Bottom Hole Assembly Layout for Behind-Casing Wash and Cement
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Solution Overview
Problem
Existing wash and cementing techniques in well decommissioning operations suffer from inefficiencies, including formation losses and stuck pipe risks, due to inadequate understanding of fluid displacement dynamics and tool geometry, leading to suboptimal performance and increased costs.
Innovation Solution
Optimizing the design of the bottom hole assembly (BHA) by using a larger diameter cementing tool and smaller diameter wash tool, with strategically positioned nozzles and extended length, to enhance fluid displacement efficiency and minimize stuck pipe risk, while considering factors like tool diameter, nozzle orientation, and axial movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a larger diameter cementing tool is used, then displacement efficiency is improved, but tool complexity increases
Solution Approach 1:
The tool assembly is segmented into distinct functional components: a wash tool with wash nozzles and a cementing tool with cement nozzles. This segmentation allows each tool to be optimized for its specific function (washing or cementing) while working together in sequence, resolving the contradiction by enabling efficient displacement through specialized design rather than a single complex tool
Solution Approach 2:
The wash tool is positioned inside the cementing tool assembly, with the wash tool having a smaller outer diameter than the cementing tool's outer diameter. This nested configuration allows both tools to be deployed together through the casing, with the wash tool performing its function first, followed by the cementing tool, thereby achieving efficient displacement without requiring an overly complex single-tool design
2Productivity
If wash fluid flow rate is increased, then washing efficiency is improved, but formation losses increase
Solution Approach 1:
The wash tool performs preliminary cleaning of the annulus before the cementing tool is deployed. By removing debris, perforation burrs, and existing fluids in advance, the wash tool prepares the annulus for efficient cement placement, reducing the need for excessive cement flow rates and minimizing formation losses during the subsequent cementing operation
Solution Approach 2:
The system maintains continuous useful action by seamlessly transitioning from the wash tool operation to the cementing tool operation. The wash tool clears the annulus continuously as it moves through the casing, and the cementing tool immediately follows to place cement in the cleaned annulus, ensuring that the beneficial effects of high-flow washing are preserved without causing formation losses
3Productivity
If tool diameter is increased, then fluid displacement capability is improved, but stuck pipe risk increases
Solution Approach 1:
Different parts of the tool assembly have different diameters optimized for their specific functions: the wash tool has a smaller outer diameter to reduce stuck pipe risk during the washing phase, while the cementing tool has a larger outer diameter to provide adequate clearance and displacement capability during cementing. This local differentiation of dimensions resolves the contradiction by matching tool geometry to operational requirements at each stage
4Productivity
If nozzle outlet position is optimized, then displacement efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The nozzles are designed to be dynamically positioned relative to the tool body, with adjustable or flexible mounting arrangements that allow for compensation of manufacturing tolerances. This dynamic positioning capability enables optimization of nozzle outlet positions for maximum displacement efficiency while reducing the stringency of manufacturing precision requirements through post-manufacturing adjustment
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
Improves the displacement efficiency of cement and wash fluids, reducing formation losses and stuck pipe risks, thereby enhancing the quality and reliability of well decommissioning operations.
Implementation Method 1
a primary pulse resulting from a fluid jet passing directly through a casing aperture
Implementation Method 2
If the jet from the tool impinges upon the inner casing surface instead of passing directly through an aperture in the casing, this will create an energetic flow within the inner annulus
Data Source
Figure 1(a)~1(b)
Figure 1(c)~1(d)
Figure 2(a)~2(b)
AI summary
The invention relates to a method of conducting a perf wash cement ("P/W/C") abandonment job in an offshore oil or gas well annulus, in particular the washing or cementing operation using a rotating head with nozzles dispensing wash fluid or cement at pressure. A new design of bottom hole assembly is proposed in which the cementing tool has a relatively large diameter in order to optimize pressure whilst the wash tool has a relatively small diameter. The wash process, for a number of reasons, appears to be less sensitive to tool diameter and making the wash tool smaller reduces the overall risk of stuck pipe. (Figure 2(a))