Effects of Carrier Bed and Reservoir Heterogeneity on Hydrocarbon Migration, Charging, and Accumulation, Hadexun Oilfield, Tarim Basin, China
Reservoirs and carrier beds in a petroleum system are commonly heterogeneous. The heterogeneity significantly controls hydrocarbon migration and accumulation. This study applied a hydrocarbon migration model based on the invasion percolation theory to simulate the formation of hydrocarbon migration pathways in heterogeneous carrier beds. The characterization of reservoir heterogeneity differs from traditional methods that utilize mainly statistical data. Our study focuses on the oil-bearing reservoirs in Donghe Sandstone in Hadexun Oilfield in northern Tarim Basin, China. Donghe Sandstone is a quartz sandstone deposited in an open marine shoreface-shelf environment during a major transgression in early Carboniferous. Sedimentary and petrographic studies delineated continuous low-permeability layers that occur as networks within the reservoirs. Such low-permeability layers had formed through diagenetic processes within reservoir rocks at variable scales and are controlled by primary depositional structures and fabrics. Major diagenetic products are abundant tabular concretions along bedding planes and cross laminae. The concretions have a low permeability and serve as fluid flow barriers, which compartmentalize the Donghe Sandstone reservoir. The simulation results using the geologically-established reservoir model indicate that hydrocarbon migration pathways and accumulations in such carrier beds and reservoirs differ greatly from those predicted by conventional models. The simulation demonstrates the forming mechanisms of substantial tilting of oil-water contact in the reservoirs. The presence of network-like flow barriers in the heterogeneous reservoirs is the main cause for the apparently irregular and tilted oil-water contacts and variable saturation of oil in the reservoirs in Hadexun Oilfield and neighboring regions.
AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017