Effects Of Tectonism On The Development And Distribution Of Carbonate Reservoirs

By identifying, dividing and evaluation the Ordovician reservoir of Maigaiti slope in Yubei3D research area, rules for the development and distribution of reservors are found out. We try to rebuild the karst palaeo-geomorghology systematically and research its tectonic evolution deeply. Prospecting area is forecasted based on the analysis in the relationship between the tectonism and the distribution of the fracture-cavity reservoir of the carbonate rocks.The multiple-epoch structural movements results in the tectonic pattern of Yuber3D research area with alternating uplifts and depressions, segmentation in E-W (east to west) direction, and complicated stratigraphic distribution. Matrix pores, fractures and dissolved pores are the reservoir space. Among them, the dissolved pores may serve as the main reservoir space. The fractures greatly improve the reservoir permeability. The fractures and pores are filled heavily by muddy sediments, organic matter, calcite and siliceous minerals, which cause the permeability becoming worse. The reservoir types can be classified into three types accoding to the features of cave and fissures:fractured, fracture-porous-hole and cave reservoirs. Vertical stratification and planar strips are the characteristics of the reservoir distribution in this place.The karst palaeogeomorphology of Ordovician is three uplifts with low lyings alternating, which tends to low in the West and high in the East. Hetian paleo-uplift, tectonic rupture and karstification affects the development and distribution of the fracture hole reservoirs in the Ordovician carbonate are greatly influenced by Hetian paleo-uplift, tectonic and karstification. In the middle of Caledonian karst, the area is uplifted by the effect of the S-N trending compressive TSF in Bachu and Maigaiti area, so that it is developed into karstification. In the middle and late Caledonian karst, the Lianglitake formation is eroded completely due to the uplift. The bare surface in Yingshan formation promotes the karst developing. In the early Hercynian karst, with the influence of the geo-stress, the area is formed the NE large-scale reverse faults and the fault-uprising belt is uplifted. The Upper Ordovician is highly eroded. The Yingshan formation suffers secondary dissolution and transformation by the atmospheric precipitation which flows along the fractures and reticular cracks. The fractures and karstification promote each other. The tectonic movement contributes the fracture system development, which providing channel for karst reservoir and controlling the direction of deep hydrothermal fluid. So the karst reservoir develops along the fault zone. The fault developed palaeokarst upland and slope area are favorable to the development of karst.