Practical Experience Gained Operating a Compact Ultradeepwater Drill Ship

This paper describes the practical experiences gained during the first year of operation of a new Panamax-size ultra deepwater drill ship. The vessel started operations in the Gulf of Mexico in July 2012. The practical experience is offset against the vessel's design expectations: improved safety, an increased drilling efficiency and reduced operational costs. The drill ship is of an integrated design covering vessel, drill tower and equipment handling. The drill ship offers an equal payload compared to other ultra deepwater drill ships but at half the displacement. This paper details the effects of the highly automated onboard material and equipment handling on the vessel's drilling efficiency and on the operational cost. The material and equipment handling is designed around the box girder drill tower that has no V-door limitation and features a drilling side and a construction side, thus minimising flat time. Stands built on one side of the tower can be stored in two set back drums, one on each side of the tower, and taken out when needed. Four pipe handlers are available for handling purposes. This paper covers the field experience with all features of the drill tower that are designed to save time and/or increase efficiency and/or enhance onboard safety. These include the drill tower's dual drawworks eliminating slip-cut procedures, the passive and active heave compensation on the drawworks, and the splittable blocks. The latter allow increasing the block speed for lighter loads. Introduction The tendency in rig building has been an evolutionary trajectory to larger and larger units - currently up to approximately 100,000mt displacement - to enable operations at remote locations, in extreme water depths and under difficult drilling conditions. The building costs and thus the day rates of these units are high. Given their size, the fuel consumption and associated costs and emissions can be significant compared to smaller units. Furthermore, their large sizes limit their field of operation as they are not able to pass certain canals or bridges. In 2007 Huisman started to design a revolutionary unit. The design objectives were to create a compact drill ship capable of drilling complex wells in ultradeepwater. Huisman utilized its integrated design approach: a team of engineers with various disciplines such as Mechanical Engineering, Naval Architecture, Electrical Engineering etc. worked simultaneously together with clients, Noble Drilling and Royal Dutch Shell, who delivered valuable operational input. After approximately 10 months of engineering and various discussion sessions with the clients, Huisman presented the HuisDrill 12000 design.

A review of vertical motion heave compensation systems

The six-degree-of-freedom (6 DOF) motion of the mother-ship, which is caused by wave fluctuation, makes offshore operations difficult. To solve this problem, various heave compensation systems were proposed, as well as the law of wave motion. These heave compensation systems included passive heave compensation system, semi-active heave compensation system, and active heave compensation (AHC) system. However, the empirical formula of wave motion is not suitable for practical offshore operations, and rare AHC systems take the characteristic of compensation into consideration. To study the compensation characteristic of the AHC system based on electric-driven marine winch in the actual sea condition and improve the accuracy of compensation, this work uses the measured data of wave motion, and deduces the motion equations of multi-axial driving system. By substituting the above elements into the AHC system and designing the sliding mode controller (SMC), the simulation results show the ideal compensation effect of the system. By comparing with experimental results, it is concluded that the driving system operates in according with the specified states, and the compensation performance of system is effective. The overall work is conductive to the research on AHC system, as well as the exploitation of marine resources.

Heave motion of supporting ships deeply affect the normally operating, safely launching and recovering of remotely operated vehicles when the sea state becomes rough. A heave compensation system can uncouple the heave movement between supporting ships and remotely operated vehicles. An active heave compensation system which includes a measurement unit, a controlling unit and a hydraulic winch is researched in the paper. For attaining the efficiency of the active heave compensation system, simulating model is built and the computer simulation is achieved. The computer simulation proved the effectiveness of the active heave compensation system. For verifying the correctness of the simulating model and acquiring the efficiency of the real active heave compensation system, an active heave compensation experiment system which includes a heave motion generating unit, a load and an active heave compensation system is built. The movement which created by the heave motion generating unit simulates the heave motion of the supporting ship. The load is a substitute of the underwater vehicle. The result of the active heave compensation experiment certifies the correctness of the simulating model and the effectiveness of the active heave compensation system.

Heave compensated response of long multi-segment drill strings

As the drilling technology has advanced, recent deepwater developments and explorations are currently taking place in Gulf of Mexico, Brazil and West Africa where deeper reserves of oil have become more accessible. The study of the subsea soil (e.g. soil investigation, positioning foundation design) is one of the activities required for the subsea field development. Electromagnetic tests, CPT tests, gravity, piston core or vibrocore samples are obtained by deploying down-hole systems from drilling vessels. However, because of the high costs and low availability of drill ships, and because ship and drill-string motion due to wind, currents and waves affect the quality of the drilling process, robotic drill rigs are currently more widely used. The following paper describes the MeBo200 as a novel underwater drill rig for geotechnical/geological explorations. The MeBo200 drilling rig is lowered to the sea floor and operated remotely from the ship to drill up to 200m into the sea floor at an ambient pressure of up to 400bar. It was developed in cooperation by MARUM Center for Marine Environmental Sciences (University of Bremen) and BAUER Maschinen GmbH. The complete system is transported within seven 20 ft containers. MeBo200 is a second generation of the MeBo, which was the first remote-controlled deep sea drill rig that uses a wireline coring technique. The weight of the MeBo200 is about 10 tons in air and 8 tons in water and therefore it does not need special drill ships to be managed reducing therefore the mobilization costs for worldwide deployment. The MeBo200 was deployed in the German sector of the North Sea in October 2014 to test the functionality of the seabed-based drill rig. Currently MeBo200 is being upgraded with CPT technology from A.P. van den Berg Ingenieursburo bv.

Large shuttle tanker based drill ships have proven to be the first commercially successful new build design alternative for ultra-deep water drilling application. Historical trends indicate that more cost-effective semisubmersible drilling units will follow the drillship designs in ultra-deep water drilling applications. Several suitable designs are being developed and cover a broad range of capabilities, performance, and cost. In evaluating the most cost effective design alternative for a particular application, it is important to understand the cost sensitivity and operational efficiency of various vessel design variables. Detailed cost, performance, and capability comparisons of new ultra-deep water semisubmersibles designs indicate significant cost sensitivity to variables such as structural complexity, design environment, vessel motion performance criterion and transit speed requirements. Design compromises in these areas may not significantly effect the drilling performance for certain applications but can result in significant cost reductions to the drilling unit. This cost reduction potential must carefully be evaluated against the compromises with consideration given to the duration, flexibility, and total information known about the projected drilling program. As more information and knowledge is obtained about specific drilling programs and consistent long term drilling programs evolve, cost effective "fit for purpose designs" will become justifiable. The evolution of commercially successful rig designs are anticipated to be developed in a conservative step by step process that can be accelerated by increased knowledge and experience. With strong deep water demands, this evolution process may occur with considerable overlap significantly reducing the overall time in which cost effective designs are perfected and proven. Future potential cost improvements in ultra-deep water drilling units will continue to strengthen the economic attractiveness of deep and ultra-deep water exploration and development projects. Introduction Except for a few isolated projects, new construction for the offshore drilling industry has been dominant for the past IS years. During the last few years however, the industry has committed to many major hull conversions and has announced orders for the construction new vessels involving over 30 drilling vessels. Several of these vessels are being built or converted for deep water drilling applications but the majority are being built to explore and develop prospects in ultra-deep water. In this discussion, deep water is referred to as water depths ranging from 1,000 to 2,000 meters and water depths greater than 2,000 meters is referred to as ultra-deep water. For the most part, the trend has followed the patterns set previously when the industry has ventured into deeper water. First existing vessels are upgraded to meet the immediate needs of the operators. Then the new building vessel of choice has once again been the drillship or monohull designs. These vessels are easily adapted to carry the heavier equipment and increased variable loads required for supporting activities in deeper water. The characteristics of the larger monohull shows promise of superior motions and increased operability when compared with the smaller vessels of the previous generations The design of the ultra-deep water mobile offshore drilling units (UDWMODU) is rapidly evolving as Operators become more familiar with their long-term requirements and rig designers optimize the variables to increase overall drilling performance in this new market.

The paper investigates warehousing and material handling practices in the civil service of Ghana. The purpose is to ascertain the level of transition from fully manual operations to the integration of technology in warehousing and material handling operations in selected Metropolitan, Municipal and District Assemblies (MMDAs). Data were collected from 40 MMDAs cross the current 10 regions of Ghana. The study noted among others that, most warehouses lacked basic mechanical equipment for effective and efficient operations. Warehouse automation was completely non-existent in all selected Assemblies. In the case of material handling, the research discovered that very little effort has been made to equip employees with the requisite handling equipment for the execution of tasks. The study further revealed that there was virtually no in-service training on effective material handling practices in the civil service of Ghana. Indeed, practitioners most often use their bare hands and feet in handling all forms of materials including hazardous chemicals. The study also indicated that, on few instances where some handling and protective equipment were made available, most employees refused to use them citing reasons that bother on culture and tradition. The study concludes that it is imperative for authorities to put in place policies to protect practitioners in the execution of tasks. Thus, there should be an efficient change management system to ensure a gradual paradigm shift from obsolete warehousing and material handling practices to a much-integrated system where aspects of manual, mechanical and automated systems are combined.

Due to the latest grid codes, wind energy conversion systems (WECSs) are required to remain connected to grid under grid voltage sags and supply reactive power into the grid. So, this paper proposes an enhanced scheme to improve low-voltage ride through (LVRT) capability of doubly fed induction generator (DFIG)-based WECSs under both balanced and unbalanced grid voltage sags. The proposed scheme is composed of active and passive LVRT compensators. The active compensator is performed by controlling the rotor- and grid-side converters of the DFIG to decrease the stator flux oscillations and inject reactive power into the grid. The passive compensator is based on a three-phase stator damping resistor (SDR) located in series with the stator windings. The proposed scheme decreases the negative effects of grid voltage sags in the DFIG system including the rotor over-currents, electromagnetic torque oscillations, and DC-link over-voltage and also injects reactive power into grid to support the grid voltage. So, the LVRT capability of DFIG is enhanced and new grid code requirements are addressed. Simulation results on a 1.5-MW DFIG-based WECS using MATLAB/Simulink demonstrate the effectiveness of the proposed LVRT scheme under both balanced and unbalanced grid voltage sags.

Automated Guided vehicle (AGV) is like a robot that can deliver the materials from the supply area to the technician automatically. This is faster and more efficient. The robot can be accessed wirelessly. A technician can directly control the robot to deliver the components rather than control it via a human operator (over phone, computer etc. who has to program the robot or ask a delivery person to make the delivery). The vehicle is automatically guided through its ways. To avoid collisions a proximity sensor is attached to the system. The sensor senses the signals of the obstacles and can stop the vehicle in the presence of obstacles. Thus vehicle can avoid accidents that can be very useful to the present industrial trend and material handling and equipment handling will be automated and easy time saving methodology.

Remote operational trials with the ITER FDR divertor handling equipment

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A parallel force/position controller is proposed for the control of loads through the wave zone in marine operations. The controller structure has similarities to the parallel force/position control scheme used in robotics. The parallel force/position controller is tested for crane control in simulations and model experiments and the results are presented in this paper. To evaluate the performance of the proposed controller, we study three different control strategies for control of loads through the wave zone: active heave compensation, wave synchronization, and parallel force/position control. The parallel force/position controller gave improved results, in particular, a significant improvement of the minimum value of the wire tension, which is important to avoid snatch loads that may break the wire. The three strategies are tested and compared in simulations and experiments. </para>

A heave compensation system consists of a drill string compensator (DSC) and an active heave compensator (AHC) cylinder, which together produce control force over an oil pressure system suitable for transmission of considerable power and compensating for heaving motion of the hull during drilling work. In this study, a heave compensator of an oil pressure system was simulated to draw a conclusion, which was verified by comparison with the result of a test conducted using an actual miniature model. The compensation rate was 95%, based on which the dynamic behaviors of an actual-size heave compensator were presumed. Furthermore, the speed of each cylinder and the acceleration of heave can be determined and used to fabricate an actual-size heave compensator.

In active heave compensation, in order to realize the smooth control of the heave compensation platform, it is necessary to use the ship motion measurement system to accurately obtain the ship displacement signal, invert the ship displacement signal, and then control the expansion and contraction of the electric cylinder so that the compensation platform remains horizontal. The ship displacement measurement system generally adopts the second integral of the acceleration sensor to obtain the ship displacement signal. During the acquisition process of the ship displacement signal, the quadratic integration process of the acceleration, and the communication process of the output control command, there is a processing lag which makes the error accumulate, resulting in a delay in the measurement of the ship motion. In order to collect the ship motion more accurately and control the heave compensation platform more precisely, this paper proposes a ship motion prediction method based on a variable step-variable sampling frequency characteristic LSTM (Long Short-Term Memory) neural network. First, we use the autocorrelation function algorithm to calculate the inherent delay of the lag in the process of signal acquisition by the measurement system. Secondly, the LSTM neural network is used to predict the inherent delay step of the lagging ship displacement signal. During the prediction process, it is found that the difference in the sampling frequency of the displacement signal will lead to a change in the step of the inherent delay—experiment in the laboratory to verify. By controlling the motion platform to simulate the motion of the ship and using the ship motion measurement system and the laser sensor system to measure the displacement signal of the motion platform synchronously, it is verified that the ship motion measurement system does have an inherent delay. Thirdly, on a sailing ship, ship displacement signals are collected by setting multiple sets of ship motion measurement systems. Finally, multiple sets of sampling frequency and multiple steps are set, and the ship motion is predicted based on the variable step-variable sampling frequency LSTM neural network. It is verified that the prediction accuracy is related to the sampling frequency of the signal collector and the prediction step of the LSTM neural network, which improves the prediction accuracy of the model and the timeliness of ship motion acquisition.

The direct shear test are widely used to measure the bulk material properties for economical design of bulk handling equipment and to estimate wall pressure inside storage structures, namely their bulk density, the angle of internal friction, shear strength, Poisson ratio, and lateral pressure ratios are required. Tests were conducted at thirty six different shear speeds (between 0.30-1.00 mm min-1) and three different normal stresses were applied (60, 120 and 180 kPa). The angle of internal friction, Poisson ratio, and lateral pressure ratios demonstrated fluctuations depending on the shear speeds. The results of the principal component analysis indicated that the first three principal components accounted for 97.40% of the total variability among the thirty six different shear speeds for all the traits investigated. The first principal component was the most important. In the result of principal component analysis, the shear speeds were divided into seven clusters. The pressures were decreased and increased with the change of the angle of internal friction and the lateral pressure ratio. The data obtained from the study will be useful in the structural design of dry bean bins to calculate loads on bins from the stored material and grain handling equipment.