The influence of CO2 huff and puff in tight oil reservoirs on pore structure characteristics and oil production from the microscopic scale

One of the challenges in extracting oil from unconventional resources using hydraulic fracturing and horizontal drilling techniques is the low primary recovery rate, which is caused by the ultra-small permeability of these resources. Consequently, it is essential to investigate gas injection methods to produce the trapped oil in shale formations. However, the injection process can cause asphaltene depositions inside the reservoir, leading to plugging of pores and oil recovery (OR) reduction. There has been limited research on using gas injection techniques to improve oil production in tight/unconventional resources, although carbon dioxide (CO2) and gas-enhanced oil recovery methods have been used in conventional resources. In order to determine whether or not the cyclic (huff-n-puff) CO2 process improves OR and aggravates asphaltene precipitation, a rigorous experimental investigation was undertaken utilizing filter membranes and Eagle Ford shale cores. After the minimum miscibility pressure was calculated for CO2, various injection pressures were selected to perform CO2 huff-n-puff experiments. Investigations were carried out at 70 °C on injection pressure, cycle number, production time, and huff-and-puff mode injection. The results demonstrated that when the pore size structure of the membranes used was smaller and gas injection cycles increased, a higher asphaltene weight percent (wt %) was determined during the static experiments (i.e., employing filter paper membranes). Miscibility improved OR in dynamic testing (i.e., using shale cores), but a more oil-wet system was detected in wettability measurements taken following CO2 huff-and-puff tests. The plugging impact of asphaltene particles on the pore structure was studied using optical microscopy and scanning electron microscopy imaging. Following the huff-and-puff tests, a mercury porosimeter revealed how severely the pores were plugged, and after the CO2 tests, the pore size distribution reduced as a consequence of asphaltene deposition. This study examines the significance of CO2 injection in OR under miscible/immiscible conditions to identify the critical parameters that could impact the effectiveness of CO2 huff-n-puff operation in unconventional formations.

Section: Findings and Discussionmentioning

confidence: 99%

Experimental Investigation of Asphaltene Deposition and Its Impact on Oil Recovery in Eagle Ford Shale during Miscible and Immiscible CO₂ Huff-n-Puff Gas Injection

Elturki

Imqam

2023

“…According to the United States Energy Information Administration’s statistical prediction of tight oil resources in 2013, the world’s recoverable reserves of tight oil technology are 48.3 billion tons, accounting for 11% of the world’s conventional petroleum technology recoverable reserves (421.68 billion tons). − Among them, Russia has the largest amount of tight oil resources (Table ). Tight oil is the main source of future global oil production growth . It is expected that global oil production will increase by 2.254 million tons/day by 2030, with nearly half of it coming from tight oil .…”

Section: Global Tight Oil Resources and Distributionmentioning

confidence: 99%

“…Tight oil is the main source of future global oil production growth. 30 It is expected that global oil production will increase by 2.254 million tons/day by 2030, with nearly half of it coming from tight oil. 31 At that time, tight oil will meet the global demand of 5% to 9%.…”

Section: Statistics Of World Tight Oilmentioning

confidence: 99%

Review of the Development Status and Technology of Tight Oil: Advances and Outlook

Liu

2023

Tight sandstone and shale oil reservoirs are one of the most promising and realistic important oil exploration fields in the 21st century. The research on the development technology of tight sandstone and shale oil reservoirs has important theoretical and practical significance for the exploration and development of tight sandstone and shale oil reservoirs in China. First, this article introduces the distribution of tight oil in the world and calculates the recoverable reserves of tight oil technology worldwide. The review also introduces the current status of tight oil exploration and development in major countries such as the United States, Canada, and China, including the distribution of tight oil resources, the main parameters of tight oil basins, and tight oil production. Second, it analyzes the current development status of tight oil in the United States, summarizes the four main factors that led to the success of tight oil exploration and development in the United States, and points out the impact of the successful development of tight oil in the United States on the global oil supply and demand relationship. Third, in the review of the main development technologies for tight oil, the current status, application, and progress of the main development technologies for tight oil are summarized and analyzed, including horizontal well drilling, fracturing and transformation technology, microscale seismic diagnosis, gas injection, and other technologies. Finally, the development examples of tight oil such as the Bakun shale in the United States are analyzed, and the application effects and experiences of horizontal well volume fracturing in regions such as the United States are summarized.

“…Qian et al 23 pointed out that huff and puff extraction is more effective than displacement methods in preventing asphaltene deposition in reservoirs. Huang et al 24 investigated the deposition characteristics of asphaltenes and reservoir damage during the huff and puff process through NMR, noting that the precipitation rate of asphaltenes decreases with increasing huff and puff rounds. Xue et al 25 studied the micromechanisms in tight sandstone reservoirs during CO 2 flooding and subsequent huff and puff using NMR.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Residual Oil Distribution in Heavy Oil Reservoirs after Multiple Hot Water Huff and Puff: A Comprehensive Analysis

Mo,

Zhang,

Tang

et al. 2024

In the development of China's Shengli deep heavy oil reservoirs, steam injection is the primary method. However, the effectiveness and efficiency of this method decline as the number of injection rounds increases. This study investigates the impact of different huff and puff rounds on the recovery rate of porous media by conducting hot water huff and puff tests on rock samples and using nuclear magnetic resonance (NMR) experiments to quantitatively determine the residual oil distribution at different injection rounds. A novel relationship has also been discovered to link oil saturation with the NMR conversion factor (C), which differs significantly from the traditional model, where C is considered a constant. Additionally, the research reveals migration patterns during the heavy oil huff and puff process. The results show that the maximum potential oil recovery achievable through huff and puff is only 45.4%, significantly lower than the oil recovery of 52.69% achieved through displacement methods. When the oil saturation exceeds 63.8%, the C value decreases exponentially. Under saturated oil conditions, the oil primarily exists as droplets larger than 10 μm. During each huff and puff process, oil is redistributed. As the number of huff and puff rounds increases, residual oil recovery is prioritized at the injection end. The local maximum oil saturation shifts progressively toward the far end. This research sheds light on the distribution patterns of residual oil in pore structures, providing support for the selection and assessment of enhanced recovery rate technologies.