Dual Gradient Drilling Subsea Pump System
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Solution Overview
Problem
Current dual gradient drilling (DGD) systems face challenges in reducing hydrostatic pressure on wellbores in deep water drilling, requiring heavier mud weights that complicate drilling returns and increase costs, with existing solutions either venting hydraulic fluid or relying on inefficient centrifugal pumps that require mud level adjustments.
Innovation Solution
A closed-hydraulic positive displacement subsea pump system that can be installed at shallower depths without venting hydraulic fluid, using an independent mud return line to control wellbore pressure without adjusting mud levels, and incorporating an annular sealing system to manage pressure differentials and extend sealing element life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a subsea pump system is installed at deeper depths to reduce hydrostatic pressure on the wellbore, then the hydrostatic pressure on the wellbore is reduced, but the frictional losses and installation costs increase
Solution Approach 1:
The patent introduces a vertical dimension to the pressure management system by installing the subsea pump at an intermediate depth rather than at the bottom of the wellbore. This dimensional change in pump placement allows the system to reduce hydrostatic pressure on the wellbore while minimizing the length of the riser column, thereby reducing frictional losses and installation costs.
2Length of stationary object
If an open hydraulic pump system is used, then the pump can be installed at shallower depths, but the hydraulic fluid must be vented which complicates the system
Solution Approach 1:
The patent extracts the venting requirement from the system by implementing a closed hydraulic circuit. The hydraulic fluid is contained within the system and circulated through a heat exchanger rather than being vented to the atmosphere, thereby eliminating the complexity associated with venting mechanisms while allowing shallow installation.
3Quantity of substance
If centrifugal pumps are used to circulate drilling returns, then the system can operate with heavier mud weights, but the pumps require frequent mud level adjustments and are less efficient
Solution Approach 1:
The patent replaces the centrifugal pump mechanical system with a positive displacement pump system. This substitution eliminates the need for frequent mud level adjustments and improves drilling efficiency while maintaining the capability to operate with heavier mud weights. The positive displacement mechanism provides more consistent and controllable flow characteristics.
4Device complexity
If heavier mud weights are used to drill the wellbore, then fewer casing strings are required, but it becomes more difficult for drilling returns to reach the surface
Solution Approach 1:
The patent introduces a subsea pump system as an intermediary mechanism between the wellbore and the surface. This intermediary actively assists in lifting the drilling returns, overcoming the resistance created by heavier mud weights. The pump acts as a mediator that enables the system to benefit from reduced casing requirements while maintaining ease of operation for returns flow.
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
Enables efficient DGD operations at shallower installation depths, reducing costs and frictional losses, while maintaining control over wellbore pressure without venting hydraulic fluid or relying on mud level adjustments, and extends the operational life of sealing elements.
Implementation Method 1
A closed-hydraulic positive displacement subsea pump system that can be installed at shallower depths without venting hydraulic fluid
Implementation Method 2
closed-hydraulic positive displacement subsea pump system
Data Source
AI summary
A dual gradient drilling system includes a subsea blowout preventer disposed above a wellhead, the subsea blowout preventer having a central lumen configured to provide access to a wellbore, a lower section of a marine riser fluidly connected to the subsea blowout preventer, a closed-hydraulic positive displacement subsea pump system fluidly connected to the lower section of the marine riser and disposed at a predetermined depth, an annular sealing system disposed above the closed-hydraulic positive displacement subsea pump system, and an independent mud return line fluidly connecting one or more pump heads of the closed-hydraulic positive displacement subsea pump system to a choke manifold disposed on a floating platform of a rig.