Fail-Safe Stage Tool for Cement Placement in Weak Zones

Solution Overview

Problem

Current stage cementing methods in wellbores often require costly and time-consuming remedial cementing due to inadequate primary cementing, particularly in formations with weak zones where cement loss occurs, leading to potential well integrity issues and structural failures.

Innovation Solution

Incorporating a sensor on the casing string below a stage tool to detect the presence or absence of cement, with the stage tool remaining closed and packer deflated if cement is present, and opening the stage tool and inflating the packer if cement is absent, allowing for targeted cement placement and mitigating pressure at weak zones.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a stage tool is incorporated in the casing string to prevent cement loss at weak zones, then cementing reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvecementing reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The stage tool is pre-installed in the casing string during the initial casing installation, before the cementing operation begins. This preliminary placement allows the tool to be ready to activate and control cement flow at the weak zone during the cementing process, preventing cement loss before it occurs rather than attempting remedial actions afterward.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stage tool acts as an intermediary device between the cement slurry and the weak formation zone. It provides a controlled pathway that allows cement to pass through at regulated rates, mediating the interaction between the high-pressure cement column and the vulnerable weak zone to prevent uncontrolled cement loss while still achieving zonal isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If primary cementing is performed without a stage tool, then device complexity is reduced, but cement may be lost to weak zones requiring expensive remedial cementing

Engineering Contradiction:

Improvedevice complexityVSAvoidcement loss

Core Design Contradiction:

Device complexityVSLoss of substance

Solution Approach 1:

The stage tool is pre-installed in the casing string during the initial casing installation, before the cementing operation begins. This preliminary placement allows the tool to be ready to activate and control cement flow at the weak zone during the cementing process, preventing cement loss before it occurs rather than attempting remedial actions afterward.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stage tool incorporates sensors that provide real-time feedback on cement placement progress and formation conditions. This feedback mechanism allows operators to monitor cementing operations and detect potential cement loss conditions, enabling timely adjustments to pumping rates or pressure to prevent cement from being lost to weak zones.

Inventive Principle:

Principle #23Feedback

3Reliability

If remedial cementing is performed to correct defective primary cementing, then well integrity is improved, but time and cost increase significantly

Engineering Contradiction:

Improvewell integrityVSAvoidtime and cost

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The stage tool is pre-installed in the casing string during the initial casing installation, before the cementing operation begins. This preliminary placement allows the tool to be ready to activate and control cement flow at the weak zone during the cementing process, preventing cement loss before it occurs rather than attempting remedial actions afterward.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stage tool provides a protective mechanism that cushions against potential cementing failures at weak zones. By having this protective device pre-installed and ready to activate, the system cushions against the harmful effect of cement loss and formation fracturing, preventing the need for costly remedial operations.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

4Manufacturing precision

If cement column height is increased above a weak zone to achieve desired cement placement, then cementing effectiveness is improved, but pressure at the weak zone increases causing formation fracturing and cement loss

Engineering Contradiction:

Improvecement placement precisionVSAvoidpressure at weak zone

Core Design Contradiction:

Manufacturing precisionVSStress or pressure

Solution Approach 1:

The stage tool acts as an intermediary device between the cement slurry and the weak formation zone. It provides a controlled pathway that allows cement to pass through at regulated rates, mediating the interaction between the high-pressure cement column and the vulnerable weak zone to prevent uncontrolled cement loss while still achieving zonal isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The stage tool allows for dynamic changes in flow parameters (flow rate, pressure) as cement progresses through the tool. By controlling the flow rate and pressure parameters at the stage tool, the system can maintain adequate cement placement height while preventing pressure from exceeding formation fracture limits at the weak zone.

Inventive Principle:

Principle #35Parameter changes

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 fail-safe method ensures effective cement placement, reducing the need for remedial cementing, enhancing well integrity, and preventing fluid mixing and structural failures by accurately detecting and addressing cement gaps, thus optimizing the cementing process.

Implementation Method 1

detecting a presence or absence of cement with the sensor

Methodology Applied

Scientific EffectWeight detection:

Implementation Method 2

a packer incorporated in the casing string just above the weak zone may be inflated to fill the annular space between the casing string and the formation and create an occlusive seal

Methodology Applied

Scientific EffectOcclusive sealing:

Implementation Method 3

A stage tool incorporated in the casing string just above the packer may then be activated and opened. Cement is pumped down the casing string and through the open stage tool to fill the annulus above the packer

Methodology Applied

Scientific EffectFluid flow control:

Data Source

PatentUS11624258B2Fail-safe stage tool and down hole sensor

Publication Date: 2023.04.11 SAUDI ARABIAN OIL CO

AI summary

A fail-safe method to cement a section of casing string to a formation is provided. The method includes providing the casing string in a wellbore, the casing string comprising a stage tool, a packer, and a sensor. The packer is located vertically below the stage tool and vertically above the sensor on the casing string. The method further includes pumping cement down the casing string and up an annulus to an expected height, the expected height being a vertical distance above the sensor, and detecting a presence or absence of cement with the sensor. If the sensor detects the presence of cement, the stage tool is kept closed and the packer is kept deflated. If the sensor detects the absence of cement, the stage tool is opened and the packer is inflated.