Log identification method in complex sand reservoirs

In order to obtain effective parameters for complex sand reservoirs, a log evaluation method for relevant reservoir parameters is established based on an analysis in the gas-bearing sandstone with high porosity and low permeability, low porosity and permeability and on various characteristics of log responses to reservoir lithologies and physical properties in the Neopleozoic sand reservoir of the Ordos basin. This log evaluation method covers the Cook method that is used to evaluate the porosity and oiliness in high porosity and low permeability reservoirs and another method in which the mineral content, derived from geochemical logs, is used to identify formation lithologies. Some areas have high calcium and low silt content, not uniformly distributed, the results of which show up in the complex formation lithologies and conventional log responses with great deviation. The reliability of the method is verified by comparison with conventional log data and core analyses. The calculation results coincide with the core analytical data and gas tests, which indicate that this log evaluation method is available, provides novel ideas for study of similar complex reservoir lithologies and has some reference value.