Quantitative Determination of Safety Integrity Level on Offshore Metering and Custody Transfer Facility

A quantitative way for determining the Safety Integrity Level of Safety Instrumented System (SIS) on Offshore Metering and Custody Transfer Facility in Campeche Bay Mexico is presented in this work. The methodology that was employed in order to assess and determine the Reliability parameters of SIS; which was carried out in three steps: 1. Identify undesirable events that can damage to personnel using the API-14C and to, the facility and the environment (by oil spill in hoses when the oil tanker is filled), 2. Estimate the severity and consequences of risk, using safety layer matrix of ISA S84.01 and, 3. Quantify the severity of each risk identified with the fault tree analysis. This last step uses the minimal cut sets, an innovative concept in petroleum industry, this provides valuable information about possible combinations of fault events, that can result in a critical failure of the system. The period of maintenance of the main SIS components (sensors, logic solver and final element), was reduced applying redundancy in the primary element. Furthermore, the results obtained of this analysis can be used by insurance companies or institutions that certify under standards of process quality and safety.

Cost-Benefit Model for Risk-Based Design of a Typical Marine Platform in Mexico

A reliability-based cost-benefit model for the risk management of oil platforms in the formulation of optimal decisions based on life-cycle consideration is proposed. The model is based on structural risk assessments and the integration of social issues and economics into the management decision process. Structural risks result from the platform’s exposure to the random environmental loading associated with the offshore site where it is located. Several alternative designs of a typical platform are proposed and assessed from the cost-effectiveness viewpoint. This assessment is performed through the generation of cost/benefit relationships that are used, later on, to select the optimal design.

Field Implementation of RBI for Jacket Structures

The present paper first gives a brief outline of the simplified and generic approach to reliability and risk based inspection planning and thereafter sets focus on a recent application of the methodology for planning of in-service NDT inspections of the fixed offshore steel jacket structures in the DUC concession area in the Danish part of the North-Sea. The platforms are operated by Maersk Oil and Gas on behalf of DUC partners A.P. Mo̸ller, Shell and Texaco. The study includes a sensitivity analysis performed for the identification of relevant generic parameters such as the bending to membrane stress ratio, the design fatigue life and the material thickness. Based on the results of the sensitivity analysis a significant number of inspection plans were computed for fixed generic parameters (pre-defined generic plans) and a data-base named iPlan was developed from which inspection plans may be obtained by interpolation between the pre-defined generic plans. The iPlan data-base facilitates the straightforward production of large numbers of inspection plans for structural details subject to fatigue deterioration. In the paper the application of the generic inspection plan database iPlan is finally illustrated on an example.

Basic Strategy of Health Monitoring on Submarine Pipeline by Distributed Optical Fiber Sensor

Submarine pipeline system is a main pattern in collection and transmission of offshore oil and gas, which sends oil and gas from offshore oil/gas field to land, and it plays an important role in the production of oil and gas. Because of the complicated and harsh condition in which pipeline system works, such as impulsion, corrosion and free-spanning vibration, failure of submarine pipeline system occurs occasionally, it causes oil leakage, environment pollution and economic losses. Health monitoring is a feasible and effective manner to ensure submarine pipeline safe and reliable during service, especially when all factors affecting pipeline failure are not still entirely realized or controlled. The basic strategy of a new real-time monitoring system for long distance submarine pipeline is introduced in this paper, which has the function of diagnosis and auto-alarm. In this system, a new distributed optical fiber sensor (DOFS), which uses optical time domain reflectometry theory based on Brillouin backscatter, is applied to monitor the strain and temperature along the pipeline. To be used for long distance submarine pipeline, this system applies Wavelength Division Multiplex (WDM) technology and series DOFSs in series so as to extend the measure scope for long distance submarine pipeline. By using signal processing system to analyze the outcome data of sensor, the strain along the pipeline can be obtained. If the strain reaches the alarm setting, the system will send out caution and meanwhile accurately give the damage position. The system can also analyses vibration frequency of pipeline, if free-spanning vibration occurs, caution will also be given, so that the operator can take some measures in time to avoid the failure of pipeline. In this paper, the makeup of distributed optical fiber sensor and developing principle are specified, system development, application and construction in engineering are analyzed as well. The brand new practical system can not only be used for submarine oil and gas pipeline but also for land oil and gas transfer system, city coal gas transfer system, electricity-transmission cable and so on. This system can be widely used in many prospects of other industries.

3D High Resolution Survey of Natural Seeps in the Campeche Sound

In order to define the zones at risk by the shallow gas and natural seeps of hydrocarbons in the Campeche Sound, a 3D geophysical study of 4 areas has been carried out in the region of the Cantarell oil field [1]. The results of this high resolution survey were correlated with previous explorations and it was possible to define the migration route and evolution of the shallow gas accumulations. The volume increase of the accumulations detected can not be explained by the lack of precision of the instruments and is more likely connected to the exploitation of the reservoir. The faults that transport the hydrocarbons from the reservoir to shallow strata define an area that contains several important platforms likely to be affected by the gas migration process. This geophysical survey was also used to define the location of three geotechnical borings for studying the degradation on the properties of the soils due to the presence of hydrocarbons that support the platforms.

Non-Linear Space-Time Evolution of Wave Groups With a High Crest

The theory of quasi-determinism, for the mechanics of linear three-dimensional waves, was obtained by Boccotti in the eighties. The first formulation of the theory deals with the largest crest amplitude; the second formulation deals with the largest wave height. The theory was verified in the nineties with some small-scale field experiments. In this paper the first formulation of Boccotti’s theory, valid for the space-time domain, is extended to the second order. The analytical expressions of the non-linear free surface displacement and velocity potential are obtained. Therefore the space-time evolution of a wave group, to the second-order in a Stokes expansion, when a very large crest occurs at a fixed time and location, is investigated. Finally the second-order probability of exceedance of the crest amplitude is obtained, as a function of two deterministic parameters.

Risk Analysis of Running a Deepwater Production Test From a Dynamically Positioned Vessel in the North-Atlantic

The present paper describes the key steps and issues involved in performing a quantitative risk analysis (QRA) for a dynamically positioned (DP) offshore vessel that is used to perform a short-term production test (PT) in North Atlantic deep waters. The basic approach is to focus on the “incremental” risk that would occur if the PT were run from a DP vessel as opposed to a fixed structure. The analysis is structured around two basic groups of risk: those specifically associated with DP vessel disconnection decisions and activities (all of which are seasonal) and those occurring during normal operation of the DP vessel. In the case of disconnection caused by hazards such as severe weather, ice, equipment or reference system malfunction, or human/operating error, a large variety of event sequences is assumed, each resulting in different consequences and risks. These are formulated for each analysis outcome in terms of loss of life, release of chemicals into the environment, damage and loss of assets and equipment, as well as overall failure cost. It is shown that the QRA provides a very useful basis for optimal decision making with respect to the feasibility, the planning, and the risk/benefit of deep-water production testing from a DP vessel.

Study of Flow Behavior in a Vibrating Pipe on Offshore Platform

The purpose of this paper is to study flow behavior in a vibrating pipe on offshore platform. The mathematical model of unsteady, incompressible, viscous flow in a vibrating pipe is established according to the basic theory of oscillating fluid mechanics. The governing equations of flow are decomposed into a system for steady flow and another for flow oscillation, with the equations of the differential coefficients of flow parameters solved by using the parametric polynomial method. Velocity and pressure distributions are obtained for different flow conditions. Numerical results indicate that the flow behavior in the vibrating pipe on offshore platform is strongly affected by fluid properties and the pipe structure. A good agreement is obtained when comparing the results with the variational solution in constant cross-section, which shows that the method proposed in this work is effective for studying flow behavior in a vibrating pipe on offshore platform.

Prediction of Green Water Events on FPSO Vessels

Most floating vessels experience some sea states, not necessarily extreme storms, which cause large volumes of green water to flow across the deck. Due to the location of safety critical equipment on the deck of FPSOs, the determination of the likely occurrences and the magnitudes of such events are critical to safe design and operation. A method for the determination of green water heights on the deck of an FPSO has been presented in references 1–5. This paper examines the long-term distributions of heights implied by these references and the identification of sea states in which extreme events are likely to occur. The method is based upon the long term distribution of sea states at the intended location, combined with the motion characteristics of the vessel. Freeboard exceedance at the bow and at a point along the side is considered for two typical FPSO configurations. The methodology presented is widely applicable to many locations but wave conditions typical of the Central North Sea are used by way of illustration. The results presented include long term probability distributions of green water height on deck at locations of interest. Relative contributions of each combination of significant wave height and peak period to the probability of the largest single event in a defined return period are determined and discussed. It is shown that the wave conditions most likely to give rise to the most severe green water events are seldom those characterized by the largest wave crest heights. Instead, there exists a complex dependence on characteristic periods associated with vessel motions and on the long-term occurrences of particular sea states. The ability to predict conditions in which the largest green water events are most likely to occur offers the possibility of providing improved operational guidelines for FPSOs, allowing action to be taken to avoid unfavourable loading conditions and/or vessel headings in certain sea conditions. However, it is also shown that it may be difficult to identify some severe green water sea states from normally available forecast data and hence it is important that appropriate provision is made at the design stage.

Benefit of Partly Displacement Controlled Condition in Sagbend

Some codes like BS8010 and DNV-OS-F101 distinguish between load controlled condition or displacement controlled (or strain based) condition. Even though the principles are clear, it is often hard to determine the difference in practice. A displacement controlled condition allows a higher utilization and is therefore beneficial, and can be applied provided that the condition can be classified as a displacement controlled condition. Many projects have had intense discussions on this matter during the last 15 years, however, without much progress. The objective of this paper is two-fold. First it will show that a discussion on load controlled versus displacement controlled is of limited value. The discussion should rather be on how to take benefit of a partially displacement controlled condition. Second, the paper gives a suggestion on how to allow for a partially displacement controlled condition, also determining the degree of displacement control. The suggestion is supported by specific FE-calculations.