scholarly journals Sensitivity Analysis and Multiobjective Optimization of CO2 Huff-N-Puff Process after Water Flooding in Natural Fractured Tight Oil Reservoirs

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Zhang Jie ◽  
Cai Ming-Jun ◽  
Ge Dangke ◽  
Lu Ning ◽  
Cheng Hai-Ying ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Oil Recovery ◽  
Orthogonal Experiment ◽  
Economic Feasibility ◽  
Oil Reservoirs ◽  
Water Flooding ◽  
Tight Oil ◽  
Co2 Flooding ◽  
Displacement Efficiency ◽  
Tight Oil Reservoirs

The CO2 huff-n-puff is an effective substitute technology to further improve oil recovery of natural fractured tight oil reservoirs after water flooding, for its high displacement efficiency and superior injectivity. The CO2 huff-n-puff process is influenced by many factors, such as miscible degree, complex fracture networks, and production schemes. What is worse, those influence facts affect each other making the process more complex. Many researchers concentrated on mechanisms and single sensitivity analysis of CO2 huff-n-puff process, whereas few optimized this process with the consideration of all influence factors and multiobjective to get favorable performance. We built multiobjective consisted of miscible degree, oil recovery, and gas replacing oil rate considering the aspects of CO2 flooding special characteristic, technical effectiveness, and economic feasibility, respectively. We have taken Yuan 284 tight oil block as a case, firstly investigated sensitivity analysis, and then optimized CO2 huff-n-puff process using orthogonal experiment design with multifactors and multiobjectives. The optimization results show CO2 huff-n-puff can significantly improve oil recovery by 8.87% original oil in place (OOIP) compared with water flooding, which offers guidelines for field operations.

scholarly journals The Characteristics of Oil Occurrence and Long-Distance Transportation due to Injected Fluid in Tight Oil Reservoirs

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Liu Yang ◽  
Jun Yang ◽  
Jian Gao ◽  
Xuhui Zhang
Keyword(s):  
Flow Characteristics ◽  
Oil Reservoirs ◽  
Water Flooding ◽  
Tight Oil ◽  
Reservoir Pressure ◽  
Distribution Characteristics ◽  
Displacement Efficiency ◽  
Long Distance ◽  
Oil Distribution ◽  
Tight Oil Reservoirs

In tight oil reservoirs, the injected fluid needs to travel a long distance to expel oil from the micro/nano-size pores to natural fractures or man-made fractures. The flow characteristics of injected fluid are not known well due to the long distance displacement and complex pore structure. In this study, the tight reservoir samples are from typical tight oilfield of China and the oil distribution characteristics are studied based on mineral composition, physical properties and pore size distribution. The long core displacement experiment is conducted based on injection of water, N2, and CO2, which aims to study the individual flooding feasibility. The results show that the oil mainly distributes in the form of spots and accumulates in the micro/nano-pores. Both oil spots and clay minerals have associated characteristics. The microfractures are not the storage space for oil spots, but can connect the oil spots to improve the mobility of the crude oil. In addition, the oil can achieve long distance migration under the injection of water, N2, and CO2, which presents different pressure distribution characteristics. The reservoir pressure of water flooding decreases first and increases later with displacement time. The reservoir pressure of N2 flooding rises gradually over displacement time. The reservoir pressure of CO2 flooding increases first and decreases over displacement time. In contrast to water flooding, N2, and CO2 can increase the reservoir energy, which contributes to tight oil production. In comparison, CO2 has better performances than N2 in terms of oil displacement efficiency. The study contributes to understanding the oil distribution characteristics and provides the guidance for field trials using different flooding techniques.

Huff-n-Puff Technology for Enhanced Oil Recovery in Shale/Tight Oil Reservoirs: Progress, Gaps, and Perspectives

2021 ◽  
Author(s):  
Muhend Milad ◽  
Radzuan Junin ◽  
Akhmal Sidek ◽  
Abdulmohsin Imqam ◽  
Mohamed Tarhuni
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Tight Oil Reservoirs

A Critical Review of CO2 Enhanced Oil Recovery in Tight Oil Reservoirs of North America and China

2019 ◽  
Author(s):  
Zhaojie Song ◽  
Yuzhen Li ◽  
Yilei Song ◽  
Baojun Bai ◽  
Jirui Hou ◽  
...  
Keyword(s):  
North America ◽  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Critical Review ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Tight Oil Reservoirs

Effects of Water Immersion and Acidification on Nano-Pores in Tight Sandstones—A Case Study of the Gaotaizi Reservoir, Songliao Basin

2021 ◽  
Vol 21 (1) ◽  
pp. 615-622
Author(s):  
Min Wang ◽  
Chenxue Jiao ◽  
Nengwu Zhou ◽  
Chuanming Li ◽  
Mingming Tang ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Water Immersion ◽  
Songliao Basin ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Core Flooding ◽  
Carbonate Minerals ◽  
Tight Sandstone ◽  
Content Type ◽  
Tight Oil Reservoirs

Hydraulic fracturing and acidification are among the most commonly used methods for stimulating the tight oil reservoirs and improving oil recovery. Therefore, examining the effects of water immersion and acidification on tight oil reservoirs is important for oilfield development plans. Core flooding testing, which analyzes the influence of core permeability variations before and after acid injection on the reservoir quality, is the conventional research method; however, it is difficult to observe the changes in minerals and pores caused by acidulation and water immersion in situ. In this study, we conduct field-emission scanning electron microscopy (FE-SEM), MAPS, the quantitative evaluation of minerals through scanning electronic microscopy (QEM-SCAN), and describe the types of pores in tight sandstone. Further, the effects of water immersion and acidification on pores in tight sandstone were studied. The results indicate that: (1) intergranular pores, intragranular dissolution pores, clay mineral intercrystalline pores, and micro-cracks were developed in the Gaotaizi tight sandstone in Songliao Basin, with the intergranular pores observed to be dominant; (2) the hydration of clay minerals induced by water injection caused plugging of pores at the nanometer– micrometer scale, and plane porosity is slightly reduced (˜0.86%); (3) acidification resulted in the dissolution of carbonate minerals, increasing the porosity of the reservoir, therefore, the increase in porosity is influenced by the carbonate mineral content. We recommend that future studies should investigate the content, type, and distribution of carbonate minerals in the operation area. During the process of reservoir stimulation, such as acidification and CO2 injection- and-production, the influence of carbonate minerals dissolution on oil production should be considered.

scholarly journals Optimization of triple-alternating-gas (TAG) injection technique for enhanced oil recovery in tight oil reservoirs

2021 ◽  
Author(s):  
Mvomo Ndzinga Edouard ◽  
Pingchuan Dong ◽  
Chinedu J. Okere ◽  
Luc Y. Nkok ◽  
Abakar Y. Adoum ◽  
...  
Keyword(s):  
Enhanced Oil Recovery ◽  
Oil Recovery ◽  
Gas Injection ◽  
Oil Reservoirs ◽  
Recovery Factor ◽  
Injection Technique ◽  
Tight Oil ◽  
Compositional Model ◽  
Injection Scheme ◽  
Tight Oil Reservoirs

AbstractAfter single-gas (SG) injection operations in tight oil reservoirs, a significant amount of oil is still unrecovered. To increase productivity, several sequencing gas injection techniques have been utilized. Given the scarcity of research on multiple-gas alternating injection schemes, this study propose an optimized triple-alternating-gas (TAG) injection for improved oil recovery. The performance of the TAG process was demonstrated through numerical simulations and comparative analysis. First, a reservoir compositional model is developed to establish the properties and composition of the tight oil reservoir; then, a suitable combination for the SG, double alternating gas (DAG), and TAG was selected via a comparative simulation process. Second, the TAG process was optimized and the best case parameters were derived. Finally, based on the oil recovery factors and sweep efficiencies, a comparative simulation for SG, DAG, and TAG was performed and the mechanisms explained. The following findings were made: (1) The DAG and TAG provided a higher recovery factor than the SG injection and based on recovery factor and economic advantages, CO2 + CH4 + H2S was the best choice for the TAG process. (2) The results of the sensitivity analysis showed that the critical optimization factors for a TAG injection scheme are the injection and the production pressures. (3) After optimization, the recovery factor and sweep efficiency of the TAG injection scheme were the best. This study promotes the understanding of multiple-gas injection enhanced oil recovery (EOR) and serves as a guide to field design of gas EOR techniques.

scholarly journals Supplementary energy development boundaries of staged fracturing horizontal wells in tight oil reservoirs

2020 ◽  
Vol 38 (6) ◽  
pp. 2217-2230
Author(s):  
Lijun Lin ◽  
Wei Lin ◽  
Shengchun Xiong ◽  
Zhengming Yang
Keyword(s):  
Horizontal Well ◽  
Evaluation Model ◽  
Horizontal Wells ◽  
Simulation Method ◽  
Energy Development ◽  
Oil Reservoirs ◽  
Water Flooding ◽  
Tight Oil ◽  
Reservoir Development ◽  
Tight Oil Reservoirs

Staged fracturing horizontal well technology is an important means of improving tight reservoir development efficiency. Taking a typical tight oil block in the Oilfield A as the studied area, the vertical well–horizontal well joint arrangement pattern is adopted in this study. The energy supplementary development effects of multiple permeability scales, different arrangement spacing, and different media (H2O, CO2) are discussed through the numerical simulation method. Combined with the principles of petroleum technology economics, the economic evaluation model for staged fracturing horizontal wells in tight oil reservoir development is proposed, thereby determining the technical boundary and economic boundary of supplementary energy development with different media. Studies indicate that the technical boundary and economic boundary of water-flooding development in the Oilfield A are 0.4 and 0.8 mD, respectively, and the technical boundary and economic boundary of CO2-flooding development are 0.1 and 0.4 mD, respectively. This study provides theoretical support for field operation of Oilfield A and guidance for selection of development mode for tight oil reservoirs.

scholarly journals The Characteristics of Oil Migration due to Water Imbibition in Tight Oil Reservoirs

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4199
Author(s):  
Liu Yang ◽  
Shuo Wang ◽  
Zhigang Tao ◽  
Ruixi Leng ◽  
Jun Yang
Keyword(s):  
Clay Minerals ◽  
Oil Recovery ◽  
Oil Production ◽  
Inhibitory Effect ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Oil Migration ◽  
Water Imbibition ◽  
Migration Dynamics ◽  
Tight Oil Reservoirs

In tight oil reservoirs, water imbibition is the key mechanism to improve oil production during shut-in operations. However, the complex microstructure and composition of minerals complicate the interpretation of oil migration during water imbibition. In this study, nuclear magnetic resonance (NMR) T2 spectra was used to monitor the oil migration dynamics in tight oil reservoirs. The factors influencing pore size distribution, micro-fractures, and clay minerals were systematically investigated. The results show that the small pores corresponded to a larger capillary pressure and a stronger imbibition capacity, expelling the oil into the large pores. The small pores had a more effective oil recovery than the large pores. As the soaking time increases, the water preferentially entered the natural micro-fractures, expelling the oil in the micro-fractures. Subsequently, the oil in the small pores was slowly expelled. Compared with the matrix pores, natural micro-fractures had a smaller flow resistance and were more conducive to water and oil flow. Clay minerals may have induced micro-fracture propagation, which can act as the oil migration channels during water imbibition. In contrary to the inhibitory effect of natural micro-fractures, the new micro-fractures could contribute to the oil migration from small pores into large pores. This study characterized the oil migration characteristics and provides new insight into tight oil production.

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