Alteration-destruction-preservation of bedrock weathering crusts and the influence on reservoir distribution in Dongying Sag, Bohai Bay basin

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

doi:10.1016/j.marpetgeo.2021.105078

Cited by 5 publications

(3 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…During the rifting period, the basin experienced multi-episodes of rifting, subsidence and filling. The rifting process ceased by the end of the Oligocene entering the post-rift thermal subsidence stage that continues until today (Liu, He, & Chen, 2018;Qiu et al, 2015;Zhu et al, 2009).…”

Section: Geological Settingmentioning

confidence: 99%

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

Li,

Liu,

Chen

et al. 2024

Geological Journal

View full text Add to dashboard Cite

The unclear understanding of the source rock characteristics for the Paleogene Dongying Formation in the Bozhong Sag leads to the lack of cognition in oil and gas exploration. This research systematically evaluated the discrepancy in geochemical characteristics of source rock intervals in the Dongying Formation based on detailed analysis using Rock‐Eval pyrolysis, total organic carbon (TOC), vitrinite reflectance (Ro), maceral components, stable carbon isotopes and biomarker parameters. It discusses the organic matter sources, depositional environment, thermal maturity and hydrocarbon generation potential in the source rock intervals of the Dongying Formation. The organic matter abundance in the third member (E3d3) and lower sub‐member of the second member (E3d2L) of the Dongying Formation is higher, with an average TOC of 2.08% and 1.03%, respectively, indicating that these source rock intervals could have good and excellent quality. The source rocks of the Dongying Formation predominately contain exinite maceral group and type II1 and II2 kerogen. The thermal evolution is mainly in the low‐mature and mature stages. The organic matter sources in the Dongying Formation are mainly dominated by mixed origin (the carbon isotope reversal of aromatics also provides a potential explanation). However, the values of 1,2,5−/1,3,6‐trimethylnaphthalene, (1,2,5,6 + 1,2,3,5)‐tetramethylnaphthalene/tetramethylnaphthalenes, methyldibenzofuran/methylphenanthrene (MDBF/MP) and dibenzofuran/phenanthrene (DBF/PHEN) parameters in the E3d3 and some samples in E3d2L decipher relatively smaller values than other source rock intervals, proving the enhancement of the contribution of lower organisms. Moreover, the terrestrial input in the bottom‐up deposition process of the Dongying Formation gradually increases. The depositional environment reveals the Dongying Formation source rocks mainly developed freshwater sulphur‐poor lacustrine facies and shallow lake‐fluvial delta facies in an open clay‐rich sedimentary environment with poor water column stratification, belonging to the typical weak oxidation–reduction depositional conditions. The comprehensive geochemical evaluation concludes that the favourable supply of lower organisms and stable clay‐rich depositional environment in the E3d3 interval of the Dongying Formation are potential explanations for the formation of lacustrine source rocks with high organic matter abundance, intermediate thermal evolution and excellent hydrocarbon generation potential, providing a good foundation for the exploration and development prospects of hydrocarbons.

show abstract

Section: Geological Settingmentioning

confidence: 99%

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

Li,

Liu,

Chen

et al. 2024

Geological Journal

View full text Add to dashboard Cite

show abstract

“…The Dongying Sag is a subtectonic unit within the Jiyang Depression of the Bohai Bay Basin and is one of the most productive oil- and gas-producing areas in eastern China. − The sag is rich in hydrocarbon resources and has a full range of reservoir types, but the extent of hydrocarbon discovery within the depression varies widely in space. After about 60 years of oil and gas exploration and development, dozens of oil fields have been built in the Dongying Sag, with a cumulative proven oil geological reserve of over 2.5 billion tonnes. , Oil found in the Archean, Paleozoic, Mesozoic, and Cenozoic reservoirs exhibits great variation in physical properties such as crude oil density, viscosity, wax content, freezing point, etc. , In the past, a lot of work has been carried out on the formation and accumulation of oil and gas in the Dongying Sag, and the development characteristics of source rocks, , the types and sources of oil and gas, , and the migration and accumulation process of oil and gas have been fully recognized and determined. − However, the physical properties of crude oils, especially the freezing point characteristics of crude oils, the spatial distribution characteristics of crude oils with different freezing points, and the geological reasons for the formation of such characteristics, have not been thoroughly analyzed.…”

Section: Introductionmentioning

confidence: 99%

“…The Dongying Sag is a subtectonic unit within the Jiyang Depression of the Bohai Bay Basin and is one of the most productive oil- and gas-producing areas in eastern China. 18 − 20 The sag is rich in hydrocarbon resources and has a full range of reservoir types, but the extent of hydrocarbon discovery within the depression varies widely in space. After about 60 years of oil and gas exploration and development, dozens of oil fields have been built in the Dongying Sag, with a cumulative proven oil geological reserve of over 2.5 billion tonnes.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Spatial Distribution Characteristics of Crude Oils with Different Freezing Points and the Genetic Mechanism of High-Freezing-Point Crude Oils in the Dongying Sag

Niu,

Wang,

et al. 2023

ACS Omega

View full text Add to dashboard Cite

The freezing point of crude oils is an important factor affecting the process of exploration, development, and transportation of crude oils. In the Dongying Sag, the freezing point of crude oils varies greatly in space, and high-freezing-point crude oils have been found in many structural belts. The freezing point of crude oils in the Dongying Sag is generally high, ranging from −40 to 80 °C. The distribution of high-freezing-point crude oils in the Dongying Sag is scattered, and they have been found at different depths, layers, and structural belts, with relatively more occurrences in specific areas. Based on the relationship between the wax content and the resin + asphaltene content, the high-freezing-point crude oils in the Dongying Sag can be classified into three types (type A, type B, and type C). Type A, type B, and type C high-freezing-point crude oils are mainly found in the gentle slope zone, depression zone, and uplift zone, respectively. The contents of wax and resins + asphaltenes in crude oils are the key factors controlling the freezing point of crude oils in the Dongying Sag. Oil source correlation using biomarkers and n -alkane carbon isotopes demonstrates that different types of high-freezing-point crude oils are generated from different source rocks, indicating that the source of crude oils is not the only factor controlling the freezing point of crude oils. The hydrocarbon-generating parent material of hydrocarbon source rocks developed in different depositional environments of the Dongying Sag is generally characterized by the dominance of bacteria and algae and is supplemented by terrestrial higher plants. This lays the material foundation for the formation of waxes during the maturation of hydrocarbon source rocks. The change of temperature and pressure conditions during the process of oil expulsion from source rocks and migration in the carrier bed will lead to phase fractionation and composition changes of oils, thus forming type A freezing point crude oils in the slope zone and type B freezing point oils in the depression zone. The increase in resin and asphaltene content caused by biodegradation and water washing in shallower buried oil reservoirs is the reason for the formation of type C high-freezing-point crude oils. The research results indicate that the organic matter composition and hydrocarbon alteration during migration and accumulation jointly control the formation of high-freezing-point crude oils in lacustrine basins. The extensive input of terrestrial organic matter into the source rocks of the lacustrine basin laid the foundation for the formation of high-freezing-point crude oils, and the migration fractionation and biodegradation of the crude oils further promoted the formation of high-freezing-point crude oils.

show abstract

Study on seismic characterization and distribution characteristics of effective reservoirs of granite weathering crust in Dongying Sag, Bohai Bay Basin

Zhu,

Liu,

Liu

et al. 2024

J Petrol Explor Prod Technol

Self Cite

View full text Add to dashboard Cite

To solve the problem of low resolution of seismic data from granite weathering crust and difficulty in predicting effective reservoir distribution. Based on the research idea of combining geology and seismology, seismic facies characteristics and effective reservoir distribution of granite weathering crust are studied by means of frequency division reconstruction processing, seismic facies analysis and sensitive attributes interpretation. This method consists of the following four main processes: (1) Using improved Morlet wavelet function for frequency division and reconstruction processing of seismic data; (2) From the perspective of geological evolution, analyzing the geological origin of seismic facies; (3) Based on the results of well- seismic combination, clarifying the types of effective reservoirs and predicting their distribution; (4) Comprehensive research indicating favorable reservoirs distribution. The results indicate that (1) a considerably improved resolution of seismic data processed by frequency division reconstruction is obtained based on the improved Morlet wavelet function. Thus, granite reservoirs then have clearer internal reflection characteristics. (2) Affected by differences in weathering, the seismic facies in granite weathering crusts can be classified as follows: Strong-amplitude facies with amplitudes of 23,700 − 32,800, corresponding to eluvium, represents the late stage of weathering crust evolution with high-intensity weathering. Medium-amplitude facies with amplitudes of 5,250 − 24,000, corresponding to dissolution layer, represents a middle stage of weathering crust evolution with moderate weathering. And weak-amplitude-blank facies with amplitudes of 0–5,330, corresponding to disintegration layer, represents an early stage of weathering crust evolution with weak weathering. (3) Effective reservoirs can be classified according to well-seismic calibrations and combined with reservoir spaces, porosities and permeabilities, and the logging and oil-bearing characteristics of the reservoirs. Type I effective reservoir comprises medium-amplitude facies, with favorable reservoir conditions and high-yield oil-bearing properties; this type is distributed in the western slopes, with an elevation of 1,300-2,500 m. Type II effective reservoir comprises strong-amplitude facies, with poor oil-bearing properties; this type is mainly distributed in the southeast and north slopes of the study area, with a relatively limited range, and the elevation is mostly below 1,500 m. Type III effective reservoir comprises weak-amplitude-blank facies, with poor reservoir conditions and poor oil-bearing properties; this type is widely distributed at various elevations. (4) The areas where medium-amplitude facies have developed are the most favorable reservoir exploration zones for granite in Dongying Sag, Bohai Bay Basin.

show abstract

Alteration-destruction-preservation of bedrock weathering crusts and the influence on reservoir distribution in Dongying Sag, Bohai Bay basin

Cited by 5 publications

References 7 publications

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

Investigation on the thermal maturity, organic matter sources and depositional environment of lacustrine source rocks in the Dongying Formation of the Bozhong Sag, Bohai Bay Basin, China

Analysis of the Spatial Distribution Characteristics of Crude Oils with Different Freezing Points and the Genetic Mechanism of High-Freezing-Point Crude Oils in the Dongying Sag

Study on seismic characterization and distribution characteristics of effective reservoirs of granite weathering crust in Dongying Sag, Bohai Bay Basin

Contact Info

Product

Resources

About