Drill Bit Cutter Side Rake Angles for Weight on Bit Reduction

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Solution Overview

Problem

Current drill bits face inefficiencies in drilling soft or plastic formations due to inadequate bit cleaning and lack of understanding on the effect of side rake angles on cutter aggressiveness and interaction at confining pressures, which affects the rate of penetration and mechanical specific energy.

Innovation Solution

The design of a drill bit with a cutting face featuring a combination of blades with cutters oriented at negative and positive side rake angles, creating a weight-on-bit (WOB) reducing effect by adjusting the side rake angles to minimize the normal force required for drilling, thereby enhancing drilling efficiency and reducing the WOB.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional drill bits with zero or positive side rake angles are used, then the bit can maintain structural simplicity and ease of manufacture, but the weight on bit (WOB) increases and drilling efficiency decreases in soft or plastic formations

Engineering Contradiction:

Improvedrilling efficiencyVSAvoidweight on bit

Core Design Contradiction:

ProductivityVSForce

Solution Approach 1:

The patent applies parameter changes by introducing negative side rake angles for inner cutters and positive side rake angles for outer cutters, deviating from conventional zero or positive side rake angle designs. This parameter modification creates a WOB reducing effect that improves drilling efficiency in soft or plastic formations while managing the forces acting on the bit

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements local quality by differentiating the side rake angles across different sections of the bit - inner cutters have negative side rake angles while outer cutters have positive side rake angles. This localized differentiation optimizes performance for specific drilling conditions and formation types, addressing the WOB issue in targeted areas

Inventive Principle:

Principle #3Local quality

2Productivity

If side rake angles are adjusted to reduce WOB, then drilling efficiency improves, but the cutter geometry becomes more complex and manufacturing difficulty increases

Engineering Contradiction:

Improverate of penetrationVSAvoidcutter orientation complexity

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent modifies cutter geometry parameters by specifying negative side rake angles for inner cutters and positive side rake angles for outer cutters. While this creates more complex cutter orientations, the systematic application of these parameter changes across different cutter positions provides a manufacturable solution that achieves improved rate of penetration

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If all cutters are oriented with zero side rake angle, then the bit design remains simple and durable, but bit cleaning efficiency is inadequate and mechanical specific energy increases

Engineering Contradiction:

Improvemechanical specific energyVSAvoidcutter configuration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies local quality by assigning different side rake angle characteristics to different cutter positions - inner cutters with negative angles and outer cutters with positive angles. This localized differentiation improves bit cleaning efficiency and reduces mechanical specific energy while maintaining a manageable level of configuration complexity

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent inverts the conventional approach by using negative side rake angles for inner cutters instead of the typical zero or positive angles. This inversion creates mechanical cleaning action that improves bit cleaning efficiency and reduces energy loss, counter to traditional design philosophy

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11802444B2Drill bit having a weight on bit reducing effect

Publication Date: 2023.10.31 VAREL EURO SAS

AI summary

A bit for drilling a wellbore includes: a body; and a cutting face. The cutting face includes: an inner section and an outer section; a plurality of blades protruding from the body, and a row of superhard cutters mounted along each blade, the cutters in the inner section having a negative profile angle and the cutters in the outer section having a positive profile angle. At least one of: at least one inner cutter is oriented at a negative side rake angle to create a weight on bit (WOB) reducing effect, and at least one outer cutter is oriented at a positive side rake angle to create the WOB reducing effect. Each of the rest of the cutters are oriented at a side rake angle such that an overall effect of the side rake angles is the WOB reducing effect.