Modern drilling ships and rigs are equipped with advanced computer systemsfor dynamic positioning, power generation and distribution, and drillingoperations. It is well-known that software errors may lead to delays andnonproductive time and may compromise safety. Although the testing andverification regime for structures and machinery systems is well-established,most of the computer systems on today's drilling vessels are put into operationwithout independent testing and verification. Hardware-in-the-loop (HIL)testing is a test methodology used in several other industries. It facilitatesthe systematic testing of control-system design philosophy, functionality,performance, and failure-handling capability, in both normal and off-designoperating conditions, and is conducted in a virtual test bed in which there isno risk to personnel, vessel, or equipment. Automatic drilling systems thatrely on software to function properly often consist of a combination ofcomponents delivered by several suppliers. This means that, to maintain safetyand to achieve the desired operational performance, control-system softwarefrom several suppliers must also run and work together as an integrated system.Marine Cybernetics has finalized the testing of drill-floor control systems forseven rigs, involving nine different vendors. This paper presents experiencesfrom these projects in terms of project execution, test timing, and vendorcooperation and participation. Examples of typical observations are alsopresented.
Shibata, Kazuya (The University of Tokyo) | Koshizuka, Seiichi (The University of Tokyo) | Sakai, Mikio (The University of Tokyo) | Tanizawa, Katsuji (National Maritime Research Institute) | Ota, Susumu (National Maritime Research Institute)
The acceleration of a free-fall lifeboat at water entry was numerically calculated employing the moving particle semiimplicit method in three dimensions. This method has an advantage in treating the large deformation of the water surface, the splash of water at water entry, and the rigid-fluid interactions. The simulated acceleration was evaluated in the normal and axial directions of the lifeboat. The simulated time history and the maximum value of the acceleration were close to those obtained experimentally. The effect of the skid angle was investigated using the method.
Trenching is a frequently used method for protection of offshore pipelines against dropped objects and fishery activities. To provide additional protection the trenches are usually back-filled. The backfill material may be soft, partly remoulded clay or sand present at the seabed or sand mix and crushed rock installed after pipe lay. Offshore pipelines may experience large axial forces due to temperature expansion. As a part of the pipeline design, the buckling failure modes must be analysed. In the buckling analyses, an important parameter is the upheaval resistance from the backfill material. To verify the design of a trenched offshore pipeline in the Norwegian Trench, a full-scale test was performed by SINTEF and NTNU. The test program included measurement of uplift resistance in soft clay, sand mix and crushed rock. This paper presents the test setup, the backfill materials and the measured uplift resistances. The measured resistances are compared with theoretical models for uplift resistance for different backfill materials. Recommendations are given regarding the uplift resistance pipes in trenches backfilled with sand mix or crushed rock.
Plank, Johann (Technische Universität München) | Tiemeyer, Constantin (Technische Universität München) | Bülichen, Daniel (Technische Universität München) | Recalde Lummer, Nils (Technische Universität München)
Oilwell-cement slurries commonly incorporate several admixtures such asretarder, dispersant, fluid-loss additive (FLA), antifreewater agent, anddefoamer. Between them, additive/additive interactions may occur that canresult in incompatibilities and reduced performances (the most frequent case)or, oppositely, in improved effectiveness. Here, an overview of somesynergistic and antagonistic effects between selected cement additives ispresented. Four combinations of additives were tested and studied. First, theinteraction between 2-Acrylamido-tertiary-butyl sulfonicacid-co-N,N-dimethylacrylamide (CaATBS-co-NNDMA) FLA and anNaATBS-co-itaconic acid retarder as well as welan gum, an anionicbiopolymer applied as an antifree-water additive, was investigated. It wasfound that the retarder, which possesses a particularly high-anionic charge,reduces the effectiveness of the CaATBS-co-NNDMA FLA by decreasing itsamount adsorbed on cement. Similarly, the anionic biopolymer can alsonegatively affect the effectiveness of the FLA through competitive adsorption,in which the biopolymer hinders the sufficient adsorption of the FLA on cement.The incorporation of stronger anchor groups (e.g., dicarboxylates orphosphonates) into the CaATBS-co-NNDMA FLA enhances its affinity for thesurface of cement and thus renders it more robust against the negative impactfrom other admixtures. Second, the compatibility between an Na+lignosulfonate (Na-LS) retarder and the CaATBS-co-NNDMA FLA wasinvestigated. Here, surprisingly, a dual synergistic effect was found. Na-LSimproves the fluid-loss performance of CaATBS-co-NNDMA, whereas thelatter greatly enhances the retarding effectiveness of lignosulfonate. Theexperiments demonstrate exceptionally high compatibility of both admixtures.The positive effect is based on coprecipitation of both polymers, whichenhances FLA adsorption on cement. At the same time, because of the thickadsorbed polymer layer, the dissolution of the clinker phases is hindered,resulting in the retardation of cement hydration. Finally, it was found thathydroxyethyl cellulose (HEC) and sulfonated formaldehyde polycondensate-baseddispersants - such as poly melamine sulfonate (PMS) or acetone formaldehydesulfite (AFS) - act synergistically; thus, the fluid-loss control provided byHEC is considerably improved. Dynamic light-scattering measurements revealedthat, in the presence of those dispersants, the association of HEC moleculesinto large hydrocolloidal assemblies was greatly enhanced. Obviously, theincreased ionic strength resulting from the polycondensate dispersants rendersthe nonionic HEC molecules less water-soluble and initiates their aggregationat an earlier stage. The larger hydrocolloidal polymer associates can plugfilter-cake pores more effectively, thus reducing cement fluid loss. The studysuggests that multiple additive/additive interactions can occur in oilwellcement. Understanding the underlying mechanisms can help both to avoid unwantedincompatibilities and to develop mitigation strategies.
Natural Gas - No abstract available.
We present a two-level strategy to improve robustness against uncertainty and model errors in life-cycle flooding optimization. At the upper level, a physics-based large-scale reservoir model is used to determine optimal life-cycle injection and production profiles. At the lower level, these profiles are considered as set points (reference values) for a tracking control algorithm, also known as a model predictive controller (MPC), to optimize the production variables over a short moving horizon on the basis of a simple data-driven model. In the process industry such a two-level approach is a well-known strategy to correct for small local disturbances that may have a negative (cumulative) effect on the long-term production strategy. We used a conventional reservoir simulator with gradient-based optimization functionality to perform the life-cycle optimization. Next, we applied this long-term strategy to a reservoir model, representing the truth, with somewhat different geological characteristics and near-wellbore characteristics not captured inthe reservoir model used for the long term optimization. We compared the performance (oil recovery) of this truth model when applying the life-cycle strategy with and without the corrections provided by the data-driven algorithm and the tracking controller. In this theoretical study we observed that the useof the lower-level controller enabled successful tracking of the reference values provided by the upper-level optimizer. In our example, a performance drop of 6.4% in net present value (NPV), caused by differences between the reservoir model used for life-cycle optimization and the true reservoir, was successfully reduced to only 0.5% when applying the two-level strategy. Several studies have demonstrated that model-based life-cycle production optimization has a large scope to improve long-term economic performance of waterflooding projects. However, because of uncertainties in geology, economics, and operational decisions, such life-cycle strategies cannot simply be applied in reality. Our two-level approach offers a potential solution to realize life-cycle optimization in an operational setting.
This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 157022, "Implementing a Process-Safety Program," by Saiee B. Julaihi, Saifuddin Shah B. Sowkkatali, and Rabiatul Adwieah Bt Shukor, Petronas Carigali, prepared for the 2012 SPE/APPEA International Conference on Health, Safety, and Environment in Oil and Gas Exploration and Production, Perth, Australia, 11-13 September. The paper has not been peer reviewed.
The thermodynamic behavior of multicomponent multiphase systems is highly nonlinear, and the coupling to the flow equations is quite complex; as a result, equation-of-state (EOS) -based simulations can be computationally prohibitive. We describe a new K-value method that captures the compositional dependence of the phase behavior. Specifically, we propose a method for selecting compositions used in the tabulation of K-values and define an operator that interpolates the K-values as a function of pressure and composition. The method employs the minimal critical pressure(MCP) to detect supercritical compositions, which allows for effective modeling of multicontact miscible displacements. We compare our K-value approach with standard EOS compositional simulation for several isothermal problems, and we demonstrate the efficiency and accuracy of the proposed method.
After years of efforts, HydrOcean and Ecole Centrale Nantes, supported by GTT, succeeded in the development of an SPH software gathering all functionalities for relevant simulations of sloshing impacts on membrane containment systems for LNG carriers. Based on Riemann solvers, SPH-Flow deals with two compressible fluids (liquid and gas) that interact with the impacted structure through a complete coupling. The liquid, the gas and the structure are modeled by different kinds of dedicated particles allowing sharp interfaces. An efficient parallelization scheme enables performing calculations with a sufficiently high density of particles to capture adequately the sharp impact pressure pulses. The development of the bi-fluid version led, in a first stage, to unstable solutions in the gaseous phase for pressures below the ullage pressure. This difficulty was presented at ISOPE-2010 and has been overcome since. Simulations of a unidirectional breaking wave impacting a rigid wall after propagating along a flume are presented in this paper. The physical phenomena involved in the last stage of the impacts are scrutinized and compared with experimental results from the Sloshel project. A comparison between calculated results at full scale and at scale 1:6 is proposed. Conclusions about scaling in the context of wave impacts are given.
It has been just over 20 years since the last review paper on core analysis appeared in Petrophysics (Skopec, 1992). Comparing the topics covered in that review with the topics of interest to industry today, one is immediately struck by the recent rise and focus in two new areas: digital rock physics and the petrophysical characterization of unconventional source-rock reservoirs, i.e., ‘shale’. This review, which consists of contributions from nine specialists in their respective fields, covers (a) wellsite coring and coring handling, (b) conventional and unconventional core analysis, (c) rock mechanics in support of reservoir engineering, and (d) digital core analysis.
The goals of core analysis today remain the same as those identified 21 years ago: to "reduce uncertainty in reservoir evaluation" and finding ways to obtain this information faster. In the past, the focus was on developing experimental protocols that could shorten the experimental time, such as the continuous-injection-resistivity protocol. Today, the focus has changed to simulating rock properties from micro- and nano-CT images. In the past, we had to be concerned about how to scale up results on a 4×7 cm core plug to reservoir scale. With today’s use of micro-CT imaging, which uses millimeter-size samples, the upscaling to reservoir scale has increased by an additional three orders of magnitude.
With the huge success and rapid development of ‘shale’ resources, the United States is fast becoming the world’s leading producer of hydrocarbons. Underpinning and supporting this effort has been the enormous interest and increase in studying the petrophysics of these reservoirs. In particular, developing shale core-analysis experimental protocols for these challenging ultralow-permeability resesrvoirs and developing characterization methods and techniques that often involve digital rock physics.