Real-time data, simulation tools speed Cascade & Chinook development, operation

A situation room was built fit-for-purpose, considering the phased project philosophy. It is equipped with off-the-shelf flat panel monitors, computers, and video and phone conference equipment.

A business process will support the use of the room to maximize the gain from these systems. The operation manager will lead a daily morning meeting to discuss past day’s events. When problems are encountered, suggestions will be provided by Petrobras staff to avoid identical problems from recurring.

A spreadsheet will display action plans that will be followed up every meeting to ensure the actions are implemented. The daily meetings will connect the FPSO team with the local onshore team by video conference. The focus of the meeting may vary from production optimization, HSE issues, specific process variable/equipment or cost reduction, to any other subject prioritized by asset management to support company goals.

PSMS

The PSMS provides Petrobras with the means to achieve the following objectives for the Cascade and Chinook assets:

• A real-time system for subsea well, MPP, FPSO topsides, and FPSO vessel data
• A reliable system that standardizes critical work flows, such as production well testing, estimating production allocations, and providing basic production surveillance
• Ability to implement the workflows in an easy-to-use and intuitive graphical interface
• Timely and collaborative decision-making for managing the asset’s reservoirs, wells, and equipment
• Enhanced decision-making process where engineers can provide support faster and with a higher degree of confidence and accuracy to the asset’s operational staff
• Minimized data management requirements, telecom resources, and system administrative and support requirements.

Production surveillance

The PSMS contains built-in tools that allow users to quickly analyze production data. The tools include pressure transient measurement and analysis (PTA) for basic production surveillance, data mining, and reporting for event root cause analysis. Access to historical trend data is via an ad-hoc method from the graphical interface.

Historical data from the PSMS is also available for other engineering applications via a manual data export. Additionally, for automated workflows requirements such as flow assurance, the PSMS is configured to make data automatically available to the DOFT Vendor flow assurance application. Other third-party applications needing PSMS data can interface via standard methods including Web services, minimizing Petrobras data management requirements.

The well test system is designed for 16 wells. The initial implementation is configured for three wells, and future wells will be configured as they come online. The well test system will be designed for regular well tests and deduct well tests. The initial implementation will be configured for regular well test and deduct well tests that will be configured as new wells come on line and deduct tests are required.

Production allocations

The PSMS reports real-time well test information and approved well test results from the PSMS well testing system. The well testing system uses the well’s subsea multiphase flow meters (MPFM) or the FPSO test separator, the Cascade inlet separator, and the Chinook inlet separator, as well test systems.

The PSMS uses the approved well test volumes and facility rate data to calculate a real-time facility battery factor. Deviation of the battery factor from a tolerance indicates to the operations and engineering staff that certain wells may need to be re-tested or measurement points on the process facility or MPFMs may need calibration or service.

The last approved well test data is used in conjunction with the well flow times to calculate estimated production allocations for each well. Measurement data from process meters (fuel gas, flare gas, process oil meters, process water meters, etc.) and selected fiscal metering equipment (gas export meters) will also be used to calculate the facility battery factor.

The PSMS provides detailed reports, including the latest well test results and test history for each producing well, field well test summary, well estimated downtime, well estimated last month’s downtime, and well estimated allocation reports for the previous day and any specific date.

The Cascade and Chinook DOFT includes both the Cascade and Chinook subsea systems from the well/reservoir boundary to the inlet separators.

Custom reports will be available, including integrating data from other systems for use in PSMS reports as required. PSMS will provide an export of selected PSMS data for use in other reports required by Petrobras.

The objective of the Cascade and Chinook DOFT is to serve as the primary operations support tool for safe and reliable production. The DOFT uses simulation results to understand current facility conditions and predict future conditions. Information from the DOFT is presented to operations team in a clear way, facilitating good decision. The DOFT consists of four separate applications – Real-time, Look-ahead, Planning, and Operator Training Simulator (OTS). Replicas of one single model are used for these applications to ease future maintenance of the system. Two identical systems comprised of all four applications are installed offshore (FPSO) and onshore (Petrobras offices, Houston).

The real-time (RT) simulator of the DOFT serves as a “virtual plant” of the modeled facility. The real-time model simulates parallel to the plant making available a wide range of information that cannot or is not measured, such as pressure, flow, and hold-up profiles inside the pipelines.

The RT indirectly receives data from the FPSO, subsea, and subsea boosting control systems via the Petrobras Historian. Measurements in the Historian are used to continuously update the real-time model’s boundary conditions (e.g. inlet and outlet pressures) and states (such as valve positions and controller set-points).

Other measurements are used to check for faults in the process, including valve blockage and hydrate formation. The RT provides the user with a large range of inferred information. This window into the pipeline is based on the results from the high-fidelity dynamic process model, and is included in the DOFT interface as profiles and trends. The following application modules are also supplied to help the operator better monitor the production facility:

• Automatic model tuning
• Hydrate monitoring
• Slug monitoring
• Scraper (pig) tracking
• Hydrate inhibitor tracking
• Leak detection.

Look-ahead simulator

The look-ahead simulator is an integral part of the real-time simulator and uses the same interface. The look-ahead simulator accepts initial conditions (state variables and parameters) saved by the real-time simulator, and uses these values as the starting point for the simulation. The control of the look-ahead feature is performed by a look-ahead timing function configured to initiate a look-ahead model manually or automatically at a user-defined frequency (e.g. every hour). The simulator runs full speed in future and serves as an early warning tool.

The look-ahead model instance is run at maximum model speed and the actual attained speed is a minimum of 36 times real time; i.e., 36 hours of look-ahead in one hour. The look-ahead simulation can be terminated at any point during the look-ahead execution and a new look-ahead can be started at that point.

Planning simulator

The planning simulator is also referred to as the “What-If” simulator and allows investigation into the predicted Cascade and Chinook system response based on scenarios. The planning mode runs independent from the real-time and look-ahead simulators and serves as a comprehensive flow assurance tool. The planning mode can be run using preconfigured scenarios investigating the effect of changes to external parameters and boundary conditions or changes introduced by operations. Examples of typical planning scenarios are:

• Start a well
• Shut in a well
• Production choke changes
• Line pack/unpack
• Shut-in with subsequent restart.

The purpose of the planning simulator is to facilitate the investigation of system behavior to different operating actions.

Since the same process model is used for all modes of the DOFT, current process conditions from the real-time model can be used as the starting condition for a planning session. This allows the user to test out operational procedures

The OTS is identical to the planning simulator except for these additional features:

• Operator interface consisting of process mimics based on control system operator screens
• Instructor interface based on planning simulator interface with instructor functionality
• Subsea and topsides emulated shutdown and interlock logic.

The Cascade and Chinook DOFT includes both the Cascade and Chinook subsea systems from the well/reservoir boundary to the inlet separators. Additional model scope is included for diesel displacement of the flowlines and for methanol supply to the trees, manifolds, and pump stations. The gas export model is included from the export gas metering in the FPSO to the Discovery tie-in.

DOFT/OTS is built with the sole idea that it will serve as a good “hands on” training platform for the operators. The OTS operator interface mimics the real control systems operator screens and the process model provides realistic process dynamic response required for a complete training package. The OTS was used to verify and correct subsea operational procedures for this project and will be used as a subsea operations training tool.

Risers/mooring lines

The turret system of the FPSOBW Pioneer includes a moored buoy that can be disconnected from the vessel and submerged in the event of a hurricane, allowing the FPSO to sail away to a safer location. Connected to the FPSO, five free-standing hybrid risers (FSHRs) are linked to the turret buoy with flexible jumpers.

To monitor the integrity of the risers, turret buoy, and the mooring line systems, several parameters are permanently supervised during the lifetime of the field and of the FPSO contract.

The long-term integrity of each riser depends on the motions caused by the FPSO, the flexible jumper loads, the buoyancy can up thrust, and the environment loads. The turret buoy motions are evaluated in both connected and disconnected states by sensors installed at the buoy and also at the FPSO Central Control Room.

Because of its general design, the Supervisory System is ideal to familiarize the operators with the important variables and parameters used to monitor the integrity of the risers and mooring lines, besides centralizing the information of these components. The FPSO operators and Petrobras personnel, trained respectively on the operation and maintenance of the Supervisory for the Risers/Mooring lines Monitoring System, can interface with all variables being monitored according to their access level in the system.

All these systems together, with visualization available both onshore and offshore, will enable Petrobras to resume oil and gas production in the fields faster after an extreme weather event, optimizing downtime for the system and operate all pieces of equipment of Cascade and Chinook project safely.