Optimizing Limited-Entry Liner Hole Distribution for Uniform Acid Stimulation
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Solution Overview
Problem
Current methods for acid stimulation in wells, particularly in carbonate reservoirs, face challenges in achieving uniform acid distribution and maximum penetration, leading to inefficient use of acid and suboptimal productivity due to limitations in acid placement and hole size distribution design in Limited-Entry-Liner (LEL) systems.
Innovation Solution
A numerical solution strategy is developed to optimize hole-size distribution in LEL liners, ensuring accurate acid coverage and pressure drop across the last hole, incorporating interstitial velocity, pump rate, and total cross-sectional hole area, while maintaining annulus pressure below fracturing pressure, and estimating wormholing characteristics to facilitate optimal acid penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bull-heading acid from the surface is used, then the stimulation treatment can be performed, but the majority of acid is spent reacting at the heel of the well resulting in mediocre stimulation
Solution Approach 1:
The wellbore is divided into multiple segments along its length, with acid injection points distributed throughout. This segmentation allows acid to be delivered to multiple locations simultaneously, ensuring uniform distribution along the well trajectory rather than concentrating all acid at the heel.
Solution Approach 2:
A fluid delivery system with multiple injection points acts as an intermediary between the surface acid source and the reservoir. This intermediary system distributes acid through controlled flow paths to multiple locations along the well, preventing direct bulk reaction at the heel and enabling uniform acid placement.
2Quantity of substance
If acid is pumped at high rate to ensure coverage, then coverage is improved, but acid penetration into the formation is limited due to insufficient interstitial velocity
Solution Approach 1:
The system provides different flow conditions at different locations along the wellbore. By positioning multiple injection points and controlling local flow rates, the system ensures that each segment receives acid at the optimal interstitial velocity for penetration, while collectively achieving comprehensive coverage along the entire well trajectory.
Solution Approach 2:
The acid delivery system dynamically adjusts flow distribution to multiple injection points based on desired penetration velocity requirements. By controlling the timing and rate of acid injection at each location, the system maintains optimal interstitial velocity for wormhole propagation while ensuring complete coverage.
3Manufacturing precision
If the hole size distribution in LEL is not optimized, then the liner can be manufactured simply, but uniform acid coverage and maximum penetration cannot be achieved
Solution Approach 1:
The system varies the size and distribution of holes in the LEL as a controlled parameter to achieve uniform acid flow. By carefully selecting hole diameters and spacing patterns, the system balances flow resistance throughout the liner length, ensuring each segment receives appropriate acid volume for uniform coverage and optimal penetration velocity.
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 approach improves simulation accuracy, leading to more efficient acid distribution and increased productivity by ensuring uniform acid coverage and maximizing acid penetration into the reservoir, thereby enhancing the well's productivity index.
Implementation Method 1
the selected acid is allowed to chemically react with the reservoir rock, which leads to dissolution and enhanced productivity
Implementation Method 2
the selected acid is allowed to chemically react with the reservoir rock, which leads to dissolution
Implementation Method 3
distribute small holes of varying sizes and frequency in the liner. These holes act as flow restrictions, which leads to mechanical diversion of flow along the liner
Implementation Method 4
Lab experiments by a number of authors clearly show that for any given rock, acid penetration depends on the interstitial velocity of acid. There exists an optimum velocity, which minimizes the amount of acid needed to generate dissolution patterns known as wormholes
Data Source
Figure 1~2
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Figure 4
AI summary
A method for stimulation of a well in a material formation which includes a workflow for the design of optimum hole-size distribution in the liner of a LEL liner system is modelled, wherein a solution strategy for providing an initial estimate of the number of holes per segment honours the acid coverage per segment and the drop in pressure (dp) across the last hole, where the initial estimate can be found from the relationship between interstitial velocity, pump rate, and total cross-sectional hole area for a particular discharge coefficient and liner configuration.