bluuebunny/crossref_metadata_2025 huggingface dataset:
Wellhead Design for Fatigue Optimization
Authors: Mattey A. J. , Ionescu M. , Osen P. , Bunæs P. , Sæther M.
Published: April 2017

Due to increased functional and pressure capacity requirements of subsea BOPs, there is a steady increase of weight and height. A down-side is that the loading of subsea wellheads due to marine riser loads is also increasing. This becomes particularly critical when deep-water rigs with large BOP stacks are used for drilling in the relatively shallow water in the Norwegian Continental Shelf. These loads may be characterized by their maximum single load and by their cyclic load variation and number of load cycles. Several wellhead system designs incorporate a rigid lockdown mechanism, where the wellhead housing is vertically pre-loaded down onto an internal reaction shoulder in the conductor housing. The pre-load and force reaction pre-stress the components that make up the lockdown mechanism. This pre-stress in particular may limit the bending capacity of the wellhead. The purpose of this study is to evaluate a lateral reaction force couple for the load transfer between the wellhead and conductor housing, instead of a traditional vertical pre-load, per the request of an operator experiencing extremely high fatigue loading in the subsea wellheads. The aim is to show favorable fatigue performance with a lateral based reaction system. Three new wellhead concept designs were developed, analyzed, and evaluated following the practices of DNVGL-RP-C203 and using generic load parameters for soft-clay and loose-sand soil types. M-N curves of all hotspots were plotted and compared against the M-N curve of a perfect 36" × 2" WT girth weld with C1 quality (considered the best fatigue performance a wellhead system can achieve for this particular conductor size) found in NORSOK U-001, Appendix B. The fatigue resistance was presented as an M-N curve. The new concept designs were refined through a series of iterations around the areas of high stresses until the worst hotspot in the system was isolated around the 36" × 2" WT conductor housing weld. The new concept designs were each evaluated and a single one was selected to continue with the fatigue optimization work. For the selected concept design, additional iterations were analyzed with and without pre-load between the wellhead housing and the conductor housing. The results are presented in the form of M-N curves for individual hotspots and for the entire wellhead system. Based on detailed FE analysis, the first iteration of all three conceptual designs showed promising results when compared to the 36" × 2" WT benchmark. For the non-preloaded conceptual design selected, analysis showed a possible solution, both with respect to fatigue resistance and structural capacity. The new conceptual wellhead design consists of only four major components. Although the overall size of the system has increased slightly compared to conventional systems, a preliminary commercial review shows reduction/simplification in manufacturing processes involved.
HPHT Well Integrity: Load-Resistance Monitoring and Predictive Analysis
Authors: Das Bibek , Samuel Robello
Published: April 2017

In recent years, in the post Macondo era, the Bureau of Safety and Environmental Enforcement (BSEE) has come out with proposals and regulations that require monitoring of Deep Water (DW) and High Pressure/High Temperature (HPHT) wells in real-time. As new wells are being drilled in DW and HPHT environment, much of this drilling is supported from the Onshore Drilling Centers located onshore miles away from the offshore field. Real time monitoring (RTM) plays an important role in identifying leading and lagging indicators of barrier failure. High bandwidth fiber optic cables are now allowing high levels of communication and real time data.

Predictive Analytics is a natural step to follow RTM. However, the challenge that stills lies ahead is whether to apply Data-driven prognosis, Model-based prognosis or a fusion approach; and which Machine Learning Algorithm is best suited to address a specific well barrier reliability issue in HPHT environment.

Producing oil and gas from deepwater reservoirs with pressures greater than 15,000 psi and temperatures of 350°F at the mudline subjects the equipment to major loads. The major loads in HPHT conditions can be attributed to: (i) heat transfer between hot fluid and equipment leading to lateral expansion/contraction loads in response to the temperature changes of the fluid; (ii) high collapse pressure due to high formation pressure; (iii) higher corrosion damage rates under sour conditions, and (iv) tensile loads due to the buoyed weight.

In light of the new BSEE requirements on load monitoring and data collection for HPHT operations, this paper discusses the major loads in HPHT conditions, and the different predictive analysis models that are available. The paper discusses particularly the load-resistance monitoring and predictive analysis approach with respect to HPHT well integrity. If we monitor the right data, extract the right features, predictive analytics can identify the integrity issues in advance, and procedures can be implemented to maintain the barrier integrity, reliability and thus prevent any fluid leakage.
Life of Field Cost Reduction Strategy: The Deployment of Facilitating Intervention Technologies for Well Construction and Deconstruction
Authors: Canny Steven A , Foubister Graeme
Published: April 2017

In an attempt to reduce the capital expenditure (CAPEX) costs of field development, the development and adoption of focused, bespoke equipment can provide significant cost savings. With rig based technology consistently accounting for over 40% of a well construction or de-construction project, it is an area with significant cost reduction potential if alternative facilitating technology is deployed.

The paper describes alternative facilitating technology. Modification and project specific integrated engineering that allows for potential cost reductions, through early engagement with an operator and project stakeholders.

A well construction project case study presents the early interfacing with a Yangon based operator, concerning the development of an Intervention and Completions Unit (ICU) for operations in a segregated well construction project, to undertake well completion and stimulation activities.

A well rejuvenation project case study presents the engineering modification of a Hydraulic Pulling and Jacking Unit (PJU) to undertake well slot preparation activities for mature asset rejuvenation activities for a Gulf of Mexico (GoM) operator.

The focused engineering presented in the well construction and well rejuvenation case studies, and the identification of functionality requirements that can be improved to operate in high cost base projects, demonstrates the potential savings that can be achieved. Detailed operational analysis appraisal, and identification of those activities with empirically high levels of non-productive time (NPT), are categorized and technology solutions are developed.

Technology solutions provide the required technical capabilities for the intended operations, whilst reducing the associated base construction, maintenance, certification and operational costs that are commonly experienced with over specified equipment. Both case studies present the benefits to the operator in the pre-engineering and design phases, allied to operational benefits.
Efficient and Safe Casing Removal with Downhole Hydraulic Pulling Assembly
Authors: Hartman C. J. , Cullum J. L. , Melder J. E.
Published: April 2017

When performing a slot recovery or a well abandonment, the casing can frequently be difficult to pull. This could be due to scale, barite buildup, or cement stringers. Other considerations are the limitations of the rig and its ability to apply the force needed to pull a long string of casing. Removing stuck or lengthy sections of casing typically requires multiple cut-and-pull attempts as well as high-capacity rigs capable of pulling high loads, resulting in increased costs and potentially nonproductive time (NPT) and associated HSE risks.

An alternate method that uses a downhole hydraulic pulling assembly enables operations to overcome these limitations and increase efficiencies. The hydraulic-activated assembly uses a pressure differential to anchor into the casing above the section to be removed while pulling as much as 1.8 million pounds through a casing spear that is engaged in the cut section. The pulling force is focused between two downhole anchor points, isolating the high loads from the derrick. This isolation protects the derrick and drillstring from upward drill pipe movement if the casing releases abruptly.

Recent operations have proven the successful retrieval of casing in multiple offshore applications. When attempting to pull 9⅝-in. casing, the rig was limited to 570,000 pounds over-pull, which was insufficient to retrieve the stuck casing string. The hydraulic pulling assembly was set in the 13⅜-in. parent casing and pulled the casing free with 1.2 million pounds of over-pull. The operation was completed in one run, eliminating multiple cut-and-pull attempts. The time saved reduced operational expenses by USD 450,000. The system has also been used to pull 13⅜-in. casing from inside 18⅝-in. casing, and has been used on fixed and floating platforms.

Deploying the hydraulic pulling assembly in cut-and-pull operations provides customers the ability to use lower-capacity rigs in plug-and-abandonment (P&A) operations and to safely pull loads up to 1.8 million pounds because the forces are confined downhole. Using specialized equipment to ensure successful cut-and-pull attempts enables safer jobs and provides a more cost-effective abandonment operation.
Technical Feasibility Study of Advanced Tomography Sensor for Inspection in Piggable Flowlines
Authors: Lehikoinen A. , Kaipio J. P. , Voutilainen A. , Laakkonen P. , Rivas-Griswold A. , Vreenegoor L. , Khosla V. , Varma R. , Broze G.
Published: April 2017

Electrical tomography (ET) techniques are used for determining material distributions within the detection volume of the sensor, and they are based on measuring the material-dependent responses of electrical excitation signals. The state of the art in electrical tomography is to use sensors around the pipe and image inwards. In this paper, we investigate an ‘inside-out’ ET sensor and the related computational approach to image the annulus between the sensor (measurement pig) and the pipe. The physical and mathematical models connect the electric fields to the permittivity and the conductivity. The estimation (computation) of the permittivity and conductivity based on alternating current/potential feeds and the measured potentials is mathematically called an (unstable) inverse problem. We construct a device and carry out laboratory experiments with water, oil, and mixtures of crude oil, water and air, as well as deposits of synthetic paraffin, calcium carbonate and real crude oil wax. We show that both the permittivity and the conductivity in the inside-out geometry can be estimated using the device and an inversion algorithm. Therefore, it was possible to detect material build-ups and identify build-up materials with the prototype system.
HSE Management System Effectiveness – A New Approach to Realize Continuous Improvement
Authors: Ezeldin H. Sam
Published: April 2017

Objectives/Scope

This paper outlines the metamorphoses between HSE compliance audits and HSE management system audits including the auditor skillsets required, the interactions between auditors and auditees expected, and the final report contents. The use of HSE management system audits to drive continuous improvement in a successful business performance will also be described.

Methods, Procedures, Process

Historically, HSE assessments have fallen into one of two categories - a compliance audit or a management system audit. While these two terms are often used interchangeably, they seek to deliver distinct outcomes, as follows: A compliance audit verifies compliance against a defined set of requirements and is used to identify gaps in compliance.A management system audit verifies the effectiveness of the management system as a whole and is used to drive continuous improvement for the entire organization.

Results, Observations, Conclusions

Auditing results shall support the concept that business success depends on balancing and interconnecting business priorities such as; Research and Development, Environment, Health and Safety, Equipment Integrity, Production, and Quality. To drive continuous improvement and business performance using a management systems audit, a Bottom Up and Top Down, (BUTD) analysis technique has shown ultimate results in our experience. We conclude that using the BUTD approach when analyzing management approaches and techniques and operator behaviors & workplace conditions and not rely only on verification of documentation and bureaucracy has resulted in the desired continuous improvement.

Novel/Additive Information

This manuscript also discusses best practices and Organization HSE performance metrics resulted from assessment Audits that seek to effectively combine the two types of audits into a comprehensive and efficient audit event.
Significant Cost Reduction of Subsea Boosting Systems by Innovative Technologies
Authors: Davalath J. , Wiles D.
Published: April 2017

The deepwater oil and gas industry is in a state of rapid structural changes to align with the current "lower for longer" commodity pricing environment. Deepwater operators' opportunities for large greenfield developments are in a rapid decline due to poor return on investment in this market environment. These types of developments require large to ultra-large capital investments for expensive deepwater drilling and completion activities as well as the high cost of new surface-piercing host facilities in deepwater. In contrast, brownfield investments in known petroleum basins offer excellent investment opportunities in the current climate. The hydrocarbon risk is also lower based on historical knowledge of reservoir asset quality and performance. One of the top opportunities for brownfield investment is low cost subsea boosting systems. These projects do not require the drilling of new wells, or significant infrastructure investments in new subsea equipment or new topside facilities (hosts, flowlines, risers, wells, etc.). Incremental investments in low cost boosting systems result in substantial increases in revenues and therefore high rates of return. The boosting system utilizes existing infrastructure, which serves to increase the capital efficiency of earlier investments in the field. Subsea boosting technology is mature and field proven. Prior designs have adopted large subsea structures with unnecessary functionalities. The costs of subsea boosting systems have been reduced by adopting several strategies: (1) simplifying the system design to reduce weight and cost, (2) simplifying the installation and intervention and (3) reducing complexity and risk. Low cost boosting systems are now the new standard that have substantially improved the business case for investment in this technology.
A new Offshore Mooring Anchor for Hard Grounds
Authors: Ozmutlu S.
Published: April 2017

This paper presents the development and the testing of a new anchor for hard seabed conditions. The anchor development involved computer modelling, laboratory scale model testing, and eventually the full scale anchor testing offshore. The goal of the development was to expand the suitability and applicability range of drag embedment anchors in hard soils and soft rocks.

The anchor development process is explained and the theoretical models for hard ground anchoring are introduced. The laboratory testing conditions and the results of laboratory tests are presented. Following the model scale qualification phase in different soil types and strengths in the laboratory, the full scale testing of the new anchor is carried out at selected offshore locations. The offshore testing conditions, the instrumentation and measurement techniques, and the results of offshore testing are evaluated and presented. In order to benchmark the performance of the new anchor, both laboratory tests and field scale tests are run against a reference anchor which is tested under the same conditions.

The model scale and field scale testing results show that the new anchor is able to penetrate into harder grounds and generate substantial holding capacity. The penetration ability and the stable holding capacity of the new anchor is around 22% to 47% higher than the existing anchors of comparable category. The offshore scale test results have proven that the new anchor has increased the offshore mooring capability in hard soils and soft rocks.

It is expected that the results of this work will allow a better understanding of anchor behavior in hard soil and soft rocks. The results and the technology developed will be beneficial to the oil/gas and energy sectors in general and the offshore mooring industry in particular. The new technology is expected to provide a practical and cost effective anchoring solution in challenging frontier areas (e.g. Arctic, Northwest Shelf Australia, Persian Gulf, and many shallow water areas of the world), and in emerging industries like Floating Renewables and dredging/offshore construction.
Supplying Additional Power Subsea through Intervention ROV Systems
Authors: Restivo A. , Glenn C. , Williams L.
Published: April 2017

Current remotely operated vehicles (ROVs) require dedicated umbilicals to provide communications, enable control, and to power three-phase motors on the subsea vehicle. The standard architecture does not permit ROV umbilical power to be used for separate devices, so additional equipment – such as dredges, pumps, or subsea hydraulic power units – requires its own dedicated power, control lines, and topside equipment.

This paper explores the ways and means of expanding existing ROV technology to enable driving additional subsea equipment using ROV umbilical power. The discussion focuses on the development of a smart subsea medium-voltage switch and a mate-able hybrid medium voltage/fiber optic connector for subsea intervention systems.

The paper has four main sections. First, the paper presents the technical requirements for a subsea switch and hybrid connector operating at water depths exceeding 3000 m. Second, the benefits of expanded power distribution from an ROV, including reduced equipment requirements, enhanced safety, and increased operational flexibility are discussed. Third, the challenges associated with designing and testing the subsea switch and hybrid connector technologies are reviewed. And fourth, the paper outlines the roadmap of expected progress toward achieving the goal of providing power to additional devices through intervention ROV umbilicals.
Model Test Campaign Overview for the Turritella FPSO for the Stones Field
Authors: Carrico Todd , Leverette Steve
Published: April 2017

Shell Offshore Inc. ("Shell") Stones Project is a record breaking Floating Production Storage and Offloading (FPSO) unit. This novel disconnectable FPSO solution incorporates numerous technologies which help to redefine the state of the art and extend the capability envelope for deepwater applications. Critical to the success of this project was the systematic development of these enabling technologies during the time frame of the project. A key component of this development process was the use of model testing. Over the course of the project, a comprehensive set of campaigns were performed. During the Front End Engineering Design (FEED) effort, model scale testing was utilized to provide insight into relevant hydrodynamic phenomenon. Later during project execution, the testing focus shifted to confirming the effect of particular design changes. This paper gives an overview of each campaign. It presents a timeline of testing and shows how their timely results were integrated into the design process.

Eight different campaigns will be discussed in the paper. They fall into three categories; Buoy Turret Mooring (BTM), FPSO, and Turret. The early campaigns focused on the disconnectable buoy and mooring systems. Given the novel aspect of the design, which is the world's largest BTM buoy, verifying and validating its hydrodynamic performance took precedence. This was performed for both connected and disconnected scenarios. The FPSO campaigns were dedicated to more traditional vessel issues. Here performance aspects of the heavily modified vessel were quantified through resistance tests, captive model maneuvering tests, wind tunnel tests, and in place greenwater tests. Lastly, the Turret Campaigns focused on measuring wave dynamics inside the moonpool while underway and assessing the performance of potential mitigating design features.
Development of a Flexible Pipe for Deep Sea Mining
Authors: Rongau J. , Viale S.
Published: April 2017

During subsea mining operations, minerals are extracted from the seabed, typically at about 2000m depth, and pumped with water through a riser pipe to a surface processing vessel. TechnipFMC, through its subsidiary Technip France, is the lead of a consortium comprising COMEX and DCNS which has been awarded a contract by BPIFrance to develop a pilot subsea mining system. The scope includes the development of a flexible riser. This flexible riser comprises an inner wear protection layer to resist the wear from the slurry, covered by a structure to withstand mechanical loads applied to the flexible during its lifetime.

In order to select the most appropriate anti-abrasion material, a large scale bench test has been built to reproduce realistic flow in a piping system and compare wear on different materials; rubber, polyethylene and stainless steels. Complete analysis of the wear patterns has been conducted with the expertise of a laboratory. A statistical comparison between materials is presented. The response to wear, depending on material, geometry and position, is better known. One of the materials shows much better wear resistance than the others and is selected for further development.

The next step is the development and qualification of the manufacturing process for the wear protection layer. This process has to be as much as possible compatible with current flexible pipe manufacturing plant. Parameters such as thickness, diameter or length of the layer should be adaptable according to needs. The compatibility with the pipe mechanical structure has to be tested as well. To meet these requirements, existing manufacturing processes are limited. At the time of writing this paper, different manufacturing methods to incorporate this wear protection layer within a continuous industrial flexible production are currently under investigation. Several prototypes will be realized for each manufacturing step. Prototyping is under test and will be presented in a forthcoming presentation.
Standardizing Business Processes within Oil and Gas Markets to Reduce Costs
Authors: Campbell E.
Published: April 2017

The objectives of this proposed paper are to: Demonstrate the potential cost reduction benefits derived from implementing a standard process for customers to purchase itemsCompare the oil and gas market to industries where common business standardization philosophies are being usedHighlight areas of potential cost savingsA review of previously published studies and common project management methods will be used.

Identifying crossover of processes from industries with a history in standardizing will assist in drawing conclusions about potential applications in the oil and gas industry. Common business philosophies including Kiezen and Stage Gate, will be reviewed and highlight common themes between oil and gas and other markets and identify cost saving potential. Applicable common management methods will be described will be supported by examples of successful implementation of the processes. The identified cross-over opportunities will be compared in cost models to demonstrate effectiveness The mature nature of the oil and gas industry presents an opportunity for standardization because we now have historic project data and can identify opportunities for adopting common practices. Papers investigating process standardization within the oil and gas industries are typically rare compared to health markets, for example.

The implementation and awareness of these business philosophies has recently increased. Due to a dramatic decline in the oil price, businesses have been forced to review their business practices and identify opportunities for cost savings. These ideologies, if implemented, have the potential to transform the competitive business market and improve efficiency within the industry, effectively reducing overall costs for companies. This is crucial to keep the oil and gas market buoyant and evolving. The comparison of common standardization business practices in the oil and gas market is often met with skepticism. More research and discussion on the subject, however, could greatly benefit the industry.
Production Chemistry: Exposing Hidden Treasures or Generating Complications?
Authors: Zhang Ping , Harris Lorraine , Demiroglu Muge , Gokool Andre
Published: April 2017

According to a recent study, more than 50 percent of the world's energy currently comes from oil and natural gas. So how does Production Chemistry discipline play a role in this? Can we use the discipline to enhance or accelerate production? And what happens if we get it wrong? Will it have a detrimental impact on production?

The Production Chemistry threats to business are getting more challenging and frequent, reflecting the changing complexity of our Project and Operations portfolio (deeper water and complex interventions, longer subsea tie backs leading to colder fluids and more wax / hydrate challenges; or smaller tieback to hosts operated by others yielding compatibility challenges).

Production chemistry threats in Project and Operations represent a significant challenge to safe and competitive operations. The impact of getting it wrong can be severe, leading to deferrals and increased operational costs. The root causes of many of these deferrals can be attributed to late or unstructured production chemistry involvement during the Project stage and limited support during Operations stage.

The objective of this paper is to highlight the importance of understanding the financial impact of production chemistry decisions to safety, production assurance, operational expenditure (OPEX) and capital expenditure (CAPEX) for Project and Operations. Moreover, this paper will highlight the criticality of engaging production chemistry at the appropriate project phase to get the desired outcome. This paper provides a number of case studies. In a number of cases, production chemistry engineers correctly evaluated the project threats during engineering design, leading to a correct selection of preventative barriers which proved to be financially favorable, and reduced HSSE risks throughout life of the asset. In addition, one case study describes the operational experiences where the impact of production chemistry was incorrectly assessed and a production loss was incurred during Operations stage.

Based on these case studies, production chemistry engineers should be cognizant of the impact of their decisions on the projects including threat assessment and barrier selection throughout the project lifetime. In addition, the production chemistry engineers should be able to effectively communicate their technical decisions and associated reasoning and values provided with the project stakeholders.
Investigations into Observed High Frequency Mooring Line Dynamic Behaviours
Authors: Jayasinghe K. , Carra C. , Potts A. E. , Kilner A. A.
Published: April 2017

As part of improvements to the integrity management practices for two in-service FPSO mooring systems, detailed reviews of existing video inspection data were undertaken. These reviews identified separate high frequency mooring system dynamic responses in frequency ranges higher than typical wave frequency responses. In relatively benign conditions associated with ROV-based inspection activities, torsional vibrations in deep water wire rope sections were observed. In a moderate water depth system, vortex induced vibration (VIV) excitation of a wire rope segment, leading to high frequency oscillations of chain links within the chain hawse tubes on a turret moored system, were also observed. These oscillation frequencies were typically an order of magnitude higher than those arising from wave frequency motions. The implication of these observed high frequency motions was that there were potential fatigue and wear degradation mechanisms that had not been accounted for in the mooring system design. A review of the observed high frequency response mechanisms - torsional vibrations and VIV excitation of mooring line segments - was performed followed by an assessment of the implications on mooring system design and ongoing integrity. The theoretical foundations for the two mechanisms were identified, and the frequency and amplitude of the resultant motions and component stress ranges evaluated. The degradation effects of the two mechanisms were then assessed in terms of both the core mechanisms and the child degradation processes they may initiate (e.g. wire rope segment VIV leading to increased chain wear). A review of different mooring system configurations and water depths was performed to identify the propensity for these mechanisms to occur and their potential for adverse impacts on mooring line integrity were evaluated. For each mechanism, the key influence parameters on the observed high frequency response were identified. The potential impacts on overall mooring system integrity were evaluated, along with the implications for the inspection strategies to verify the ongoing condition of the mooring components. These mechanisms show that mooring system designers must be aware of the dynamic responses that can be excited with typical mooring systems. Without paying due attention to these potential effects at the design stage and during operation, the degradation mechanisms that may be initiated by these effects may be detrimental to the overall long-term integrity of the mooring system.
Investigations Into Break Strength of Offshore Mooring Chains
Authors: Potts A. E. , Farrow G. , Kilner A. A.
Published: April 2017

The first phase of the Chain FEARS (Finite Element Analysis of Residual Strength) Joint Industry Project (JIP) aimed to develop guidance for the determination of a rational discard criteria for mooring chains subject to severe pitting corrosion which, based on current code requirements, would otherwise require immediate removal and replacement.

Critical to the ability to evaluate the residual strength of a degraded chain, is to have an accurate estimate of the chain in its as-new condition, providing a benchmark for any loss in strength associated with severe corrosion or wear. A Finite Element Analyses (FEA) residual capacity assessment method was developed and correlated against available break strength test data of degraded links as part of the JIP. FEA were conducted of as-new chain links in accordance with this validated methods, which when compared with current Class Rules specified Minimum Break Load (MBL) demonstrated a significant disparity between Predicted Break Load (PBL) and the codified MBL, particularly for larger chain sizes. It was identified, consequent on this inconsistency in MBL with respect to chain size that inconsistency in proof loading would also result for chains of larger size.

Consequently further investigations were carried out with the objective of:Determining an alternative formulation for the break strength of studlink and studless chain, thereby allowing comparison with the current Class Rules break strength formulation.Assessing the extent and effect of inconsistencies in the Conventional Proof Load FormulationEstablishing the origin and the technical basis for the Conventional MBL formulae.Assessing the validity of the Code MBL with respect to Actual Break Load (ABL) of common studlink mooring chain and the implications of using an alternative Amended Formulation for as-new chain strength.

The basis for the determination of the current Class Rules on chain strength is established and in doing so serves to explain the a significant disparity between PBL and the codified MBL that is evident particularly for larger chain sizes. An alternative formulation for the break strength of as-new studlink and studless chain is presented. It is recommended that further investigation be conducted to establish an alternative proof load formulation optimized for fatigue endurance.
A New Quantitative Predicting Method for Water-Sensitivity Damage
Authors: Yang Renfeng , Jiang Ruizhong
Published: April 2017

The possibility that the productivity is seriously reduced if the producing formation is exposed to the fresh water has been recognized for many years. Many experiments and theoretical studies have been carried out to elucidate the mechanism of water sensitivity. Despite years of field observations and laboratory research, methods of predicting quantitatively the susceptibility of formation to water-sensitivity have not been developed to complete reliability. Until now, there was no model to predict the productivity decreasing according to the experiment results except time consuming simulation.

Based on the latest researches on water sensitivity characteristics and mechanism, core experiments were set up to analyze the permeability and relative permeability parameters changing along with the salinity decreasing under different reservoir properties. Based on material balance equation, analytical function of relative permeability, Backley Leverett theory and Welge equation, a new productivity decline model which can quantitatively predict water sensitivity influence is derived with all the coefficients clearly. The new model has been proven to accurately predict the production performance. The changing coefficients could be obtained through analyzing permeability loss and relative permeability changes through laboratory measurements.

The most significant innovation is that the production performance could be quantitatively predicted rely on the laboratory results. It can be concluded from experiment analysis that the permeability loss was slow after the first fast, and the relative permeability parameters also changed (residual oil saturation and irreducible water saturation becomes bigger, and the relative permeability of both oil and water phase becomes smaller at the same water saturation) along with salinity decreasing because of the clay swelling and the colloidal clay particles captured at a local pore constriction. Then the change of the coefficients in new model could be calculated and the production performance could be predicted. The proposed model has been tested using production data from several reservoirs and the results have demonstrated that the proposed new model works satisfactorily.

The novelty of the new dynamics model is in the ability to solve the production prediction approach for water-sensitive reservoirs according to experiment measurements without time consuming simulation.
Numerical Simulation of Water and Sand Blowout When Drilling through Shallow Water Flow Sediments during Deepwater Drilling
Authors: Gong Zhiwu , Ren Shaoran , Zhang Liang , Zhang Panfeng , Xu Yan , Yu Lu
Published: April 2017

A geological model of typical shallow water flow (SWF) sediment in deepwater basins is constructed based on its basic characteristics, and a reservoir simulation model is then established that incorporates two-phase flow as the basis for the simulation of water and sand blowout process during penetrating SWF formations. The model assumes that sands can start flowing along with water at a critical pressure difference when drilling through SWF formations. The cumulative water and sand blowout as SWF formations are penetrated are calculated and the influencing factors, such as SWF zone size, overpressure factor of SWF formations and penetration rate, are incorporated into the model to quantitatively analyze their impacts on the water and sand blowout from SWF zones. The data are useful for the assessment of the severity of SWF hazards. The results show that the cumulative water blowout and sand blowout will be as high as 100m3 and 1m3, respectively, when a typical SWF sediment is totally penetrated. SWF formation overpressure factor has a remarkable effect on SWF blowout, while SWF zone size has more moderate effects. However, the effects of SWF sediment size are expected to become increasingly significant as time proceeds. 10% increase of overpressure factor of SWF formation will result in around 90% increase of cumulative water blowout and 150% increase of cumulative sand blowout after the SWF zone is totally penetrated, while 10% increase of SWF zone size will lead to about 20% elevation of cumulative water blowout and 25% ascending of cumulative sand blowout. The water and sand blowout can be effectively reduced while increasing the penetration rate, which indicates that elevating the penetration rate can be a useful measure for the control of SWF hazards during deepwater drilling operations.
Heavy Lift Dynamics, Sewol Ferry Offshore Salvage
Authors: Stewart W. P. , George P. , Ashley W. , Guha A. , Achanta V.
Published: April 2017

The Sewol Ferry sank off Korea in 2014 with the loss of 304 lives. The remains of 9 victims remain within wreck and cannot be reached by divers. This paper describes some of the heavy lift engineering involved in the salvage of the 146-meter long ferry, in one piece, from a depth of 44 meters in the ocean, resting on its port side.

A method for calculating the interaction of the vessel stern with the seabed (ground reaction) is described as the bow of the 8,000-ton vessel is raised to place lifting beams to be used in the side lift.

Significant difficulties, associated with geotechnical issues, resulting in project delays are descried.

Calculation methods are presented for determining the large trapped water mass and the large frequency and depth dependent added mass of the submerged vessel (greater than 120,000 tons). Coupled dynamic time domain simulations of the initial bow lift, followed by the side lift onto a floating vessel are presented. A total of 34 HMPE synthetic slings are used to attach a 1,200-ton purpose-built lifting frame to the ZPMC 12,000-ton revolving crane.

Wave forecast data from three sources are compared with continuously measured data from a directional wave buoy at the site. The difficulties in predicting and controlling the heel of the vessel with a combination of added buoyancy, slings and geotechnical forces are described for the failed attempt at the first bow lift and for the final bow lift. Dynamic sling tensions are shown calculated for the upper HMPE slings and the lower steel rope vertical and balance slings from the lifting frame to the lifting beams. Detailed static and quasi-dynamic FEA results are described for the Sewol hull, together with buckling checks.
Making the Most of Probabilistic Marine Forecasts on Timescales of Days, Weeks and Months Ahead
Authors: Steele Edward , Neal Robert , Bunney Christopher , Evans Benjamin , Fournier Nicolas , Gill Philip , Mylne Kenneth , Saulter Andrew
Published: April 2017

Marine forecasts are essential to operational planning, with decisions able to be guided by a host of different weather products spanning a period of days, weeks and even months ahead. The correct selection and subsequent application of these different types of weather products has the potential to save many thousands of dollars per day in operational downtime, however this is only possible when the science underpinning these marine forecasts is properly understood by the user. In the current economic context, this is especially relevant to the offshore industry – whose use of forecasting technology is traditionally very conservative, and therefore whose planning is often more reactive – allowing large savings (e.g. mobilization / demobilisation costs) if robust decisions are made as early as possible. Two established methods for the interpretation of probabilistic data based on cost-loss and weather regime analysis are described and applied to ocean wave forecasting. It is suggested the selection of methods will be dependant on the timescales of interest, with the cost-loss analysis optimised for supporting decisions at timescales on days to weeks ahead and the weather regime analysis optimized for supporting decisions at timescales of weeks to months ahead. The application of these methods are illustrated from the point of view of a North Sea asset manager planning the mobilization of equipment / personnel under conditions of calm weather, and the protection of equipment / personnel under conditions of severe weather. For such a user, efficient operational planning will be best supported by the use of marine forecasts across all such timescales, from days to months ahead. It is intended that this will enable more informed decision-making, and help reduce operational costs, by promoting increased confidence in longer-range forecasts than are typically used by the offshore oil & gas and marine renewable energy sector.
Decommissioning: A Call for a New Approach
Authors: Ars Francois , Rios Renato
Published: April 2017

As the one sure thing in the life of a human being is death, the only one sure thing for an oil or/and gas well is the operator's compliance to its permanent plugging and abandonment. Around the world, regulators are tightening rules and controls that are not necessarily being reflected in the budgets allocated for decommissioning. Coupled with a low oil price, this insidious issue has the potential to weight on several operators’ end-of-lease capital of expenditures and shareholders expectations.

The complexity of dismantling offshore production and well infrastructures in the oil and gas industry has substantial potential impacts to health, safety and the environment. In fact, each well is a potential path to bring polluting fluids to water and surface. Furthermore, Plug and Abandon responsibilities and liabilities do not necessarily end with the operator lease, carrying a major overburden if not done right.

The lack of offshore installation's standardization of the past decades tends to be confused as a reason to think that each decommissioning job is different. However, if more knowledge is built and shared across the industry, it is possible that the sump costs of abandoning can be minimized altogether while best practices for permanent isolation are implemented. This paper is a call for a new approach of total sharing well abandonment and installation decommissioning practices moderated by an independent third party. This third party will provide with access to specialized technologies, engineering and compliance certifications to current industry standards to governmental regulations. This will help achieve the most cost-efficient solution for the industry.
Digitizing Flexible Riser Annulus Testing by Automated Portable Test Equipment
Authors: Amundsen Torbjørn , Nilsen-Aas Christoffer , Kanestrøm Øystein , Tveit Øyvind
Published: April 2017

Automation of testing of flexible risers and the subsequent capture of the results into a data reservoir, will improve integrity management, reduce maintenance costs, and increase operational safety. Overall, data quality, quantity, consistency and immediacy are much improved, hence providing a more reliable basis for predictive analyses.

With more than 3000 flexible risers in operation worldwide one of the most common methods to verify the integrity of the flexible risers is to perform annulus volume testing on a regular basis to assess:

– Integrity of the outer sheath – Annulus vent port flow – Liquid filling of the annulus

Based on annulus vent gas monitoring technology designed for permanent installation offshore, an automated portable unit has been developed. By using predictive analyses, it is now possible to give feedback to the user if the results are within the expected range so that mitigating actions can be taken immediately. By automating and digitizing the required testing of flexible risers, service personnel are not required to follow the equipment which is beneficial in remote locations. Automated processes also make it easier to ensure consistent test methods.

The main objectives of this paper are to;

– Show that automated equipment can perform the annulus volume testing without mobilizing personnel from shore – Demonstrate that it is possible to predict the expected development of the riser condition by digitizing data from thousands of annuli test results.

Two major oil companies have tested the automated portable inspection unit offshore on North Sea installations, with good results.
Enabling Drilling Operations Using Structured Data and Measured Response
Authors: Holden Harald , Marre Ignacio , Holm Heidi Gryteland , Næss Randi
Published: April 2017

The scope of this paper is to show how digitized, structured data, as a combination of design data, operational data, riser analyses and measured riser response can be used to enable drilling operations on a subsea exploration with well challenging soil or/and harsh environmental conditions.

The structural integrity of the well foundation and soil support has been verified by combining the structured data obtained from measurements with the design information. A sensor system has been fitted to the riser and BOP on mobile drilling units to monitor soil and structural integrity. The combination of pre-operational assessments and monitoring during operations has been carried out for 7 consecutive drilling campaigns, with two different semi-submersible drilling rigs. The work presented in this paper will give a comparison between the measured response and the up-front design analysis, and show show to combine the design information with operational data and measured response to enable future operations.

During the design phase of a subsea exploration well a wide range of design assumptions must be considered. The range in high and low estimates for parameters such as soil support or riser and BOP mass and damping forces may be considerable. In general conservative parameters must be selected, leading to worst case scenarios, which again may lead to limited operational windows, introduce high cost mitigating actions or in worst case prevent operations from being carried out.

This paper will present the benefit of using actual measured response and operational parameters back into the design loop when planning upcoming drilling campaigns. Structured operational data and measured response is used to improve analysis models; which lead to reduced conservatism. For cases of re-entry on an existing exploration well with heavier equipment, the measured soil support can be used to rule out some worst-case scenarios, and enable the upcoming operation. A case example of an exploration campaign enabled by the design loop will be shown.