Characteristics and developing patterns of gneiss buried hill weathering crust reservoir in the sea area of the Bohai Bay basin

Wang, Deying; Wang, Qingbin; Liu, Xiaojian; Zhao, Meng; Hao, Yiwei

doi:10.18654/1000-0569/2019.04.13

Cited by 20 publications

(6 citation statements)

References 14 publications

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“…Due to the different weathering resistance of minerals, mineral composition is vital to the development of secondary pores and fractures in the weathering crust [6,54,55]. Bright minerals, such as feldspar and quartz, are brittle and can be easily affected by tectonic stresses, which makes the granite become integrated and form structural fractures [56].…”

Section: Petrology and Mineralsmentioning

confidence: 99%

Characteristics and Genetic Mechanism of Granite Weathering Crust of Songnan Low Uplift, Qiongdongnan Basin, South China Sea

Li,

Guo,

2024

Minerals

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Recently, a large-scale gas reservoir was discovered in granitic buried hills of the Songnan Low Uplift in the Qiongdongnan Basin. However, the strong heterogeneity of granite reservoirs limits further exploration and evaluation. Based on observations of sixty core samples and sixty thin sections, mineral composition, zircon dating, apatite fission tracks, physical properties, image logs, outcrop surveys and seismic interpretations, the characteristics of granite weathering crust of the Songnan Low Uplift are analyzed, and its controlling factors and evolution process are evaluated. The results show that weathered granite in the study area can be divided into several zones, from top to bottom: eluvium–slope zone, sandy zone, weathered fracture zone and horizontal undercurrent vuggy zone. The reservoirs in the eluvium–slope zone are dominated by microfissures and intergranular dissolution pores and have an average porosity of 4.68% and permeability of 2.34 md; the reservoirs in the sandy zone are composed of intergranular and intragranular dissolution pores and have an average porosity of 11.46% and permeability of 4.99 md; the reservoirs in the weathered fracture zone consist of various fractures and have an average porosity of 3.91% and permeability of 2.5 md; the reservoirs in the horizontal undercurrent vuggy zone are subhorizontal fractures and vugs and have an average porosity of 2.7% and permeability of 0.23 md. The development of granite reservoirs is jointly influenced by petrology and minerals, long-term exposure in a warm humid paleoclimate, faults, diverse topographies and shallow buried depth. Based on the above, our study establishes a development model of weathering crust and suggests that only the gentle slope and platform remain strongly weathered zones. After undergoing a complex evolution process of formation–destruction/denudation–regeneration–preservation, the current weathering crust of the Songnan Low Uplift is finally established. The results of this study have important theoretical and application value for the hydrocarbon exploration of buried hills in the Qiongdongnan Basin and provide a reference example for other granite reservoirs worldwide.

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Section: Petrology and Mineralsmentioning

confidence: 99%

Characteristics and Genetic Mechanism of Granite Weathering Crust of Songnan Low Uplift, Qiongdongnan Basin, South China Sea

Li,

Guo,

2024

Minerals

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“…The Bohai Bay Basin is an important oil and gas basin in eastern China, with an area of approximately 20 × 10 4 km 2 , and the annual crude oil production is more than 7000 × 10 4 t, which is more than 1/3 of the total crude oil production in China. ,,, The basin is a multistage fault depression basin formed by tectonic movements such as the Indosinian, Yanshanian, and Himalayan periods, with structural characteristics of alternating uplift and depression . The Bohai Sea is in the eastern part of the Bohai Bay Basin.…”

Section: Geological Settingmentioning

confidence: 99%

“…With the continuous expansion of oil and gas exploration to the deep and ultradeep layers, the Archean metamorphic buried hill in the Bohai Sea has attracted much attention in recent years as an important field of oil and gas production in the Bohai Bay Basin. − Archaean buried hills are widely distributed in the Bohai Sea. The discovery of giant oil-gas fields such as JZ 25-1 South, PL 9-1, BZ19-6, BZ13-2, and others has shown the great exploration potential of buried metamorphic rock hills in the Bohai Bay Basin. , The metamorphic buried hill reservoir has no primary pores, the reservoir space is mainly secondary pores and fractures formed by later reconstruction, and the development of the reservoir is not affected by the burial depth.…”

Section: Introductionmentioning

confidence: 99%

Classification and Quantitative Characterization of Archean Metamorphic Buried Hill Reservoirs in the Bohai Sea

Ren,

Lv,

et al. 2023

ACS Omega

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Based on productivity test data and physical property test results from multiple wells, a classification scheme of Archean metamorphic buried hill reservoirs in the Bohai Sea is established by means of mathematical function fitting. By combining data from cores, casting thin sections, scanning electron microscopy, imaging logging, and high-pressure mercury injection and nitrogen adsorption tests, we clarified the reservoir composition and pore structure characteristics of different types of reservoirs are clarified. Furthermore, taking the BZ19-6 and 13-2 wells in the Archean metamorphic buried hills as an example, the development sites of different types of reservoirs are analyzed and the reservoir development model is established. The results show that the Archean metamorphic buried hill reservoirs in the Bohai Sea can be divided into three categories and six subcategories, including type I reservoirs with porosities greater than 8% or permeabilities greater than 1 × 10 –3 μm 2 and type II reservoirs with porosities of 5–8% or permeabilities in the range of 0.1–1 × 10 –3 μm 2 . Reservoirs with porosities of 2–5% and permeabilities of 0.01–0.1 × 10 –3 μm 2 are type III reservoirs. Each type of reservoir can be further divided into a fracture-pore type and a fracture type according to the relative contribution of the porosity and permeability to the reservoir. From type I to type III, the dissolution degree and fracture development gradually weaken, the pore size gradually decreases, and the pore volume gradually decreases. The distribution of favorable reservoirs is comprehensively controlled by weathering and tectonic transformation. The presence of a weathered glutenite zone, weathered leaching zone, or weathered disintegration zone is favorable for the development of type I reservoirs in the weathering crust. In the inner part of the buried hill, the presence of a fracture zone with a thickness of more than 10 m or a dense fracture zone with a thickness of more than 40 m is favorable for the formation of type I reservoirs.

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“…Subsequently, geological processes such as tectonic movements and weathering leaching contribute to the formation of fractures or karst caves during later stages, resulting in pronounced heterogeneity within buried hill reservoirs, which hampers accurate prediction of their spatial distribution. However, these geological processes lead to distinct variations in reservoir reconstruction [3,4], consequently leading to evident zonation patterns in terms of spatial types and properties within buried hill reservoirs. Therefore, investigating zonation developmental characteristics is highly significant for predicting superior reservoir zones and formulating effective exploration and development strategies.…”

Section: Introductionmentioning

confidence: 99%

Prediction Technology of a Reservoir Development Model While Drilling Based on Machine Learning and Its Application

Wang,

Mao,

Yang

et al. 2024

Processes

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In order to further understand the complex spatial distribution caused by the extremely strong heterogeneity of buried hill reservoirs, this paper proposes a new method for predicting the development pattern of buried hill reservoirs based on the traditional pre-drilling prediction and post-drilling evaluation methods that mainly rely on seismic, logging, and core data, which are difficult to meet the timeliness and accuracy of drilling operations. Firstly, the box method and normalization formula are used to process and normalize the abnormal data of element logging and engineering logging, and then the stepwise regression analysis method is used to optimize the sensitive parameters of element logging and engineering logging. The Light Gradient Boosting Machine (LightGBM) algorithm, deep neural network (DNN), and support vector machine (SVM) are used to establish a new method for predicting the development pattern of buried hill reservoirs. Lastly, a comprehensive evaluation index F1 score for the model is established to evaluate the prediction model for the development pattern of buried hill reservoirs. The F1 score value obtained from this model’s comprehensive evaluation index indicates that the LightGBM model achieves the highest accuracy, with 96.7% accuracy in identifying weathered zones and 95.8% accuracy in identifying interior zones. The practical application demonstrates that this method can rapidly and accurately predict the development mode of buried hill reservoirs while providing a new approach for efficient on-site exploration and decision-making in oil and gas field developments. Consequently, it effectively promotes exploration activities as well as enhances the overall process of oil and gas reservoir exploration.

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Characteristics and developing patterns of gneiss buried hill weathering crust reservoir in the sea area of the Bohai Bay basin

Cited by 20 publications

References 14 publications

Characteristics and Genetic Mechanism of Granite Weathering Crust of Songnan Low Uplift, Qiongdongnan Basin, South China Sea

Characteristics and Genetic Mechanism of Granite Weathering Crust of Songnan Low Uplift, Qiongdongnan Basin, South China Sea

Classification and Quantitative Characterization of Archean Metamorphic Buried Hill Reservoirs in the Bohai Sea

Prediction Technology of a Reservoir Development Model While Drilling Based on Machine Learning and Its Application

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