LOOKING FOR THE BREAKTHROUGH OF THE EXPLORATION FOR OIL AND GAS IN CHUXIONG BASIN IN TERM OF THE NEW EXPLORATION CONCEPT:ON THE EXPLORATION PROSPECTS OF DEEP BASIN GAS IN CHUXIONG BASIN

As the formation of structural traps postdated the main period of hydrocarbon generation and expulsion, the exploration targeting structural traps has been unsuccessful for a considerable time. The (deep basin gas theory and) exploration outcomes indicate that deep basin gas accumulations can form and occur in the depressionional centers or the updip slope zones in the basin. The basic geological conditions, which are required for deep basin gas to accumulate, have been found to be present in the basin. The upper Triassic coal measures are thick and highly matured. Their hydrocarbon generation intensity falls in the range of (40~60)×10~(8) m~(3)/km~(2). Tight sandstone reservoirs are widely developed and these reservoirs are continuous over most of the depressional areas. In addition to the favorable source rocks and reservoirs, seal rocks are adequate. Overstacking of the source, reservoir and seal rocks in the upper Triassic led to the formation of several source-reservoir-seal assemblages: older source rocks overlain by younger reservoirs, older reservoirs overlain by younger source rocks and locally generated hydrocarbons reservoired in the same stratigraphic interval. Additionally, hydrocarbons could migrate upwards through faults to form secondary conventional oil/gas pools in the Jurassic strata. The western and northern depressions and their slopes are the favorable exploration areas for deep basin gases. It is believed that significant breakthrough can be achieved in the natural gas exploration in the Chuxiong basin if the deep basin gas theory and a dynamic evolution philosophy are applied in our exploration approach.