Pore Structure Characterization and Classification of in-Source Tight Oil Reservoirs in Northern Songliao Basin

2015 ◽  
Vol 89 (s1) ◽  
pp. 29-30 ◽  
Author(s):  
Zihui FENG ◽  
Hongmei SHAO ◽  
Cheng WANG ◽  
Xi LU
Keyword(s):  
Pore Structure ◽  
Songliao Basin ◽  
Structure Characterization ◽  
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.

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.

Characteristics and origin of the pore structure of the lacustrine tight oil reservoir in the northwestern Jiuquan Basin, China

2019 ◽  
Vol 7 (3) ◽  
pp. T625-T636
Author(s):  
Chunyan Fan ◽  
Xianglu Tang ◽  
Yuanyin Zhang ◽  
Yan Song ◽  
Zhenxue Jiang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Oil Reservoirs ◽  
Tight Oil ◽  
Oil Reservoir ◽  
Type I ◽  
Thin Sections ◽  
Tectonic Events ◽  
Tight Oil Reservoir ◽  
Tight Oil Reservoirs ◽  
Intercrystalline Pores

The pore structure controls the formation processes of tight oil reservoirs. It is meaningful to study the characteristics and origin of the pore structure of the tight oil reservoir. We have analyzed the pore structure of the tight oil reservoir by thin sections, scanning electron microscopy, and mercury intrusion porosimetry. We analyze the origin of the pore structure based on sedimentological, diagenetic, and tectonism processes. The porosity of the tight oil reservoirs is mainly approximately 2%–10%, and the permeability is mainly from 0.01 to 0.3 mD. The pores of the lacustrine tight oil reservoir can be classified into the primary pore and the secondary pore. The main pores are matrix micropores and clay intercrystalline pores, as well as a few dissolved pores. However, the primary residual intergranular pore has almost disappeared, leading to a poor connectivity with a general size between 20 and 50 μm. The pore throat is divided into three categories (type I, type II, and type III) according to the porosity, permeability, and throat size and distribution. We determine that the pore structure of the lacustrine tight oil reservoir is related to sedimentary, diagenetic processes, and later tectonic events. The compaction and cementation are the main factors, whereas the dissolution and tectonic events have minor effects.

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