Abstract:

Fractures in lowˉpermeability reservoirs not only provide accumulation space and also act as seepage channels.However，present research on these fractures ismostly confined to qualitative descriptions.An accurate calculation of certain fracture parameters，such as openess，density，porosity and permeability，is of great imporˉtance in fracture quantitative descriptions and also a fundamental factor for the developmentofoil and gas fields.This paper documents a study that tries to construct a relationship between the ancient earth stress during the fracture form ing period and fracture parameters and that between the present earth stress and the parameters，determ ine the characters and directions of ancient earth stress through a structure analysis，and calculate the direction and strength of the present earth stress by using suchmeans as sonic velocity，hydrofrcturing，and sound em ission.The results are introduced into the fracture parameter calculatingmodel to simulate and calculate the openess，density，porosity and permeability of the fractures in the3 rd sand set of the Paleogene Fuˉ2member in the Qiaohekou oilfield.It is concluded that fractures are highly developed in the structural high near the main fault and the differences in fracture permeability reflect the differences of their directions.Core statistics and log interpretation verify the correctness of the stimulation results of the model.

Key words: Qiaohekou oilfield, earth stress, fracture porosity, fracture permeability, finite element analysis