bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Production Log Data from Horizontal Wells Drilled in Organic Shales
Authors: Miller Camron , Waters George , Rylander Erik 
Published: September 2011

Abstract
Production logs from more than 100 horizontal shale wells in multiple basins have been acquired and interpreted. An evaluation of this data set confirms that production is highly variable along the length of the wellbores. In some basins, two-thirds of gas production is coming from only one third of the perforation clusters. Furthermore, when looking at all basins, almost one third of all perforation clusters are not contributing to production. This highlights a significant opportunity to improve overall completion effectiveness and economics in these high profile projects.
Observations of near-wellbore reservoir quality and completion efficiency can be attained from the analysis of this data. Rock properties such as mineralogy, natural fracture density, and closure stress in the near wellbore region impact reservoir quality and hydraulic fracture conductivity. Completion parameters such as the staging of stimulation treatments, the number of perforation clusters per frac stage, and perforation cluster spacing can all impact the productivity of an individual perforation cluster. Correlations between productivity and key geologic, petrophysical and completion parameters can be made. The result is a better understanding of the parameters that are controlling completion effectiveness, and corresponding productivity in horizontal organic shale wells.
Numerical Simulation of Shale-Gas Production: from Pore-Scale Modeling of Slip-Flow, Knudsen Diffusion, and Langmuir Desorption to Reservoir Modeling of Compressible Fluid
Authors: Shabro V. , Torres-Verdin C. , Javadpour F. 
Published: September 2011

Abstract
We combine a new pore-scale model with a reservoir simulation algorithm to predict gas production in gas-bearing shales. It includes an iterative verification method of surface mass balance to ensure real-time desorption-adsorption equilibrium with gas production. The pore-scale model quantifies macroscopic petrophysical properties of formations using an algorithm of gas transport in porous media that simultaneously considers the effects of no-slip and slip flow, Knudsen diffusion, and Langmuir desorption. Subsequently, the reservoir model populates petrophysical properties derived from the pore-scale analysis at every numerical grid and at each time-step to calculate the production history and pressure distribution in the reservoir. This approach examines the contribution of different transport processes (i.e. advective flow, Knudsen diffusion, and desorption) to quantify their corresponding contributions to overall flow. Previously, we showed that slip flow and Knudsen diffusion play a significant role in explaining the higher-than-expected permeability observed in shale-gas formations with pore-throat sizes in the range of nanometers. It is shown that Langmuir desorption from organic-matter surfaces is important in the calculation of stored gas in gas-bearing shales. Modeling results show that gas desorption maintains the reservoir pressure via the supply of gas. In comparison to conventional reservoir descriptions, the contributions of slip flow and Knudsen diffusion increase the apparent permeability of the reservoir while gas production takes place. The effects of both mechanisms explain the higher-than-expected gas production rates commonly observed in these formations.
Transmission and Scanning Electron Microscopy Investigation of Pore Connectivity of Gas Shales on the Nanoscale
Authors: Curtis Mark E. , Ambrose Ray J. , Sondergeld Carl H. , Rai Chandra S. 
Published: September 2011

Abstract
Shale reservoirs represent a significant and increasing portion of natural gas production within North America. In order to better understand gas deliverability of these reservoirs, the flow paths and their connectivity within shales need to be understood at a fundamental level. The pores within gas shales are on the nanoscale and below optical resolution. This necessitates methods such as electron microscopy to image them. Recently, the introduction of Focused Ion Beam/Scanning Electron Microscopy (FIB/SEM) technology to the petroleum industry has enabled the imaging of these nanoscale pore structures in three dimensions (3D) for the first time. Imaging of 125 μm3 shale volumes has been performed on different gas shales and the pore systems within these volumes have been reconstructed. Throughout our investigations it has been difficult to obtain pore connectivity across the reconstructed shale volumes. High pressure mercury injection capillary pressure (MICP) measurements on gas shales suggest that the connections between many of these pores are less than 2 nm. Because the size of the smallest pores and pore throats detected within gas shales approaches the resolution limits of SEM, higher resolution techniques must be employed.
Transmission electron microscopy (TEM) can image the internal structure of thin shales specimens and enables much higher resolution imaging than SEM. Utilizing this imaging technique in conjunction with other methods we discuss our investigations of pores and their connections that are below the SEM imaging resolution used in previous studies. Initial imaging suggests that isolated pores previously imaged with the SEM exhibit connectivity. It is the connections of pore spaces that control the gas flow in shales and such insights will have far reaching implications in better understanding this flow.
Drilling Performance Improvements in Gas Shale Plays using a Novel Drilling Agitator Device
Authors: Barton Steve , Baez Franklin , Alali Aref 
Published: September 2011

Abstract
High friction of the drill string against the wellbore has become a concern in the process of drilling, irrespective of whether it is a vertical, directional or horizontal application. This source of additional torque and drag will lead to low rates of penetration, poor tool face control, short runs, severe drill string and bit wear, and at the same time, could cause problems while running casing, liners and completions. In directional and horizontal applications, this high friction could also lead to high well tortuosity, which will limit the amount of step out and can even impair productivity.
The implementation of a unique tool, referred to as a Drilling Agitator Tool (DAT), has demonstrated clear improvement in drilling performance by reducing stick slip and torque at the drill string. This has enabled reduction in drag and thus improved weight transfer to the bit when drilling through highly interbedded formations, directional applications or long horizontal sections. It has also shown greater accuracy in maintaining tool face control once the static friction was minimized. This DAT relies on three main mechanisms: a power section, a valve and bearing section, and an excitation section. The tool operation vibrates the drill string with a low frequency and low amplitude axial vibration.
This paper illustrates case studies from the Haynesville, Fayetteville and Barnett Shale Plays, where the DAT has proven to help reduce torque and Stick-Slip when run on rotary in vertical applications, as well as Motor assemblies through directional and horizontal sections. These improvements in drilling performance have resulted in longer runs and faster rates of penetration compared to offset wells, thus reducing the number of bits and improving the economics in drilling these shale plays.
Reservoir Engineering for Unconventional Gas Reservoirs: What Do We Have to Consider?
Authors: Clarkson C. R. , Jensen J. L. , Blasingame T. A. 
Published: September 2011

Abstract
The reservoir engineer involved in the development of unconventional gas reservoirs (UGRs) is required to integrate a vast amount of data from disparate sources, and to be familiar with the data collection and assessment. There has been a rapid evolution of technology used to characterize UGR reservoir and hydraulic fracture properties, and there currently are few standardized procedures to be used as guidance. Therefore, more than ever, the reservoir engineer is required to question data sources and have an intimate knowledge of evaluation procedures.
We propose a workflow for the optimization of UGR field development to guide discussion of the reservoir engineer's role in the process. Critical issues related to reservoir sample and log analysis, rate-transient and production data analysis, hydraulic and reservoir modeling and economic analysis are raised. Further, we have provided illustrations of each step of the workflow using tight gas examples. Our intent is to provide some guidance for best practices. In addition to reviewing existing methods for reservoir characterization, we introduce new methods for measuring pore size distribution (small-angle neutron scattering), evaluating core-scale heterogeneity, log-core calibration, evaluating core/log data trends to assist with scale-up of core data, and modeling flow-back of reservoir fluids immediately after well stimulation. Our focus in this manuscript is on tight and shale gas reservoirs; reservoir characterization methods for coalbed methane reservoirs have recently been discussed.
Minimising HSE Impacts During Design and Construction of a Major Gas Pipeline Through the Baltic Sea
Authors: Valeur Jens Rosendal , Strøbæk Neel , Andersson Nicklas 
Published: September 2011

Abstract
During the period 2010-2012, two parallel gas pipelines (the Nord Stream Project) are being installed in the Baltic Sea, between Vyborg in Russia and Greifswald in Germany. The pipeline system will enable an annual transport of 55 bcm of natural gas from the large Russian gas fields to the European gas grid.
Comprehensive environmental and safety studies were carried out already in the design phase. The outcome of these studies was used in iterations with the pipeline design process, ensuring that the final pipeline design has minimal impact on the environment as well as on human activities in the Baltic Sea. Also, due consideration has been given to ensuring the health and safety of construction personnel and minimizing the environmental impacts during construction.
Major changes to the design were made in order to minimise project impacts, i.e.
– An originally planned intermediate service platform was "engineered out", eliminating the risk of ship collisions in the operation phase, – The pipeline route was optimised to avoid sensitive nature areas and heavily used ship traffic routes, – Extensive geophysical surveys were carried out in order to identify and mitigate interaction with dumped chemical and conventional munitions and cultural heritage objects, – It was insured by theoretical analysis verified by measurements that the pipeline with the chosen route did not have a negative impact on inflow and mixing of water in the Baltic Sea, – Environmental monitoring and subsequent feedback to the construction vessels were carried out during seabed intervention works near sensitive habitats.
Unique for this project is the major design changes that have taken place as a result of the HSE analysis. One outcome of this has been that all five affected countries have given permit to the project in a relatively short time period, even though it is the first major pipeline project in the Baltic Sea.
The State of Business Continuity Preparedness In The Supply Chain – An Operator's View
Authors: Wright Boyd , Teed David 
Published: September 2011

Abstract
Centrica's analysis of business risk confirmed several years ago that reliance on key contractors and its supply chain brought significant threats to the business. Centrica's business model reflects a similar exposure to that faced by other operators in relation to the dependency upon the major contracting companies, although Centrica also "contracts out" duty holdership of two of its producing platforms in the North Sea. We therefore recognized quite early on in our business continuity management programme that we could be exposed to an operational disruption through one of our key suppliers not having effective plans in place to cope with an incident that causes an unexpected loss of resource. During the past 3 years we have carried out regular supplier continuity reviews, with some interesting results. This paper outlines the issues and risks that should be understood by other operators and their suppliers to ensure that, as an industry, we can safeguard our credibility and the continuity of operations.
Practical interview, workshop and exercise methods have been effectively utilized to gain an appreciation of the maximum levels of service disruption that we could be exposed to. Our key contractors are scored on their level of business continuity preparedness. Appropriate risk mitigation activity was then identified to help reduce the likelihood or impact of a serious disruption to our operations.
This ongoing review has proved extremely useful for our management team to appreciate the actual state of preparedness of key contractors and identify any weak links in the supply chain. A common attitude expressed by suppliers showed an element of "risk blindness", often stated as: "we will just deal with the situation, should it ever happen". It is essential that the benefits of pre-planning become more widely appreciated, otherwise our industry could face some unwelcome impacts as the result of future incidents.
Being seen to manage an effective response and recovery, when faced with an unexpected event, is not only important for the credibility and sustainability of individual organizations but also for their customers, partners and the industry as a whole. This paper also includes some useful learning points in relation to how other industries have successfully addressed business continuity in their supply chains.
Component Inspection and Repair Using 3D Modelling Photogrammetry Technology
Authors: MacCormick Marie , Hall Anthony , Trower Alastair 
Published: September 2011

Abstract
3D modelling photogrammetry technology uses high-quality digital still images to construct geometrically accurate 3D models suitable for detailed measurements, Finite Element Analysis, 3D printing, and comparison to as-built components. Model manipulation and construction of interior geometry can also be performed to generate alternative configurations if needed.
Photographs are collected either subsea or topside, and pixels are matched between overlapping images to produce a 3D point cloud representing the component geometry. The point cloud is refined using the least squares method to achieve a model accuracy of better than 1mm under ideal conditions.
Resulting models can be exported in a variety of formats that are compatible with 3D drafting or Finite Element Analysis software packages. Image overlay can be applied to the models to better identify points-of-interest.
Welaptega has used this technology for a variety of applications, including:
Riser corrosion: the surface of a topside section of a heavily corroded riser was 3D modeled to determine corrosion depth and evaluate the riser's fitness for operation. Flange alignment: Leaking mating pipe flanges were 3D modeled to determine if misalignment was the source of the leak. The relative orientations of the flanges were determined by aligning a plane with each flange. Pipeline curvature analysis: An18-inch natural gas pipeline was impacted and dragged by an anchor, resulting in a dent and an unknown degree of curvature. A 3D model of the section of pipe surrounding the point of impact was constructed to determine the radius of curvature and perform finite element analysis. FlexJoint inspection: 3D models were constructed of FlexJoints in support of a regular inspection program. Points-of-interest and signs of wear were identified, measured, and monitored for progression using the 3D models. Wellhead repair: A wellhead was damaged when impacted by a falling Blow-out Preventer during recovery operations. A 3D model was constructed of the wellhead, and imported into design software for comparison to as-built drawings. The 3D model was also used to design a bespoke Internal Tree Cap hold-down tool to ensure well integrity.
In all cases, the 3D models provided critical information about component conditions, enhancing clients’ abilities to make decisions regarding repair.
Drilling Challenges in the North Atlantic Margin
Authors: Bagala S. , Getliff J. , Zaske J. , Watt I. 
Published: September 2011

Abstract
Chevron and its Partners are facing several challenges in the North Atlantic Margin exploration and development. These challenges affect drilling design and operations, which should take in account several important factors occurring concurrently in this area: deepwater conditions;complex lithological sequence and target imaging uncertainty;geomechanical conditions.
Hole section design is strongly affected by the uncertainty of the subsurface data, in particular the seismic data, where the presence of thick basalt flows, as strong reflectors, induce relatively poor seismic imaging of intra–basalt or sub–basalt drilling targets. This issue is mitigated with contingency plans for final hole section size and casing string setting depths. The complex lithological sequence, geomechanical conditions and lithological uncertainty also affect drilling fluid design and bit/bottom hole assembly (BHA) selection. The consideration of some of these factors had the outcome of using thixotropic muds to counter serious lost circulation events. A further successful outcome was the design and implemention of riserless drilling techniques, a first for Chevron Upstream Europe and Halliburton Baroid UK, to counter the threat of shallow water flows in the top hole sections. The paper demonstrates how a multi – disciplinary approach in both drilling design and operations is beneficial to successful drilling optimization in the North Atlantic Margin, a geographically and geologically challenging area.
Applying Fault-Tolerant, Hot Swappable Control Architectures in Subsea Environments
Authors: McLin Rick 
Published: September 2011

Abstract
Topside oil and gas installations have relied on control and safety system architectures for fail-safe, fault-tolerant, hot-swappable hardware for many years. But such systems have not been available for subsea installations – until recently.
The concept of a hot swappable subsea control or safety system may seem strange. After all, replacing failed subsea hardware usually entails shutting down underwater production, sending a surface vessel to the site and deploying a ROV to make repairs.
But the recent development of new system architectures has led to the creation of subsea versions of topside systems that can tolerate multiple faults, without compromising control or safety functions. These new systems also offer the capability to hot swap failed hardware.
West Franklin - How Geophysical Tenacity Led a Modest Franklin Satellite to a Full-Blown Field Development
Authors: Patel Kailesh , Ugolini Jean-Marc , Millancourt Francois-Jean , Falconer Chris , Soyeur Christophe , Neillo Valerie 
Published: September 2011

Abstract
The West Franklin HP/HT Field discovered in 2003 by the well 29/5b-F7z was drilled on a simple structure defined using the 1996 Elgin/Franklin 3D seismic - vintage data which has since been superseded by state-of-the-art seismic processing techniques. The original PSTM displayed relatively continuous seismic reflectivity with large uncertainty on imaging and interpretation.
The highly productive porous sandstone interval within the Upper Jurassic Fulmar Formation was identified as a high amplitude reflector due to a strong decrease in impedance. Anisotropic PSDM processing followed by an acoustic inversion study highlighted the probable extension of this ‘Porous Zone’ to the west and underlined the high potential for a second appraisal/development well.
Positive results from the second well 29/5b-F9y in 2007 showed dramatic thickening and improvement in reservoir quality to the west and initiated additional PSDM processing of the original 1996 data. Following developments in tomography and migration algorithms, strong imaging improvements were observed from the integrated anisotropic velocity model updates and by reducing the amount of destructive interference from multiples. The resulting interpretation allowed for a better understanding of the salt tectonics and in predicting Fulmar reservoir thickness to the west.
A 7km Long Offset 3D survey acquired by CGGV in 2009 with subsequent PSDM processing is bringing further imaging improvements over areas of amplitude degradation leading to potential upsides. A first 4D monitor acquisition over Elgin/Franklin in 2005 (before production had started on West Franklin in 2007) is being followed-up by a second 4D monitor in 2011, aimed at providing additional information on the depletion pattern around the field. Such strategy in ongoing investment in seismic data will further unlock the resource potential over and around West Franklin in the coming years, ensuring a mature area remains in the spotlight.
Ageing Infrastructure Offshore - A Risk-Based Approach to Supporting Investment/Divestment
Authors: Flint Marcus , Angelsen Sture , Amundsgård Øyvind 
Published: September 2011

Abstract
With increasing focus on the state of offshore installations as many approach and often exceed their original design life, there is a need for practical and cost effective methods to assess facility condition and assist operators and authorities in making decisions about the future investment / divestment of these assets. This paper presents one technique being developed and used by DNV for this requirement.
Normal asset integrity and condition assessments concentrate on work processes of the organisation which, though valuable, do not produce quantified results for decision making, or they concentrate on very detailed equipment assessment based on RCM or RBI techniques which can provide information, but take a long time to complete.
The technique outlined in this document provides an efficient methodology to develop a semi-quantitative result. This is sufficient in many cases to make the major decisions necessary to support Opex and Capex budgeting for continuing operations or to support the technical due diligence for change of operatorship in acquisition or divestment.
Using straightforward tools and principles, the paper leads through the top down approach covering: the consideration of current systems and their operational status; consequences of failure in terms of safety, production and environment, and how reliability and obsolescence are taken into account. Together these factors enable a risk ranking to be established which prioritises future budget and work requirements.
Inputs to the process are taken from a combination of historical operations and maintenance records, on-site examination of equipment and direct experiences of selected site personnel. Through these means, the technique combines a desk study with important buy-in of the local operations staff.
Samples of recent work in Africa and elsewhere will be demonstrated and refinements to the technique and other possible applications will be discussed.