Fundamentals of Subsea Drilling Operations (f: Floating Rigs 1 - Semi Sub Rigs)

Introduction to Floating Rigs

Overview of the Video

• The video introduces floating rigs, specifically focusing on semi-submersible rigs.

• Acknowledgment is given to viewers for their support through likes, subscriptions, and comments. This engagement helps tailor future content.

Presentation Outline

• The presentation will cover:

• Introduction to the topic.

• Merits and concerns of semi-submersible rigs.

• Examination of deck plans and rig move modes.

• Discussion on station keeping with examples.

• Overview of rating and classification samples for semi-submersibles.

Understanding Semi-Submersible Rigs

Design Characteristics

• Semi-submersible rigs consist of vertical cylinders or long rectangular cubes that store water for balance. These columns are connected to the main deck, which can be round or square in cross-section.

• They are self-propelled, allowing them to reach drilling locations independently or be towed like jack-up rigs.

Stability and Performance

• Semi-submersibles exhibit superior stability compared to drill ships, especially during adverse weather conditions due to effective station keeping capabilities. They can be anchored or dynamically positioned based on operational depth requirements.

Advantages and Concerns

Advantages

• Effective station keeping in rough weather conditions allows these rigs to remain steady while anchored or dynamically positioned at depths up to 10,000 feet. This optimizes cost-effectiveness in operations requiring extensive equipment at significant depths.

Concerns

• Challenges include difficulties with launching and retrieving the subsea BOP (Blowout Preventer) system, low water-tight integrity issues, and vulnerability of the mooring system during severe weather events such as hurricanes. These factors raise safety concerns for personnel aboard during extreme conditions.

Deck Plan Analysis

Deck Layout Features

• The main deck plan includes:

• Helideck location.

• Pipe racks on both port and starboard sides.

• Crane placements for operational efficiency.

• Areas designated for risers connecting the rig to wells beneath the surface.

Accommodation Facilities

• Below the main deck lies accommodation areas including recreation rooms, cinema rooms, and other essential facilities directly under the helideck for crew comfort during operations. Additionally, multiple windlasses are strategically placed around the rig's perimeter for anchoring purposes.

Rig Movement Techniques

Transportation Methods

• Rigs can be transported by being connected to vessels or carried on barges using tow systems known as dry towing methods before reaching their operational locations. Station keeping techniques involve either mooring systems or dynamic positioning systems (DPS).

Rig Movement Strategies

• Various configurations exist for moving a rig:

• Symmetrical arrangements with nine lines.

• Asymmetrical setups with staggered angles (30°, 60°, etc.) depending on specific operational needs and environmental conditions encountered during transit.

Dynamic Positioning Systems

Control Mechanisms

• Dynamic positioning systems operate as closed-loop systems where real-time data regarding position and heading is fed into a control system that maintains optimal positioning against external forces like currents or winds acting upon the rig structure.( t =428 s )

Control Systems in Dynamically Positioned Systems

Overview of Control Systems

• The control system functions as the "brain" of the dynamically positioned system (DPS), managing information flow to maintain operational stability.

• It activates thrusters and communicates with the power system to ensure the structure remains in its designated position, counteracting external forces like waves.

Importance of Engineering Competence

• The discussion highlights the need for engineers to be highly competent and safety-conscious, especially in light of past incidents such as the Deepwater Horizon disaster. This emphasizes ongoing training and education in engineering practices.

• A commitment to technical competence is essential to prevent future accidents, underscoring a proactive approach towards safety in engineering fields.

Technical Specifications of Semi-Submersibles

• Key specifications for semi-submersibles include an air gap of approximately 13 meters, a length of 11 meters, and a breadth of 14.25 meters, which are crucial for understanding their operational capabilities.

• Operating drafts are noted at about 23.5 meters while survival drafts stand at around 21.5 meters; these metrics provide insight into their design and functionality under various conditions.

Conclusion and Call to Action

• The speaker encourages viewers to engage with the content by liking, commenting, sharing, and subscribing for updates on new videos related to engineering topics discussed throughout this session. This engagement is vital for community building around safety and technical knowledge in engineering practices.