Jack-up Rig Research Articles

Improving People’s Lives: Minimizing Impact

President's column Last December I had the pleasure of returning to the Kingdom of Saudi Arabia and touring the giant Manifa oil field. Manifa produces a heavy, sour crude oil from six, long (up to 40 km), stacked reservoirs in shallow water (Arukhe 2014). The shallow waters have abundant sea grasses and corals and are teeming with marine life. Shrimping and fishing are important parts of the local economy. The development of the Manifa field is a fascinating story showing how creative solutions can minimize impact on the environment. Manifa was discovered by Saudi Aramco in 1957. The discovery well targeted both the shallower formations productive in the large Safaniya coastal field and the deeper Arab formations so productive onshore. Neither zone was productive; however, the discovery found excellent productive layers in between, including three that were only produced in small volumes onshore and three that had never before proved productive. The heavy, sour crude was similar to Khursaniyah, one of the three major types of crude present in large quantities in the Kingdom. Demand was less for this crude than for Safaniya and Arab crudes but the market for heavy sour crudes was improving (Aramco World 1963). The first development was in 1962, and the field was brought on stream in 1964. The field produced for 20 years before being mothballed in 1985 because of low demand (Aldossary 2015). Manifa’s history can be contrasted with that of Prudhoe Bay in Alaska. While specific reserve estimates for Manifa are not public information, both fields are very large. The Prudhoe Bay field was discovered in 1968 and did not begin production until 1977. Prudhoe production peaked at about 1.5 million BOPD in 1989. Prudhoe Bay crude averages 27.6 °API and had a significant domestic market to serve. Manifa crude is 26–31 °API and has from 2.8% to 3.7% sulfur content (Croft and Patzek 2009), with less of a market at the time. It is fairly astonishing that roughly comparable fields would go down such radically different paths. Manifa would remain mothballed until 2006. Saudi Aramco redeveloped the field consistent with a very long life production time horizon for its large reservoirs (Saudi Aramco 2016). But the old way of approaching shallow offshore fields would not be acceptable. The use of jackup rigs in these shallow waters would have required excessive dredging, and the size of the reservoir eliminated the possibility of effective development from the shore. A new approach to development would be needed. A creative plan to develop man-made islands connected by a causeway would allow conventional onshore rigs to be used to develop this offshore field. A long causeway was considered, but early designs would have decreased water circulation vital to distributing nutrients and oxygen vital to marine life. With more than 4 million man-hours of work in the design phase, a solution was developed to build 27 man-made islands connected by 41 km of causeways. To ensure needed water circulation, the causeway does not go all the way across the bay and 14 bridges were built into the causeway to further improve circulation (Aldossary 2015). Production commenced in 2012 ahead of schedule and under budget in a development that earned a UNESCO Environmental Responsibility Award nomination. It is an impressive development of which Saudi Aramco is rightly proud, with eventual production capacity of 900,000 BOPD or more. As our helicopter approached the massive processing facility, I looked at the three large flare stacks. There was nothing being flared. Was the field shut in? No, the design and normal operations of the field use all of the produced gas and creative operations practices mean that almost no gas is flared. Excess electricity produced by the facilities goes into the power grid.

The jackup rig construction market in the US gulf coast

ABSTRACTThe US jackup construction industry has historically been the major provider of newbuilt drilling rigs operating in state waters and on the US. Outer Continental Shelf. From 2000 to 2010, a total of 26 jackups were delivered to the US market by two US shipyards. The purpose of this paper is to examine the US construction market that supplies jackup rigs in the region. Cost, labour, and material estimates for rig construction are developed and it is estimated that between 1000 and 3500 people were directly employed by the rig newbuild industry in the US Gulf Coast between 2000 and 2010. The US jackup construction industry is geographically localised and generates about $360 million in annual revenue, but its long-term outlook is uncertain because shallow water drilling in the region has been declining for the past two decades as capital flows to onshore resource plays and the deepwater sector. Regression models for rig construction cost are used to calibrate capital expenditures and steel weight requirements.

잭업리그 스퍼드캔의 물 분사용 홀 형상 최적화

잭업리그 스퍼드캔의 물 분사용 홀 형상 최적화

Tandem Downhole-Isolation-Valve System Eliminates Snubbing

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper SPE 173043, “First Ever North Sea Deployment of Tandem DIV System Eliminates Snubbing—A Case Study,” by Gary Mueller, Weatherford, prepared for the 2015 SPE/IADC Drilling Conference and Exhibition, London, 17–19 March. The paper has not been peer reviewed. The operator of an offshore jackup rig in the North Sea required safe and efficient deployment of the completion string without killing the well during tripping. A solution other than a snubbing unit was needed because of the length of the completion string, which included 12 swellable packers for 13 zones. To provide for a safer, less-expensive, and efficient method of tripping pipe, the operator chose a downhole-isolation-valve (DIV) solution that allowed for the process to be performed in a conventional manner under conditions of complete well control. Introduction During the past decade or so, the industry has developed drilling methods to address more-complex and - challenging prospects such as ultradeep prospects, deepwater applications, and high-pressure/ high-temperature wells in order to continue meeting the worlds’ demand for energy. This seemingly insatiable demand has led to the development and widespread use of unconventional techniques such as underbalanced drilling (UBD) or near-balanced drilling and various forms of managed-pressure drilling, including pressurized-mud-cap drilling (PMCD) and constant- bottomhole-pressure drilling with their attendant well-control and safety challenges. Some of these challenges are Moderate to severe lost-circulation conditions and consequent nonproductive time (NPT) Formation damage as a result of having to kill the well before tripping pipe Pore-pressure and fracture-gradient similarity leading to kick and loss cycles and well-control problems A necessity for snubbing techniques to trip the pipe in and out of the hole above the “pipe light” depth, with the attendant added cost and risk Overall operational safety and environmental issues Operational economics and the effect of resulting NPT As a result of these challenges, mitigating drilling hazards has become an extremely important facet of drilling operations and has prompted the development of procedures and equipment designs to address them, one of which is the DIV.

Perforation drilling for easing spudcan–footprint interaction issues

The interaction between a spudcan and an existing footprint is a major concern during jack-up rig installation. No guidelines were provided in the recently finalised version of ISO guidelines 19905-1 in regards to mitigating spudcan–footprint interaction issues except some proposed considerations due to scarce of detailed investigation. This paper reports a measure for easing spudcan–footprint interaction issues, with the efficiency of perforation drilling tested through model tests carried out at 1g. The soil conditions tested simulate soft seabed strength profiles close to the mudline, varying the undrained shear strength. The most critical reinstallation locations of 0.5D and 1D (D=spudcan diameter) and existing footprint depth of 0.33D were investigated. The removal of soil (through perforation) inside the spudcan perimeter, with an area of 9% perforated, reduced the induced maximum moment, horizontal force, and horizontal sliding distance by up to 80%, 83%, and 76% respectively.

A comparison of full profile prediction methods for a spudcan penetrating sand overlying clay

Spudcans are the traditional footings used for offshore mobile jack-up rigs. However, the installation of spudcans in sand overlying clay may lead to punch-through failure, which can cause serious damage to the jack-up rig and endanger personnel. This article compares three new methods proposed in the literature and an interpretation of the International Organization for Standardization (ISO) guideline for predicting the full penetration resistance profile. The penetration resistance profile for each of the methods is characterised by two key calculations: the peak resistance in the sand and the bearing capacity within the underlying clay. The punch-through distance – an indicator of the potential for and severity of punch-through failure – is estimated from these calculations. In comparison with 71 geotechnical centrifuge tests, the ISO guideline provides poor predictions, consistently underestimating the peak resistance in the sand and the underlying bearing capacity in the clay. Although all three of the new methods provide a superior response, by assessing the accuracy, scatter and geometric skew of the predictions, two of the methods are shown to be biased in at least one of the key calculations used to define the penetration resistance profile, thus producing bias in the prediction of the punch-through distance. However, one method yields largely unbiased predictions.

Using a thin sand layer to ease spudcan extraction in clay

Difficulties are encountered, in soft clay and silt sediments, during extraction of the spudcan foundations of “mobile” jack-up rigs. This paper reports results from centrifuge model tests undertaken to provide a simple, effective, and practical means for easing spudcan extraction in soft normally consolidated and lightly overconsolidated clay. The tests were carried out on model spudcans of two different geometries typically used in the field. The spudcans were extracted from penetrations of 2∼3 diameters and after an operation period of ∼19 months. The measured pore pressure at the bottom face of the spudcan during extraction process provided insight into the development of suction at the interface between the spudcan base and the underlying soil. The tests were carried out with and without a sand layer placed locally in between the spudcan and the mudline at the onset of penetration. In the field, a gravel layer can be placed by means of a flexible fall pipe system. The presence of a sand layer (with a thickness less than the spudcan tip length) beneath the penetrated spudcan assisted in easing leg extraction difficulties allowing the base suction to be reduced by 73%∼83% and hence the breakout force by 31%∼32%. For a given penetration depth, the installation resistance was also increased by 24%∼26%. This yielded a 15%∼17% reduction of spudcan penetration depth under a given preload and hence the breakout force as much as 50%. Guidelines and cautions for using the proposed measure are provided. Additional advantages of the new recommended method in enhancing the efficiency of the conventional measures of lessening spudcan extraction difficulties are discussed.

Collisions damage assessment of ships and jack-up rigs

Ship collision with offshore installations is one of the key concerns in design and assess of platforms performance and safety. This paper presents an analysis on collision energy and structural damage in ship and offshore platform collisions for various collision scenarios. The platform or rig is treated as either rigid or flexible and its sensitivity on collision energy and structural damage is studied. An application example where an ice-strengthened supply vessel collides against a jack-up rig is analysed and the crushing resistance of the involved thin-walled structures is evaluated.

Underwater Noise from a Wave Energy Converter Is Unlikely to Affect Marine Mammals

Underwater noise was recorded from the Wavestar wave energy converter; a full-scale hydraulic point absorber, placed on a jack-up rig on the Danish North Sea coast. Noise was recorded 25 m from the converter with an autonomous recording unit (10 Hz to 20 kHz bandwidth). Median sound pressure levels (Leq) in third-octave bands during operation of the converter were 106–109 dB re. 1 μPa in the range 125–250 Hz, 1–2 dB above ambient noise levels (statistically significant). Outside the range 125–250 Hz the noise from the converter was undetectable above the ambient noise. During start and stop of the converter a more powerful tone at 150 Hz (sound pressure level (Leq) 121–125 dB re 1 μPa) was easily detectable. This tone likely originated from the hydraulic pump which was used to lower the absorbers into the water and lift them out of the water at shutdown. Noise levels from the operating wave converter were so low that they would barely be audible to marine mammals and the likelihood of negative impact from the noise appears minimal. A likely explanation for the low noise emissions is the construction of the converter where all moving parts, except for the absorbers themselves, are placed above water on a jack-up rig. The results may thus not be directly transferable to other wave converter designs but do demonstrate that it is possible to harness wave energy without noise pollution to the marine environment.

Efficiency of Time Comparing with Modular Rigs for Workover Operation

In the past - 300ft Leg Jack-Up Rig predominantly used to Drill and Complete wells. In depleted phase currently, MH field is witnessing dominantly well work-over / repair scope to sustain production. Seabed inconsistencies caused by pug marks left by previous Jack-Up rigs and sea-bed pipe line network hinder Jack-Ups to approach platform and rework wells. Specificity of Jack-Up Rigs to approach Specific Platforms due to signature pug-marks left behind Increase in market demand for large Jack-Up rigs, increased day rates to very high levels. Above technical and economic compulsions drove decision making and acceptability to consider modular rigs over other alternatives. In order to ensure optimum performance of your rig, reduce downtime and maintain safety of your personnel, planned maintenance and accurate inspections are essential. Drilling's Rig Inspection Workshop (RIW) teaches the inspection and maintenance procedures required to ensure equipment integrity onland rigs, platform rigs and jack-up rigs. Candidates learn to implement the relevant standards and understand industry requirements so that they can verify the condition of a rig's equipment and improve safety, thus reducing the number of accidents and protecting the asset.

Improving Drilling-Operation Efficiency by Use of a Mud Cap

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 167985, “Improving Drilling-Operations Efficiency on an Ultranarrow- Margin HP/HT MPD Well by Use of a Mud Cap,” by Joy Oyovwevotu, SPE, Senergy; Eric Low, SPE, Bowleven; and Steve Nas, SPE, Schlumberger, prepared for the 2014 SPE Drilling Conference and Exhibition, Fort Worth, Texas, USA, 4–6 March. The paper has not been peer reviewed. This paper describes the planning and execution of use of mud-cap fluid in the drilling of an ultranarrow-margin (0.50-lbm/gal window at the planning stage) high-pressure/ high-temperature (HP/HT) well from a jackup rig. Significant operational efficiency was gained from the use of cap fluids, making it possible to drill a well that otherwise would have been nearly impossible to drill with minimum lost time. Introduction The IM field is located in Block MLHP-7 in the Rio Del Rey basin offshore Cameroon in a water depth of 58 m (Fig. 1). At the target reservoir level, Well IM-5 was predicted to be a marginal HP/HT well with an estimated reservoir temperature of 181°C and a reservoir pressure of 9,971 psi (16.80 lbm/gal) at a depth of 3475-m true vertical depth subsea (TVDSS). The Middle Isongo sand, intersected by Well IM-3, was the primary gas/ condensate target, consisting of deepwater sands with interbedded shales. The Middle Isongo target package consisted of three reservoir sands, the deepest two of which had not been penetrated in any of the earlier offset wells; this was the primary target of Well IM-5. A secondary target for Well IM-5 was the Intra Isongo, occurring between the Upper Isongo and the Middle Isongo main target. The well design allowed the 12¼-in.-hole section to be drilled conventionally with statically overbalanced mud weight (MW), but it was impossible to drill the 8½-in. hole without using statically underbalanced MW with managed pressure drilling (MPD). Consequently, it was decided that the 12¼-in. hole would be drilled with MPD so that the crew could become familiar with the procedures and practices that would be needed when the 8½-in.-hole section was drilled. Given the uncertainty in the pore-pressure and fracture-gradient forecast, drilling the 8½-in.-hole section with statically underbalanced MW using MPD was seen as the most efficient means of well construction.

Effect of water jetting parameters on the penetration behavior of jack-up spudcan in surficial sand condition

The water jetting system for a jack-up spudcan requires the suitable design considering the platform/spudcan particulars, environments, and soil conditions, either the surficial clay or surficial sand. The usage of water jetting depends critically on soil conditions. The water jetting is usually used for the smooth and fast extraction of the spudcan in the surficial clay condition. It is also required for inserting spudcan up to the required depth in the surficial sand condition, which is investigated in this paper. Especially, it should be very careful to use the water jetting during an installation of spudcan in the surficial sand condition, because there is a risk of overturning accident related to the punch-through. Therefore, in this study, the effect of water jetting flow rate and time on the change of soil properties and penetration resistance is analyzed to better understand their interactions and correlations when inserting the spudcan with water jetting in surficial sand condition. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the multi layered soil (surficial sand overlaying clays) is considered as the soil condition. The environmental loading and soil-structure interaction (SSI) analysis are performed by using CHARM3D and ANSYS. This kind of investigation and simulation is needed to decide the proper water jetting flow rate and time of spudcan for the given design condition.

Understanding rig rate formation in the Gulf of Mexico

We examine the largest cost component in offshore development projects, rig rates. High rig rates in recent years have restricted development of new oil and gas fields, as well as IOR projects and thus increased the cost for importing countries. Thus, it is important to understand developments in rig rates. Using econometric analysis, we examine the effects on jackup rig rates from gas and oil prices, rig capacity utilisation, contract length and lead time, and rig-specific characteristics like drilling depth capacities and rig classification. Having access to a unique data set from the Gulf of Mexico (GoM), containing contract information, we are able to estimate how contract parameters crucial to the relative bargaining power between rig owners and oil and gas companies affect rig rates. We find that increasing lead times and contract lengths enhance the bargaining power of the rig companies and are likely to be associated with higher rates for new contracts. Further, we find that gas prices are more important for jackup rig rates in the GoM area than oil prices — ten percent increase in gas prices leads to nine percent increase in rig rates in the long run, according to our results.

Selection of Power From Shore for an Offshore Oil and Gas Development

With a step-out distance of 161 km and a design power of 55 MW, Martin Linge offshore gas field will be the longest ac submarine cable power supplying an entire offshore oil and gas platform from the shore. This field development comprises a platform with a jack-up rig and a floating storage offloading unit. This paper discusses the criteria that have been considered to select a power-from-shore concept instead of an offshore gas turbine power plant, which is the current practice in the offshore oil and gas industry. Since in a first approach, for such a long step-out distance, the choice of power from shore would be to select a dc transmission line, this paper discusses the design and the main technical challenges of this long step-out ac transmission development. Finally, the system approach that is required for the development of the onshore and offshore parts of the project is described.

Conditional Stochastic Processes Applied to Wave Load Predictions*

The concept of conditional stochastic processes provides a powerful tool for evaluation and estimation of wave loads on ships and offshore structures. This article first considers conditional waves with a focus on critical wave episodes. Then the inherent uncertainty in the results is illustrated with an application where measured wave responses are used to predict the future variation in the responses within the next 5‐30 seconds. The main part of the article is devoted to the application of the First Order Reliability Method for derivation of critical wave episodes for different nonlinear wave-induced responses. A coupling with Monte Carlo simulations is shown to be able to give uniform accuracy for all exceedance levels with moderate computational time, even for rather complex nonlinear problems. The procedure is illustrated by examples dealing with overturning of jackup rigs, parametric rolling of ships, and slamming and whipping vibrations.

Conditional Stochastic Processes Applied to Wave Load Predictions

The concept of conditional stochastic processes provides a powerful tool for evaluation and estimation of wave loads on ships and offshore structures. This article first considers conditional waves with a focus on critical wave episodes. Then the inherent uncertainty in the results is illustrated with an application where measured wave responses are used to predict the future variation in the responses within the next 5–30 seconds. The main part of the article is devoted to the application of the First Order Reliability Method for derivation of critical wave episodes for different nonlinear wave-induced responses. A coupling with Monte Carlo simulations is shown to be able to give uniform accuracy for all exceedance levels with moderate computational time, even for rather complex nonlinear problems. The procedure is illustrated by examples dealing with overturning of jackup rigs, parametric rolling of ships, and slamming and whipping vibrations.

Effect of plate slope and water jetting on the penetration depth of a jack-up spud-can for surficial sands

The spudcan requires the suitable design considering the soil, platform, and environmental conditions. Its shape needs to be designed to secure sufficient reaction of soil so that it can prevent overturning accidents. Its shape also has to minimize the installation and extraction time. Even in the same soil condition, the reaction of soil may be different depending on the shape of spud can, mainly the slope of top and bottom plates. Therefore, in this study, the relation between the slope of plates and the reaction of soil with and without water jetting is analyzed to better understand their interactions and correlations. For the investigation, a wind turbine installation jack-up rig (WTIJ) is selected as the target platform and the Gulf of Mexico is considered as the target site. A multi layered (sand overlying two clays) soil profile is applied as the assumed soil condition and the soil-structure interaction (SSI) analysis is performed by using ANSYS to analyze the effect of the slope change of the bottom plate and water jetting on the reaction of soil. This kind of investigation and simulation is needed to develop optimal and smart spudcan with water-jetting control in the future.

Observing the effects of sustained loading on spudcan footings in clay

Spudcan foundations of mobile jack-up rigs are penetrated into the seabed under seawater ballast preload, which is shed prior to rig operations commencing. During pauses in the installation process and during operation, soil beneath the spudcan foundations stiffens and strengthens due to consolidation. On the application of further loading or during spudcan extraction, this causes increased resistance, which in extremis can result in punch-though type failure. This note reports results from a series of experiments with particle image velocimetry measurements that were performed in a drum centrifuge to facilitate observation of the effects of a load-hold period on the soil movements around a model spudcan during subsequent further loading. The results show that the dimensionless load-hold period dominates the enhancement in the penetration resistance, due to significantly more soil being mobilised following a long load-hold period. These observations might be useful to (a) predict the enhancement in bearing capacity factor due to a load-hold period during installation or operation and (b) predict the footing extraction resistance during jack-up re-deployment.

다양한 형상의 Jack-up Leg에 대한 해양 동역학적 수치해석

In this study, the hydrodynamic characteristics of various types of jack-up legs for a wind turbine installation vessel were analyzed. Using the modified Morison equation, the wave and current excit ation forces on the jack-up legs were calculated. A modal analysis was performed to predict the dynamic responses for various types of jack-up legs. The Newmark-beta time integration scheme was used to solve the equation of motion in waves in the time domain. The maximum displacement and maximum bending stress were computed for four different types of legs, and their results were compared to select an optimum leg type. Finally, a six-leg jack-up rig with the selected optimal legs was modeled, and its natural period and hydrodynamic behaviors were evaluated.

Improving Drilling-Operations Efficiency on an Ultranarrow-Margin High-Pressure/High-Temperature Managed-Pressure-Drilling Well With Use of a Mud Cap

Summary As the industry pushes the boundary of technology to drill narrow-margin wells, combining safe drilling practices with drilling efficiency is becoming ever more challenging. The practice of drilling with managed-pressure drilling (MPD) by use of statically underbalanced mud weight (MW) is gaining increasing acceptance in high-pressure/high-temperature (HP/HT) well construction. This paper describes the planning and execution of using mud-cap fluid in the drilling of an ultranarrow-margin (0.50-lbm/gal window at the planning stage) HPHT well from a jack-up rig. Drilling equivalent circulating density with overbalanced MW at acceptable flow rate would have exceeded the formation-fracture gradient and resulted in a loss of well integrity. To avoid this outcome, the HP/HT section of the well was drilled with statically underbalanced MW. Displacing well to kill-weight fluid at acceptable flow rates before any trip out of hole was not viable. Planning focused on how to maximize operational efficiency with a cap fluid to trip in and out of hole without compromising openhole integrity and well safety. In this paper, we discuss the design of the mud-cap fluid, selection of change over depth, risks associated with use of the cap fluid, determination of available window for mud-cap placement and removal, planning and execution of mud-cap placement and removal, challenges of running and displacing the cap fluid with a liner, and lessons learned from the repeated use of the technique throughout the well-construction phase, including coring and wireline logging under MPD conditions. Significant operational efficiency was gained from the use of cap fluids, making it possible to drill a well that would otherwise have been near impossible to drill with minimum lost time.