CSS-SAGD Well Pairing for Oil Sands Steam Short Circuits
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Solution Overview
Problem
Current in situ thermal recovery methods for oil sands, such as Fast-SAGD, face challenges in heterogeneous reservoirs due to pressure differentials leading to steam short circuits and reduced efficiency, making them less practical for real-world applications with permeability variations.
Innovation Solution
A method combining cyclic steam stimulation (CSS) with steam assisted gravity drainage (SAGD), where CSS is applied to a series of horizontally extending wells, and SAGD is applied to vertically-spaced well pairs, with a single well laterally spaced from the pair, to enhance oil recovery and reduce energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Fast-SAGD is applied to heterogeneous reservoirs, then oil production rate is improved, but steam short circuits occur due to pressure differentials reducing efficiency
Solution Approach 1:
The reservoir is divided into multiple compartments with different pressure regimes. CSS wells operate at high pressure to fracture and stimulate production, while SAGD well pairs operate at lower pressures to maintain thermal efficiency. This segmentation allows each system to operate in its optimal pressure range without interfering with the other, preventing steam short circuits while maintaining high oil production rates.
Solution Approach 2:
Instead of operating all wells at the same pressure regime, the invention inverts the conventional approach by operating CSS and SAGD wells at different pressures. The CSS wells are operated at higher pressures to create fractures and enhance flow, while SAGD wells operate at lower pressures to maintain thermal efficiency and prevent steam short circuits. This pressure inversion resolves the contradiction between productivity and energy loss.
2Productivity
If CSS is applied to stimulate production, then oil mobility is improved, but steam consumption increases significantly
Solution Approach 1:
The reservoir stimulation is segmented into two distinct phases: CSS phase for mobility enhancement and SAGD phase for efficient thermal recovery. CSS is applied selectively to specific wells to improve oil mobility and create fractures, while SAGD is applied to well pairs for efficient bitumen mobilization. This segmentation allows the system to achieve both high oil mobility and reduced steam consumption by using each method where it is most effective.
Solution Approach 2:
The system dynamically switches between CSS and SAGD operations based on reservoir conditions and production objectives. CSS is used initially to improve oil mobility and create flow paths, then SAGD is implemented to efficiently mobilize and produce bitumen. This dynamic approach optimizes steam consumption by using CSS only when needed for mobility enhancement rather than continuous operation.
3Loss of energy
If SAGD is applied for efficient bitumen recovery, then steam-oil ratio is reduced, but the process is less tolerant to reservoir heterogeneity
Solution Approach 1:
The recovery system is segmented into CSS components and SAGD components operating in parallel. CSS wells provide adaptability to heterogeneous reservoirs by creating fractures and stimulating flow in variable permeability zones, while SAGD well pairs provide efficient thermal recovery in more homogeneous zones. This segmentation allows the overall system to achieve both low steam-oil ratios and high tolerance to reservoir heterogeneity.
Solution Approach 2:
The combined CSS-SAGD system provides multi-functionality: CSS wells serve both as stimulation wells and as production wells, while SAGD well pairs serve as the primary thermal recovery system. The system can adapt to different reservoir conditions by adjusting the relative contribution of CSS and SAGD components, making it universally applicable to various reservoir heterogeneities while maintaining efficient steam-oil ratios.
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 CSS-SAGD process achieves higher oil production rates and energy efficiency compared to conventional CSS and SAGD methods, with reduced steam-oil ratio and increased oil recovery, making it more cost-effective and adaptable to diverse reservoir conditions.
Implementation Method 1
steam is first injected into a well at a temperature of 300 to 340 degrees Celsius... to heat the bitumen
Implementation Method 2
The bitumen then flows via gravity into the producer well
Data Source
AI summary
A method of recovering oil from an oil sands reservoir comprises first applying cyclic steam stimulation (CSS) to a series of generally horizontally extending wells in the reservoir; then applying steam assisted gravity drainage (SAGD) to at least one vertically-spaced well pair in which one well in each well pair is part of the series of wells to which CSS was applied, while producing oil from at least one single well in the series of wells. In this case, each single well is adjacent to and offset from at least one of the well pairs. The method can then further comprise applying a SAGD blowdown to an injector well of each well pair and producing oil from a producer well of each well pair and from the single well to economic limit.