A new approach for characterization and prediction of natural fracture occurrence in tight oil sandstones with intense anisotropy

Gong, Lili; Fu, Xiaofei; Wang, Zhaosheng; Gao, Shuai; Jabbari, Hadi; Yue, Wenting; Liu, Bo

doi:10.1306/12131818054

Cited by 49 publications

(27 citation statements)

References 42 publications

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“…Fractures govern well patterns in low-permeability oilfields through controlling the seepage system (Tamagawa and Pollard, 2008;Laubach et al, 2018). Fracture permeability varies as a function of fracture density, filling degree, and current in-situ stress (Baytok and Pranter, 2013;Gong et al, 2019b;Wang Z. et al, 2020). The NE-SW strike fractures in the study area are characterized by their high density, large aperture, being weaklyfilled, and approximately parallel to the regional maximum horizontal principal stress (Connolly and Cosgrove, 1999).…”

Section: Discussionmentioning

confidence: 99%

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Wang

Muhtar

et al. 2021

Front. Earth Sci.

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Natural fractures play an important role in the seepage system of Paleogene sandstone reservoirs at Nanpu Sag. Characteristics and formation mechanisms of natural fractures and stress-sensitivity permeability are comprehensively investigated and their impact on water injection is discussed based on core and log data (FMI and diplog data) as well as stress-sensitivity permeability measurement. Results show that high-angle shear fractures, including NE-SW strike fractures and NW-SE strike fractures, are widely developed in the study area, which were primarily developed during the late Paleogene and late Neogene. The present maximum horizontal principal stress is orientated at N60°–80°E, approximately parallel to the NE-SW fractures, contributing greatly to the seepage system at the early oilfield development stage. Fractures in the study area can be divided into three phases and are characterized by obvious stress-sensitivity permeability, which is closely related to fracture aperture and throat size. Since the fracture occurrence enhances stress sensitivity of permeability, it is necessary to regulate well pattern based on dynamic behaviors of fractured reservoirs at different development stages.

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Section: Discussionmentioning

confidence: 99%

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Wang

Muhtar

et al. 2021

Front. Earth Sci.

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“…Therefore, fracture is an important evaluation index for tight oil reservoirs, and it is a favorable factor in the enrichment stage and development stage of tight oil. The natural fractures provide the main path for fluid flow in tight oil reservoirs and can control the flow direction in the subsurface (Gong et al, 2019).…”

Section: Third Step: Multi-scale Fracture Evaluationmentioning

confidence: 99%

Evaluation Methods of Profitable Tight Oil Reservoir of Lacustrine Coquina: A Case Study of Da'anzhai Member of Jurassic in the Sichuan Basin

Pang

Tao

Zhang

et al. 2020

Acta Geologica Sinica (Eng)

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Based on core observation, cast and fluorescent thin sections, FESEM and ESEM, coquina in Da'anzhai Member of Jurassic in Sichuan Basin were examined systematically. Together with production data and logging evaluation, a method for lacustrine coquina evaluation based on geological theory was established up. In the article, two aspects of the study were elaborated, characteristics of favorable reservoirs, and a "five-step" evaluation method for favorable coquina reservoir. According to the correlation between porosity and production data, porosity is not effective in finding high quality coquina reservoir of this area. Whereas micro research of reservoir samples from a high productivity well revealed that sparry coquina is the best lithofacies, with the most developed micro storage space of various kinds. After the favorable reservoir was sorted out, a five-step method evaluating the coquina reservoir was worked out. Correlation of GR value and rock types suggests that GR<30 API is an effective evaluation parameter in identifying profitable reservoir lithofacies. Meanwhile, the combination of profitable reservoir rock thickness and production data revealed that the reservoirs with the highest potentiality are those with thickness of 3-18 m. Fractures are more developed in faults, folds and structural noses in the study area. Organic acid is discharged massively before the peak of hydrocarbon generation, leading to the formation of dissolution pores in the reservoir. The evaluation of organic acid was made by using the source rock indexes. After evaluating the four factors, and compiling their distribution maps, the maps were overlapped to predict favorable reservoir zones, and 7 first class and 9 second class favorable zones of coquina were picked out.

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“…The development degree of fractures in shale is also affected by the total organic carbon content (TOC), mineral composition, mechanical stratigraphy, abnormal pressure and other factors [26][27][28][29][30][31][32]. Therefore, heterogeneous geomechanical model can be established by integrating these influencing factors for fracture prediction [33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Quantitative Prediction of Natural Fractures in Shale Oil Reservoirs

et al. 2021

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Natural fractures are the key factors controlling the enrichment of shale oil. It is of great significance to clarify the distribution of natural fractures to guide the selection of sweet spots for shale oil. Taking the Qing-1 Member shale oil reservoir in the northern Songliao Basin, China as an example, a new method considering the factors affecting fracture distribution was proposed to quantitatively predict the structural fractures. And the effect of natural fractures on shale oil enrichment was discussed. Firstly, the types and characteristics of fractures in shale oil reservoirs are characterized by using core and outcrop data. Combined with the experimental analysis, the influences of fault, mechanical stratigraphy, mineral composition and content, TOC, and overpressure on fracture intensity were clarified. Then, the number and density of fractures are quantitatively predicted according to the power-law distribution of fault length. Next, geomechanical simulation and fracture prediction were carried out on the model which was established with comprehensive consideration of the influencing factors of fracture distribution. Finally, the fracture distribution is evaluated comprehensively based on above prediction. The prediction results in this work are consistent with the core measurements.

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A new approach for characterization and prediction of natural fracture occurrence in tight oil sandstones with intense anisotropy

Cited by 49 publications

References 42 publications

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Seepage Behavior of Fractures in Paleogene Sandstone Reservoirs in Nanpu Sag, Bohai Bay Basin, Eastern China

Evaluation Methods of Profitable Tight Oil Reservoir of Lacustrine Coquina: A Case Study of Da'anzhai Member of Jurassic in the Sichuan Basin

Quantitative Prediction of Natural Fractures in Shale Oil Reservoirs

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