A Combined Method for Gas-Bearing Identification on Complex Sandstone Reservoir

Langgu Depression is a matured oil and gas exploration area with complicated lithology and physical property, its greatly changeful formation fluid, low-resistivity hydrocarbon reservoirs and non-uniform logging series make it hard to identify gas reservoirs. According to sensitivity analysis of gas in this area, a new combined gas-bearing identification method is proposed based on the various well logging series. The result shows that the new gas identification chart, based on neutron gamma logging, turns out effectively eliminate the influence of physical properties and formation water salinity, works well in the identification of gas reservoirs in the old wells. And the fluid factor based on array acoustic logging is sensitive to the development of gas reservoirs, can be used for the gas reservoirs identification in the new wells with array acoustic logging. Concrete field examples show that the new combined method greatly enhances the identification ability and prediction accuracy towards gas-bearing layers.