Downhole Card Calculation in Deviated Wellbores

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Solution Overview

Problem

Existing sucker rod pump systems in deviated wells face inaccuracies in downhole data calculation due to neglecting mechanical friction, leading to distorted downhole cards and potential damage from inefficient operation.

Innovation Solution

A method that models the wellbore trajectory, parameterizes deviated segments, and maps the rod string to these segments to compute drag forces and side loads, which are then used as boundary conditions in the wave equation to solve for more accurate downhole position and load data, considering both viscous damping and Coulomb friction.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If mechanical friction is neglected in downhole data calculation, then the calculation process is simpler, but the downhole card becomes distorted and accuracy deteriorates

Engineering Contradiction:

Improvecalculation process complexityVSAvoiddownhole data accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The wellbore trajectory is divided into multiple linear segments between survey points, allowing mechanical friction to be calculated and applied separately for each segment. This segmentation enables accurate modeling of Coulomb friction in deviated wells while maintaining a manageable calculation structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The calculation method incorporates Coulomb friction parameters (mechanical friction coefficient) alongside viscous damping parameters, changing the physical parameters considered in the wave equation solution. This allows accurate representation of mechanical friction effects in deviated wellbores.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If mechanical friction is accounted for in deviated wells, then downhole data accuracy improves, but the calculation complexity increases

Engineering Contradiction:

Improvedownhole data accuracyVSAvoidcalculation process complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The wellbore trajectory is pre-modeled and divided into segments before the wave equation calculation. Survey points are predetermined, and the geometric parameters (inclination, azimuth) are calculated in advance, allowing mechanical friction to be systematically applied without adding excessive complexity during the main calculation phase.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary computational framework that bridges the wave equation solution with mechanical friction effects. The drag force calculation acts as an intermediary step, translating wellbore geometry and rod position into friction forces that are then incorporated into the wave equation boundary conditions.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If standard wave equation solution is used without mechanical friction, then computational efficiency is maintained, but operational accuracy deteriorates leading to potential pump damage

Engineering Contradiction:

Improvecomputational efficiencyVSAvoidoperational accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies mechanical friction calculations selectively to deviated well segments rather than the entire wellbore. By identifying and processing only the segments where Coulomb friction is significant (based on inclination angle thresholds), the method maintains computational efficiency while improving accuracy where it matters most.

Inventive Principle:

Principle #16Partial or excessive action

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 provides more precise downhole data, improving the accuracy of pump operation analysis and preventing costly maintenance by accurately accounting for mechanical friction in deviated wells, thus enhancing operational efficiency and reducing the risk of pump damage.

Implementation Method 1

solving a wave equation having viscous damping and coulomb friction factors as boundary conditions

Methodology Applied

Scientific EffectViscous damping: Viscous Damping

Implementation Method 2

solving a wave equation having viscous damping and coulomb friction factors as boundary conditions

Methodology Applied

Scientific EffectCoulomb friction: Friction

Data Source

PatentEP3176361B1Calculating downhole card in deviated wellbore using parameterized segment calculations

Publication Date: 2021.03.31 WEATHERFORD TECHNOLOGY HOLDINGS LLC

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AI summary

In a deviated wellbore, a pump system computes downhole data from surface data by solving a wave equation that takes both viscous damping and Coulomb friction into consideration. Mechanical friction between the rods, couplings, and tubing is considered in the calculation of downhole data in the deviated wellbore by modelling the wellbore's trajectory, parameterizing various deviated segments (buildups, slants, drop-offs, etc.) in the trajectory, mapping the rod string to the segments, and incrementally evaluating position of the mapped string over time in order to compute drag forces and side loads experienced by the rod string during operation. These computed drag forces and side loads are then used in the solution of the wave equation to solve the surface load and position data and provide more accurate downhole position and load data.