Carbonate fractured-vuggy reservoirs in Tahe oilfield have complex geological characteristics

which is mainly reflected in the various forms such as pore

fracture and cave developed in the reservoir

poor continuity of spatial distribution

complex combination mode

and the residual fracture-vuggy storage space formed in surface karst system by weathering. During the development

it is easy to form the bottom water coning along the high angle crack. The remaining oil between the wells outside the water channels and the “attic oil” stored by the residual fault are enriched in large quantities. In the earlier stage

the macrosco

pic mechanism of gravity displacement by using density difference in N

2

injection of seam-hole reservoir is clarified by means of physical simulation. However

the displacement mechanism of the “attic oil” and the residual oil between wells is not clear. Through the simulation experiments of the effects of the injected N

2

on the physical properties of crude oil under the conditions of 55 MPa and 130 ℃

the micro mechanism such as the effects of N

2

on dissolution

expansion

capacity increase

extraction and dissolution of crude oil under the condition of high temperature and high pressure reservoir. Based on the fractured-vuggy geological characterization

visual physical model is made to observe the displacement mechanism of gravity displacement and water coning suppression during N

2

injection. After field application

the feasibility and popularization potential of the technology are further proved.