Vertical Stress Estimation via Point Load Segmentation

Solution Overview

Problem

Conventional methods for determining pore fluid pressure in subterranean drilling overestimate or underestimate pressures due to assumptions about gravitational load transfer, which are not accurate in capturing the decay of surface topology and density heterogeneities with depth.

Innovation Solution

A method and system that divide the earth formation into regions, estimate vertical stresses using a point load-based approach, and calculate horizontal stresses to improve the accuracy of pore fluid pressure predictions by accounting for the decay of surface influences with depth.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If vertical integration of density data is used to estimate total vertical stress, then the calculation is simple and conventional, but the accuracy deteriorates due to overestimation or underestimation of stresses and pore pressures

Engineering Contradiction:

Improvecalculation simplicityVSAvoidstress and pore pressure accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The domain is divided into a first region and a second region, allowing different stress estimation methods to be applied to different depth zones. This segmentation enables the patent to capture the decay of surface topology and density heterogeneity effects with depth while maintaining calculation feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions are assigned different quality characteristics in terms of stress estimation methodology. The first region uses one approach while the second region uses another, reflecting the local variation in how surface influences decay with depth. This local differentiation improves accuracy without requiring a completely complex global model.

Inventive Principle:

Principle #3Local quality

2Ease of operation

If conventional vertical integration of density is used, then the method is conventional and easy to implement, but it fails to account for decay of surface topology and density heterogeneity effects with depth

Engineering Contradiction:

Improvemethod implementation easeVSAvoidstress distribution accuracy

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The domain is divided into a first region and a second region, allowing different stress estimation methods to be applied to different depth zones. This segmentation enables the patent to capture the decay of surface topology and density heterogeneity effects with depth while maintaining calculation feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the estimation parameters between regions - using different approaches for vertical stress estimation in the first versus second region. This parameter change reflects the physical reality that surface influences decay with depth, improving reliability while remaining operationally feasible.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If gravitational load of an element is assumed to be completely transferred to the element below it, then the calculation is straightforward, but this assumption results in overestimation or underestimation of total vertical stresses

Engineering Contradiction:

Improvecalculation model complexityVSAvoidtotal vertical stress accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The domain is divided into a first region and a second region, allowing different stress estimation methods to be applied to different depth zones. This segmentation enables the patent to capture the decay of surface topology and density heterogeneity effects with depth while maintaining calculation feasibility.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions are assigned different quality characteristics in terms of stress estimation methodology. The first region uses one approach while the second region uses another, reflecting the local variation in how surface influences decay with depth. This local differentiation improves accuracy without requiring a completely complex global model.

Inventive Principle:

Principle #3Local quality

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 accurate predictions of pore fluid pressures and stress distributions, enhancing wellbore stability, sand production predictions, and compaction/subsidence analysis by accounting for the decay of surface influences with depth.

Implementation Method 1

Conventionally, total vertical stress is estimated by vertical integration of density data. The effect of these factors on total vertical stresses decays with depth below the surface or below the heterogeneity.

Methodology Applied

Scientific EffectGravitation: Gravitation

Implementation Method 2

estimating a second vertical stress in the second region by a point load based method using the first vertical stress

Methodology Applied

Scientific EffectStress distribution:

Data Source

PatentEP2668523B8Apparatus and method for predicting vertical stress fields

Publication Date: 2017.12.06 BAKER HUGHES CO

AI summary

A method of estimating stress in an earth formation is disclosed. The method includes: dividing a domain including at least a portion of an earth formation into a first region and a second region; estimating a first vertical stress in the first region and representing the first vertical stress as at least one point load; estimating a second vertical stress in the second region by a point load based method using the first vertical stress; and estimating at least one horizontal stress based on the second vertical stress.