Abstract
China’s Paleozoic deep carbonate effective reservoirs, mainly non-porous reservoirs, are generally formed under the interaction of late diagenesis, hydrothermal fluids, and structural fractures. Faults and their deformation mechanism and internal structure of fault zones play an important role in the formation of carbonate reservoirs and hydrocarbon accumulation. Based on the detailed analysis of outcrop data in Xike’er area, Tarim Basin, this paper systematically studies the deformation mechanism and internal structure of reverse fault in the carbonate rock, and discusses the reservoir characteristics, control factors and development rules. The study shows that the deformation mechanism of the fault in carbonate rocks is faulting and fracturing, and the dual structure of fault core and damage zone is developed. The fault core is mainly composed of fault breccia, fault gouge and calcite zone, and a large number of fractures are formed in the damage zone, which are cemented by calcite locally. The mineral composition and rare earth element tests show that the fault core has the dual effect of hydrothermal fluids and atmospheric fresh water, which is easy to be cemented by calcite; while the damage zone is dominated by atmospheric fresh water, which is a favorable zone for the development of fracture-vuggy reservoirs. Therefore, the damage zone is the “sweet spot” area of carbonate oil and gas enrichment, and generally shows strip distribution along the fault.
Highlights
Carbonate reservoir is an important part of global oil and gas
This paper mainly studies the structural characteristics and genetic mechanism of reverse fault in the carbonate rock
The practice of oil and gas exploration shows that the reservoir properties of matrix of Ordovician carbonate rocks in the Tarim Basin are low, and the porosity is generally less than 5%
Summary
Carbonate reservoir is an important part of global oil and gas. Its conventional oil and gas reserves account for about 60% of the world’s total reserves, and its production accounts for about 50%. Taking the field reverse fault in Xike’er area of Tarim Basin as the anatomical object, the internal structural characteristics and formation mechanism of reverse fault are discussed through the Analysis of internal structure characteristics and geochemical tests of macro to micro fault zone, and the reservoir control mode of reverse fault is clarified, which has important practical significance for improving the success rate of carbonate oil and gas exploration. The study area is located in the Akesu-Keping area of the Tarim Basin, and comprises the Bachu Uplift in the west (Figure 1A) It is composed of a series of marine carbonate rocks formed in open platform margin and evaporative lagoonal to restricted platform margin during the Cambrian- Lower Ordovician Periods. The testing accuracy of trace elements with the content of ppm-ppb level is high, the error is less than 5%
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