Abstract:

Micro-pore connectivity affects the seepage and production of shale gas, but there are less research on shale connectivity currently. Taking the Wufeng-Longmaxi formation shale gas reservoir in Pengshui area as an example, the connected pore assemblages of shale gas reservoirs were classified, and then the pore-throat connections of different types of shales were discussed based on a variety of experimental methods. Four types of connected pore assemblages were classified in shale, that is, organic pore interconnection, organic pore-micro-fracture interconnection, organic pore-clay pore interconnection, and clay pore-intergranular pore interconnection. Organic-rich shale, mainly composed of interconnected organic pore assemblages, conforms to the short-conduit pore-throat assemblage model with the minimum pore-throat ratio. While medium-low organic shale, mainly composed of interconnected organic pore-clay pore assemblages, is a composite model of short-conduit and tree-shaped pore with the relatively large pore-throat ratio. When the ratio of TOC/clay mineral content decreases, the tree-shaped pore-throat ratio increases and the pore-throat ratio decreases. The combination of small pore throat ratio and high content organic pore interconnection is conducive to reducing water lock damage caused by fracturing fluid retention.

Key words: shale reservoirs, pore assemblages, pore-throat connectivity, pore-throat structure, Pengshui area