Underwater Inspection Using ROV

ADNOC Drilling operates a growing fleet of 22 jack up units. These units require various inspections and tests to ensure that their integrity is maintained while conducting the drilling operations. One of these inspections is the underwater inspection which is required to be carried out twice every 5 years. Traditionally, this inspection is carried out by divers at the shipyard where it is safe for divers to carry out cleaning, visual inspections and NDT of structural welds. Moving the rig to a drydock or a shipyard is a costly and involves a lot of activities related to safety in addition to the out of service time. Loss of revenue is experienced while the rig is out of service, as well as costs associated to the survey, shipyard costs, vessel costs etc. all combining to create an expensive inspection process. ADNOC Drilling Marine and Group Technology adapted a new method for performing the full scope of the underwater inspection offshore using small remotely operated vehicles (ROV), most of the scope is carried out while the rig remains in full operation (while drilling).

Integrated Geomechanical Operations for Successful Field Development: A Case Study from Western Offshore, India

This paper deals with the field development study for an offshore field in the western part of India. The main points of focus are holistic execution of integrated workflows for the delivery of subsea oil and gas wells from a jack up platform in this region. Given that the encountered formations encountered in wells posed significant challenges during the drilling phase, a field level geomechanics study was commissioned to understand and mitigate any challenges and effect smooth drilling and logging operations. Understanding the geomechanical effects by analysing the offset wells drilled in the region provided significant insights into the potential challenges faced while exploring target formations. The proposed well locations were drilled in a structurally complex geological setting. From the analysis of previously drilled wells in the region, it was evident that the variation in insitu properties of the lithologies and the extreme heterogeneity and vugular nature of the encountered carbonates caused significant drillability issues with subsequent losses, excessive cuttings, and several back reaming cycles impacting rig time and leading to generally poor borehole conditions. On the other hand, the shales encountered at shallower depths presented a different challenge, especially with a high swelling tendency, adding to progressively worsening hole conditions and significant fluid invasion. Finally, the basal clastics and the depleted zones with variable rock strengths added to the borehole instability issues, with particular zones projecting losses while others showed influxes. In light of such a plethora of issues, an integrated approach including dynamic real time monitoring of operations, structured LWD and wireline logging programmes, a high level petrophysics, formation evaluation and borehole acoustics for shear radial profiling was carried out. A fit for purpose geomechanical model was built encompassing the results of these analyses and was continually updated in real time during the operations phase. Given the variability in the pressures, temperatures and operational mud weights in each section, execution for successful delivery of the wells was further aided by identification of the optimal mud systems, critical casing setting depths and real time drilling optimization, ensuring good borehole quality throughout for further logging and testing programmes.

Spectral Response of Stationary Jack-Up Platforms Loaded by Sea Waves and Wind using Perturbation Method

The paper addresses non-linear vibrations of offshore jack-up drilling platforms loaded by sea waves and wind in their stationary condition using the perturbation method. Non-linearity of dynamic equations of motion for fixed offshore platforms yields from two factors. The first is load excitation generating non-linear velocity coupling in a dynamic system. This coupling is inherent in the modified Morison equation, involving the excitation function in the form of the sum of the inertial and velocity forces of sea waves, taking into account relative wave–structure kinematics. Moreover, the wind acting on the exciting side causes similar effects. The second source is the subsoil–structure interaction problem, modelled by a system of springs and dashpots that yields stochastic non-linearity of the dynamic system. The matrix equations of structural motion in FEM terms are set up. The perturbation method is adopted to determine the mechanical response of the system, making it possible to determine response spectra of the first and the second approximations for displacements and internal forces of the platform. The paper is the continuation of research detailed in the paper [1]. It is assumed, that the fluctuation parts of the dynamic loading forces are in line with the direction of sea wave propagation. Sea current and lift forces effects are neglected in this study. A numerical example refers to structural data of the Baltic drilling platform in the stationary configuration, i.e. when three legs support the deck above the seawater level.

Reducing ABEX Uncertainties through Hybrid LSTK Contracting: A Factory EPSm Pilot Case Study in South East Asia

Well abandonment and the associated abandonment expenditure (ABEX) are necessary stages in the post cessation of production (Post COP) phase of the asset lifecycles. There are significant risk factors present, which vary in the frequency and severity based on a multitude of factors pertaining to environment, age, well construction techniques and stratigraphy, to name a few. In the case of well isolation and abandonment operations there are opportunities to innovate through factory project execution techniques and commercial approaches, which are enhanced where standardization and commonality of well architecture is present. These techniques focus on reducing risk factors and creating value where conventional thought suggests there is marginal cashflow benefit, in asset retirement obligation expenditure. Through a reduction in the total cost of ownership (TCO), project financial performance below the estimated provisions, can unlock cashflow from relief adjustments on long term liabilities. The Engineering, Procurement, Services management (EPSm) lump sum partial turnkey contracting approach was developed to assist operators in unlocking cashflow in ABEX provisions, through risk reduction via front end well engineering and integration of service provision, allied to fixed price lump sum contracting to control project cost creep due to unforeseen events. A pilot project was undertaken in South East Asia, delivering 64 permanently abandoned wellbores in 38 consecutive days, representing over 8,300-man hours and over 3,500 operating hours. The EPSm contracting approach delivered lump sum partial turnkey well abandonment services in a high-volume factory well abandonment retirement environment. Operations were executed through a dedicated jack-up drilling rig trimmed to an asset retirement specification to reduce OPEX and increase efficiency. The operational project framework implemented pre-abandonment offline operations prior to rig arrival, then simultaneous operations (SIMOPs) concerning 2 primary worksites: the wellhead platform weather deck and the jack-up rig cantilever. Standalone concurrent Phase I slickline operations comprising of two units, were performed offline on the wellhead platform with pressure control equipment to execute primary reservoir isolation operations. Phase II & III operations were executed above, on the jack-up rig cantilever through the drilling riser and pressure control equipment, executing the overburden and surface isolation operations, minimizing online operating time of the jack-up rig. Key Learnings from the pilot project are presented, along with pilot project key performance indicators. The project learning curve, and human performance factors provide insights to areas where there are synergies and opportunities to further reduce risk and the total cost of ownership through an Engineering, Procurement, Services management (EPSm) contracting approach.

Application of Controllable Splitting Grouting Technology in Loess Foundation Reinforcement

Taking the foundation settlement accident of a large heating boiler foundation in a city in collapsible loess area as an example, controllable splitting grouting can be achieved by controlling the grouting pressure, grouting pipe opening form, grouting volume and grouting method etc., so as to stabilize foundation settlement and improve foundation bearing capacity, for the boiler with large uneven settlement, for boilers with large uneven settlement, quicklime piles are used to jack up the foundation after splitting grouting to stabilize the foundation, the foundation is lifted with quicklime piles after splitting grouting to stabilize the foundation. The results show that the grouting amount of soil is within the design range, the grout splits in the soil several times to form a slurry vein, the settlement is stable after boiler reinforcement, the quicklime method can jack up the foundation and reduce the uneven settlement of the foundation, and the use of controllable splitting grouting can basically eliminate the slight collapsibility grade loess, which provides a new idea for solving the similar problem of uneven settlement of collapsible loess foundation buildings.

Hydrodynamic Forces of DP Jack-Up Leg when Operating in Vicinity of Seabed

Leg placement and removal are the two most critical operational modes for dynamically positioned jack-ups when working close to an offshore asset. Any positional deviation may lead to collision and damage to the asset. The industry operates with a weak link between the dynamic positioning (DP) system and the jacking system. Current DP systems operate without any sensors identifying the hydrodynamic force variations on the legs and spudcans, which vary between different leg and spudcan designs. When the spudcan is near to the sea bottom, the hydrodynamic force must be reported to avoid large positional deviations driven by the DP system. This article promotes a mechanism to measure these forces using Computational Fluid Dynamics (CFD) analysis to analyze the jack-up behavior, when the spudcan assembly is operating close to the sea bottom. Introduction A jack-up’s dynamic positioning (DP) control system requires minimum 23–30 minutes for the mathematical model to learn the vessel’s hydrodynamic behavior and response to the environment. Although when moving between locations, DP jack-up vessels provide time for the DP model to learn the hydrodynamic behavior, the spudcan that holds the vessel position and headings does not allow the mathematical model to learn. The residual current remains constant until the spudcan is in the seabed. As a result, the DP mathematical model-building process does not help the DP system to estimate the additional forces in the form of residual current. Soon after the spudcan detaches from the seabed, the vessel drift occurs because the vessel thrusters’ response need a rapid response of thrust and azimuth (directions). The DP system manufacturers currently use a sensorless approach to account for the hydrodynamic forces on the legs and spudcans to build a factor into the mathematical model. The jack-up DP system addresses two simultaneous forces on the legs. The leg element in the air is subject to aerodynamic effects and the leg and spudcan elements in the water are subject to hydrodynamic effects. DP systems currently use drag coefficients (Cd) to compute drag forces, however the hydrodynamic force variations during the complete lowering and raising processes are never completely considered. This weak link in the overall operation leads to positional error and is generally unrecognized by the vessel operators. The risk falls to DP officer and the jacking master to handle. The DP and jacking simultaneous operations mode (SIMOPS) may easily last between 15 and 90 minutes, depending on jacking speed, operational water depth, and field procedures, on approach to the asset. The area of operation is close to the asset, which increases the risk of collision with the asset. Most of the studies on jack-up vessels focus on impact force acting on the leg during touchdown or penetrations, such as Elkadi et al. (2014) and Kreuzer et al. (2014).