Drill String Pressure Sticking via Annular Displacement
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Solution Overview
Problem
Differential pressure sticking causes excessive friction between the drill string and the wellbore sidewall, leading to immobilization of the drill string, resulting in significant monetary losses due to stuck pipe recovery efforts and wellbore reconstruction.
Innovation Solution
An apparatus and method involving the injection of a displacement fluid into the annulus between the wellbore sidewall and the drill string to displace drilling fluid, with a bleed valve reducing the pressure of the displacement fluid, allowing for the axial movement of the drill string by applying tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If displacement fluid is injected into the annulus to displace drilling fluid, then hydrostatic pressure around the drill string is reduced, but the complexity of the operation increases due to the need for fluid injection and pressure control equipment
Solution Approach 1:
A displacement fluid is introduced as an intermediary substance between the drilling fluid and the external environment. This displacement fluid serves as a mediator to transfer pressure reduction from the surface injection point down to the stuck drill string in the wellbore, enabling pressure control without direct contact with the stuck portion.
Solution Approach 2:
The invention utilizes hydraulic principles by injecting a fluid (displacement fluid) under controlled pressure into the annulus. The fluid injection system employs hydraulic pressure to displace the drilling fluid and reduce hydrostatic pressure around the drill string, while the bleed valve provides hydraulic pressure relief when needed.
2Reliability
If drilling fluid is present in the wellbore to maintain hydrostatic balance, then formation pressure is controlled, but friction between the drill string and wellbore sidewall increases due to differential pressure sticking
Solution Approach 1:
The invention changes the pressure parameter of the fluid in the annulus by introducing a displacement fluid and using a bleed valve to reduce hydrostatic pressure. This parameter change (pressure reduction) directly addresses the differential pressure sticking problem by decreasing the net force pressing the drill string against the wellbore sidewall, thereby reducing friction.
3Ease of operation
If the drill string is pulled with tension to free it from sticking, then axial movement is achieved, but the stuck pipe cannot be freed if friction exceeds the maximum pulling power of the rig
Solution Approach 1:
The invention applies preliminary anti-action by reducing the hydrostatic pressure around the drill string before attempting to pull the drill string free. By injecting displacement fluid and using the bleed valve to decrease pressure, the net force pressing the drill string against the wellbore sidewall is reduced in advance, thereby reducing friction before the pulling operation is attempted.
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
Effectively reduces hydrostatic pressure around the drill string, decreasing friction and enabling the drill string to be freed from sticking, thereby minimizing costly recovery and reconstruction efforts.
Implementation Method 1
injecting a displacement fluid into an annulus defined between a sidewall of a wellbore and an exterior of a drill string differentially stuck in the wellbore, thereby displacing drilling fluid in the wellbore through an internal passage of the drill string
Implementation Method 2
a bleed valve operable for bleeding the injected displacement fluid out of the annulus, thereby decreasing pressure of the injected displacement fluid within the annulus
Implementation Method 3
Differential pressure sticking can cause excessive friction between portions of the drill string and a sidewall of the wellbore, which can immobilize the drill sting within the wellbore
Data Source
AI summary
Apparatus and methods for reducing differential pressure sticking of a drill string stuck against a sidewall of a wellbore by decreasing hydrostatic pressure around the drill string within the wellbore. Drilling fluid is displaced out of the wellbore by injecting a displacement fluid into an annulus defined between the sidewall and an exterior of the drill string, and pressure of the injected displacement fluid within the annulus is decreased by bleeding the injected displacement fluid out of the annulus.