With the continuous development of oil and gas exploration towards complex, low permeability
and unconventional reservoirs, technologies such as vertical well staged fracturing and
horizontal well multi-stage fracturing are more and more widely used. At present, shale
reservoirs are generally developed by volume fracturing technology, in which identifying
fracture type and scale is an international problem that needs to be solved in-field. At
present, the fracturing effect evaluation is mainly divided into three categories, which can
not evaluate the fracturing effect well:
(1) Physical monitoring means: micro seismic, potential monitoring method and wide area
electromagnetic method are used to realize fracture identification, but this method has high
cost, difficult construction, low accuracy, and can not obtain parameters such as
permeability and formation pressure.
(2) Post fracturing pressure recovery test: it is not easy to obtain accurate formation
parameters and original formation pressure in the pressure recovery test of shale reservoir,
and the fracture half-length parameter obtained is an average value of multiple fractures,
so the description of fracturing effect is not detailed enough.
(3) Post fracturing data analysis: the ground pressure and flow in the production data
fluctuate greatly, and the wellbore multiphase pipe flow makes the pressure conversion have
a large error, and it can be implemented for a long time after fracturing, which also makes
it difficult for the flowback data analysis method to obtain accurate formation parameters.
In order to better improve the effect of reservoir exploration and development and evaluate
and analyze the fracturing effect, it is urgent to put forward a real-time, accurate and
low-cost fracture identification method on site.