Reservoir Flow
Unit Characterization of Complex Channel Sandstone Units in Baolang
Oilfield, Yanqi Basin, West China
Yao, Guangqing1,
Fengde Zhou1, Timothy R. Carr2,
Jiahao Wang1, Shangru
Sun3 (1) China University of Geosciences, Wuhan,Hubei, China (2) Kansas Geological
Survey, University of Kansas, Lawrence, KS (3) Henan oilfield company , Sinopec, Nanyang, China
Low permeability reservoirs (k≤50 md) are common in the Mesozoic continental units of western
and central China. One example, the Baolang oilfield (Jurassic) located in the Yanqi Basin, Xinjiang,
West
China,
has entered a period of rapid decrease in productivity. An incomplete model for
this complex reservoir has contributed to the rapid increase in water cut and
low estimated ultimate oil recovery. This study applied an integrated approach
to undertake a detailed recognition and division of the reservoir flow units at
Baolang field. Available data include cores, digital
well-logs, petrophysical data, and production
histories. The overall framework is a complex of heterogeneous clastic reservoir units deposited as braid-delta and distributary braid-channel sand bodies. Routine core plug
data (porosity and permeability) were used to define five types of flow units
by generating a flow zone index (FZI). Based on FZI, the petrophysical
parameters in un-cored well were calculated by well-log data, and reservoir geological
model was constructed across the field. Flow-unit types defined by the FZI have
a strong relationship with the pore texture, permeability, and are controlled
by lithofacies and diagenesis.
Reservoir production and whole core data indicate fracturing present in the
reservoirs can enhance permeability. In the defined flow units, predicted
reservoir quality has a strong relationship to water injectivity
and produced oil and water volumes at Baolang Field.
At Baolang Field, the integrated characterization
studies of sedimentary facies and transformation to
flow-unit analysis have significantly improved the oil recovery ratio, and may
be applicable to other complex clastic reservoirs.