different injection rates and three different fluid pairs on the resulting oil recovery and saturation maps is evaluated through visual and quantitative analyses. Experimental result shows relatively fast oil recovery and a sharp imbibing front at high injection rate (q=40mL/hr), while lower recovery rate and smoother saturation gradient was observed at low rate (q=4mL/hr) case. Water saturation in the imbibed zone remains constant suggesting a dynamic equilibrium in the mobility of immisible phases (air/water or oil/water). Co-current and counter-current flow mechanisms are evident from experimental observation at different fluid pairs where cocurrent flow dominates in the case of water displacing air, while countercurrent flow dominates in the case of water displacing kerosene. We also describe saturation profiles are highly sensitive to fluid properties. Results from this investigation provide a comprehensive set of data for the validation of numerical models and strengthen fundamental understanding of multiphase flow in fractured reservoir.
Openhole Gravel Packing of Fishhook Wells with Zonal Isolation- Uphill Heel to Toe Packing
Authors: Sulaiman Sateria , Jansen Rene , Brassart Philippe , Kumar Manish , Alexander Joe , Tibbles Raymond , Moses Nicholas , Nordin Amirul 
Published: June 2014

Abstract
The mode of gravel transportation in openhole packing is determined by the deviation angle of the interval - typically a gravity assisted (bottom up) mode occurs for deviations less than 50 degrees and alpha-beta mode for deviations exceeding 60 degrees. Experience in various fields in Brunei indicates a lower success rate when gravel packing intervals in the 50-60 degree deviation range using conventional gravel packing techniques. In fishhook wells, the critical 50-60 degree deviation range is equivalent to the uphill wellbore geometry 120-130 degree deviation range.
This paper discusses the technique used to gravel pack two fishhook wells with deviations of 126 and 131 degrees respectively. The objectives of the completions were threefold:
Achieve a complete annular pack, Provide the capability for zonal isolation Maintain bottomhole pressures below the fracturing pressure. Deliver a low skin completion.
The world's first successful Shunt tube uphill gravel pack in a fishhook well was executed in September 2010. The same type of completion was performed for a second time a few months later. Completion design, component optimization, fluid design, gravel pack simulation and downhole gauge analysis for these wells are discussed.
Well Deliverability Forecasting of Gas Condensate and Volatile Oil Wells below Saturation Pressure
Authors: Ogunrewo O. , Herens T. , Gringarten A. C. 
Published: June 2014

Abstract
Development of a condensate bank in gas condensate wells producing below the dew point pressure causes productivity losses as gas mobility at the wellbore is reduced. The same is true in volatile oil wells producing below the bubble point pressure due to the existence of a gas bank.
Using compositional simulation, this paper investigates the use of back-pressure plots expressed in terms of pressure, singlephase pseudo-pressure, and two-phase pseudo-pressure to describe well productivity losses below saturation pressure for gas condensate or volatile oil wells.
It is shown that the theoretical stabilized back-pressure deliverability straight line at krg =krgi cannot be obtained using pressure and single-phase pseudo-pressure back-pressure plots whereas it can matched with two-phase pseudo-pressures, provided that non-Darcy and capillary number effects are included in the two-phase pseudo-pressure calculations. Bottom-hole back-pressure plots using two-phase pseudo-pressures can then be used to quantify productivity and mobility reductions and to separate the effect of the bank from other effects such as multi-layering, thus allowing identification of appropriate remediation measures. These results are verified with data from actual gas condensate and volatile oil reservoirs.
The Upscaling of Discrete Fracture Models for Faster, Coarse-Scale Simulations of IOR and EOR Processes for Fractured Reservoirs
Authors: Hui Mun-Hong Robin , Mallison Bradley , Heidary-Fyrozjaee Mohsen , Narr Wayne 
Published: June 2014

Abstract
Improved and enhanced oil recovery (IOR/EOR) processes, such gas injection and waterflooding, are difficult to model accurately in fractured reservoirs due to complicated multiphase physics and the strong property contrast between permeable natural fractures and tight matrix rock. Traditionally, fractured reservoirs are modeled using coarse dual-porosity (DP) simulation models that idealize the fracture system. Consequently, important recovery physics can be missed, causing misleading flow predictions. We present an unstructured discrete-fracture-matrix (DFM) approach for three-phase, fully compositional simulations of IOR/EOR processes. We generate detailed DFM grids that represent several thousand realistic discrete fractures and different well configurations. These grids are then discretized for IOR/EOR flow simulations. We apply the flow-based multiple subregion (MSR) technique with two subregions to generate unstructured coarse-scale fracture models that are directly based on the DFM sector models. We next employ MSR upscaling to create corresponding structured DFM-based dual-porosity, dual-permeability (DPDK) models, computing parameters like shape factors and effective fracture permeabilities. We lastly generate conventional DPDK models by invoking simplifying assumptions and analytical equations. Using DFM results as reference solutions, we find the following order of decreasing accuracy: MSR, DFM-based DPDK, and conventional DPDK models. The DPDK models result in significant inaccuracies at individual wells when important fluid movement (e.g., gas breakthrough) is missed. The errors at sector scale are lower due to cancellation of errors at wells. The simulation results indicate that oil recovery and injected fluid breakthrough behavior are a complicated function of the reservoir heterogeneity, well configurations, and phase behavior. Large modeling errors can potentially lead to the selection of a sub-optimal injectant. One to two orders of computational speedup are achieved from the upscaling. These findings point to the need for systematic upscaling of realistic DFM representations to generate fast and accurate coarse fracture models for the assessment of field-development IOR/EOR schemes.
Monitoring Multilateral Flow and Completion Integrity with Permanent Intelligent Well Tracers
Authors: Abay Hailu K. , Garbhan Gibbons , Nyhavn Fridtjof , Husebø Signe 
Published: June 2014

Abstract
Optimizing production from a multilateral well requires understanding and characterization of the well and completion performance in the flow path from the reservoir to the separator. Situations when crucial information may be gathered includes transient flow phases such as cleanup and restart after shut-ins. Understanding the inflow from the near-wellbore into each lateral and monitoring the functionality of completion components are important tools in establishing completion effectivness and wellbore performance. This paper describes new applications of chemical tracers in multilateral horizontal wells and utilizes flowbacks in understanding cleanup efficiency, confirming inflow from the toe-section of long horizontal wells and monitoring the functionality of ICV components based on a case study on four multilateral wells in the Alvheim field, Norway.
A new generation of chemical tracers were embedded in a polymer matrix and installed in ICD screens on four long horizontal multilateral wells. In total, 27 unique oil tracers were used for 12 months of oil marking period designed for monitoring early production. The oil tracers were released when the tracers were in contact with oil and mobilized to topside sampling point with the produced fluids when the wells were opened for cleanup. The samples were analyzed in a laboratory and the tracer responses were used to study cleanup efficiency and to monitor ICV during sequential cleanup of laterals. The tracers were also used to understand the inflow contribution from the toe section of each lateral. The case study showed that intelligent well tracers provide a direct proof of contribution from the toe-sections of the multilateral wells and enabled monitoring of ICV functionality and synchronization.
Exploration of Media Convergence to Enhance Blended Training Effectiveness
Authors: Lee Roger K. , Krause Brad 
Published: June 2014

Abstract
Today's oil and gas industry has become even more challenging and demanding. Operational optimization has long been a primary performance metric, and there is a renewed focus on safety and accountability. Core to these requirements is the training needed for individuals to gain the necessary competencies to perform operational tasks safely and consistently.
Therefore an important question arises: What is the most effective method for teaching drilling procedures and operations to a diverse population of field personnel? Instructor-led training (ILT) is the most commonly used format and is often limited to the use of presentation slides in a classroom leading to a gap between the learning that occurs in the classroom and the application required on the job site. The preferred format is "on-the-job training" (OJT) where learning occurs at the job site with the actual tools and components. The approach is complicated as it requires trainees to be present on a job site, which may lead to inefficiencies and safety issues.
To address the challenge, the oilfield service organization completed an initiative to bring the job site to the classroom. The strategy focused on creating and applying documentaries, short films, and video clips for enhancing training effectiveness. Central to the strategy was the utilization of interactive exercises and activities associated with the videos ensuring the learners were actively engaged. This paper explains the project plan created to identify the video products needed, the resources required to produce the video, and the plan to complete the job.
Temperature Prediction Model for a Horizontal Well with Multiple Fractures in a Shale Reservoir
Authors: Yoshida Nozomu , Zhu Ding , Hill A. D. 
Published: June 2014

Abstract
Downhole temperature measurements either by permanent sensors or temporarily conveyed tools provide information that has been used in many production diagnosis applications. This paper presents a study that correlates the temperature behavior to the flow profile in a multi-stage fractured horizontal well. The ultimate goal is to interpret well performance and to optimize fracture treatment design from monitored temperature data.
This study has developed flow and thermal models for horizontal wells with transverse fractures. The system was divided into a horizontal wellbore and a reservoir having multiple fractures in the study. The wellbore flow and thermal model were formulated based on mass, momentum and energy balance. Numerical reservoir simulation was adopted for the reservoir flow problem, and the reservoir thermal model was formulated by a transient energy balance equation considering viscous dissipation heating and temperature variation caused by fluid expansion besides heat conduction and convection. In the reservoir system, the primary hydraulic fractures perpendicular to the horizontal well were modeled with thin grid cells explicitly, and the fracture network around the horizontal well was modeled as an enhanced permeable zone with respect to the unstimulated matrix permeability. The reservoir grids between two fractures were logarithmically spaced to capture transient flow behavior. The reservoir flow and thermal model was coupled with the wellbore model to predict the temperature distribution in a horizontal wellbore. The results of the model show two main mechanisms in this thermal problem: heat conduction by formation heating/cooling effects at non-perforated zones, and wellbore fluid mixing effects with reservoir inflow at fracture locations (fluid entry points).
The examples in the paper illustrated that the models can be used to predict temperature profiles in stimulated horizontal wells for identical or non-identical transverse fractures. Sensitivity studies were performed to evaluate the influences of fracture conductivity and half-length on temperature behavior in the defined system. The results indicate that the wellbore temperature is primarily sensitive to fracture geometry (fracture half-length). It is possible to interpret the fracture geometry using temperature data after the flow rate is stabilized after certain period of production. In addition, wellbore temperature is also sensitive to fracture conductivity. However, the signal of high fracture conductivity diminishes, and after the surface flow is stabilized, the signal might not be identified by temperature measurement. Real time temperature data measurement is helpful for the evaluation of fracture conductivity.
Predicting Porosity and Permeability of Carbonate Rocks From Core-Scale to Pore-Scale Using Medical CT, Confocal Laser Scanning Microscopy and Micro CT
Authors: Shah S.M. , Yang J. , Crawshaw John P. , Gharbi O. , Boek Edo S. 
Published: June 2014

Abstract
Carbonate rocks have a very complicated and heterogenous porous structure in comparison with sandstone reservoir rock. To understand the transport processes in any porous medium, we need to enhance our knowledge of the geometry and topology of the porous media. Therefore, in this work we present advances with different multi-scale imaging techniques to obtain 2D and 3D images from core-scale (1mm) using Medical CT scanning to pore scale (1- 10µm) using Confocal Laser Scanning Microscopy (CLSM) and Micro CT imaging. First, we have developed a novel technique of CLSM to obtain 2D images with a large field of view, which is advantageous for scanning heterogenous carbonate rocks. We have obtained statistical data about total, macro and micro-porosity from 2D large field of view CLSM images and have validated the results using mercury intrusion capillary pressure (MICP) data. Second, we have obtained initial results using our Medical CT scanner for spontaneous imbibition of water in carbonate cores and measured the water saturation as a function of time. Also we have observed and compared the capillary heterogeneity in a simple sandstone core with a heterogeneous carbonate core sample. Finally, we have obtained 3D pore scale images of carbonate samples using our Micro CT scanner at different resolutions. By using image processing techniques for different phase segmentations, we study the effect of resolution on the measured porosity and permeability using Lattice Boltzmann simulations and pore network models. This gives valuable information about pore-throat connection and pore-throat sizes. Finally, we correlate the data for porosity and permeability for different carbonate rock samples taken at different resolutions.
Drilling Hazards Inventory: The Key to Safer -and Cheaper-Wells
Authors: Hoetz G. , Jaarsma B. , Kortekaas M. 
Published: June 2014

Abstract
Safety and cost control are critical success factors in the realm of drilling. Actual well costs frequently exceed planned costs due to unexpected drilling incidents related to potentially avoidable geohazards. It is estimated that - in the Netherlands on average - around 20% of drilling time is spent recovering from such unexpected incidents. A significant part of this non-productive time (NPT) can be avoided if geohazards are identified upfront.
The risk assessment for a well trajectory is largely based on the experience from offset wells: boreholes in the neighbourhood that have been drilled earlier or holes drilled through similar geological settings. Easy access to relevant historic drilling data and the records of geohazards encountered in offset wells is essential for effective de-risking of future drilling programs. Currently operators typically have their own databases containing this type of information. However, their databases are often incomplete and lack data from competitor wells. Obviously, the risk assessment would greatly benefit from access to a complete set of drilling hazard data, whilst making use of "best practices" in data analyses and incident classification.
EBN B.V., the Dutch state E&P company with 0.5 million BOE/d equity production, is involved in most of the 40+ wells being drilled annually in the Netherlands. Recognising its major vested interest in improved drilling performance, EBN launched a Joint Industry Project to capture the knowledge of drilling hazards across the Industry. An important tool to classify drilling incidents is the Drilling Incidence Triangle. Based on this new concept, those drilling incidents that have a geological component are selected, analysed and made accessible for the Industry partners.