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Collaborating Authors
Geostock
Abstract Structural geology (a branch of geology aiming at describing the structures – joints, faults, folds, etc. – at various scales) can be used in the field of rock mechanics and rock engineering, and particularly in underground engineering works (tunnelling and rock caverns) to gather more reliable data for empirical stability analyses and deterministic calculation models. Methods of structural geology are presented and their applications in rock mechanics/rock engineering are highlighted in particular through the observation of faults and joints arrest. Structural geology allows a better understanding of the origin, the chronology and the mechanical behaviour of discontinuities, and therefore a more accurate rock mass characterization and rock mass classification, as well as a validation of the actual stress regime. Examples selected from different countries of using structural models are also given with emphasize on the necessity and the way to build a 3D model at each stage of an underground project, from site selection to investigation and construction, to ensure the quality and validity of rock mechanical data and assumptions. Introduction In the last five years, several publications and oral presentations insisted on the importance of structural geology in the field of rock mechanics (e.g. during Sinorock 2009 in Hong Kong or the ISRM congress in Beijing in 2011). They highlighted the necessity of using structural geology and structural data as input parameters for rock mass characterization and rock mass modelling. This wish is praiseworthy and corresponds to a real need. The situation is due to the lack of structural geologists on the market: structural geology being less taught in university and often replaced by engineering geology, geologists or engineering geologists are easily involved in big projects (e.g. dams, hydropower plants, tunnelling, etc.) whereas it is nowadays quite uncommon to meet structural geologists in teams in charge of design, modelling or even supervision of site works. In addition, most structural geologists are academics and very few are full-time practitioners, especially in the field of rock mechanics. This short paper cannot be exhaustive but set out the various possibilities offered by structural geology. The objective is less ambitious and is limited to the presentation of practical examples in different geological situations in which a structural knowledge can provide a real help for modelling or for characterizing the rock mass through the two most geology-based rock mass classifications, the Q system (Barton et al. 1974) and the RMR (Bieniawski 1989). Since the vocabulary also acts as a brake, this paper deliberately uses simplified technical vocabulary and concepts, hoping that this will bring rock mechanical engineers to working closer with structural geologists.
- Geology > Structural Geology (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
ABSTRACT During feasibility and design stage, for large underground rock caverns, through an integrated investigation approach an interpretative geological model is developed with geologically critical areas predicted as geological hotspots for special interventions during construction. The initial geological model developed - which is essentially a structural model evidencing major faults, fractured zones and dykes - is updated continuously during construction of water curtain system and main cavern with focus on geological hot spots through an active design process. This active design process involves additional investigations during construction for hot spots, 3D geometrical analysis, geotechnical assessment of the cavern and verification of rock supports by detailed geotechnical back analysis using actual excavated data from water curtain and cavern heading. The geological model is improved and updated further after cavern heading and at every stage of benches for prediction of likely adverse conditions, if any, in the next benches. The predictive assessment is corroborated by observed geotechnical monitoring results; and for segments with abnormal deflections, FEM analysis is performed. The present article outlines the review and updation process of predictive structural analysis and geological models for large underground rock cavern excavations being practised in execution of one such storage project in India with an objective to reduce exposure to underground risks and ensure preparedness to address adverse scenarios.
Snubbing Operations Using Hydraulic Workover Unit Successfully Deploys Expandable Liner Hangers Into Gas Storage Wells
Gregoire, Nicolas (Fluxys) | Ricaud, Yves (Geostock) | Bossewinkel, Wim (Halliburton) | De Clute-Melancon, Daniel Aaron (Halliburton) | De Vries, Albertus N. (Halliburton) | Van Wonderen, Marc (Halliburton)
Abstract When wells exhibit fluid-loss problems, lower completion scenarios that employ conventional liner hangers and inflatable annulus packers often exhibit problems as well. These scenarios can include 1), the occurrence of gas migration through the cement, and 2), liner-top, packer-seal failure. To prevent these problems from occurring in two gas storage wells, expandable liner hangers (ELH) that can provide gas-tight seals without requiring liner cementation were suggested. The ELHs have elastomeric elements bonded to the hanger body to provide anchoring and sealing capacity. As the hanger body is expanded, the elastomeric elements are compressed in the annular space, eliminating the casing annulus and providing liner-top pressure integrity. This scenario would provide a more effective solution for the problems experienced with conventional methods. The major challenges were how to deploy the two liner hangers into the two wells with a hydraulic work-over (HWO) unit and how to snub them into the hole with well pressure on the annulus. This paper will describe how a conventional rotary drilling rig was used to drill into the top of the well, and a snubbing unit used to drill into the reservoir section and then used to deploy the expandable liner hangers. To verify the adequacy of the deployment system design, a "Complete-the-Well-On-Paper" (CWOP) exercise was followed by a pre-job trial with the HWO unit. The ELHs were run through the unit to double check space out and potential for damage from the HWO slips with complete success. The next step was to run the equipment on location and into a live well. The case history will describe how the challenge to deploy and set the two expandable liner hangers with an HWO unit was met successfully. Introduction An onshore operator in Continental Europe is involved in natural gas transport, transit grid, and storage infrastructure. Storage capacity is provided for shippers so that they will have a buffer that allows the continued supply of gas to customers to meet demand. Storage services include not only storage capacity but also injection capacity and send-out capacity to fill and empty the storage facilities. The underground storage for the high calorific gas is in buffers in aquifers. The working storage volume is presently 600 million normal cubic meters of natural gas, but the client planned to expand the underground storage capacity by 15% over a four-year period. The working volume of 600 million cubic meters would then increase significantly. The send-out capacity would increase from 500,000 to 625,000 normal cubic meters per hour, and injection capacity would increase from 250,000 to 350,000 normal cubic meters per hour. To expand the existing gas storage capacity, additional injection /production wells were needed. Thus, a drilling campaign for two wells to penetrate the reservoir was planned for December of 2007. The reservoir formation is a fractured limestone, and therefore, there was a strong possibility that severe total losses combined with gas on surface while drilling the reservoir would be experienced. Maximum gas pressures were expected to be up to 150 bar. For safety reasons, the wells were to be drilled in two different phases. The planned strategies for each of the two phases follow.
- North America > United States > Texas (0.28)
- North America > Canada (0.28)
- Europe > Norway > Norwegian Sea (0.24)
Underground Storage In Sydney, Some Uncommon Rock Mechanics Features of an Uncommon Project In Australia
You, Thierry (Geostock) | Kandel, Jean Claude (Geostock) | Gatelier, Nicolas (Geostock)
ABSTRACT Underground hydrocarbons storage is a very specific domain for the designer. He is usually free to adjust the section, shape and layout to cope with the geological and geotechnical conditions. This paper presents a panorama of the geotechnical design of mined underground storage caverns, then lists a number of uncommon features encountered in a storage excavated in Sydney, Australia, the Elgas LPG project that had to face major non-isotropic conditions with numerous local variations, impacting on the achievement of the design profiles. Changes in geotechnical design methodology and practice are examined through this project, now in operation, which will have lasted altogether almost ten years. ZUSAMMENFASSUNG Die untertaegige Speicherung von Kohlenwasserstoffen unterliegt in der Planung sehr spezifischen Bedingungen. Der planende Ingenieur hat bei der Dimensionierung und Formgebung der Speicherhohlraeume gewisse Freiheiten, muss jedoch vorgefundene geologische und geotechnische Bedingungen beruecksichtigen. Der vorliegende Beitrag gibt zunaechst einen allgemeinen Ueberblick ueber die geotechnische Planung von bergmaennisch aufgefahrenen Speicherhhohlraeumen. Darueber hinaus werden Besonderheiten betrachtet, mit denen das Elgas LPG-Speicherprojekt in einer bergmaennisch aufgefahrenen Kaverne in Sydney, Australien konfrontiert war. Hierbei ging es um die Beruecksichtigung anisotroper Bedingungen mit zusaetzlichen Heterogenitaeten im Gestein und den daraus erwachsenden Schwierigkeiten, die geplante Hohlraumform zu verwirklichen. Ueber einen Zeitraum von fast 10 Jahren, in denen das jetzt in Betrieb befindliche Projekt unterschiedliche Betriebsphasen durchlaufen hat, wurden verschiedene geotechnische Entwurfsverfahren auf ihre Anwendbarkeit geprueft. RESUME Le stockage souterrain d'hydrocarbures est un domaine très specifique pour le concepteur, car celui-ci dispose d'une large liberte pour adapter les sections, les formes et les implantations aux conditions geologiques et geotechniques de l'environnement choisi. Après un panorama de la conception geotechnique des stockages souterrains d'hydrocarbures par la methode dite des cavites minees, l'accent sera mis sur un certain nombre de particularites rencontrees lors du projet de stockage de GPL de Elgas à Sydney en Australie, creuse dans de très fortes conditions d'anisotropie du massif rocheux, avec de nombreuses variations locales et toutes les implications que cela peut avoir sur le maintien des formes. L'evolution des approches methodologiques geotechniques durant la dizaine d'annees de developpement de ce projet depuis les premières etudes jusqu'à l'exploitation actuelle est egalement presentee. 1. General description of geotechnical design of mined storage The design of underground LPG storage in mined caverns has been presented in various papers [1] [2] [3] [4] with reference to their stability and product containment criteria. In the following, a brief overview of some of the main geotechnical features relating to the design of stable underground caverns in difficult conditions is presented [5]. While the task of the geotechnical engineer or design team for storage caverns is in many ways comparable to that of designers of related works such as tunnels, it can be thought of as being easier in some aspects and more difficult in others. The task is made easier because:the site will usually have been selected in good engineering ground, the designer is generally free to choose the most appropriate layout, especially the geometry and the orientation of the tunnels, cross-sections and locations can be matched to the local geological conditions. (Figure in full paper) In contrast, it is harder because of:the importance of the required hydrodynamic containment conditions (for example, groundwater pressure drawdown when a pervious feature is encountered may not be allowed)
- Reservoir Description and Dynamics > Storage Reservoir Engineering > Natural gas storage (1.00)
- Facilities Design, Construction and Operation > Natural Gas Conversion and Storage > Liquified natural gas (LNG) (0.95)
- Reservoir Description and Dynamics > Reservoir Characterization > Reservoir geomechanics (0.84)
Abstract The reduction of Greenhouse Gases emission is a growing concern of many industries. Following the mitigation solutions recommended by the Kyoto Protocol, underground sequestration of CO2 is a way to meet this goal, as oil and gas fields offer huge CO2 storage capacities, while preserving the environment. The oil and gas industry has a long commercial practice of gas injection: EOR, natural gas storage. Using a depleted oil or gas reservoir for CO2 storage has several interesting advantages among which the relatively large pressure range available for injection, allowing the storage of significant gas quantities for a low compression power, without altering the cap-rock integrity. Besides, the availability of reservoir dynamical and geological characterization and existing production/injection wells contributes to the optimization of the project, both technically and economically. This CO2 storage can be permanent in the case of mineral trapping or very long term (several thousand years) in the case of hydrodynamic trapping. The long-term risk analysis of the CO2 behavior and its impact on the environment is a key objective of the project. That is why the selection of an appropriate reservoir is crucial to the success of the sequestration. Two major steps have been identified while sequestering CO2. The injected CO2 dissolves and diffuses in oil and water and follows the pressure gradient (hydrodynamic trapping). Then, the dissolved CO2 reacts with the minerals within the formation and induces dissolution/precipitation reactions (mineral trapping), that may impair the well injectivity and/or the cap-rock sealing properties. For the first time, this study investigates both sides using reservoir simulator with improved CO2 thermodynamics (ATHOS) and reactive transport simulator (DIAPHORE) to evaluate the extend of mineral trapping (kinetically controlled reaction) and long term behavior of CO2 within the reservoir and its neighboring geological formations (cap rock, aquifer). This work is funded by Institut Français du Pétrole (IFP), Geostock, TotalFinaElf and sponsored by the French Ministry of Industry (FSH). Introduction The Kyoto Protocol of the United Nations Framework Convention on Climate change calls for Annex I Parties (developed countries) to reduce emissions of greenhouse gases (GHG) by an average of 5.2% below the 1990 levels by 2008 to 2012. Non-Annex I Parties (developing countries) have no new obligations to reduce greenhouse gases. In addition to these reduction objectives, the Kyoto Protocol outlines a set of mechanisms to support sustainable development, technology transfer and capacity building objectives of the United Nations Framework Convention on Climate Change. These mechanisms are collectively known as the Kyoto Mechanisms. Under the Kyoto Protocol, a key issue is the capture and storage of CO2. Underground CO2 storage in depleted oil or gas reservoirs offers interesting and eventually permanent long-term environmentally safe possibilities. The long-term risk analysis of the CO2 behavior and its impact on the environment is a key objective of the project initiated by Institut Français du Pétrole (IFP) with TotalFinaElf and Geostock with the financial support of the French Ministry of Industry (FSH). In this research project, underground CO2 sequestration focuses on oil and gas reservoirs either depleted or in production in order to optimize the economy of the oil recovery and CO2 sequestration trapping at the end of field life. Capture and deposition of CO2. Technologies for capture and storage of CO2 exist already today. However, they are neither developed nor optimized for these purposes and they are expensive. A huge development effort has been initiated in many countries to capture and store CO2.. It has been described and summarized extensively within the IEA Greenhouse Gas Programme.
- Energy > Oil & Gas > Upstream (1.00)
- Government > Regional Government > Europe Government > France Government (0.95)
- North America > United States > Texas > Permian Basin > Yeso Formation (0.99)
- North America > United States > Texas > Permian Basin > Yates Formation (0.99)
- North America > United States > Texas > Permian Basin > Wolfcamp Formation (0.99)
- (24 more...)
ABSTRACT: In order to improve the location of induced seismicity recorded by a triaxial downhole geophone, we present a method locating seismic events with respect to a reference event. This method requires similar seismic events called "doublets", usually assumed to be generated by a same geological discontinuity. RESUME: Pour ameliorer la localisation de la sismicite induite, enregistree par un capteur triaxe en profondeur, nous presentons une methode localisant les evenements en relatif par rapport à un evenement de reference. Cette methode necessite I'existence d'evenements sismiques d'une grande similitude appeles "doublets", produits à priori par la rnerne discontinuite gèologique. ZUSAMMENFASSUNG: Um die Lokalisierung der von einem in Tiefe gelegten Dreiachssensor registrierten induzierten Erdbebenhaufigkeit verbessern, haben wir eine Verfahrensweise entwickelt, die Relativerfassungen in gezug auf einen Referenzerfassung lokalisiert. Diese Methode erfordert sehr ahnliche seismische "dublette" geheißte Erfassungen, die von dieselbe geologische Unterbrechung produziert werden. INTRODUCTION Hydraulic fracturing, geothermal energy extraction or salt leaching show an important induced seismicity. This seismicity is very often characterised by the existence of several families of similar events called doublets (figure 1). Taking into account the great simililarity between doublets inside the same family, it is assumed that they have all been generated by the same mechanism. The location of the doublets allows to specify the orientation of the geological discontinuity. Classically, with a triaxial downhole geophone, the seismic hypocentral location is performed using the hodogram method. This method derives the P wave incident angle (azimuth and nutation) from the analysis of the 3D particle motion, and the distance from the time difference between P and S arrivals. This method gives a location for each event independently of the previous locations. Applying this method to a family of doublets, it can be shown that the variable signal to noise ratio introduce a random error on the absolute location of each event, reducing the location accuracy, and blurring the swarm of seismicity. In order to improve the location accuracy, we studied a method using the simililarity between doublets (Moriya H., & al., 1994). This method consists in locating the doublets with respect to a reference event. The reference event is usually located by the classical hodogram method, but all the other doublets are localised with respect to it by computing their relative angle and distance differences. Among a class of doublets, the reference event is the event with the best signal to noise ratio. This ensures a reliable determination of incidence angle, and a good time picking of wave arrivals. THE DISTANCE DIFFERENCE COMPUTATION Hodogram method: the reference event location The reference event is located using the hodogram method (figure 2). By the projection of the 3D panicle motion on the three axis of the downhole transducer, we compute the three eigen vectors (inertia matrix). Using trigonometric functions, the three Eulerian angles (azimuth, nutation, and proper rotation) are determined (Cliet C, & al., 1988) The length of the time window is selected in order to minimize the time delay dispertion computed by the correlation (fig.3c) One can observe a variation of the time delay as a function of the length of the time correlation window. The best accuracy of the time delay corresponds to the minimum standard deviation between the three axis. The evolution of the time correlation window, from one to 10 periods (figure 3c), shows a time delay stability around a same average for the three axis, after 5 or 6 periods (minimum standard deviation). The error of the arrival time picking will also be minimum at this value of the correlation window.
ABSTRACT The paper describes the interest of using AVO (amplitude versus offset) processing techniques in offshore drilling site surveys for shallow gas assessment. Presently, shallow gas evaluation is mostly based on the aspects of the amplitude anomalies of seismic reflectors. This practice is undoubtedly conservative as amplitude anomalies may not correspond to gas charged horizons; hence, the need to qualify seismic amplitude anomalies, in particular in environments where such anomalies are numerous. With this objective, AVO processing techniques enable discrimination of events which are gas charged or not. The paper presents results of HR surveys with map and seismic sections for which AVO techniques were used. Examples from THAILAND, TONKING GULF and INDONESIA are presented, showing practical consequences for drilling site selection and drilling programs. INTRODUCTION In offshore drilling site surveys, the requirement for a more accurate assessment of shallow gas is presently increasing. Up to now the standard practice for determining shallow gas is based on the amplitude anomalies or "bright spot" effect on the High Resolution (HR) seismic sections. As is well known, characterisation of bright spots is worked out from equalized and relative amplitude sections (variation of the reflection amplitude, variation of the signal frequency, polarity reversal, decrease of velocity and pull down effect, attenuation of the energy under gas, diffraction at the extremities of the reflection...). However, the method is somewhat inaccurate as the above criteria may not show clearly and as anomalous amplitudes do not only correspond to gas charged layers. Since the objective is security, interpreters are conservative and, as a consequence, many places may erroneously be considered potentially hazardous for drilling. The problem is aggravated when the environment is actually intensively gas charged (like a delta for instance) : the anomalies found are so numerous that almost no "safe" drilling location can be recommended. Hence the need of better qualification of gas charged horizons. The AVO TOOL FOR HR SEISMIC The AVO (Amplitude Versus Offset) processing techniques, in theory, enable the identification of the presence of disseminated gas within sediments. These techniques are based on the variation of the amplitudes of seismic reflections with the offset source- receiver. They are today, commonly used in deep seismic for oil and gas evaluation but not in shallow HR seismic. Following R.T. SHUEY, 1985, it can be shown that the reflection coefficient R can be expressed as a function of the incidence angle ? : (mathematical equation)(available in full paper) In case of a gas charged layer, both impedance and Poisson ratio decrease across the interface. The product Ro*G is therefore doubly affected by the presence of gas and provides an effective tool for its identification. With the primary objective of qualifying gas charged and none gas charged layers within the range mudline to 800 m deep, a number of systematic trials were performed during the last 18 months on various fields where shallow gas occurs. The data acquisition parameters are the classical ones for HR seismic : 48 traces, 12.5 m between traces, shot point interval 6.25 m, I ms sampling rate, record length 1.5 s. In order to ensure the range of investigation required (0-800 m) a 600 m long streamer is necessary for velocity analysis control as well as for a comprehensive AVO processing. In addition the recording geometry (positioning - trigger) must be really accurate, that is constantly controlled.
- North America > United States > Texas (0.29)
- Asia > Indonesia (0.26)
- Asia > Thailand (0.25)
- North America > Canada > Alberta > Woodlands County (0.24)
Storing oil underground overcomes the detrimental environmental effects of tank storage at the ground surface. But due consideration must be given to other factors. Preventing disturbance to the original groundwater pattern requires a thorough survey of the water table before mining operations begin, arrangements for maintaining a high water table during construction, and monitoring of subsurface water levels and quality during operations. The danger of an accident enabling oil to escape from the top of the shaft must also be prevented, by providing safety valves which operate automatical1y when the oil pressure drops. Underground storage offers environmental benefits in connection with other substances such as industrial and nuclear wastes. INTRODUCTION Even if the prime advantage that led to the development of underground oil storage was not environmental protection, there can be no doubt that it has made an important contribution in this area. The excellent safety record of the steadily increasing number of underground facilities throughout the world demonstrates their advantages over the more conventional tank farm as regards safeguardmg the countryside. Today, environmental protection must be one of the developer's foremost preoccupations before, during and after commissioning of a new store, and the increasingly large place given to environmental impact studies is ample evidence of this. With this trend in mind, we have taken a hard look at the specific precautions needed in connection with underground storage, working towards increasingly sophisticated means of protecting groundwater so as to retain the original properties of the rock formation and prevent migration of the stored products, and avoid any danger of an oil burst at the ground surface as a result of wilful damage as well as under normal operating conditions. Because of its excellent environmental safety, underground storage must inevitably spread to embrace other substances, for which present-day techniques do not provide adequate protection, such as industrial wastes whose neutralization would present an over-arduous pollution problem and radioactive wastes, for which underground repositories are the most logical answer, and should become a reality within the next decade. PROTECTION OF THE COUNTRYSIDE The advantages of underground storage as regards protection of the countryside need no elaboration, because it has been in use for many decades. We shall merely illustrate the fact by describing the Manosque oil storage facility, which has a capacity of 7.5 million cubic metres in a salt dome underlying public forest land. Most of the Land is Untouched by the Engineering Works The topside site area needed for a storage cavity of several hundred thousand cubic metres only represents about fifteen square metres for the top end of the shaft, with the stand pipes and valves only rising to a height of less than three metres. Each shaft head is surrounded by a concrete slab covering about 1,500 square metres, which is fenced off. The control buildings and pump house are practically the only constructions visible in the landscape. And even these have been grouped together at Manosque, so that they only cover an area of three hectares.
- Geology > Geological Subdiscipline > Environmental Geology > Hydrogeology (0.73)
- Geology > Structural Geology > Tectonics (0.48)
- Health, Safety, Environment & Sustainability > Environment > Naturally occurring radioactive materials (0.49)
- Health, Safety, Environment & Sustainability > Environment > Waste management (0.35)
- Reservoir Description and Dynamics > Reservoir Characterization > Exploration, development, structural geology (0.34)
In some designs, the rock at the face of an unlined storage cavity may be stressed beyond its maximum strength, and the article presents how an analytical model can be used to describe the conditions of failure in the rock and their effects on stability. It is henceforth possible to use underground storage techniques at moderate depths in soft rocks or at great depths in hard, brittle rocks. INTRODUCTION Underground storage first developed by making use of very favourable geological conditions like those available in salt domes or large expanses of crystalline rock. The design of facilities to store oil, and liquified or gaseous gas is a relatively simple matter in this kind of context. Over the last decade or so, however, because of the move to capitalize on the unusually high standard of environmental protection and safety associated with underground storage, attention has been focused on extending it to a much wider range of stored products in much less favourable geological conditions and there are even cases of such projects now in the design stage. The new products to be stored produce very different stress conditions in the rock. Liquified natural gas and ethylene involve low-temperature stresses. Residual fuel oil, compressed air and nuclear wastes apply thermal stresses. The alternating and sudden pressure changes associated with the operation of compressed air storage facilities are a severe test of stability. The advantages of underground storage have induced engineers to examine its application in much less favourable geologies, and Geostock is currently engaged in conceptual and project design studies for facilities in weak to very weak soft rock, even down to almost unconsolidated clays. Such formations are very commonly found in the large alluvial plains where the world's major cities are built, so that safety is an obvious criterion. In such rock, it is quite possible that the cavities will not be inherently stable if rock strength is ina dequate to withstand the applied loads. Conventional design rules derived from theoretical rock me chanics models do not enable us to estimate the permissible limits in such design, or to optimize support. In order to provide a means of examining the feasibility of such projects, Geostock has been running a programme of research jointly with the Laboratoire de Mecanique des Solides of the Ecole Polytechnique in Paris since 1974, to investigate materials behaviour when stresses are equal to or in excess of their maximum strength as obtained from crushing tests. A set of experimental data has also been analysed to calibrate the results of this theoretical research, and check the accuracy of the findings. We shall first briefly review the shortcomings of conventional models before going on to describe the main features of the new model and compare findings with a variety of case histories. The article concludes with comments on the new opportunities offered by this model for designing underground storage facilities in poor engineering rock where stress conditions are complex, in strong rock where stresses are expected to exceed rock strength, or where support optimization is a prime consideration.
- Geology > Rock Type (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)