Acidizing Spearhead Reduces Near-Wellbore Tortuosity in Hydraulic Fracturing

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Solution Overview

Problem

Hydraulic fracturing in multi-zone subterranean formations is hindered by near-wellbore tortuosity, leading to increased pressures, reduced treating rates, and premature screenouts due to complex fracture geometry, which complicates the stimulation of zones and reduces production efficiency.

Innovation Solution

Pumping an acidizing solution at or above fracturing pressure to create or enlarge fractures, followed by a displacement fluid, which reduces tortuosity and allows for lower pressure fracturing, improving wellbore-fracture connection and reducing near-wellbore friction pressure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional hydraulic fracturing is used in multi-zone formations, then fracture stimulation can be achieved, but near-wellbore tortuosity causes increased treating pressure and reduced injection rates

Engineering Contradiction:

Improveinjection rateVSAvoidtreating pressure

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The patent applies preliminary action by injecting acidizing solution before the fracturing fluid to dissolve carbonate materials and create a more direct fracture pathway. This pre-treatment reduces near-wellbore tortuosity and frictional forces, allowing subsequent fracturing fluid injection at lower pressures and higher rates.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the chemical parameters of the fracturing system by introducing acidizing solution (hydrochloric or organic acid) to alter the formation properties near the wellbore. This chemical modification dissolves soluble materials that contribute to tortuosity, fundamentally changing the flow path characteristics for subsequent fracturing.

Inventive Principle:

Principle #35Parameter changes

2Speed

If higher pumping rates and pressures are used to overcome tortuosity, then fracture propagation can be maintained, but the risk of premature screenout increases

Engineering Contradiction:

Improvefracture propagation speedVSAvoidscreenout risk

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The acidizing solution is injected in advance to clean and enlarge the fracture pathway, removing obstacles that would cause screenout. This preliminary cleaning action allows proppant to flow more freely at lower injection rates, reducing the risk of premature screenout while maintaining fracture propagation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The acidizing solution acts as an intermediary between the fracturing fluid and the formation, preparing the pathway by dissolving carbonate materials and reducing friction. This intermediary treatment modifies the formation properties to facilitate smoother proppant flow and reduce screenout risk.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple zones are fractured sequentially with mechanical isolation, then selective stimulation is achieved, but operational time and costs increase

Engineering Contradiction:

Improveselective zone stimulationVSAvoidoperational time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent enables continuous operation by using acidizing solution that can be injected without requiring mechanical plug insertion between zones. The acid treatment can proceed continuously through multiple perforated intervals, eliminating the downtime associated with mechanical isolation and significantly reducing total operational time.

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent uses hydraulic pressure to inject acidizing solution through the wellbore, utilizing the existing hydraulic system to deliver the treatment to multiple zones without mechanical intervention. This hydraulic approach replaces the mechanical plug system, enabling faster, continuous multi-zone treatment.

Inventive Principle:

Principle #29Pneumatics and hydraulics

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 method reduces the required treating pressure, increases injection rates, and minimizes the risk of screenouts, enabling more efficient and rapid fracturing of multiple zones with higher proppant concentrations and reduced operational time and costs.

Implementation Method 1

pump small volumes (typically less than 10 bbls) of hydrochloric (HCl) or organic acid as 'spearheads' in front of the fracturing treatment for the purpose of dissolving carbonate material and other soluble materials plugging the perforations

Methodology Applied

Scientific EffectDissolution: Solvation

Implementation Method 2

pumping an acidizing solution at or above fracturing pressure into the formation to create or enhance fracture geometry in the formation

Methodology Applied

Scientific EffectChemical etching: Chemical Bonding

Data Source

PatentUS8789596B2Method of increasing efficiency in a hydraulic fracturing operation

Publication Date: 2014.07.29 BAKER HUGHES CO

AI summary

Multiple zones of a subterranean formation penetrated by a multi-zoned completed well may be fractured by pumping into one or more zones an acidizing solution at or above the fracturing pressure of the subterranean formation. After fractures are created or enhanced in the formation, a displacement fluid is pumped into the formation to farther advance the acidizing solution into the fractures.