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- Title
The characteristics and major factors controlling on the E<sup>2</sup><sub>3</sub> dolomite reservoirs in saline lacustrine basin in the Yingxi area of Qaidam Basin.
- Authors
Huang Cheng-gang; Guan Xin; Ni Xiang-long; Chang Hai-yan; Zhang Shi-ming; Yang Sen
- Abstract
In recent years,important breakthrough progress and discovery has been made in exploration of petroleum from deep reservoirs of E23 in western Qaidam Basin. Based on core observation, petrographic and structural microscopic characteristics analysis, and geochemical analysis, the characteristics and major factors controlling the development of dolomite reservoirs in the Yingxi area in Qaidam Basin are studied. Dolomicrite was the main effective reservoir rock of E23 in the Yingxi region, whose physical characteristics are “low porosity-extra low permeability”. The reservoir spaces of the dolomite are mainly intergranular pore, but including some micro-cracks.Oil and gas can be produced stably in the Yingxi Oilfield because most oil and gas are preserved in these “small size-large quantity” pores. Research results of the geochemical characteristics of reservoir show that the dolomite is penecontemporaneous metasomatic type which formed in the salty conditions. Main evidence includes: (1)micro pore structure characteristics, (2)high Ca/Mg molar ratio of no ideal components, (3)low content of “Mn” element geochemical characteristics, (4)“carbon negative-oxygen positive” isotope geochemistry and the low temperature characteristics reflected by it, (5)low degree of order structure which is caused by the rapid nucleation and crystallization unstable environment. The shrinkage intergranular pores were formed by ion exchange in the crystal lattice in the special salty environment, and its pore size is controlled by the abundance of Mg2+ at that time. Therefore, the physical property of the reservoir is indirectly controlled by the paleo salinity. These intergranular pores have a strong ability to resist compaction and they can still be preserved in the deep, ultra deep strata. The origin model of dolomite determines its wide distribution in the plane. So the research findings expanded a new exploration field about lacustrine dolomite in western Qaidam whether in the plane distribution or in depth.
- Subjects
TSAIDAM Basin (China); CHINA; DOLOMITE; PETROLEUM prospecting
- Publication
Natural Gas Geoscience, 2017, Vol 28, Issue 2, p1
- ISSN
1672-1926
- Publication type
Abstract
- DOI
10.11764/j.issn.1672-1926.2016.12.005