Mobile Offshore Drilling Units Research Articles

Port State Control of Offshore Supply Ships, MODU and FPSO Units

The Port State Control system aims to ensure that all ships are subject to regular inspections, with particular attention to the ships of insufficient quality. To this end, during the inspection, priority is given to ships that are considered risky. Thetis database is an information system that contributes to the implementation of the Port State Control within the EU (European Unit). It contains data on inspections performed in the EU ports and the Paris Memorandum area. The Paris Memorandum has 27 member states and covers the waters of European coastal states and the North Atlantic basin from North America to Europe. The main goal of the Paris MoU (Memorandum of Understanding) is to eliminate substandard ships through a harmonized Port State Control system. Namely, inspections should ensure that ships meet international safety standards, are safe for the environment, and provide adequate living and working conditions for workers. The primary responsibility for ensuring these standards rests with the ship owner/shipper while the responsibility for ensuring such compliance rests with the flag state. The aim of this analysis is to determine the number of inspections performed in the ports of the Republic of Croatia and the Republic of Italy, to identify the cause of ship detentions and the most common deficiencies of offshore supply vessels, MODU (Mobile Offshore Drilling Units) and FPSO (Floating Production Storage and Offloading) Units. In the observed period, the impact of the crisis caused by the COVID-19 pandemic was significant, resulting in the decline in the numbers of inspections performed in 2020 and 2021. In 2022, the number of inspections increased, but it still has not reached its pre-pandemic level. During the period that was the subject of research, port state inspections in the Republic of Croatia and the Republic of Italy revealed 241 deficiencies. Five areas with the largest number of deficiencies are: Certificate & Documentation, Safety of Navigation, Fire Safety, ISM, and Life-saving appliances, which follow the trend of the lack in the areas of the Paris Memorandum. The greatest increase in deficiencies was recorded in the areas of Labor Conditions-Health protection, Certificate & Documents (Crew Certificate, Documents), Emergency System and Fire safety area, which led to an increase in the number of offshore supply ships retention during the first half of 2022.

Dynamic drift-off warning limits for dynamically positioned MODU with Deepwater Artificial Seabed (DAS) system coupling

A new Deepwater Artificial Seabed (DAS) drilling system, which enables the shallow-water rated drilling equipment to operate in deep and ultra-deep water, has been developed for dynamically positioned Mobile Offshore Drilling Unit (MODU), with a focus on key issues of well access and riser design. Nevertheless, the MODU may drift-off due to the critical failures of the dynamic positioning (DP) system and thus the well integrity will be gravely threatened. This study is committed to establishing the quantitative criteria of drift-off warning limits, which consist of the yellow limit, red limit and physical limit, for dynamically positioned MODU with the coupled DAS drilling system. To achieve this aim, a three-phase methodology is proposed on the basis of a fully coupled model of the MODU-DAS drilling system. Furthermore, a hybrid method integrating the orthogonal experimental design, back propagation neural network, and Garson's algorithm is developed to systematically investigate the importance of the correlative influencing factors on the drift-off warning limits in consideration of both the efficiency and accuracy of the numerical calculations. The validity of the proposed methodology is demonstrated by a case study. The results indicate that the dynamic drift-off warning limits are able to assist in decision-making of safe DP operations on the MODU and the operating depth of the artificial seabed is the most critical factor affecting the envelope of drift-off warning limits. These findings and recommendations could improve the safety of DP drilling operations.

Transient response of an innovative Deepwater Artificial Seabed (DAS) system under tendon failure conditions

An innovative Deepwater Artificial Seabed (DAS) drilling system is developed to overcome the demanding technical and economic limitations for offshore drilling activities in deep and ultra-deep waters, with a focus on important issues of well access. However, tendon failure poses significant threats to the well integrity of the DAS drilling system. This study is committed to investigating the transient effects of tendon failure on the response of the fully coupled DAS drilling system. A nonlinear model, which couples the Mobile Offshore Drilling Unit (MODU), artificial seabed, riser system, intact and fractured tendons, is established firstly. Based on this, the transient response characteristics are systematically investigated in consideration of tendon breakage scenarios, covering the artificial seabed motion, the tendon tension, the strength of the drilling riser and tieback casing systems. The results indicate that the transient motion responses of the artificial seabed behave as large translational and rotational movements nonlinearly under tendon failure conditions. However, the heave motion of the inner artificial seabed, by contrast, is quite small due to the decoupling effect between the outer and inner artificial seabed in the vertical direction. Besides, the maximum tensions in neighboring tendons increase sharply caused by the transient effects of tendon failures, which may lead to cascading failure effect, even a total loss of the DAS drilling system. These findings can contribute to the safe design and operation of the DAS drilling system.

Low Frequency Wave Loads and Damping of Four MODUs in Severe Seastates With Current

Abstract Model tests have been performed with four mobile offshore drilling units (MODUs) with the aim of identifying wave drift forces and low-frequency damping. The MODUs configuration is different, namely on the number and diameter of columns; therefore, the sample is representative of many of the existing concepts. The model scale is the same as well as the wave and current conditions. The experimental program includes irregular waves with systematic variations of the significant wave height, wave peak period, current velocity, and vessel heading. A nonlinear data analysis technique (cross bi-spectral analysis) is applied to identify the surge and sway quadratic transfer functions (QTFs) of the slowly varying excitation, together with the linearized low-frequency damping. The paper also presents a semi-empirical formula developed in the scope of the EXWAVE JIP to correct potential flow mean wave drift force coefficients of Semis in high seastates with current. The empirical QTFs are then compared with numerical predictions. Comparisons with potential flow coefficients lead to conclusions on the role of viscous drift. The semi-empirical formula is assessed based on comparisons with test results and concluded that it provides a significant improvement compared to potential flow predictions.

Stability Assessment of Drill Ship Using Probabilistic Damage Stability Analysis

Drill ship is a ship-shaped structure with a drilling unit at its center and with oil compartments, which is moored and kept in position using anchors. These ships should be capable of working in deep sea for a long time, hence affected by harsh ocean environment. Drill units are said to have greater heave motion, and the height of the derrick influences the vessel’s stability. MARPOL Oil Outflow Analysis is performed for damaged crude oil carriers or tankers and Mobile offshore drilling units (MODU) in damaged condition. In the present study, probabilistic analysis is performed on drill ship to understand its stability behavior under damaged condition. Stability assessments are carried out by considering single and multiple damage locations. Oil outflow analysis is carried out for different damage cases of oil tank. Probabilistic damage assessment is done for load cases up to 50% flooding, to obtain stability charts. These charts will be useful to understand variations in stability parameters under damaged conditions.

Characterization of Miscellaneous Effluent Discharges from a Mobile Offshore Drilling Unit to the Marine Environment.

A study was performed to evaluate the potential biological impacts from 8 different miscellaneous discharges from an oil and gas mobile offshore drilling unit (MODU) including deck drainage, desalination unit waste, boiler blowdown, fire control system test water, noncontact cooling water, and bilge water. Samples were evaluated for toxicity using a rapid (<1 h) initial screening test (echinoderm [Dendraster excentricus] fertilization test), and if toxicity was found, further testing was conducted using 3 chronic whole-effluent toxicity tests. This additional testing included the embryo larval development 72-h echinoderm (D. excentricus); 7-d mysid (Americamysis bahia) survival, growth, and fecundity invertebrate test; and 7-d topsmelt (Atherinops affinis) survival and growth fish test. Toxicity identification evaluations were performed on 3 discharges that consistently elicited a toxic response during whole-effluent toxicity testing. To place the results of the toxicity testing into the context of environmental risk, the spatial extent of potential biological effects was investigated using the CORMIX mixing zone model. The output of the modeling indicated that discharge of selected effluents did not result in concentrations, or duration of exposure, that would elicit toxic effects to organisms living in the surrounding environment. The present study provides a comprehensive data set that was used to characterize potential toxicity and environmental risk of MODU "miscellaneous discharges" which could help inform future risk assessments of these discharges. Environ Toxicol Chem 2019;38:2811-2823. © 2019 SETAC.

Virtual prototyping: a case study of positioning systems for drilling operations in the Barents Sea

ABSTRACTThis study proposes a framework for comparative study on three different positioning solutions for mobile offshore drilling units (MODUs) using high modulus polyethylene (HMPE) ropes, including active mooring with an HMPE rope, conventional dynamic positioning (DP) and active hybrid position-keeping (AHP-K). The goal of the positioning systems is to keep the MODU above the wellhead with acceptable riser-angle loading, minimal energy consumption, reduced underwater noise generation, and harmful emissions. This is the first time a holistic study has been performed on positioning that factors in the financial and environmental costs. The time domain simulation, which includes sea-state, wind, and current profiles, is performed with a well-developed software architecture and control algorithms for MODU position-keeping. The case study addresses a MODU drilling in the Barents Sea. Simulation results show that AHP-K is more efficient compared to the other two positioning solutions for drilling operations in the studied environment.

The 2010 Oil Spill in the Gulf of Mexico: Flow-Rate Estimation Based on Satellite-Images Analysis1

Abstract The Deepwater Horizon Mobile Offshore Drilling Unit (MODU) was one of several classes of floatable drilling systems. The explosion on April 20, 2010 led to fatalities and the worst oil spill in the U.S. We present an independent estimate of the oil-flow rate into The Gulf caused by the drill-pipe rupture. We employed the NASA Moderate-Resolution Imaging-Spectroradiometer (MODIS) satellite photographs, starting from the days immediately following the disaster, to determine the magnitude of spill. From these images, we obtained the surface area of the spill and calculated the oil flow rate by two different methods based on contrasting luminance within that area. The first assumes a constant thickness for the total area with upper and lower bounds for the thickness. The second separates the area into different patches based on the luminance levels of each. The probability density function (PDF) of such luminance plots showed natural groupings, allowing patches be identifiable. Each patch maps to a specific thickness. This second approach provides a more accurate average thickness. With the assumption that evaporation and other loss amounted to ∼40% of the spill, we obtained, from the first method, a flow rate ranging from 9,300 barrels per day (BPD) to 93,000 BPD. A value of 51,200 BPD was obtained using patch-separation method. This latter estimate was a plausible value, obtained from the current analysis, but with no details presented in an Extended Abstract in OMAE2012, is remarkably consistent with the “official U.S.-Govt. estimates.”

Drilling Riser Model Test for Software Verification

Marine drilling riser is subject to complicated environmental loads which include top motions due to mobile offshore drilling unit (MODU), wave loads, and current loads. Cyclic dynamic loads will cause severe fatigue accumulation along the drilling riser system, especially at the subsea wellhead (WH). Statoil and BP have carried out a comprehensive model test program on drilling riser in MARINTEK's Towing Tank in February 2015. The objective is to validate and verify software predictions of drilling riser behavior under various environmental conditions by the use of model test data. Six drilling riser configurations were tested, including different components such as upper flex joint (UFJ), tensioner, marine riser, lower marine riser package (LMRP), blow-out preventer (BOP), lower flex joint (LFJ), buoyancy elements, and seabed boundary model. The drilling riser models were tested in different load conditions. Measurements were made of microbending strains and accelerations along the riser in both in-line (IL) and crossflow (CF) directions. Video recordings were made both above and under water. In this paper, the test setup and test program are presented. Comparisons of results between model test and RIFLEX simulation are presented on selected cases. Preliminary results show that the drilling riser model tests are able to capture the typical dynamic responses observed from field measurement, and the comparison between model test and RIFLEX simulation is promising.

Integrated Simulation Increases Efficiency of Deepwater Risk Management

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 180351, “Deepwater Well Control: Integrated Simulation for Risk Management,” by Fritz Golding, Noble; John Spath, Talos Energy; and Bob Newhouse, Newhouse Consultants, prepared for the 2016 SPE Deepwater Drilling and Completions Conference, Galveston, Texas, USA, 14–15 September. The paper has not been peer reviewed. As deepwater drilling moved into the dynamic-positioning (DP) era, many drilling contractors and operators lacked an evidence-based approach for identification of potential process-safety and well-control failure points. In an effort to better understand well issues, operational-procedure adequacy, well-control intervention practices, and human factors, a global offshore drilling contractor created a program of fully integrated deepwater-DP-drilling simulation exercises to scrutinize all critical aspects of deepwater well-control operations. The result is a proactive, behavior-based risk-management process. A Sea Change in Drilling Beginning in the early 2000s, offshore drilling experienced significant growth in demand. This increased demand, driven by rising commodity prices and the macro economic phenomenon of rapid economic development in China and India, combined with enhanced technological developments enabling drilling in deeper water, led the industry into a new era. With the move to deeper water and enhanced DP operations, the industry faced unprecedented demand for drilling units and, therefore, new personnel. In the early 2000s, more than 150 new deepwater mobile offshore drilling units (MODUs) were under construction, creating a need for tens of thousands of new crew members. A sector that had historically hired frontline workers and grown them into drillers and managers over a period of years suddenly needed to hire thousands of new employees each year with virtually no time for them to learn on the job. In addition, both old and new crews were dealing with new technology, resulting in daunting training challenges. Many of the new crew members were going directly to the latest and most-complex rigs being built. New Approach to Training Needed. The effect of all this change and innovation on crew development has been pronounced. Research indicates that technology-intensive systems require considerable operator and crew expertise for effective use. But drilling operations also require the wealth of tacit (undocumented) knowledge that many long-term drilling professionals possess. The older and newer generations do not necessarily share a mental model for tasks that require their collaboration, and any given task may itself involve hundreds of steps that have become automatic for people with long experience but that often have not been recorded because of the long-standing practice of on-the-job training. While technical-skills training remains vitally important, teamwork and interdependence among drilling, DP, and power-management crews on DP MODUs remain critical to process safety. The merging of groups of professionals from these different disciplines into an integrated team capable of working collaboratively has become more important than ever. The company recognized that the most effective training programs for DP MODU operations must address both the individual technical skills and competencies and the human factors necessary for safe and efficient operations.

섬유로프 계류시스템의 크리프 효과가 부유체의 운동응답 및 계류선의 장력 변화에 미치는 영향에 관한 연구

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

Implementation of the Contingency Plan On Offshore Units Including Mobile Offshore Drilling Units

Abstract The article discusses practical application of the contingency plan (called also the emergency response plan) to the risks that may occur on an offshore unit. The author, based on her own professional experience, discusses the plan and illustrates its use in practice based on selected elements of the plan for mobile offshore drilling units engaged in the exploration of resources beneath the seabed. The paper discusses the requirements of Directive 2013/30/EU, which is includes obligation to implement the contingency plan relating to offshore units, in order to prevent accidents resulting from offshore oil and gas operations.

A risk management approach to safe mooring systems in Australia

In March 2015, during cyclone Olwyn, a mobile offshore drilling unit (MODU) experienced a mooring failure and loss of position event. The MODU was blown some three nautical miles off location in the vicinity of subsea and surface infrastructure. There are serious safety, environmental, financial, and reputational risks that can be presented by a loss of mooring position. In response, NOPSEMA hosted a workshop with members of APPEA, the International Drilling Contractors Association (IADC) and with mooring contractors with a view to collectively improve the management of risks associated with the mooring of MODUs in Australia’s tropical waters, both in the short and longer term. Following this workshop, NOPSEMA issued an Information Note for the 2015/16 cyclone season, describing the regulators’ expectations of industry duty holders in respect of MODU mooring system management. At the same time, APPEA’s Drilling Industry Steering Committee (DISC) members aligned on the key principles underpinning a MODU mooring system approach. In late 2015, the APPEA DISC members commissioned a working group to develop a guidance framework for MODU mooring management in Australian tropical waters. DISC aims to work closely with industry partners such as IADC and specialist mooring contractors in the development of this framework. DISC has tasked the working group to have the guidance framework ready for the 2016/17 cyclone season, and for presentation at the 2016 APPEA Conference. The completed case study, presented at the APPEA Conference, provides an excellent example of a goal-setting and continuous improvement regulatory regime working as designed and intended.

Dynamic simulation of the wireline riser tensioner system for a mobile offshore drilling unit based on multibody system dynamics

In this study, a wireline riser tensioner (WRT) system was dynamically simulated to analyze the dynamic response of the riser string in a mobile offshore drilling unit (MODU) such as a drilling rig or a drillship. The main function of the WRT system is to sustain the tension to avoid buckling, regardless of the MODU motion. The WRT system consists of a tensioner ring, a wireline, pneumatic cylinders, and air pressure vessels (APVs). It reduces the vertical (heave) motion of the top of the riser string caused by the MODU motion. In this study, the equations of motion of the drilling rig and the WRT system were formulated based on multibody system dynamics. The discrete Euler–Lagrange equation was used to formulate the equations of motion. For the external forces, both the hydrostatic and hydrodynamic forces were considered. Several simulations were performed with various sea states to analyze the motion of the riser string and the efficiency of the WRT system. Furthermore, the gas volume inside the APVs was changed to investigate its impact on the efficiency and performance of the WRT system.

Investigation of jack-up leg extension for deep water operations

Since the first jack-up was built, jackups have become the most popular type of mobile offshore drilling unit (MODU) for offshore exploration and development purposes in shallow water. The most pivotal component of the jack-up unit is the leg, which can directly affect the global performance of the unit. In this paper, an investigation into extending the length of the jack up leg is carried out in order to study the enhancement of the rig capability to drill in deeper water approaching the range of the Semisubmersible Drilling Unit (SSDU) (300-1000ft). A study of the performance of a deep-water jack-up unit is performed with different leg lengths. Typical leg scantling dimensions and identical external loads are assigned, and then a detailed Finite Element Analysis (FEA) model is created in order to simulate the jack-up leg unit’s structural behavior. A Multi-point Constraint (MPC) element together with the spring element is used to deal with the boundary conditions. Finally, a comparative analysis for five leg lengths is carried out to illustrate their performance, including the ultimate static strength, and weight.

Numerical analysis and verification of pile penetration into stiff-over-soft clay

Abstract A numerical model for jack-up penetration process was built based on the geotechnical centrifugal model test by Hossain M S. The soil flow mechanism and the relationship between penetration depth and penetration resistance were analyzed based on numerical results. The distribution pattern of the spudcan bottom pressure was investigated for the first time. The numerical results are in good agreement with Hossain M S experimental results, which indicates that the proposed model is reliable. The numerical results show that, soil flow failures, such as surface and interface swelling, cavity formation, and soil backflow, happen in the penetration process; the lower the strength ratio between stiff and soft clay is, the smaller the volume of stiff block under the spudcan is, the more continuous and uniform the stiff clay distribution above the spudcan is, and the deeper the cavity is. The higher the soil unit weight, the more the backflow stiff soil above the spudcan and the shallower the cavity. The soil unit weight has almost no effect on the stiff soil shape and volume under spudcan. The higher the strength ratio between stiff and soft clay or the lower the soil unit weight is, the more likely the punch-through occurs. The bottom pressure first increase, then decrease, and increase sharply, from inside to outside, which proves that the linear assumption of the spudcan bottom pressure in ‘Rules for Mobile Offshore Drilling Units’ does not conform to the fact.

A Primer on the Offshore Contract Drilling Industry

Mobile offshore drilling units (MODUs) are specialized marine vessels used to drill subsea wells to find and produce hydrocarbons. The contract drilling industry is critical to the offshore oil and gas supply chain, and market dynamics are an important factor in the costs to drill an offshore well. In this article, an introduction to the industry is provided with an emphasis on the factors that influence rig day rates and market structure.

Lessons Learned Following Macondo - Safety Enhancement

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper OTC 23436, ’Lessons Learned Following Macondo - Safety Enhancement on the US Outer Continental Shelf,’ by J.G. Lantz, P.E. Little, J.P. Nadeau, and J.D. Reynolds, US Coast Guard, prepared for the 2012 Offshore Technology Conference, Houston, 30 April-3 May. The paper has not been peer reviewed. The US Coast Guard is responsible for protecting the marine environment, promoting the safety of life and property, and ensuring security on the US outer continental shelf (OCS). Though the Macondo incident was not initiated by failures within areas of US Coast Guard jurisdiction and safety systems regulated by the US Coast Guard generally performed well under the extreme conditions, the US Coast Guard is reviewing its regulatory construct and seeking “lessons learned” from this tragic incident. Authority and Regulatory Construct The US Coast Guard, within the US Department of Homeland Security (DHS), has broad authority under the Outer Continental Shelf Lands Act to regulate the safety of life and property on facilities and vessels engaged in US OCS activities and the safety of navigation. The US Coast Guard also is responsible for promoting workplace safety and health by enforcing requirements related to personnel, workplace activities, and conditions and equipment on the US OCS. A US OCS activity is any activity on the US OCS associated with exploration, development, production, transportation by pipeline, storage, or processing of mineral resources, including hydrocarbons. A US OCS facility is any artificial island, installation, pipeline, or other device permanently or temporarily attached to the seabed, erected for the purpose of exploring for, developing, producing, transporting by pipeline, storing, or processing mineral resources from the US OCS. This term does not include ships or vessels for transporting produced hydrocarbons. Lessons Learned From Macondo The Deepwater Horizon accident was a catastrophic event initiated by failure of well containment, an area that falls under the jurisdiction of the US Bureau of Safety and Environmental Enforcement (BSEE). Volume 1 of the report of the US Department of Interior and DHS joint-investigation team (JIT) revealed that, in general, the safety systems aboard the Deepwater Horizon regulated by the US Coast Guard had a beneficial effect, despite the extreme nature of the event. Of the 126 people onboard, 115 survived the explosions and subsequent fire. All survivors were able to evacuate the mobile offshore drilling unit (MODU) by way of the installed life-saving equipment, except for at least six who jumped from the rig into the water. Even though significantly damaged by explosions and initial effects of the fire, the Deepwater Horizon was able to stay afloat for more than 48 hours while engulfed in a major fire, fed by an uncontrolled fuel source.

미국 멕시코만 오염사고 분석을 통한 국가방제정책 개선방안 연구

On April 20, 2010, semi-submersible offshore drilling unit Deepwater Horizon was exploded and sank, and 4.9 million barrels(about 778 thousand tons) of crude oil was spilled into Gulf of Mexico. As more than one year has been passed since incident, a lot of investigation reports and lessons learned have been made public and also a lot more will be released soon. This paper studies final report of National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, which was organized by executive directive of U.S. President Barack Obama, and interim report of Joint Investigation team of U.S. Coast Guard and BOEMRE of Report of Investigation into Circumstances Surrounding Explosion, Fire, Sinking and Loss of Eleven Members Aboard Mobile Offshore Drilling Unit Deepwater Horizon. The review is focused on response to oil spill. And paper suggests how to improve national marine pollution response policy. In paper, Korean governments is suggested to reinforce capability for instructing and supervising responsible party`s source control measures, to review how to introduce in-situ burning and vessel of opportunity program into our country, and to continue monitoring on progress of developments of R&D projects related to oil spill response in U.S..

Planning and Execution of Highly Overbalanced Completions From a Floating Rig: The Ursa-Princess Waterflood Project

Summary The Ursa-Princess Waterflood (UPWF) targets the Lower Yellow sand, the main reservoir in the Mars-Ursa basin in Mississippi Canyon, approximately 60 miles south of the mouth of the Mississippi River in the Gulf of Mexico (GOM). The Lower Yellow sand, a world-class Upper Miocene turbidite reservoir, has been on production in the Ursa and Princess fields since 1999, and has been drawn down nearly to the bubblepoint. The waterflood is intended to increase and stabilize reservoir pressure, and to improve sweep efficiency. To accomplish this, four subsea injectors were designed and constructed to inject treated seawater at 40,000 B/D each for a target life of 30 years. Because the Lower Yellow reservoir was already highly depleted, unique risks were identified in the planned subsea completion operations, to be conducted from a mobile offshore drilling unit (MODU). Seawater, used as a completion fluid, was expected to be up to 4,000 psi overbalanced to the reservoir, depending on the well location. This created the risk of either an uncontrollable fluid-level drop in the marine riser or an extreme impairment to the sandface completion. In order to maintain well control with a fluid level at the surface and still deliver low-skin completions, multiple design and procedural issues needed to be addressed, including the following: Control systems on the rig and riser system to prevent uncontrollable fluid-level drop. Perforating systems to minimize impairment in a highly overbalanced environment without adding undue risk to well control. Pill designs that could both control fluid loss at the sandface and clean up effectively. Downhole completion systems capable of functioning either under very high pressure differentials or against very high loss rates. Development of high-burst screens suited to the use of fluid-loss-control pills as a contingency provision in the event that mechanical fluid-loss devices failed. As more deepwater reservoirs approach depletion, specialized tools and procedures will be required to continue to deliver safe and effective sandface completions from floating rigs. This paper details many of these considerations and summarizes the execution experience and results for one such reservoir.