Structural division of granite weathering crusts and effective reservoir evaluation in the western segment of the northern belt of Dongying Sag, Bohai Bay Basin, NE China

Zhu, Maolin; Liu, Zhen; Liu, Huimin; Li, Xiaoke; Liang, Shangzi; Gong, Jian; Zhang, Pengfei

doi:10.1016/j.marpetgeo.2020.104612

Cited by 13 publications

(19 citation statements)

References 12 publications

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“…Based on the characteristics of the above-mentioned different types of reservoirs, a multifactor classification standard was established and a double-layer structure model of the weathering crust was proposed. The complete vertical structure of the weathering crust was divided into a completely weathered layer (regolith–dissolution zone) and a semi-weathered layer (fracture zone) from top to bottom (Zhu et al 2020).…”

Section: Resultsmentioning

confidence: 99%

Methods for determining the characteristics of weathered granite reservoirs: application to Binxian Uplift, Dongying Sag, Bohai Bay Basin

Chen

Liang

2022

Geol. Mag.

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With the discovery of high-productivity oilfields in granite buried hills, it is necessary to systematically investigate the types of granite weathered reservoirs at different depths and their spatial distribution. However, previously subdivided reservoirs have been assumed to exhibit the same vertical zoning in different structural parts, contradicting the fact that the degree of weathering varies with the topography. In addition, comprehensive and quantitative methods for classifying reservoir types are lacking. Taking the Binxian Uplift of the Dongying depression in Bohai Bay Basin as an example, we therefore established a comprehensive identification standard for dividing granite reservoirs using lithology division, logging curve statistics, a dual-medium matrix–fracture model and seismic facies identification. Subsequently, by combining logging and seismic methods, the vertical stacking types and distribution properties of weathered granite reservoirs in various structural positions were analysed. The reservoirs were divided vertically into three zones: regolith, dissolution and fracture. Quantitative logging response standards for the different reservoirs were established using acoustic, density, natural gamma and resistivity logging. In terms of the seismic response, the regolith, dissolution and fracture zone corresponded to high-, medium- and low-amplitude seismic facies, respectively. A dynamic double-layer structure of the reservoir was established, comprising a completely weathered layer and a semi-weathered layer. The reservoir division method proposed in this paper can be used in other areas, and the research results can help promote the exploration of granite buried hill reservoirs.

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Section: Resultsmentioning

confidence: 99%

Methods for determining the characteristics of weathered granite reservoirs: application to Binxian Uplift, Dongying Sag, Bohai Bay Basin

Chen

Liang

2022

Geol. Mag.

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“…Studies on weathering crusts of the Penglai 9-1 oil and gas fields in the Bohai Bay Basin and the Dongping district in the Qaidam Basin indicate that a gentle slope of the structure provides a favorable location for the development and maintenance of highquality reservoirs [10,15,16], and the structure of weathering crust varies with different topographies [25,65,66].…”

Section: Topographymentioning

confidence: 99%

“…The average productivity of pre-Cambrian granite rocks in the Bongor Basin has been more than 300 m 3 /day since 2012 [7]. The Penglai oilfield in the Bohai Bay Basin is the largest granite reservoir in China, with an oil-bearing area of 80.2 km 2 and more than 2 × 10 8 tons of reserves [8][9][10]. In addition, the Paleoproterozoic granite of the JZ25-1S oil and gas field in Liaodong Bay also contains about 9 × 10 7 m 3 of hydrocarbons [6,11].…”

Section: Introductionmentioning

confidence: 99%

“…To date, many scientists have carried out extensive works on granite weathering crust reservoirs. Vertical zonation of the weathering crust is determined based on weathering intensity indices such as granite color, rock structure, mineral composition, logging characteristics, reservoir space types and geochemical indicators [8][9][10][12][13][14][15][16][17][18][19]. There are also various geological models of weathering crust established in previous studies [9,10,16,[20][21][22].…”

Section: Introductionmentioning

confidence: 99%

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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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“…Regarding the identification of effective reservoirs, some scholars define reservoirs that can be developed under the current technical conditions as effective reservoirs based on reservoir tests and production data (Zhou et al, 2022); other scholars have considered these reservoirs as ones capable of storing and percolating fluids and producing industrially valuable volumes of liquids (hydrocarbons or a mixture of hydrocarbons and water), which can be extracted by existing technologies (Huang et al, 2021). It has also been argued that, in the general context of low porosity and low permeability, reservoirs with relatively high porosity and permeability are considered as effective reservoirs (Wang et al, 2014;Zhu et al, 2020). Previous discriminations of effective reservoirs were mainly based on the physical property data of cores and logging data that determine the lower limit of the physical properties of effective reservoirs (Sun et al, 2019;Huang et al, 2020;Li et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Criteria and favorable distribution area prediction of Paleogene effective sandstone reservoirs in the Lufeng Sag, Pearl River Mouth Basin

Wang

Chen

et al. 2022

Adv. Geo-Energy Res.

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As the focus of conventional oil and gas exploration is changing from shallow to deep layers, the identification of deep effective reservoirs is crucial to exploration and development. In this paper, based on the geological anatomy of oil and gas reservoirs, a new discriminatory criterion and evaluation method for effective reservoirs is proposed in combination with the analysis of reservoir formation dynamics mechanism. The results show that the hydrocarbon properties of the reservoir vary with the ratio of the capillary force between the sandstone reservoir and its surrounding rock. The effective reservoir is discriminated and the reservoir quality is evaluated based on the capillary force and depth of the surrounding media and the sandstone reservoir for adjacent plates. When the capillary force ratio is greater than 0.6, fewer effective reservoirs are developed. The effective reservoir is determined by the capillary force ratio of the sandstone reservoir and the surrounding rock medium to mechanically explain the geological phenomenon that low-porosity reservoirs can also accumulate hydrocarbons. Our findings have significant guiding value for Paleogene oil and gas exploration in the Zhu I depression of Pearl River Mouth Basin.

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Structural division of granite weathering crusts and effective reservoir evaluation in the western segment of the northern belt of Dongying Sag, Bohai Bay Basin, NE China

Cited by 13 publications

References 12 publications

Methods for determining the characteristics of weathered granite reservoirs: application to Binxian Uplift, Dongying Sag, Bohai Bay Basin

Methods for determining the characteristics of weathered granite reservoirs: application to Binxian Uplift, Dongying Sag, Bohai Bay Basin

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

Criteria and favorable distribution area prediction of Paleogene effective sandstone reservoirs in the Lufeng Sag, Pearl River Mouth Basin

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