Huff-n-puff Gas Injection Optimization in Shale Reservoirs
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Solution Overview
Problem
Current huff-n-puff gas injection methods in shale reservoirs struggle to optimize oil recovery factors, often resulting in lower recovery compared to primary depletion due to suboptimal injection and production pressures and rates.
Innovation Solution
The method involves determining the maximum injection rate and pressure during the huff period, and the maximum gas and oil production rates and minimum production pressure during the puff period, based on facility capacities, reservoir conditions, and operation constraints. The huff and puff times are set to reach specific pressure thresholds, and the process can be performed without a soaking period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional huff-n-puff gas injection methods are used with suboptimal injection and production pressures and rates, then the process can be implemented with simple operations, but the oil recovery factor remains lower than primary depletion
Solution Approach 1:
The patent systematically varies multiple parameters including injection pressure (4000-8000 psi), production pressure (2000-6000 psi), huff time (1-12 months), puff time (1-12 months), and gas type (CO2, N2, CH4) to identify optimal combinations that maximize oil recovery factor while maintaining operational feasibility
Solution Approach 2:
The patent implements dynamic adjustment of injection and production rates based on real-time pressure monitoring and reservoir conditions, transitioning from static conventional operations to dynamic optimized control that adapts to changing reservoir states throughout the huff-n-puff cycles
2Productivity
If higher injection pressure is applied to improve oil recovery, then more oil can be extracted from the reservoir, but the operational constraints and facility capacities are challenged
Solution Approach 1:
The patent applies partial action by injecting gas at controlled rates that may not fully saturate the reservoir immediately, allowing progressive pressure buildup and oil displacement over multiple cycles, thereby achieving significant recovery without requiring excessive injection pressure that would exceed facility capacities
Solution Approach 2:
The patent performs preliminary pressure buildup during the huff period before production begins, allowing the reservoir to reach optimal pressure conditions in advance, which then enables more efficient oil production during the puff period without requiring continuously high injection pressure
3Productivity
If longer huff and puff times are used to maximize oil recovery, then more oil can be produced, but the time required for each cycle increases
Solution Approach 1:
The patent employs periodic huff-n-puff cycles that repeat over time, where each cycle consists of a huff period (pressure buildup) followed by a puff period (production). This periodic action allows continuous oil recovery through multiple iterations, with each cycle building upon the previous one to achieve cumulative recovery without requiring indefinitely long single cycles
Solution Approach 2:
The patent ensures continuity of useful action by maintaining active huff-n-puff cycles continuously over extended periods (years), with minimal idle time between cycles, thereby maximizing oil recovery through sustained operation rather than allowing prolonged downtime or single extended cycles
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 optimized huff-n-puff process significantly increases the oil recovery factor in shale reservoirs, maximizing liquid oil production and providing an alternative to other enhanced oil recovery methods that may not be feasible for low permeability shale reservoirs.
Implementation Method 1
Gas injection technology injects gases to extract oil. The most common used gas is carbon dioxide (CO2) since it is an abundant byproduct of industrial processes.
Implementation Method 2
cyclic gas injection (huff-n-puff) to improve oil recovery in shale oil reservoirs
Data Source
AI summary
Methods for optimization of liquid oil production by huff-n-puff in shale reservoirs to achieve an improved (and optimal) oil recovery factor. The process determines and utilizes the optimum huff and puff times, number of cycles and soaking time under practical operation and reservoir conditions. The huff time in the process is a period so long that the pressure near the wellbore reaches the set maximum injection pressure during the huff period. The puff time in the process is the time required for the pressure near the wellbore to reach the set minimum production pressure during the puff period. Soaking is typically not necessary during the huff-n-puff gas injection in shale oil reservoirs. The number of huff-n-puff cycles is determinable by the time in which the economic rate cut-off is reached.