Sedimentary facies of Paleogene lacustrine dolomicrite and implications for petroleum reservoirs in the southern Qianjiang Depression, China
| Autor: | Jianghui Meng, Xiaoqiang Ma, Junjun Shen, Xiaosong Qiu, Kongquan Chen, Yang Liu, Fangfang Chen |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
dolomite reservoir
QE1-996.5 self-sourced reservoir favorable depositional facies qianjiang depression 020209 energy Geochemistry Geology 02 engineering and technology Environmental Science (miscellaneous) sedimentary facies 010502 geochemistry & geophysics 01 natural sciences chemistry.chemical_compound chemistry Depression (economics) Facies 0202 electrical engineering electronic engineering information engineering General Earth and Planetary Sciences Petroleum China Paleogene 0105 earth and related environmental sciences |
| Zdroj: | Open Geosciences, Vol 11, Iss 1, Pp 513-532 (2019) |
| ISSN: | 2391-5447 |
| Popis: | Paleogene lacustrine dolomicrite of Unit II of the lower Xingouzui Formation in the southern part of the Qianjiang Depression, China forms “tight carbonate” hydrocarbon reservoirs that can be divided into the following four dolomicrite types: dolomicrite, muddy dolomicrite, sandy dolomicrite, and gypsiferous dolomicrite. These four dolomicrite types occur in the following three distinct combinations, which are referred to as subfacies: (1) interbedded dolomicrite (or sandy dolomicrite) and dark-gray siliciclastic mudstone, interpreted as open lacustrine deposits, (2) grayish-dark siliciclastic mudstone with thinly-bedded muddy dolomicrite or gypsiferous dolomicrite, interpreted as restricted lacustrine deposits, and (3) grayish-green mudstone with thinlybedded brown-yellow siltstone, interpreted as lacustrine shoreline deposits. The spatial distribution of these subfacies was controlled by the paleo-provenance system, paleo-microgeomorphology, and lake level fluctuations. In the open lacustrine subfacies, dolomicrite or sandy dolomicrite are often vertically interbedded with dark argillite rocks, forming a suitable petroleum source rockreservoir association. The dolomicrite and sandy dolomicrite reservoirs possess many secondary crystalline pores and few dissolution pores, with mesopore porosities in the range of 15%–25%. The dark mud shale interval has total organic carbon (TOC) values exceeding 4% (averaging 1.29%). The organic matter is mainly type II2, with vitrinite reflectance values averaging 0.57, which indicates potential for the generation of immature oil. The oil-source correlation results indicated that the n-alkanes of the crude oil and source rock samples from Unit II of the lower Xingouzui Formation exhibit single peak values, with a main peak (post-peak) in C22 and a Pr/Ph ratio $#x003C; 1 in a C2920R $#x003E; C2720R $#x003E; C2820R distribution. These features indicate that source-reservoir interbedding is characteristic of selfsourced reservoirs. The interbedded dolomicrite (or sandy dolomicrite) and dark-gray siliciclastic mudstone, i.e., subfacies (1), is a favorable target for hydrocarbons in the study area. |
| Databáze: | OpenAIRE |
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