Exploration approach and techniques for the Neogene lithologic reservoirs in the southwestern Huizhou Sag, Pearl River Mouth Basin

The exploration of lithologic reservoirs is one of the difficult fields in the Pearl River Mouth Basin. The key problems are how to accurately identify exploration zones and effectively implement lithologic traps. Throughout successive rounds of researches about geology and geophysics of the lithologic reservoirs in this field, an exploration approach double controlled by "source" and "facies" was formed, which effectively guided the exploratory zones' selection of lithologic reservoir. It has been proved by drilling that the Huizhou 26 subsag in the southwestern Huizhou district is rich in hydrocarbon. Next to the Huizhou 26 subsag, the Huizhou 21 structure and the Huixi low uplift, which are relatively higher, are favorable for oil and gas enrichment when connected with source rocks through fractures. During the Neogene sedimentary period in this area, shelf sand ridge and sand sheet isolated from delta system were the major sedimentary features in the Huizhou 21 structure, while the Huixi low uplift was featured by channel and mouth bar sand within delta front. These two kinds of sands pinched out laterally easily, which were both favorable for the formation of lithologic traps. Some key technologies, including high-resolution sequence stratigraphy analysis under rare wells, seismic attribute slice analysis under sedimentary model and recons-titution of isochronic genetic sand bodies, contributed a lot to the depiction of the pinchout boundaries of these target sands, which substantially implemented the lithologic traps in this area. With this exploration approach and these key technologies, the Neogene lithologic reservoir exploration achieved good results in the Huizhou 21 structure and the Huixi low uplift in the southwest Huizhou Sag.