High Resiolution Sequence Stratigraphy And Hydrocarbon Accumulation Model Of Fuyu Reservoir In Sanzhao Depression

As an important exploration field of increasing reserves and yield in northern Songliao Basin, Fuyu reservoir of Sanzhao depression has in turn launched comprehensive petroleum geology study, fine reservoir description and reservoir sandbody seismic forecasting techniques since 1960s, when industrial oilflow was drilled out, but for complicated fault property and hard forecasting of river sandbody, important breakthrough in hydrocarbon exploration has not been reached. In this paper, we followed the guidance of high-resolution sequence stratigraphy, reservoir sedimentology and reservoir dynamics theory, took Fuyu reservoir of Sanzhao depression as the subject of study, systematically launched the study of key controlling factors of reservoir forming and space-time matching relationship, as high-resolution sequence stratigraphy division and correlation, microfacies of single sand body level, fault characteristics, paleo-tectonic evolution, oil and water distribution and petroleum migration path imitation etc.High-resolution sequence stratigraphy study shows that it can identify a base level decrease-to-increase conversion surface (erodsion surface) and five base level increase-to-decrease conversion surface (flooding surface) of Fuyu reservoir in sanzhao depression; and according to sedimentary responses of sequence boundaries at all levels, to flooding as the sequence boundary surface, Fuyu reservoir can be divided into a long-term cycle,4 medium-term cycles,17 short-term cycles and 35 ultra short-term half-cycles. We established a isochronicly stratigraphic framework of single sand body level for study area, and proposed that stratigraphic framework of Fuyu reservoir is from slow water withdrawal to fast water advance, and maximum withdrawal of water is at the bottom of FI group, hydrocarbon distribution is controlled by the long and medium term cycle, and is mainly located in the reservoir sand of late fall or early rise period of medium-term cycles in early rise period of long-term cycles. Sedimentary features study of ultra-short-cycle shows that typically river-controlled shallow delta deposition was developed in Fuyu reservoir, distributary channel sandbody was the main microfacies and other microfacies was not well developed. Vertical evolution of microfacies shows at the top of Fuyu reservoir (FI1-FI3 layer) developed delta front, at the lower part (FI4-FIII4 layer) developed delta plain, and at the bottom developed (FIII5 layer) delta front microfacies. Study of heavy minerals, formation thickness and fine anatomy of dense well pattern sand of development area indicates the study area is mainly affected by northern and southwestern Baokang source, and southeastern Changchun-Huaide source is not developed. Fault characteristic studies suggest that fault T2 is controlled by basement fault, the lower crater, diagonal tension and differences in extension and so on, and concentrated into band in plane, while combined as "flower-like" in profile. Inherited move boundary fault in fault-intensive zone is the main source fault that links overlying source rocks and underlying reservoir of Fuyu reservoir during hydrocarbon accumulation.Fuyu reservoir is " graben-horst" combination model controlled by fault-intensive zone and the paleo-tectonic evolution. Within the fault-intensive zone is graben, while both sides fault-intensive zone is horst or fault terrace, so oil of syncline is mainly distributed between fault-intensive zones. Fault-intensive zone of slope area is usually "horst in upheaval" under the control of later tectonic reversal, wholly located at high structural position and is preponderant transporting passage, so oil of slope area is mainly distributed within or near fault-intensive zone.The study shows that the paleo-tectonic evolution, sandbody distribution and the fault characteristics reason matching is the key for dominate oil transportation and accumulation in Fuyu reservoir. Eventually, we set up three oil and gas accumulation model in different parts of Sanzhao Depression, and depict 52 enrichment target area, which will provide guidance for further exploration and development of Fuyu reservoir in northern Songliao basin.