Subsea Pressure Exchanger for Dual Gradient Drilling Mud Return
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Solution Overview
Problem
In subsea dual gradient drilling, existing pumps such as diaphragm and disc pumps face issues with shortened lifespan, inefficiency, and logistical challenges due to high internal pressures and heat transfer, leading to formation damage and high operational costs.
Innovation Solution
A pressure exchanger (PX) is used as a mud lift pump to transfer hydraulic energy between high-pressure and low-pressure fluids, eliminating the need for large pumps and subsea power, while being compact, durable, and easy to maintain, with minimal electrical requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diaphragm pump is used to pump used mud from sea floor to surface, then the pump can handle high pressure, but the diaphragm lifespan is shortened due to rupturing
Solution Approach 1:
The invention removes the diaphragm component from the pump system entirely, replacing it with a diaphragmless positive displacement pump design that uses a progressing cavity mechanism to move fluid without relying on a flexible diaphragm separator, thereby eliminating the rupture failure mode
Solution Approach 2:
The invention replaces the mechanical diaphragm-based separation system with a hydrodynamic progressing cavity pump mechanism that uses rotor-stator interaction to create sealed pockets for fluid transport, eliminating the need for flexible membrane components
2Productivity
If a disc pump is used to pump used mud, then the pump structure is simple, but the efficiency is only 15-25% resulting in large pump size and excess heat
Solution Approach 1:
The invention replaces the traditional disc pump mechanical system with a progressing cavity pump that uses a rotor rotating within a stator to create progressive cavities that move fluid along the cavity path, achieving higher efficiency through positive displacement rather than centrifugal action
Solution Approach 2:
The invention uses hydraulic principles in the progressing cavity pump where the rotor-stator interaction creates sealed hydraulic pockets that move fluid through the pump, enabling efficient energy transfer and minimizing losses to heat
3Device complexity
If mud is pumped all the way back up to surface via annulus in riser drilling, then the system is simple, but large pumps and thick riser piping are required causing high bottom hole hydrostatic pressure
Solution Approach 1:
The invention divides the fluid return path into two separate segments: the annulus path for drilling mud circulation and a dedicated mud return line for used mud removal, allowing independent optimization of each path and enabling lower pressure in the annulus system
Solution Approach 2:
The invention introduces a separate mud return line as an intermediary pathway that handles the used mud transport, allowing the primary annulus system to operate at lower pressures while still achieving effective mud removal from the wellbore
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
The PX increases the lifespan and efficiency of the mud return system, reduces the size of the valve system, and allows for efficient pressurization of used drilling mud with minimal energy consumption, addressing the inefficiencies and logistical challenges of traditional pumps.
Implementation Method 1
A pressure exchanger (PX) is used as a mud lift pump to transfer hydraulic energy between high-pressure and low-pressure fluids
Data Source
AI summary
A system includes a mud return system. The mud return system includes a pressure exchanger (PX) configured to be installed in a body of water, to receive used drilling mud, to receive a second fluid, to utilize the second fluid to pressurize the drilling mud for transport, via a mud return line, from a first location at or near the sea floor to a second location at or near a surface of the body of water.