Double Filter Cake Wellbore Isolation via Degradable Particulates
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Solution Overview
Problem
Existing methods for temporary isolation of hydraulic fractures in oil and gas production face challenges with degradable materials being unavailable in sufficient quantities and non-degradable particulates causing formation damage by infiltrating pore spaces, leading to irreversible permeability reduction and reduced well stimulation effects.
Innovation Solution
A method involving sequential pumping of two slurries into the well, one containing degradable particulates and fibers, and another with non-degradable particulates and fibers, forming a double filter cake for temporary isolation, which is non-damaging and allows for hydraulic refracturing and well killing operations without damaging the formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-degradable particulates are used for temporary isolation, then the isolation effectiveness is improved, but the formation permeability is reduced irreversibly due to infiltration into pore spaces
Solution Approach 1:
The isolation system is segmented into two distinct functional components: degradable particulates that provide temporary isolation and protect the formation, and non-degradable particulates that provide robust sealing. This segmentation allows each component to perform its specific function without causing formation damage, as the degradable material sacrifices itself to protect the formation while the non-degradable material remains as a stable seal.
Solution Approach 2:
The invention uses a composite slurry system combining degradable particulates (such as starch, cellulose, or gelatin) with non-degradable particulates (such as calcium carbonate or barite). This composite approach leverages the temporary isolation and formation-protection properties of degradable materials while incorporating the robust sealing capability of non-degradable materials, achieving both effective isolation and formation protection simultaneously.
2Object-affected harmful factors
If degradable particulates are used for temporary isolation, then the formation permeability is preserved, but the availability in sufficient amounts is limited
Solution Approach 1:
The invention merges degradable particulates with non-degradable particulates into a single slurry composition. This combination allows the non-degradable particulates to supplement the degradable material, ensuring sufficient quantity and concentration of isolating agents are achieved without compromising formation permeability, as the non-degradable component does not infiltrate and damage the formation pores.
Solution Approach 2:
The non-degradable particulates act as an intermediary that provides structural support and additional sealing capability while the degradable particulates perform the temporary isolation function. This intermediary role allows the system to achieve sufficient isolation effectiveness without requiring excessive amounts of degradable material, thereby overcoming the limitation of material availability.
3Reliability
If small inert particulates are pumped into the well for isolation, then the isolation effect is achieved, but the well stimulation effect is eliminated due to permeability decrease
Solution Approach 1:
The invention changes the chemical parameter of the particulates by using degradable materials that can chemically break down over time. This parameter change allows the isolation effect to be temporary rather than permanent, enabling the formation permeability to be restored after the isolation period, thereby preserving the well stimulation effect while achieving the necessary isolation during maintenance operations.
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
The double filter cake effectively isolates wellbore intervals with high fluid losses, allowing for hydraulic refracturing and well killing while ensuring the permeability of the rock is restored post-operation, maintaining well productivity without additional cleanout operations.
Implementation Method 1
pumping the first slurry into the well until a first filter cake is formed
Implementation Method 2
pumping a second slurry into the well until a second filter cake is formed
Implementation Method 3
degradable particulates (synthetic polymers hydrolyzable in the well environment, such as, e.g., polylactic acid (PLA) or polyglycolic acid (PGA))
Data Source
AI summary
A method for temporary isolation of a well interval is proposed, the method comprising: pumping a first slurry into the well, the slurry comprising a viscous carrier fluid, degradable particulates, and degradable fibers, until a first filter cake is formed; and pumping a second slurry into the well, the slurry comprising a viscous carrier fluid, non-degradable particulates, and degradable fibers, until a second filter cake is formed. The first and the second slurries are not mixed when pumped into the well. To ensure optimum interval isolation, the ratio of the volume of the first slurry to the volume of the second slurry should be in the range 1:5 to 2:1.A method for hydraulic refracturing within an interval with several hydraulic fractures and a non-damaging well killing method are also proposed.The technical result is manifested in no formation damage and degradation of the sealing layer formed.