Barite is the most common weighting material for drilling fluids, which contain several heavy components including lead, cadmium, mercury, and arsenic. Some of these heavy materials can discharge into the sea, which is not allowed especially in the case of oil-based drilling fluid. The supply of barite is geographically limited, with high transportation costs. To overcome the high cost, shortage, and common problems of barite, an alternative weighting material, ilmenite (5 µm), is introduced which is heavier than barite and more stable at high temperature. Also, the micronized ilmenite was introduced to overcome the ECD challenges in some drilling operations at reasonable cost.
Extensive lab work was done in order to: 1) optimize the rheological properties of the drilling fluid, 2) determine the optimum pH that gives stable dispersion, 3) assess the thermal stability, 4) optimize the filtration parameters (filtrate volume and filter cake thickness), and 5) characterize the ilmenite-based filter cake.
Zeta potential results showed that ilmenite was stable when mixed with water at a pH above 7 and it was dispersed and stable when mixed with the drilling fluid components. Drilling fluids have a density range from 100 to 120 pcf and a plastic viscosity of 28-32 cp. No phase separation was observed after hot rolling for 16 hrs at 300°F. The optimized water-based drilling fluid formula had a small filtrate volume (12 cm3) and thin filter cake (0.2 in.) under dynamic conditions. SEM analysis showed that ilmenite filter cake was heterogeneous and contained ilmenite particles in the layer closer to the rock surface. The layer closer to the drilling surface had a mixture of xanthan gum and modified starch, which were used to optimize the rheological properties at 250°F. This study will provide a complete evaluation of the drilling fluids with ilmenite as a weighting material and will help drilling engineers to better design drilling fluids for HPHT wells.
The extreme conditions and harsh environment for which FPSO's andhydrocarbon gathering facilities are being considered introduces distinctchallenges to effective and efficient project management and execution. The presentation is based on the experiences gathered during the design phasesof two contemporary harsh environment FPSO's and the associated subsea,flowline, pipeline and riser systems (Chevron Rosebank and GAZPROMShtokman). This presentation will focus on the adjustments that must beconsidered to "standard" project execution and management in order toincorporate the elemental distinctions without sacrificing efficiency, logicalsequencing, safety or project schedule. Specifically, the presentationwill focus on the following:
The paper is intended to inform the audience as to the distinctivecharacteristics of harsh environment design management contrasted with the morefamiliar benign environment design projects.
A numerical modeling procedure was developed, using the finite-elementsimulator ABAQUS/Standard, to predict the local buckling and post-bucklingresponse of high strength pipelines subject to combined state of loading. Thenumerical procedures were validated using test data from large-scaleexperiments examining the pure bending and local buckling of high strengthlinepipe. The numerical simulations were consistent with the measuredexperimental response for predicting the peak moment, strain capacity,deformation mechanism and local buckling response well into the post-yieldrange.
A parametric study on the local buckling response of high strength plainpipelines was conducted. The influence of pipe diameter to wall thickness ratio(D/t of 40, 60 and 80), pipe segment length to diameter ratio (L/D of 3.5, 5, 7and 12), yield strength to tensile strength ratio (Y/T of 0.7, 0.8 and 0.9) andinitial geometric imperfections on the local buckling response was examined.The loading conditions included internal pressure and end rotation. Mechanicalresponse parameters examined included moment-curvature, ovalization, localstrain and modal response.
Marshall, P.W. (Department of Civil and Environmental Engineering, National University of Singapore) | Sohel, K.M.A. (Department of Civil and Environmental Engineering, National University of Singapore) | Liew, J.Y. Richard (Department of Civil and Environmental Engineering, National University of Singapore) | Jiabao, Yan (Department of Civil and Environmental Engineering, National University of Singapore) | Palmer, A. (Department of Civil and Environmental Engineering, National University of Singapore) | Choo, Y.S. (Department of Civil and Environmental Engineering, National University of Singapore)
There is a wide range of offshore structures which may be constructed byeither steel or concrete materials to be used in the arctic region, such assteel tower platforms, caisson-retained islands, shallow-water gravity-basecaisson, jack-up structures, bottom-founded deep-water structures, floatingstructures, well protectors, seafloor templates and breakwaters. One commonfeature of these structures is that they must be able to resist the highlateral forces from the floating ice and transmit these forces to thefoundation. This study explores the use of Steel-Concrete-Steel (SCS) curvedsandwich system for arctic caisson structures. SCS sandwich system, whichcombines the beneficial effects of steel and concrete materials, has promisingbenefits over conventional plates and stiffeners design and heavily reinforcedconcrete design because of their high strength-to-steel weight ratio and highresistance to contact and impact loads. Shear connectors have been proposed toprovide bonding between the external steel plates and high-performancecementitious core materials. Finite element analyses and large-scale testresults showed that SCS sandwich panels without mechanical bond enhancement arevulnerable to interfacial shear failure and impairment of structural integritywhen subject to shrinkage and thermal strains, accidental loads, and impact.The proposed SCS sandwich system features mass-produced mechanical shearenhancement and/or cross-ties. It can reduce structure complexity, particularlyin the number of weld joints which are prone to fatigue, hence increasingservice life, cutting down the cost of fabrication, and reducing the manpowercost to operate, inspect, and maintain the structure in the long run.Considering local ice load, the punching shear and shell bending strength ofthe SCS sandwich composite shell is studied experimentally. Test results showedthat the SCS sandwich panels, which are designed using the ISO ice load, arecapable of resisting the localized contact and punching loads causedthereby.
In recent years there has been substantial interest and growing demand forLNG Carriers to operate in cold regions. As a result there is a pressing needfor rules and standards to give clear requirements for shipbuilders to developsuitable designs for cold climate operations. In parallel to the systems andfeatures fitted for the safety of the LNG Carriers, is the preparedness andsupport of the crew for the challenges of operating in these harsh,cold-climate regions. Sources of hazard can include accidental immersion incold water, freezing and non-freezing cold injuries, unusual day or nightlengths, and weather conditions affecting visibility and the sea state. Thispaper provides an insight into the background and development of winterisationrules and an explanation of some of the key features fitted to existingwinterised LNG Carriers, whilst outlining many of the physical and cognitiverisks to seafarers in conditions of extreme cold, including their personalsafety and their ability to control the vessel and its systems. It introducessome of the systems redundancy features to mitigate the risks due to remotenessand methods for managing the resulting risks. These, include proceduraladaptations to manage exposure times and the operability of the ship, anddesign adaptations to reduce or remove hazards to the people on board and theways in which they can work.
Winterisation; Low temperatures; Icing; Classification Rules; LNG Carriers,Human Performance; Cold Climate Operations.
Reel-laying is a fast and cost-effective method to install offshore pipelines. During reel-laying, repeated plastic strain is introduced into the pipeline which may, in combination with ageing, affect strength and ductility of the pipe material. The effect of reel-laying on the pipe material is achieved by small- or full-scale reeling simulations followed by mechanical testing according to corresponding standards. In this report an appropriate test setup for full-scale reeling simulation is presented. The fitness-for-use of the test rig is demonstrated by finite element calculations as well as by full-scale reeling simulations on different pipes of various grades. Plus, small-scale reeling simulations with subsequent ageing and mechanical testing are performed on the same pipe material. A comparison of results from mechanical tests after small- and full-scale reeling simulations is given. Additionally results from collapse tests on pipes after full-scale reeling simulations are presented, and the influence of repeated bending of the pipe on its collapse behavior is discussed.
Two main concepts are normally used for laying offshore subsea pipelines. In the S- and J-lay method a pipeline is fabricated on the deck of a lay barge by welding individual lengths of pipe as the pipe is paid out from the barge. The pay-out operation must be interrupted periodically to permit new lengths of pipe to be welded to the string. The S- and J-lay method requires skilled welders and their relatively bulky equipment to accompany the pipe-laying barge crew during the entire laying operation; welding must be carried out on board and often under adverse weather conditions. Further, the S- and J-lay method is relatively slow, with even experienced crews laying only few miles of pipe a day. This can subject the entire operation to weather which can cause substantial delays and make working conditions quite harsh.
For burst design, engineers routinely assume that the casing annular space is filled by a fluid equivalent. This assumption ignores mechanical resistance provided by solid cement. Some studies addressed this shortcoming by modeling the cement sheath as a solid with elastic failure criteria. Prior work used cement elastic modulus and Poisson's ratio to classify cement as "ductile" (soft) or "brittle" (hard). In the current study, numerical results from finite-element analysis (FEA) indicate that casing burst resistance is increased by the presence of the cement sheath. This study focuses solely on improvement offered by the cement sheath to casing burst resistance and ignores consequences of cement failure on overallwell integrity. Comparisons are provided for casing burst resistance, assuming various backup profiles. These include fluid hydrostatics, solid cement matrix (both elastic and plastic response), and cement as "loose" particles. The fluid hydrostatics include mud weight in hole, cement-slurry density, mixed-water density; normal pressure (saltwater column), and actual pore pressure. Calculations show that these fluid profiles are conservative when used as burst-resistance backup. Original cement-slurry density is least conservative. Because well designers are familiar with fluid profile backup assumptions in casing burst design, recommendations are provided to approximate cement behavior as particles with a fluid profile. This allows ease of calculation and is consistent with current practice. Guidelines are provided to explicitly calculate the enhanced casing burst resistance caused by the particulate cement.
For more than 60 years, internal plastic coatings have been used for corrosion protection on tubing, casing, line pipe and drill pipe. One of the historic concerns with the use of internal plastic coating is the threat of mechanical damage and subsequent corrosion cell generation. Through the earlier years of usage of internal plastic coatings, applicators relied solely on enhanced surface preparation and adhesion to ensure minimal exposure of the steel substrate if damage were to occur. Even with this minimization, the potential for corrosion was still a concern for some. Due to this, a focus on developing internal coatings that offered higher degrees of abrasion resistance was initiated. At this time, several materials have been developed that offer abrasion resistances up to twenty times greater than what had previously been seen. These abrasion resistant materials allow internal coatings to be used in applications that were previously filled with alloys and GRE liners. These applications include: production/injection wells that rely on frequent mechanical intervention, rod pumping wells, completion string systems and environments containing high amounts of entrained solids. This paper outlines the development of these products including the different chemistries used and their abrasion resistance, impact, laboratory evaluation of their abrasion resistance and initial case histories of applications where internal coatings have historically been excluded.
ADCO has recently managed a major project called 1.8 MMbd Bab Thamama G and Habshan 2 consists of additional wells, flow lines, new process units and modification of existing surface facilities that are required to increase oil production in the Bab field by a sustainable rate of 80 MBOPD.
The facilities will include four additional Remote Degassing Stations (RDSs), namely RDS-7, RDS-8, RDS-9 & RDS-10 that gather from numerous production flow lines and deliver the raw crude to the BCDS through transfer lines.
Overall Project Objectives is to achieve EPC completion by Q4 2012, improve on ADCO's HSE targets, and Implement project within approved budget
The purpose of this paper is to share ADCO's experience during project execution, both in terms of technical and project quality management issues. The paper highlights the challenges faced, achievements and lessons learnt during execution of the project.
Mitigation of increased risk and consequences of failures due to higher service severity, Cost/time optimization drive due to material delivered from new and cheap suppliers with less quality level, Increasing inspection tasks of materials from different sources, and Management of the Third Party Inspection (TPI) to control all scattered activities locally and overseas were some of the major quality challenges during execution of the project.
The projects quality control practices implemented throughout the lifecycle of the project, starting with conceptual and preliminary engineering, through detailed engineering, procurement and construction are highlighted in the paper.
Major lessons learnt, quality control improvements tools, and other project quality issues are discussed in the paper.