Towable Subsea Processing Unit for Well Fluid Separation
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Solution Overview
Problem
Subsea processing systems face challenges such as complex installation, high costs, and reduced accessibility due to bulky equipment and the need for multiple installation vessels, along with issues like wax deposition in cold flow conditions, which limit their applicability in deep and challenging waters.
Innovation Solution
A towable subsea processing unit with a pipeline bundle extending between towheads, where at least one towhead includes on-board processing facilities for water separation and wax control, allowing for prefabrication and testing onshore, reducing the number of subsea interfaces and enabling flexible, reliable, and cost-effective installation and operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If subsea processing units are made bulky to ensure reliability and processing capacity, then processing reliability is improved, but installation complexity and cost increase due to need for multiple installation vessels
Solution Approach 1:
The subsea processing system is divided into modular processing modules that can be independently installed and connected. Each module contains specific processing functions (separation, heating, cooling) and can be deployed separately, reducing installation complexity while maintaining overall system reliability through modular redundancy and distributed processing capability.
Solution Approach 2:
Processing modules are integrated within or attached to the subsea pipeline structure itself, rather than being separate bulky units. The processing equipment is nested within the pipeline framework, utilizing the existing structural space and reducing the need for additional large-scale installation vessels and complex external support structures.
2Productivity
If subsea processing units are made bulky to accommodate all processing functions, then processing capacity is improved, but accessibility for maintenance and repair deteriorates
Solution Approach 1:
The processing system is segmented into discrete functional modules (separation module, heating module, cooling module) that can be independently accessed, maintained, and replaced. This modular architecture allows maintenance personnel to work on individual modules without needing to access or dismantle the entire processing system, significantly improving maintenance accessibility while preserving full processing capacity.
Solution Approach 2:
Maintenance access features and diagnostic capabilities are built into the modular design from the outset, allowing for easier preliminary assessment and faster maintenance operations. Each module includes standardized connection points and access hatches that facilitate routine maintenance without requiring complex disassembly procedures.
3Use of energy by moving object
If wellstream temperature is reduced for cold flow transportation, then energy consumption is reduced, but wax deposition increases restricting flow
Solution Approach 1:
Heating is applied locally at specific points along the subsea pipeline rather than heating the entire wellstream continuously. Heating modules are strategically positioned at locations where wax deposition is most likely to occur, providing targeted thermal treatment to prevent wax formation only where needed, thereby minimizing overall energy consumption while effectively controlling wax deposition.
Solution Approach 2:
Instead of continuous heating, the system uses periodic or intermittent heating cycles to prevent wax deposition. The heating modules are activated based on temperature sensors and flow conditions, applying heat only when and where wax formation is detected or predicted, reducing energy consumption compared to continuous heating while maintaining effective wax control.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution simplifies the installation and operation of subsea processing systems by integrating processing units into towable bundles, reducing installation costs and weather sensitivity, and enabling longer tie-back distances without the need for insulation or active heating, thus enhancing the reliability and efficiency of subsea oil and gas production.
Implementation Method 1
The pipeline bundle 26 acts as a heat exchanger to cool the wellstream
Implementation Method 2
The pipeline bundle 26 acts as a heat exchanger to cool the wellstream
Implementation Method 3
cool the wellstream enough to force wax to deposit
Implementation Method 4
force wax to deposit on the inner wall of the flowline
Data Source
Figure 1~3
Figure 4
Figure 5
AI summary
A towable unit (32) for subsea processing of well fluids comprises a pipeline bundle (26) extending between, and capable of acting in tension between, a first towhead (28) at an upstream end of the bundle and a second towhead (30) at a downstream end of the bundle. At least one of the towheads has an on-board processing facility for processing the well fluids, which facility effects at least separation of water phases that are present in the well fluids.