Semi-submersible Drilling Platform Research Articles

TotalEnergies Drills Lebanon’s Qana Prospect Amid New Global Interest in EastMed Gas

_ As of September, TotalEnergies together with partners Eni and QatarEnergy will have spud exploration well 31/1 on Block 9 of Lebanon’s Qana prospect. It is the consortium’s second attempt in 6 years to strike gas in the EastMed where upstream riches at the crossroads of markets east and west struggle against the fiercest of global geopolitical headwinds. Lebanese media hailed the 16 August arrival of the Transocean Barents semisubmersible drilling platform at Block 9 with guarded optimism, reporting on the Barents journey from the North Sea like a sports play-by-play, detailing the landing of the first crew transport helicopter and the offloading of pipe and other equipment delivered by ship to the Port of Beirut. The Lebanese Petroleum Administration busily dotted the i’s and crossed the t’s on the drilling license application that TotalEnergies EP Lebanon had submitted in June while MP Ibrahim Kanaan, head of the parliament’s finance and budget committee, announced creation of the Lebanese Sovereign Fund for Oil and Gas to protect future revenues from political interference. “The rig will start working in Lebanon in September ... before the end of the year we will know if there is a discovery,” Lebanon’s caretaker Energy Minister Walid Fayyad told Reuters at an event earlier this summer in Abu Dhabi. Built to operate in harsh environments the Barents will drill in deep water, its crew hoping to hit the sweet spot that is the Tamar Sands Formation from which Israel, Cyprus, and Egypt are already producing gas for domestic needs and for export. Assuming commercial gas reserves are confirmed in Qana, Lebanon will join the club of EastMed gas producers—a development that would ease Beirut’s seemingly endless energy crisis, give the financially bankrupt country a share of revenues for gas exported to Europe and Asia, and attract further global investment. The World Bank has described Lebanon’s economic collapse as possibly one of the top three most severe worldwide since the 1850s. But while all seems like business as usual, this is the EastMed where political and military conflicts that dog oil and gas projects throughout the world can escalate quickly, driven by political fragmentation and violence within and across borders of countries with the most to gain from big international projects. What might be called a harsh environment in the UK sector of the North Sea where the Barents worked most recently differs greatly from what can be called harsh in the EastMed where technology can’t solve all of a hydrocarbon project’s problems. Drawing Lines in the Sand Beirut awarded exploration licenses in 2017 to drill on its offshore Blocks 4 and 9 to the Total-lead consortium with Eni and, at the time, Russia’s independent gas producer and LNG exporter Novatek. This past January, QatarEnergy farmed in for a 30% stake after Novatek exited. TotalEnergies and Eni each now hold 35%. In the 6 years following the license award, the consortium drilled only one well on the Lebanese shelf—a dry hole on Block 4 in 2020. Though data suggested that the Qana prospect in Block 9 might be different, TotalEnergies delayed further appraisal drilling pending settlement of the maritime boundary between Israel and Lebanon.

Cosimulation of a direct-acting riser-tensioner system – validation with field measurements and sample simulations

In this paper, the cosimulation methodology, presented in earlier works by the authors, is extended to a full scale riser-tensioner system, with the semi-submersible platform and the riser stack being modelled in the ocean engineering software, OrcaFlex, and the hydro-pneumatic tensioner being modelled in the multiphysics software, SimulationX. An interface file coded in Python is used to couple the two models to run the cosimulation. Field measurements from an on-board data acquisition system, mounted on an operational semi-submersible drilling platform, is used to benchmark model performance. The motion time–history of the platform, available in the field data, is used to specify heave motions of the model platform. A planned disconnect sequence is simulated, and the results are compared with field measurements. Subsequently, sample simulations are presented to demonstrate the possibilities of the proposed co-simulation methodology, including a simulation of the whole disconnect procedure, covering the connected, pull-off, disconnected, and soft hang-off phases of the system.

Numerical study on the temporal and spatial distribution law of natural gas explosion load on an ultra-deepwater semi-submersible drilling platform

Offshore drilling platforms are widely used in the field of marine resource exploration and exploitation. Nature gas leakage may occur during operation and production, resulting in explosion accidents. In order to improve the platform's safety assessment capabilities and optimize the layout plan of the future platform, the temporal and spatial distribution characteristics of natural gas explosion load on the platform will be studied without considering the structure response. Therefore, this paper uses FLACS software to establish a model of the latest ultra-deepwater semi-submersible drilling platform, and uses 100% methane premixed gas cloud with an equivalent ratio of 1:1 to simulate the accumulation of natural gas on the platform to study the whole process and distribution law of flammable gas cloud explosion load. At the same time, the interference of other influencing factors can also be excluded when studying the influence of ignition position on the explosion consequences. The results show that the explosion load is an ellipsoidal propagation mode and is more sensitive to the ignition position, and some obstacles have an obvious excitation effect on the explosion development process. The research results of this paper can provide reference for the design and risk prevention of future drilling platforms.

Effects of wave loads on the strength of semisubmersible drilling platform

In order to reduce the failure risk of the structures of semisubmersible drilling platform during its service life, this research studies the effects of ocean wave loads on the strength of the platform’s structures. The response spectra of the platform obtained from model test in wave tank were used to verify the accuracy of the numerical model employed in this research. Eight wave load cases, which may affect the strength of the platform but not involved in the classification societies such as ABS and DNV, were newly considered in this research. The results of the research indicate that a) four of the eight newly added wave load cases are found to be greatly affecting the strength of the platform and need to be considered in designing the structures; b) torsional moment and shearing force caused by the ocean wave would cause the stress of the structures of platform at a high level and need to be carefully evaluated.

Development status and trend analysis of anti-icing semisubmersible drilling platform

In order to speed up the development of Arctic resources, it is the focus of polar drilling equipment research and development to develop a new anti-ice drilling platform which adapts to the harsh environment of polar regions and reduces the construction and operation costs. By briefly analyzing the structure of the existing antiice drilling platform, the design points of the anti-ice semi-submersible drilling platform are obtained, and the development status of the anti-ice semi-submersible drilling platform is analyzed. Finally, the development trend of the anti-ice semi-submersible drilling platform structure is summarized.

Performance of an Advanced Intelligent Control Strategy in a Dynamic Positioning (DP) System Applied to a Semisubmersible Drilling Platform

Oil drilling and extraction platforms are currently being used in many offshore areas around the world. Whilst those operating in shallow seas are secured to the seabed, for deeper water operations, Dynamic Positioning (DP) is essential for the platforms to maintain their position within a safe zone. Operating DP requires intelligent and reliable control systems. Nearly all DP accidents have been caused by a combination of technical and human failures; however, according to the International Marine Contractors Association (IMCA) DP Incidents Analysis, DP control and thruster system failures have been the leading causes of incidents over the last ten years. This paper will investigate potential operational improvements for DP system accuracy by adding a Predictive Neural Network (PNN) control algorithm in the thruster allocation along with a nonlinear Proportional Integral derivative (PID) motion control system. A DP system’s performance on a drilling platform in oil and gas deep-water fields and subject to real weather conditions is simulated with these advanced control methods. The techniques are developed for enhancing the safety and reliability of DP operations to improve the positioning accuracy, which may allow faster response to a critical situation during DP drilling operations. The semisubmersible drilling platform’s simulation results using the PNN strategy show improved control of the platform’s positioning.

Research on the Integration Design of Double Well Head Drilling System for Semi-submersible Drilling Platform

In order to upgrade the capability in offshore drilling and exploring, it is imperative to design and study deep water drilling system. Firstly, surveying and researching the present situation and development status of deep water drilling system. Secondly, analysing the characteristics and configuration of the deep water drilling rig used for semi-submersible drilling platform, also selecting key equipment. Finally, designing and coming up with a dual-frame derrick drilling system with 3660 meters water depth and 15250 meters drilling depth, compared with the trade technology, its advantage: achieving top drive core and realizing continuous drilling, allowing duplex main wellhead operation, the two wellhead could be working at the same time, and a well is being used to piping, and another well is being used for drilling. As a result of saving the non-drilling time and increasing the drilling efficiency. It is of great significance to the development of marine energy sources.

Numerical Solution of Two-Point Static Problems for Distributed Extended Systems by Means of the Nelder–Mead Method

The authors describe a numerical algorithm for reducing two-point static problems of distributed extended systems in the field of body and surface forces to a nonlinear programming problem that can be solved by numerical methods. Variations in the dimension of the physical problem being solved do not change the entire numerical algorithm, but only lead to replacement of some of its blocks. Numerical examples illustrating the described algorithm are given. The problems of determining power and geometric characteristics of deep water intake of nuclear power plants, assessing the quality of the diverter and determining the stiffness coefficient of the anchor coupling of semi-submersible drilling platform are considered as examples of nonlinear programming problems.

Optimal generation scheduling for a deep-water semi-submersible drilling platform with uncertain renewable power generation and loads

Owing to the depletion of oil reserves and the low efficiency of traditional deep-water semi-submersible drilling platforms, the application of photovoltaic generation and energy storage systems in marine power systems has been increasingly attracting attention. However, the intermittent and uncertain nature of solar energy brings crucial challenges in maintaining stable and sustainable operations. Furthermore, unlike land-based power systems, the deep-water semi-submersible drilling platform depends on a dynamic positioning system to be fixed in an area of deep water for producing oil, but irregular and stochastic waves make the outputs of a dynamic positioning system uncertain, increasing the difficulty and complexity of energy management. This paper develops a novel hybrid day-ahead probabilistic scheduling method to reduce the total fuel cost of the whole system and improve the energy efficiency; the method combines Taguchi's orthogonal algorithm with particle swarm optimization and a probabilistic load flow method. A detailed model of the deep-water semi-submersible drilling platform is established to validate the proposed method, which is compared with various classical methods. With the help of the proposed method, the total operation cost and greenhouse gas emissions are reduced from $7562.52 to $7333.68, and from 18.95 tons to 16.81 tons, respectively. Furthermore, compared to the two-point estimation method, the experimental times drops by half, which minimizes the computational burden. The simulation results clearly demonstrate the necessity for day-ahead energy scheduling, and the advantages of the proposed method.

Research on facility layout optimization algorithm of deep-water semi-submersible drilling platform

We aimed to create a facility layout design of semi-submersible drilling platform (DSDP) with performance constraints. The Boltzmann survival mechanism of simulated annealing algorithm was introduced into the replacement strategy of genetic algorithm to form an improved genetic algorithm called genetic and simulated annealing algorithm (GASA). The new algorithm alleviates the “combination explosion” and premature convergence of the traditional genetic algorithm. The layout problem of DSDP is efficiently solved by using this new algorithm. When the number of layout objects increases, GASA’s performance is better than that of the genetic algorithm.

Динамическое взаимодействие моноблоков между собой и с судном при монтаже буровых платформ наплывным способом в условиях волнения

Динамическое взаимодействие моноблоков между собой и с судном при монтаже буровых платформ наплывным способом в условиях волнения

Load Assessment on the Horizontal Braces of Semi-submersible Drilling Platform Under Ocean Wave

In order to make sure the horizontal braces of semi-submersible drilling platform are safe during its service life, this research studies the load assessment on the horizontal braces of a platform under harsh wave loads. The hydrodynamic structure model of the platform has been established, and hydrodynamic conditions have been determined firstly. The model test in a wave tank is used to verify the accuracy of the established model in this research. Then, the loads response of the horizontal braces under several typical wave loads which affect the strength of floating structures greatly are evaluated. The results of the research indicate that (a) the splitting force between pontoons and vertical bending moment are found affecting the strength of the horizontal braces greater than the other loads; (b) both the splitting force and vertical bending moment would occur when the platform encounter beam wave; (c) the horizontal braces are loaded on 4.16% of splitting force between pontoons and 2.78% of the vertical bending moment respectively during its service life.

A new type of anti-heave semi-submersible drilling platform

Abstract A new type of semi-submersible drilling platform is designed. The numerical simulation software is used to analyze the heave response of the new platform in the frequency domain and time domain, and the semi-submersible drilling platforms with double-floating four-column structure and heave plate structure are compared with the new platform. This paper introduces the design principles of the new platform and the theoretical basis, mathematical model and boundary conditions during correlation analysis. The numerical simulation results show that the maximum and mean values of the heave response of the new platform are significantly reduced in the frequency domain analysis compared with the double-floating four-column and the heave-plate structure platform; and the new platform has a significant increase in the natural heaving period of the new platform, which can effectively prevent the occurrence of resonance. In the mooring time domain coupling analysis, the surge, sway and roll response of the new platform is small, and the heave response is greatly reduced. In the spectral analysis, the new platform has a smaller peak response and better wave frequency characteristics. The new platform has excellent anti-heave performance, reasonable structure and feasibility, and can provide reference for the design and selection of new generation semi-submersible drilling platform.

A simple early warning method for large internal solitary waves in the northern South China Sea

Internal solitary waves (ISWs) are ubiquitous phenomena in many coastal oceans, especially the northern South China Sea (SCS). They can pose a serious threat to the deep-water drilling platforms and other ocean engineering structures. In this paper, we describe a simple and economical early warning method by estimating ISW propagation speeds using the measurements by a single acoustic Doppler current profiler (ADCP). This method is based on the Korteweg-de Vries (KdV) equation. As an example, a set of observational data collected by mooring buoys at the Liwan block (19–20°N, 115–116°E) of the northern SCS are used to calculate the propagation speeds and directions of measured ISWs. The accuracy of estimated ISW propagation speeds is also tested by tracking the signals of ISWs using two ADCP moorings and it is found that the prediction deviation is less than 10%. The force and torque exerted by an ISW on a semisubmersible drilling platform are also estimated according to Morison’s equation and other empirical formulas, which can provide a reference for safety controls on offshore platforms.

Sensitivity analysis of wave slamming load with respect to wind load for semi-submersible platform design

A design of offshore floating structure is mainly based on the extreme response analysis due to the forces experienced. The extreme response can induce the negative air gap response and potential impact to the deck bottom of floating structure. It is important to predict the slamming load in order to check the strength of local structures which withstand the wave slamming. In recent years, studies of the effects of wind load on air gap response and slamming load are ignored. When the platform suffers the extreme wave, the wind is also harsh. Moreover, the wind load can affect the motion response of the platform. The wind load cannot be simulated easily by model test in towing tank whereas it can be simulated accurately in wind tunnel test. Though the model test results are not accurate enough for air gap and slamming load evaluation due to the loss of wind effect, they can be used as a good basis for tuning the radiation damping and viscous drag in numerical simulation. This paper aims at presenting the sensitivity analysis results of wave slamming load with respect to the wind load for the design of semi-submersible platform. As an example of semi-submersible drilling platform design, the wind tunnel test has been carried out, and the sea-keeping model test is also performed in towing tank, while the wind load effect is ignored. According to the model test results, a numerical model is tuned and validated by ANSYS AQWA. Sensitivity analysis studies of the relative velocity between water particle and platform surface and the wave slamming load with respect to the wind load are performed in time domain by the tuned numerical model. Five simulation cases about the presented platform are simulated based on the results of wind tunnel tests and sea-keeping tests. The sensitivity analysis results are valuable for the floating platform design.

Applying a New Adaptive Genetic Algorithm to Study the Layout of Drilling Equipment in Semisubmersible Drilling Platforms

This study proposes a new selection method called trisection population for genetic algorithm selection operations. In this new algorithm, the highest fitness of 2N/3 parent individuals is genetically manipulated to reproduce offspring. This selection method ensures a high rate of effective population evolution and overcomes the tendency of population to fall into local optimal solutions. Rastrigin’s test function was selected to verify the superiority of the method. Based on characteristics of arc tangent function, a genetic algorithm crossover and mutation probability adaptive methods were proposed. This allows individuals close to the average fitness to be operated with a greater probability of crossover and mutation, while individuals close to the maximum fitness are not easily destroyed. This study also analyzed the equipment layout constraints and objective functions of deep-water semisubmersible drilling platforms. The improved genetic algorithm was used to solve the layout plan. Optimization results demonstrate the effectiveness of the improved algorithm and the fit of layout plans.

APPLICATION OF THE RANS FLOW MODEL FOR THE ANALYSIS OF THE MOTION OF FLOATING OBJECTS IN WAVES

The present paper describes a proposal of the method for simulating the motion of freely floating and moored objects in waves, based on the RANS (Reynolds Averaged Navier-Stokes Equations) flow model. Attempts on using this model for simulating the floating body dynamic started quite recently due to its large requirements for the computer power. Only in the past few years such analyses became more common, however, no unique approach can be observed due to large variety of existing possibilities, numerical methods etc. The paper includes the description of the proposed method, which consists in mesh generation technique, efficient wave generation method, and the mooring system module, as well as two samples of marine applications: analyses of the motion of fishing vessel in head waves and the motion of moored semi-submersible drilling platform. The results were verified basing on the towing tank

Numerical analysis of hydrodynamic interaction between the linear waves of Caspian Sea and Amirkabir semi-submersible drilling platform

Semi - submersible drilling platforms are huge bulk structures for extracting the oil products from great depth of seas. For such bulk structures, the Morrison's equations are no longer valid for determining the loads applied to the semi-submersible drilling platforms. The diffraction theory should be used for evaluating the hydrodynamic interactions between the platform and the sea waves. In this theory, the Laplace equation is solved by considering the boundary conditions of the diffraction theory. In this paper, after a brief description of the diffraction theory, the hydrodynamic interactions between the Iran's Amirkabir semi-submersible drilling platform and the regular linear waves of Caspian Sea is investigated numerically using boundary element method in the ANSYS/AQWA software. The induced waves exciting forces and moments with different wave heading angles are estimated for six degrees of freedom relative to the waves frequencies using the diffraction theory. The performed hydrodynamic analysis is also validated with the previous works performed for Spar platforms. }}

Technology Focus: Offshore Facilities (February 2012)

Technology Focus Last year, we reviewed some of the more-prominent examples of how the industry continues to respond to the need for safe and cost-effective production facilities in ever-more-challenging environments. We also highlighted the increasingly important role that constructive collaboration can play in facilitating the desired outcomes for all parties. This year, we illustrate how this same theme of constructive collaboration has been applied effectively at the other end of an offshore facility’s life span, in the major decommissioning program for the Frigg field. Most of us are very familiar with the term offshore hookup, but soon we may become equally familiar with what offshore “hookdown” really involves. We also take a look at an approach for safely extending the useful life of aging offshore-production infrastructure, in locations where the subsea tieback of new fields warrants the associated investment. Our focus is not entirely on end-of-life scenarios though. New offshore-platform concepts continue to evolve to suit the changing needs of operators. Some of these aim to offer the reduced well cost of fixed structures with the redeployment advantages offered by floating structures. One of the most challenging new frontiers for the offshore industry and for society at large is the Arctic region. More specifically, it is development of underwater hydrocarbons where the presence of ice affects the nature of the development. Moving into any new frontier first requires gathering sufficient environmental data to be able to predict quantitatively the character and envelope of conditions at that location throughout the field’s production lifetime. We take a look at how these issues are being addressed in the specific case of the proposed Shtokman-field floating production facility. As we return for this annual JPT Focus on the technology associated with offshore oil/gas facilities, it is timely to mention the launch of the new SPE magazine Oil and Gas Facilities, primarily geared toward the whole offshore-facilities sector. This effort represents a significant initiative to broaden the appeal and relevance of SPE to the wider oil/gas community, and any feedback that you may have in this regard would be welcomed warmly. Recommended additional reading at OnePetro: www.onepetro.org. OTC 21708 Decommissioning of Frigg and MCP01—A Contractor View by T. Gram, Aker Solutions, et al. OTC 22505 The First Dry-Tree Semisubmersible Drilling and Production Platform Sold by Roberto Noce, Moss Maritime, et al. OTC 22078 Design Considerations for an Arctic Intervention Vessel by Tor Einar Berg, Marintek, et al.

The wind tunnel tests of wind pressure acting on the derrick of deepwater semi-submersible drilling platform

The increasing importance of the sustainability challenge in ocean engineering has led to the development of floating ocean structure. In this study, according to the 1/100 scale model of the HYSY-981 semi-submersible platform, the investigation on the wind resistant properties of the platform is measured through wind tunnel tests. The wind pressure coefficients of the derrick in 0∼90°wind directions were obtained by calculation. The distribution of the wind pressures on windward side of the derrick was studied. These results may serve as a reference on the design for wind loads acting on the platform.