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 Experimental Study on the EOR Performance of Imbibition and Huff and Puff in Fractured Tight Oil Reservoirs

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Zilin Zhang ◽  
Bo Huang ◽  
Liang Zhang ◽  
Guangqing Zhou ◽  
Yanhui Liu ◽  
...  
Keyword(s):  
Mass Transfer ◽  
Oil Recovery ◽  
Mass Transfer Rate ◽  
Spontaneous Imbibition ◽  
Oil Reservoirs ◽  
Recovery Factor ◽  
Co2 Injection ◽  
Tight Oil ◽  
Core Flooding ◽  
Tight Oil Reservoirs

Abstract Injection of imbibition fluids or CO2 during hydraulic fracturing is an effective stimulation method for tight oil reservoirs. Selecting appropriate agents is significant to optimize the integrated scheme of fracturing and production in tight oil reservoirs. In this study, a series of lab experiments, including spontaneous imbibition, dynamic imbibition, and huff and puff, were carried out using real tight cores, water absorption apparatus, and core flooding equipment. The EOR performances of imbibition fluids and CO2 in fractured tight cores were compared. The mass transfer of imbibition fluids and CO2 in tight oil reservoirs and its influence on the sweeping volume and EOR mechanisms were discussed. The results show that (1) the spontaneous imbibition rate of imbibition fluids in tight cores is slow, and the oil recovery factor by spontaneous imbibition in cracked cores is relatively high, up to 13.42%. (2) In the dynamic imbibition experiments, the final oil recovery by CO2 injection was significantly higher than that by injecting imbibition liquids. Because of the excellent miscibility effect of CO2, oil production by CO2 injection mainly occurred in the primary displacement stage. Comparatively, the EOR effect of imbibition fluids mainly played its role during production after well shut-in, which can increase the oil recovery factor by 7.35%-11.64%. (3) The influence of the huff and puff mode of CO2 on EOR performance is greater than that of imbibition fluids due to its more sensitive compressibility and mass transfer rate. Generally, a high oil recovery factor can be obtained if the depletion production is conducted first, and a huff and puff operation is followed. (4) Comprehensively understanding the mass transfer characteristics of CO2 and imbibition fluids in tight oil reservoirs can guide the fracturing parameter design, such as the order of fracturing fluid slugs, the optimal soak time, and fracture spacing.

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

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 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.

Prediction of Refracturing Timing of Horizontal Wells in Tight Oil Reservoirs Based on an Integrated Learning Algorithm

Energies ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6524
Author(s):  
Xianmin Zhang ◽  
Jiawei Ren ◽  
Qihong Feng ◽  
Xianjun Wang ◽  
Wei Wang
Keyword(s):  
Support Vector Machine ◽  
Learning Algorithm ◽  
Prediction Method ◽  
Horizontal Wells ◽  
Songliao Basin ◽  
Oil Reservoirs ◽  
Support Vector ◽  
Tight Oil ◽  
Integrated Learning ◽  
Tight Oil Reservoirs

Refracturing technology can effectively improve the EUR of horizontal wells in tight reservoirs, and the determination of refracturing time is the key to ensuring the effects of refracturing measures. In view of different types of tight oil reservoirs in the Songliao Basin, a library of 1896 sets of learning samples, with 11 geological and engineering parameters and corresponding refracturing times as characteristic variables, was constructed by combining numerical simulation with field statistics. After a performance comparison and analysis of an artificial neural network, support vector machine and XGBoost algorithm, the support vector machine and XGBoost algorithm were chosen as the base model and fused by the stacking method of integrated learning. Then, a prediction method of refracturing timing of tight oil horizontal wells was established on the basis of an ensemble learning algorithm. Through the prediction and analysis of the refracturing timing corresponding to 257 groups of test data, the prediction results were in good agreement with the real value, and the correlation coefficient R2 was 0.945. The established prediction method can quickly and accurately predict the refracturing time, and effectively guide refracturing practices in the tight oil test area of the Songliao basin.

Sign in / Sign up

Export Citation Format

Share Document