Acid-Sensitive Surfactant Emulsion for Wellbore Filter Cake Removal
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Solution Overview
Problem
Conventional invert emulsion drilling muds with surfactants form filter cakes that are difficult to remove without damaging the wellbore or formation, affecting wellbore productivity.
Innovation Solution
A wellbore servicing method using an invert emulsion fluid with an acid-sensitive surfactant and an emulsion reversing fluid containing an acid precursor, which generates acid after a predetermined delay, allowing for the conversion of the filter cake from a water-in-oil to an oil-in-water emulsion, facilitating its removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional surfactants are used to stabilize invert emulsion drilling muds, then the emulsion stability is improved, but the filter cake becomes difficult to remove without damaging the formation or wellbore
Solution Approach 1:
The patent uses acid-sensitive surfactants that change their chemical properties (protonation state) in response to pH changes. During drilling, the surfactant remains deprotonated and stabilizing. During removal, acid is introduced to protonate the surfactant, fundamentally changing its properties and causing emulsion breakdown and filter cake removal.
Solution Approach 2:
The patent introduces an acid precursor into the drilling mud formulation before drilling begins. This precursor remains dormant during drilling operations and only activates later to protonate the surfactant and break down the filter cake, preparing the system in advance for easy filter cake removal.
2Productivity
If acids are used to remove filter cakes, then the filter cake removal efficiency is improved, but the formation and wellbore may be damaged
Solution Approach 1:
The patent uses an acid precursor as an intermediary substance that converts to active acid only when and where needed. The precursor acts as a safe carrier that can be circulated through the wellbore without damaging the formation, then transforms into active acid to break down the filter cake, eliminating the need to handle or circulate damaging concentrations of active acid.
Solution Approach 2:
The patent extracts the harmful active acid from the drilling fluid circulation system and replaces it with a harmless acid precursor. The active acid is only generated in situ at the filter cake interface when needed for removal, preventing formation damage from exposure to active acid during circulation and handling.
3Productivity
If invert emulsion fluids are used during drilling, then the drilling performance is improved, but the filter cake formed is difficult to remove
Solution Approach 1:
The patent formulates the invert emulsion drilling mud with acid-sensitive surfactants that will change properties in response to subsequent acid treatment. This allows the mud to perform optimally during drilling (stable emulsion, good filter cake formation) while being pre-configured for easy removal later through pH-triggered surfactant protonation and emulsion breakdown.
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
Enables thorough and complete removal of filter cakes, improving wellbore clean-up and hydrocarbon production while minimizing formation damage and environmental hazards.
Implementation Method 1
the acid precursor is configured to generate a quantity of acid after a predetermined delay period beginning at placement within a wellbore
Implementation Method 2
converting the filter cake from a water-in-oil to an oil-in-water emulsion, facilitating its removal
Data Source
AI summary
A wellbore servicing method comprising circulating an invert emulsion fluid through a wellbore to form a filter cake within the wellbore, wherein the invert emulsion fluid comprises an oleaginous fluid, a non-oleaginous fluid, and an acid-sensitive surfactant, contacting at least a portion of the filter cake with an emulsion reversing fluid, wherein the emulsion reversing fluid comprises an acid precursor, wherein the acid precursor is not an acid, and wherein the acid precursor is configured to generate a quantity of acid after a predetermined delay period beginning at placement within a wellbore, allowing the emulsion reversing fluid to remain in contact with the filter cake for a soak period, and removing the filter cake from the wellbore. A wellbore servicing composition related to same.