Managed Pressure Drilling Backpressure Control for Swab Surge Compensation
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Solution Overview
Problem
During managed pressure drilling (MPD) operations, the tripping of the drillstring causes swabbing and surging effects, leading to fluctuations in bottom-hole pressure, which can result in formation damage or influxes due to the piston effect between the mud and the drillstring, and the tools on the bottom hole assembly being pulled out or run in.
Innovation Solution
A method and system that circulate fluid in a closed loop between the drillstring and the borehole, identifying trips that produce piston effects, determining the speed of the drillstring, and automatically adjusting the surface backpressure to maintain downhole pressure within formation tolerances by calculating discrete increments of backpressure adjustments based on hydraulic modeling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the drillstring is pulled out of hole quickly to improve productivity, then the tripping speed increases, but the swabbing effect causes bottom hole pressure to decrease below formation pressure, leading to influx of formation fluids
Solution Approach 1:
The system applies preliminary anti-action by predicting the swabbing pressure loss based on the planned tripping speed and formation pressure, then pre-adjusting the surface backpressure to compensate for the expected pressure drop. This prevents the bottom hole pressure from falling below formation pressure during the tripping operation.
Solution Approach 2:
The system uses real-time feedback from pressure sensors monitoring bottom hole pressure and formation pressure to continuously adjust the surface backpressure. The control system compares actual pressure readings with target pressure values and dynamically modifies the choke opening to maintain pressure balance during drillstring movement.
2Productivity
If the drillstring is run in hole quickly to improve productivity, then the tripping speed increases, but the surging effect causes bottom hole pressure to exceed formation fracture pressure, leading to mud losses to formation
Solution Approach 1:
The system applies preliminary anti-action by predicting the surging pressure increase based on the planned tripping speed and formation fracture pressure, then pre-reducing the surface backpressure to compensate for the expected pressure rise. This prevents the bottom hole pressure from exceeding formation fracture pressure during the tripping operation.
Solution Approach 2:
The system uses real-time feedback from pressure sensors monitoring bottom hole pressure and formation fracture pressure to continuously adjust the surface backpressure. The control system compares actual pressure readings with target pressure values and dynamically modifies the choke opening to maintain pressure balance during drillstring movement.
3Measurement precision
If manual monitoring and adjustment of backpressure is used to maintain bottom hole pressure, then pressure control accuracy improves, but the complexity of operation increases and response time decreases
Solution Approach 1:
The system applies self-service by implementing an automated control system that independently monitors bottom hole pressure, calculates the required backpressure adjustments, and actuates the choke without human intervention. The system uses sensors to detect pressure changes, a control algorithm to determine the optimal choke opening, and an actuator to automatically adjust the choke position, eliminating the need for manual operation while maintaining high precision pressure 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 approach effectively maintains constant bottom-hole pressure, preventing formation damage and influxes by compensating for swabbing and surging effects during drillstring movement, ensuring the downhole pressure remains within safe limits.
Implementation Method 1
identifying a trip to move the drillstring in the borehole, the trip expected to produce a piston effect that changes a downhole pressure of the fluid in the borehole
Implementation Method 2
The drilling system circulates fluid in a closed loop between a drillstring and the borehole
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A system and method are used in drilling a borehole in a formation. A trip to move a drillstring in the borehole is identified, where the trip is expected to produce a piston effect that changes a downhole pressure of the fluid in the borehole. A peak speed to move the drillstring in the borehole is calculated for the trip, and adjustments to a surface backpressure of the drilling system is calculated for the trip at the calculated peak speed to keep the downhole pressure within a tolerance of the formation. The drillstring is moved in the trip according to the calculated peak speed, and the downhole pressure change produced by the piston effect is counteracted by automatically adjusting the surface backpressure according to the calculated adjustments.