Conformance Control via Nucleic Acid Complexes
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Solution Overview
Problem
Current conformance control methods for enhancing oil recovery face challenges in effectively plugging high-permeability zones, leading to sub-optimal recovery factors due to improper delivery of chemicals and potential incorrect salt precipitation, which can result in reduced production and inefficient oil recovery.
Innovation Solution
A method involving the use of single-stranded nucleic acid molecules that form complexes to selectively reduce permeability in high-permeability regions, allowing for enhanced oil recovery from low-permeability areas by directing flood fluids through nucleic acid complex formation, using separate fluids injected from different locations to minimize unwanted interactions and plugging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemicals are injected to plug high-permeability zones, then conformance control is improved, but chemicals may precipitate in incorrect locations reducing production
Solution Approach 1:
The patent applies preliminary action by first injecting a preflush of highly salt-concentrated brine through the injection well, which travels through the reservoir and establishes a salt concentration gradient. This preliminary brine injection ensures that when ethanol is subsequently injected, the salt precipitation occurs only in high-permeability zones where the brine and ethanol mix, rather than precipitating in low-permeability zones or incorrect locations. This sequential approach resolves the contradiction by preparing the reservoir in advance to control where plugging occurs.
Solution Approach 2:
The patent uses ethanol as an intermediary substance that mediates between the salt-concentrated brine and the high-permeability zones. The ethanol is injected separately and travels through the reservoir, mixing with the pre-injected brine specifically in high-permeability conduit zones. This mixing causes localized salt precipitation that plugs the high-permeability zones without affecting low-permeability zones. The ethanol acts as a carrier and trigger mechanism that ensures precipitation occurs only where needed, resolving the harmful effect of incorrect precipitation.
2Reliability
If ethanol and brine are mixed in high-permeability zones, then salt precipitation plugs these zones, but ethanol may mix with other salt bearing solutions leading to precipitation in incorrect locations
Solution Approach 1:
The preflush of highly salt-concentrated brine is injected first and travels through the entire reservoir, establishing a controlled salt distribution. This preliminary action ensures that when ethanol is injected later, the only location where both ethanol and high concentrations of salt are present is in the high-permeability zones where the brine has accumulated. This sequential timing and spatial separation prevents ethanol from mixing with salt bearing solutions in incorrect locations, thereby controlling precipitation location precisely.
Solution Approach 2:
The patent employs periodic action by injecting the brine and ethanol in separate sequential phases rather than simultaneously. The brine injection phase is completed first, establishing a stable salt concentration distribution in the reservoir. Then, in a separate periodic phase, the ethanol is injected. This temporal separation ensures that the mixing and precipitation occur only in the intended high-permeability zones where the two fluids meet, preventing premature or misplaced precipitation that would occur with simultaneous injection.
3Reliability
If conventional chemicals are used for plugging, then high-permeability zones can be sealed, but delivery to the correct reservoir location is challenging
Solution Approach 1:
The patent applies self-service by utilizing the natural flow dynamics of the reservoir itself to deliver the plugging agents. The brine and ethanol are injected separately and allow the reservoir's own pressure gradients and permeability differences to guide them to the high-permeability zones. The high-permeability conduit zones naturally attract and concentrate both fluids, causing them to mix and precipitate salt exactly where needed without requiring external guidance mechanisms or complex delivery systems. The reservoir essentially services its own plugging requirement through natural flow paths.
Solution Approach 2:
The ethanol serves as an intermediary delivery mechanism that exploits the reservoir's natural flow characteristics. It is injected as a separate fluid phase that travels through the reservoir and preferentially accumulates in high-permeability zones. The ethanol acts as a carrier that brings the plugging function (salt precipitation) to the correct location by mixing with the pre-positioned brine only in high-permeability areas. This intermediary approach simplifies delivery by using the ethanol's natural flow behavior rather than requiring complex targeting systems.
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 effectively reduces permeability in high-permeability zones, diverting flood fluid flow to low-permeability zones, thereby increasing oil recovery factors and minimizing the risk of wellbore plugging, while maintaining control over complex formation and stability through salt concentration and cross-linking agents.
Implementation Method 1
the first fluid comprises a first single stranded nucleic acid molecule and the second fluid comprises a second single stranded nucleic acid, and wherein said first and second nucleic acid molecules are capable of hybridising or otherwise binding to one another under appropriate conditions such that a nucleic acid complex is formed
Implementation Method 2
The ethanol leads to the salt precipitating, which serves to plug these high-permeability zones
Data Source
Figure 1~2
AI summary
The present invention relates to an improved method of enhancing oil recovery by use of conformance control. More particularly, the method of conformance control involves the provision of a plugging material which is designed to be formed within an area of high-permeability in preference to an area of low permeability in order that subsequent water, gas or chemical flooding can enhance oil recovery from the area/region of low permeability.