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Hele-Shaw Modeling of CO2-Assisted Gravity Drainage with Bottom-Water Support: An Experimental Study
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Abstract<p>Gas-assisted gravity drainage (GAGD) has emerged as a promising enhanced oil recovery (EOR) method that utilizes the natural buoyancy of injected gas to mobilize oil in gravity-dominated systems. The scope of this work is to experimentally evaluate the performance of CO2-assisted GAGD in the presence of bottom-water support, a common reservoir condition that complicates gas flooding efficiency. The primary objectives are to (i) assess the impact of injection pressure and oil production rate on oil recovery, (ii) determine the operational conditions that maintain gravity dominance and delay breakthrough, and (iii) identify the trade-offs between maximizing recovery and minimizing gas losses.</p><p>A Hele-Shaw glass model was employed to simulate a reservoir system consisting of an oil zone underlain by an active water aquifer. A Free-Fall Gravity Drainage experiment served as the baseline for comparison. CO2 injection tests were then performed by systematically varying injection pressure (0.5–2 psig) and production rate (50% and 100% valve openings). To ensure efficient experimental design, Hammersley Sequence Sampling was applied to distribute test conditions evenly across the operational space. Flow dynamics were captured with time-sequence images, while cumulative oil recovery and breakthrough times were monitored. Statistical analyses, including analysis of variance (ANOVA) and multiple linear regression, were conducted to quantify the relative contributions of the studied parameters and to validate experimental observations.</p><p>The experimental results demonstrate that injection pressure is the most influential parameter controlling ultimate recovery, while production rate primarily affects breakthrough timing and frontal stability. Maximum recovery of 88.4% was achieved at an injection pressure of 2 psig combined with a restricted production rate. At low pressures, production rate showed limited effect, but at higher pressures, unrestricted production accelerated breakthrough and destabilized the oil bank, leading to early gas channeling and reduced sweep efficiency. Image analysis confirmed that higher injection pressure accelerated oil displacement but introduced risks of unstable flooding without controlled production. Statistical analysis reinforced the qualitative findings, with Analysis-Of-Variance (ANOVA) confirming the dominance of injection pressure and regression models accurately predicting recovery trends. The combined insights emphasize the operational trade-offs: while higher injection pressures increase recovery potential, production restrictions are essential to avoid premature gas override and sustain stable displacement fronts.</p><p>This study provides new experimental insights into CO2-assisted GAGD performance under bottom-water support, an area rarely addressed in the literature. The integration of Hele-Shaw physical modeling with statistical analysis and flow visualization offers a novel approach for quantifying operational parameters and their interactions. The findings not only highlight practical strategies for optimizing GAGD field operations but also expand the fundamental understanding of gravity-driven CO2 flooding processes in reservoirs with active aquifers.</p>
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Publication Date
Tue Jun 30 2020
Journal Name
Association Of Arab Universities Journal Of Engineering Sciences
Immiscible CO2-Assisted Gravity Drainage Process for Enhancing Oil Recovery in Bottom Water Drive reservoir
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The CO2-Assisted Gravity Drainage process (GAGD) has been introduced to become one of the mostinfluential process to enhance oil recovery (EOR) methods in both secondary and tertiary recovery through immiscibleand miscible mode. Its advantages came from the ability of this process to provide gravity-stable oil displacement forenhancing oil recovery. Vertical injectors for CO2 gas have been placed at the crest of the pay zone to form a gas capwhich drain the oil towards the horizontal producing oil wells located above the oil-water-contact. The advantage ofhorizontal well is to provide big drainage area and small pressure drawdown due to the long penetration. Manysimulation and physical models of CO2-AGD process have been implemented

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Publication Date
Thu Sep 01 2022
Journal Name
Fuel
Experimental evaluation of Carbon Dioxide-Assisted Gravity Drainage process (CO2-AGD) to improve oil recovery in reservoirs with strong water drive
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Publication Date
Thu Aug 01 2024
Journal Name
Fuel
Experimental influence assessments of water drive and gas breakthrough through the CO2-assisted gravity drainage process in reservoirs with strong aquifers
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Mature oil reservoirs surrounded with strong edge and bottom water drive aquifers experience pressure depletion and water coning/cresting. This laboratory research investigated the effects of bottom water drive and gas breakthrough on immiscible CO2-Assisted Gravity Drainage (CO2-AGD), focusing on substantial bottom water drive. The CO2-AGD method vertically separates the injected CO2 to formulate a gas cap and Oil. Visual experimental evaluation of CO2-AGD process performance was performed using a Hele-Shaw model. Water-wet sand was used for the experiments. The gas used for injection was pure CO2, and the “oleic” phase was n-decane with a negative spreading coefficient. The aqueous phase was deionized water. To evaluate the feasibilit

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Publication Date
Fri Aug 28 2020
Journal Name
Iraqi Journal Of Science
Numerical Simulation of Immiscible CO2-Assisted Gravity Drainage Process to Enhance Oil Recovery
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The Gas Assisted Gravity Drainage (GAGD) process has become one of the most important processes to enhance oil recovery in both secondary and tertiary recovery stages and through immiscible and miscible modes.  Its advantages came from the ability to provide gravity-stable oil displacement for improving oil recovery, when compared with conventional gas injection methods such as Continuous Gas Injection (CGI) and Water – Alternative Gas (WAG). Vertical injectors for CO2   gas were placed at the top of the reservoir to form a gas cap which drives the oil towards the horizontal oil producing wells which are located above the oil-water-contact. The GAGD process was developed and tested in vertical wells to increase oil r

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Publication Date
Mon Apr 22 2019
Journal Name
Spe
Evaluation of Gas and Downhole Water Sink-Assisted Gravity Drainage GDWS-AGD Process in Saturated Oil Reservoirs with Infinite-Acting Aquifer
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Abstract<p>A hybrid Gas-Enhanced and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) process has been suggested to enhance oil recovery by placing vertical injectors for CO2 at the top of the reservoir with a series of horizontal oil-producing and water-drainage wells located above and below the oil-water contact, respectively. The injected gas builds a gas cap that drives the oil to the (upper) oil-producing wells while the bottom water-drainage wells control water cresting. The hybrid process of GDWS-AGD process has been first developed and tested in vertical wells to minimize water cut in reservoirs with bottom water drive and strong water coning tendencies. The wells were dual-compl</p> ... Show More
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Publication Date
Fri Feb 10 2023
Journal Name
Energies
Well Placement Optimization through the Triple-Completion Gas and Downhole Water Sink-Assisted Gravity Drainage (TC-GDWS-AGD) EOR Process
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Gas and downhole water sink-assisted gravity drainage (GDWS-AGD) is a new process of enhanced oil recovery (EOR) in oil reservoirs underlain by large bottom aquifers. The process is capital intensive as it requires the construction of dual-completed wells for oil production and water drainage and additional multiple vertical gas-injection wells. The costs could be substantially reduced by eliminating the gas-injection wells and using triple-completed multi-functional wells. These wells are dubbed triple-completion-GDWS-AGD (TC-GDWS-AGD). In this work, we design and optimize the TC-GDWS-AGD oil recovery process in a fictitious oil reservoir (Punq-S3) that emulates a real North Sea oil field. The design aims at maximum oil recovery us

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Publication Date
Mon Apr 17 2023
Journal Name
Day 2 Tue, April 18, 2023
Development of a Multi-Completion Gas and Downhole Water Sink-Assisted Gravity Drainage (MC-DWS-AGD) to Improve Oil Recovery and Reduce Water Cut in Reservoirs with Strong Water Aquifers
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Abstract<p>Gas and downhole water sink assisted gravity drainage (GDWS-AGD) is a promising gas-based enhanced oil recovery (EOR) process applicable for reservoirs associated with infinite aquifers. However, it can be costly to implement because it typically involves the drilling of multiple vertical gas-injection wells. The drilling and well-completion costs can be substantially reduced by using additional completions for gas injection in the oil production wells through the annulus positioned at the top of the reservoir. Multi-completion-GDWS-AGD (MC-GDWS-AGD) can be configured to include separate completions for gas injection, oil, and water production in individual wells. This study simulates</p> ... Show More
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Publication Date
Fri Jan 01 2021
Journal Name
Macromolecular Characterization Of Hydrocarbons For Sustainable Future
Feasibility of the Gas and Downhole Water Sink-Assisted Gravity Drainage (GDWS-AGD) Process to Enhance the Recovery of Oil in Reservoirs with Strong Aquifer
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Gas and Downhole Water Sink, Gravity Drainage, GDWS-AGD, Enhance the Recovery of Oil

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Publication Date
Mon Dec 01 2025
Journal Name
Journal Of Engineering
Experimental Evaluation of Free-Fall Gravity Drainage in Water-Drive Reservoirs: Impact of Aquifer Strength and Reservoir Heterogeneity/Homogeneity
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This study experimentally investigated Free-Fall Gravity Drainage (FFGD) under combination-drive conditions in a two-dimensional Hele-Shaw model representing a water-drive reservoir. An initially high gravity potential from the oil column enabled early oil drainage before aquifer support became dominant. Three water-drive strengths were tested, demonstrating that a stronger aquifer (1.15 psig) accelerated oil recovery to approximately 75% of the original oil in place (OOIP) within 60 minutes, resulting in a final recovery of 79.5%. However, this was accompanied by rapid water breakthrough after 2.5 minutes and high-water cuts exceeding 90%. In contrast, a weaker aquifer (0.725 psig) stabilized the oil–water contact, delaying w

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Publication Date
Mon Dec 18 2017
Journal Name
Al-khwarizmi Engineering Journal
Experimental Study of Mixed Convection in an Enclosure with a Cold Movable Top Wall and Hot Bottom Wall
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Mixed convection heat transfer to air inside an enclosure is investigated experimentally. The bottom wall of the enclosure is maintained at higher temperature than that of the top wall which keeps in oscillation motion, whereas the left and right walls are well insulated. The differential temperature of the bottom and top walls changed several times in order to accurately characterize the temperature distribution over a considerable range of Richardson number. Adjustable aspect ratio box was built as a test rig to determine the effects of Richardson number and aspect ratio on the flow behavior of the air inside the enclosure. The flow fields and the average Nusselt number profiles were presented in this wo

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