Patent ID: 11927094
Assignee: SOUTHWEST PETROLEUM UNIVERSITY
Field: Measurement (Instruments)
Classification: CPC E  G | IPC E  G

Claim 2:
3. The comprehensive geological-engineering classification evaluation method for low-permeability reservoirs, as recited in claim 2, wherein the pore structure index is calculated by a formula (2):

PIS=1.075×(AC+CNL)/DEN−0.45×VSH−27.745  (2)

wherein in formula (2), PIS is the pore structure index, AC is the acoustic time, VSH is the shale content, CNL is neutrons, and DEN is density;
the formation pore pressure is calculated by a formula (3);

PP=σV−σe  (3)

σe=0.00556DEPTH+0.09717AC+11.2367 ln(GR)−64.7978  (4)

wherein AC is the acoustic time, GR is natural gamma, σv is a pressure of an overlying strata, σe is an effective stress.