| PDF: | |
| Time: | 2020 |
| Journal: | Acta Petrolei Sinica |
| Volumn: | 41 |
| Issue: | 12 |
| Pages: | 1744-1773 |
| Type: | EI |
| Author: | Huafeng Tang,Pujun Wang,Weihua Bian,Yulong Huang,Youfeng Gao,Xiaojuan Dai |
Abstract: | Volcanic oil and gas reservoirs are widely distributed in more than 40 basins in 13 countries around the world, and are one of the important areas of hydrocarbon exploration. After nearly 20 years of accumulation, the research on volcanic reservoirs has achieved great results and become a research hotspot. The research results show that there are 11 classes including 28 types of pores in volcanic rocks, among which primary gas pores, explosive fractures and condensation shrinkage joints are unique types. The combination of primary pores and fractures and secondary pores and fractures forms high-quality reservoirs. Most of volcanic rocks in the basin are medium-low porosity and medium-low permeability reservoirs, and high-and medium-high permeability reservoirs are developed in local area. The porosity and permeability of volcanic rocks decrease with the increase of burial depth. Usually above 3 km, the porosity and permeability of (sed) volcanic pyroclastic rocks are higher than those of lavas, and the opposite is true below 3 km. Generally speaking, various lithologies can develop favorable reservoirs, but in specific blocks, only specific lithologies can develop favorable reservoirs. There are 5 lithofacies and 7 sub-lithofacies which can become favorable facies zones. The distribution mode of reservoirs is restricted by the volcanic stratigraphic unit. For example, lava flow lobe and lava dome form a pattern of \"good in upper layers and poor in lower layers\". The physical properties of lava flow reservoirs are superior to those of lava dome. The physical properties of reservoirs in the central facies zone of the volcanic edifice are better than those of the proximal facies zone, and those of the distal facies zone are the worst. Most favorable reservoirs are distributed within 200 m below the eruptive interval unconformity boundary or tectonic unconformity boundary. The volcanic reservoir in the basin is the product of comprehensive multi-diagenesis superposition, and has a complicated formation process. Especially, when the volcanic strata have undergone multiple times of uplifting and burial, the evolution process of the reservoir is more complicated. In this process, escape of volatile components, condensing shrinkage, weathering before burial, and devitrification present the unique genesis types of volcanic reservoirs. The soluble components under acidic conditions provide the material basis for alteration/dissolution. The research of the characteristics and distribution laws of volcanic reservoir has basically reached the quantitative stage, while that of reservoir forming mechanism is still in the qualitative stage. Quantitative research of reservoir modeling and pore genesis based on volcanic stratigraphic units should be the focus of the next step. |