Browsing by Subject "Offshore"
Now showing 1 - 14 of 14
Results Per Page
Sort Options
Item A Systematic Approach to Offshore Fields Development Using an Integrated Workflow(2010-10-12) Alqahtani, Mari H.I present a systematic method to primary develop existing black oil fields. This method uses integrated reservoir development workflow (IRDW) that relies on integrated asset model (IAM). Developing any existing field means providing a plan that generally serves the development goal(s) specified by management. However, serving the development goal(s) by itself does not guarantee an optimal development plan. Plans that do not rely on an IAM are less accurate. Some plans do not include economics in their evaluation. Such plans are technically accepted but usually impractical or unprofitable. Plans that only evaluate the field based on current, or short-term, conditions are potential candidates for bottlenecks, thus costly reevaluations. In addition, plans that do not consider all suitable options are misleading and have no room for optimization. Finally, some plans are based on ?rules of thumb,? ease of operations, or operators? preference, not on technical evaluation. These plans mostly lower long-term profitability and cause further production problems. To overcome these problems, project management must form a multidisciplinary team that uses the IRDW. The IRDW guides the team through its phases, stages, and steps to selecting the optimal development plan. The IAM consists of geological, reservoir, wellbore, facility, and economic models. The IRDW dictates building an IAM for the base (do nothing) case and for each development plan. The team must evaluate each scenario over the lifetime of the field, or over the timeframe the management specifies. Net present value (NPV) and Present value ratio (PVR) for all options are compared to the base case and against each other. The optimum development plan is the one that have the highest NPV and highest PVR. The results of the research showed that forming a multidisciplinary team and using a LDFC saves time and it guarantees selecting the optimal development plan if all applicable development options are considered.Item Analytical and Experimental Studies of Drag Embedment Anchors and Suction Caissons(2011-08-08) Beemer, RyanThe need for experimental and analytical modeling in the field of deep water offshore anchoring technologies is high. Suction caisson and drag embedment anchors (DEA) are common anchors used for mooring structures in deep water. The installation process of drag embedment anchors has been highly empirical, employing a trial and error methodology. In the past decade analytical methods have been derived for modeling DEA installation trajectories. However, obtaining calibration data for these models has not been economical. The development of a small scale experimental apparatus, known as the Laponite Tank, was developed for this thesis. The Laponite Tank provides a quick and economical means of measuring DEA trajectories, visually. The experimental data can then be used for calibrating models. The installation process of suctions caissons has benefited from from a more rational approach. Nevertheless, these methods require refinement and removal methodology requires development. In this thesis, an algorithm for modeling suction caisson installation in clay has been presented. An analytical method and modeling algorithm for removal processes of suction caissons in clay was also developed. The installation and removal models were calibrated to field data. These analytical and experimental studies can provide a better understanding of installation of drag embedment anchors and the installation and removal of suction caissons.Item Comparison between Gulf of Mexico and Mediterranean Offshore Reservoirs(2014-12-15) Tang, JiaweiDeepwater oil and gas are simply conventional reserves in an unconventional setting. They consist of a resource class of their own largely because they face a common set of challenges in the course of their identification, characterization, development and production. However, there have already been successful deepwater reservoir developments, in sedimentary environments such as the Gulf of Mexico, offshore Brazil and West Africa. Especially in Gulf of Mexico, the offshore reservoirs are analyzed and exploited on a large scale, rendering a good case for deepwater exploration. Recently there have been large deepwater reservoirs discovered in the Mediterranean Basin. Except for the main reservoir type, the two regions? situations are similar to each other including large water depth, great production potential and significance in the role played in their regions? energy industry, respectively. Before the exploration starts, the analysis and forecast of the reservoir properties and quality are always the priority. This research is to characterize these reservoirs in a way that will be useful for further exploration. A previous study of US reservoirs including both terrestrial and offshore Gulf of Mexico reservoirs showed correlations of depth vs pressure, temperature, and mobility. Similar works are done for the newly discovered reservoirs in Gulf of Mexico, and the same approach is applied to the analysis of Mediterranean reservoirs. Basically, the study showed important trends related to water depth that explains why deepwater reservoirs may offer exceptional potential over terrestrial and shallow water reservoirs. The research done in this thesis is based on the following aspects: (1) previous analysis for Gulf of Mexico, (2) the new reservoir data analysis for both Gulf of Mexico and Mediterranean, (3) evaluation and comparison of the two regions. The deepwater reservoirs in two regions are similarly impacted by the water depth. Both reservoir pressure and porosity are altered higher by water. Also, some reservoir properties like permeability can be possibly inferred under specific condition. Based on the study, it is obvious that offshore reservoirs of the two regions have the potential for high deliverability and deserve exploration.Item Curing Properties of Epoxy Resins for Use to Abandon Wells Destroyed by Hurricanes in the Gulf of Mexico(2012-02-14) Gao, SuiningSome Gulf of Mexico (GOM) wells destroyed by hurricanes have become environment and safety hazard and cannot be abandoned by conventional methods since pumping and circulating cement into the casing is impossible when the platforms have been completely destroyed and toppled. This project tested the curing properties of several epoxy resin systems in different environments. A bisphenol-F/epichlorohydrin (BPF) resin cured by curing agent MBOEA system was successfully tested in the laboratory as a potential plugging material to abandon wells destroyed in the GOM. The BPF/MBOEA resin system had the most suitable curing time in a synthetic seawater environment. The system could be successfully weighted by barite up to 16.8 ppg and cured properly. Weighting allows the resin system fall more efficiently through the casing annulus. This laboratory verification of properties will lead to field test in the test wells.Item Design of large diameter monopiles for offshore wind turbines in clay(2016-08) Senanayake, Asitha Indun Madusanka Joshua; Gilbert, Robert B. (Robert Bruce), 1965-; Wang, Shin-Tower; Cox, Brady; Manuel, Lance; Murff, James DOffshore wind power has great potential as a clean and renewable energy source that is capable of reducing our reliance on fossil fuels. The main drawback of offshore wind power is its comparatively high capital cost. One area in which this cost can be reduced is by optimizing the design of these structures. More efficient foundation designs is key in this regard. The p-y method is extensively used for the design and analysis of laterally loaded piles due to its simplicity and versatility. Matlock (1970) or the API RP 2GEO (2011) “soft” clay p-y model is the guideline of choice for normally consolidated to moderately overconsolidated clays. However, this p-y model is not yet verified for piles with very large diameters and low aspect ratios. Design of wind turbine monopiles is governed by serviceability limits such as the natural frequency of the structure and the accumulated tilt under long-term low-amplitude cyclic loads, but these guidelines have not been verified for serviceability limit state designs. The main objectives of this study were to: (a) assess the ability of the Matlock (1970) p-y model to accurately model the behavior of laterally loaded piles at both small and large displacements, (b) investigate the effect of gapping on the backside of laterally loaded piles and develop a theoretical framework to quantify its effect and predict its occurrence, (c) re-examine the derivation of lateral bearing capacity factors (N p ) used in published p-y models, (d) evaluate the effect of large numbers of small-amplitude cyclic load on the stiffness and the post-cyclic ultimate capacity of laterally loaded piles, (e) assess the ability of the Matlock (1970) p-y model to adequately account for pile diameter effects, (f) assess the ability of the Matlock (1970) p-y model to accurately predict the behavior of a pile in a variety of undrained shear strength versus depth profiles, (g) assess the ability of published p-y models to accurately predict the natural frequency of wind turbine structures. The methodology consisted of analyzing field tests, laboratory model tests (1-g and centrifuge), and numerical modeling. An extensive database of field tests and laboratory centrifuge tests was compiled. This data was then supplemented by a series of 1-g model tests in a variety of clay test beds (normally consolidated to heavily overconsolidated, kaolinite and Gulf of Mexico clay) carried out at The University of Texas at Austin and 3-d finite-elements models using Abaqus carried out by Ensoft Inc. The following conclusions were drawn from this study: (a) Matlock (1970) p-y model underestimates the lateral soil resistance on piles in normally consolidated and overconsolidated clays, regardless of pile diameter or aspect ratio, (b) the effect of gapping plays an important role in determining the pile response as it can lead to a loss of capacity and a reduction in stiffness, (c) lateral bearing capacity factors used in the Matlock (1970) model are too low, (d) the degradation in the stiffness of the pile response, when subjected to cyclic loading, was limited to approximately 30% and occurred within the first 100 cycles, (e) the method of normalizing used in the Matlock (1970) model successfully accounts for pile diameter effects, (f) estimates of the natural frequency of wind turbine structure based on the API RP 2GEO (2011) p-y model are lower than those based on the Matlock (1970) and Jeanjean (2009) p-y models.Item Dynamic response and reliability analysis of an offshore wind turbine supported by a semi-submersible platform(2015-12) Thomas, Edwin, M.S. in Engineering; Manuel, LanceWind Energy is the fastest growing renewable energy source in the world. The trend is expected to continue with falling costs of technology, energy security concerns and the need to address environmental issues. Offshore wind turbines have a few important advantages over land-based turbines; offshore sites experience stronger and less turbulent winds, there are fewer negative aesthetic impacts in an offshore location, there is greater ease in the transport of wind turbine components over sea than on land, etc. Large offshore wind turbines mounted atop floating platforms offer a viable solution for deepwater sites. Of the various floating platform concepts that are being considered, a moored semi-submersible platform is considered in this study. The dynamic response and reliability analysis of a 13.2~MW offshore wind turbine supported by a moored semi-submersible platform is the subject of this study. A model for this integrated system has been developed and its various physical, geometric, and dynamic properties have been studied in this and another associated study. Loads data for the extreme and fatigue analysis of such systems are generally attained by running time-domain simulations for a range of sea states that are representative of the expected site-specific metocean conditions. The selected site of interest in the North Sea has a water depth of 200 m. The Environmental Contour (EC) method is used to identify sea states of interest that are associated with a target return period (50 years). These sea states are considered in short-term (1-hour) simulations of the integrated turbine-platform-mooring system. The dynamic behavior of the integrated wind turbine system is studied. Critical sea states for the various response loads are identified and the sensitivity of the system to the metocean conditions is discussed. Estimation of 50-year response levels (for turbine loads, platform motions, and the mooring line tension at the fairlead) associated with the target probability is subsequently carried out using 2D and 3D Inverse First-Order Reliability Method (FORM) approaches.Item Experimental Assessment of Water Based Drilling Fluids in High Pressure and High Temperature Conditions(2012-10-19) Ravi, AshwinProper selection of drilling fluids plays a major role in determining the efficient completion of any drilling operation. With the increasing number of ultra-deep offshore wells being drilled and ever stringent environmental and safety regulations coming into effect, it becomes necessary to examine and understand the behavior of water based drilling fluids - which are cheaper and less polluting than their oil based counterpart - under extreme temperature and pressure conditions. In most of the existing literature, the testing procedure is simple - increase the temperature of the fluid in steps and record rheological properties at each step. A major drawback of this testing procedure is that it does not represent the continuous temperature change that occurs in a drilling fluid as it is circulated through the well bore. To have a better understanding of fluid behavior under such temperature variation, a continuous test procedure was devised in which the temperature of the drilling fluid was continuously increased to a pre-determined maximum value while monitoring one rheological parameter. The results of such tests may then be used to plan fluid treatment schedules. The experiments were conducted on a Chandler 7600 XHPHT viscometer and they seem to indicate specific temperature ranges above which the properties of the drilling fluid deteriorate. Different fluid compositions and drilling fluids in use in the field were tested and the results are discussed in detail.Item Experimental in-plane behavior of a generic scale model drag embedment anchor in Kaolinite test beds(2011-05) McCarthy, Katelyn Barbara; Gilbert, Robert B. (Robert Bruce), 1965-; Rathje, Ellen M.The trajectory and capacity are key components of the design of drag embedment anchor and drag-in vertically loaded anchors. This experimental testing program quantifies two factors that describe the anchor trajectory and capacity: the equilibrium bearing factor (Ne) and the tangential bearing factor (Ne). These factors can aid in the development of a numerical model of anchor behavior. A magnetometer device is used to track the orientation and location of the anchor during drag embedment. The results of the experimental testing program were compared with the results from a predictive model. The experimental program consisted of drag embedment tests with various testing conditions including different anchor line diameters and different initial pitch orientations. The results with the different anchor lines indicated that thinner anchor lines cause the anchor to dive deeper in the soil. The different initial pitch results indicate that regardless of the initial pitch of the anchor, the anchor rotates to a unique pitch trajectory within 2 fluke lengths.Item On the development of a semi-submersible offshore floating platform and mooring system for a 13.2 mw wind turbine(2015-12) Liu, Jinsong; Manuel, LanceOver the past decades, wind energy has emerged as an alternative to conventional power generation that is economical, environmentally friendly, and importantly renewable. Specifically, offshore wind energy is being con- sidered by a number of countries to harness the stronger and more consistent wind resource compared to that over land. To meet the projected “20% energy from wind by 2030” scenario that was announced in 2006, 54 GW of added wind energy capacity needs to come from offshore according to a National Renewable Energy Laboratory (NREL) study. In this study, we discuss the development of a semi-submersible floating offshore platform with a catenary mooring system to support a very large vi 13.2 MW wind turbine with 100 m blades. An iterative design process is applied to baseline models with Froude scaling in order to achieve preliminary static stability. Structural dynamic analyses are performed to investigate the performance of the new model using a finite element method approach for the tower and a boundary integral equation (panel) method for the platform. The steady-state response of the system under uniform wind and regular waves is first studied to evaluate the performance of the integrated system. Response amplitude operators (RAOs) are computed in the time domain using white- noise wave excitation; this serves to highlight nonlinear as well as dynamic characteristics of the system. Finally, the stochastic dynamic response of the system is studied to assess the global performance for sea states defined by wind fields with turbulence and long-crested irregular waves.Item Regional character of the lower Tuscaloosa formation depositional systems and trends in reservoir quality(2012-12) Woolf, Kurtus Steven; Wood, Lesli J.For decades the Upper Cretaceous Lower Tuscaloosa Formation of the U.S. Gulf Coast has been considered an onshore hydrocarbon play with no equivalent offshore deposits. A better understanding of the Lower Tuscaloosa sequence stratigraphic and paleogeographic framework, source-to-sink depositional environments, magnitude of fluvial systems, regional trends in reservoir quality, and structural influences on its deposition along with newly acquired data from offshore wells has changed this decades-long paradigm of the Lower Tuscaloosa as simply an onshore play. The mid-Cenomanian unconformity, underlying the Lower Tuscaloosa, formed an extensive regional network of incised valleys. This incision and accompanying low accommodation allowed for sediment bypass and deposition of over 330 m thick gravity-driven sand-rich deposits over 400 km from their equivalent shelf edge. Subsequently a transgressive systems tract comprised of four fluvial sequences in the Lower Tuscaloosa Massive sand and an overlying estuarine sequence (Stringer sand) filled the incised valleys. Both wave- and tide-dominated deltaic facies of the Lower Tuscaloosa are located at the mouths of incised valleys proximal to the shelf edge. Deltaic and estuarine depositional environments were interpreted from impoverished trace fossil suites of the Cruziana Ichnofacies and detailed sedimentological observations. The location and trend of valleys are controlled by basement structures. Lower Tuscaloosa rivers were 3.8m – 7.8m deep and 145m – 721m wide comparable to the Siwalik Group outcrop and the modern Missouri River. These systems were capable of transporting large amounts of sediment indicating the Lower Tuscaloosa was capable of transporting large amounts of sediments to the shelf edge for resedimentation into the deep offshore. Anomalously high porosity (>25%) and permeability (>1200md) in the Lower Tuscaloosa at stratigraphic depths below 20,000 ft. are influenced by chlorite coating the detrital grains. Chlorite coatings block quartz nucleation sites inhibiting quartz cementation. Chlorite coats in the Lower Tuscaloosa are controlled by the presence and abundance of volcanic rock fragments supplying the ions needed for the formation of chlorite. Chlorite decrease to the east in sediments derived from the Appalachian Mountains. An increase in chlorite in westward samples correlates with an increase of volcanic rock fragments derived from the Ouachita Mountains.Item Reliability-based Design of Offshore Mooring Systems(2013-02-05) Mousavi, Mir EmadThis study proposes new methods for the reliability-based design of structural systems, with emphasis on offshore mooring systems. After a brief introduction to the mooring systems, two main objectives are discussed in this dissertation. The first objective is the calculation of the probability of failure of a structural system, which is an important input for a reliability-based design or any quantitative risk assessment. Two different methods are proposed for calculation of the probability of failure: a method based on the Monte Carlo simulations and a method based on the basic rules of probability, which is called the Progressive Reliability Method (PRM). Both methods are flexible to the definition of system failure. For example, the probability of a serviceability or ultimate-strength failure can be assessed using any of the two methods. It is shown that the two methods produce similar results, but PRM is preferred because it is exact and usually faster to implement. The second main objective in this dissertation is to develop a method for the optimization of the design of a structural system, given a target probability of failure. In this method, using the structural analysis of a preliminary design, the ratio of the optimal to the preliminary mean capacity of each component, which is called the Optimality Factor, is determined. Two design strategies are considered. First, an optimal design is intended to achieve the maximum system integrity. System integrity is defined as the balanced contribution of system components to its reliability. To quantify the system integrity, the Integrity Index is defined, and its calculation for various systems is discussed. Second, a designated failure scenario is considered, where some components serve as a fuse to protect some other components. This design strategy is especially applicable to mooring systems with drag anchor foundations because normally, if a drag anchor is pulled out from the seabed, it can cause significant damages to nearby subsea facilities. Using the rules of probability, a method is then developed to calculate the optimality factor of each component.Item Stochastic Programming Approach to Hydraulic Fracture Design for the Lower Tertiary Gulf of Mexico(2013-07-27) Podhoretz, SethIn this work, we present methodologies for optimization of hydraulic fracturing design under uncertainty specifically with reference to the thick and anisotropic reservoirs in the Lower Tertiary Gulf of Mexico. In this analysis we apply a stochastic programming framework for optimization under uncertainty and apply a utility framework for risk analysis. For a vertical well, we developed a methodology for making the strategic decisions regarding number and dimensions of hydraulic fractures in a high-cost, high-risk offshore development. Uncertainty is associated with the characteristics of the reservoir, the economics of the fracturing cost, and the fracture height growth. The method developed is applicable to vertical wells with multiple, partially penetrating fractures in an anisotropic formation. The method applies the utility framework to account for financial risk. For a horizontal well, we developed a methodology for making the strategic decisions regarding lateral length, number and dimensions of transverse hydraulic fractures in a high-cost, high-risk offshore development, under uncertainty associated with the characteristics of the reservoir. The problem is formulated as a mixed-integer, nonlinear, stochastic program and solved by a tailored Branch and Bound algorithm. The method developed is applicable to partially penetrating horizontal wells with multiple, partially penetrating fractures in an anisotropic formation.Item Texas offshore wind power and water desalination potential(2015-05) Beceiro, Jose Daniel; Spence, David B.; Webber, Michael E., 1971-Texas leads the nation in oil and gas production as well as renewable energy production. Texas also leads the nation in installed wind power and is the 6th largest wind market in the world. Over the past decade, Texas has gone from nearly zero megawatts of installed wind to now over 14,000 megawatts. Texas has an immense onshore wind resource that has been exploited. However, another of Texas' large untapped energy resources has yet to be explored -- offshore wind. Texas is also experiencing one of the most severe and longest sustained drought cycles in the state's history. Texas is blessed with a vast supply of ocean water and brackish groundwater trapped in aquifers, but energy-intensive water desalination plants are required to purify the water to potable standards. Offshore wind has the ability to turn large-scale water desalination into an economical solution. This thesis focuses on offshore wind and water desalination technology development, cost competitiveness with competing renewable energy and thermo electric generation resources on the ERCOT nodal grid, and the opportunity to couple water desalination facilities with offshore wind farms to enhance overall project economics, reduce the cost of electricity, and increase the supply of fresh water. An economic model evaluating offshore wind-powered water desalination is utilized to demonstrate the viability of implementing these technologies across the state.Item The Wicked Problem of Oil & Gas Development in the Beaufort and Chukchi Seas: Current Permitting and Evaluation of Marine Spatial Planning as a Potential Management Tool(2014-06-02) Johannes, Emilie AnnChanging climatic conditions and shifting global economics have thrust the Arctic into the spotlight for many scientists, academics, and policymakers as well as those in offshore industries, particularly in shipping and oil and gas. This research provides an overview of current U.S. Federal and State of Alaska environmental permitting requirements for offshore oil and gas development in the Beaufort and Chukchi Seas, highlighting the wicked problem of Arctic development: activities undertaken in the region are highly complex, involving significant political, social, environmental, and technical challenges. The economic opportunities that these Seas afford, and the high risks posed by pursuing these opportunities, call for the development of effective management strategies to avoid environmental catastrophes and maintain safe conditions for the stakeholders involved. The general questions guiding this research are: 1) How do Federal and State management of Beaufort and Chukchi Sea offshore oil and gas resources differ and how do the environmental permitting processes reflect this difference? 2) Is marine spatial planning (MSP) a viable tool for integrating these regulatory processes into a comprehensive planning process that balances stakeholder engagement, economic interests, and protection of the marine environment, all elements of the wicked problem? The analysis shows that MSP is worthy of consideration at the local or State level as a tool to help address these wicked problems elements, potentially allowing for a smoother permitting process.