Palaeogeomorphology Characteristics Of The Central Uplift Zone In Neritic Area Of Liaohe And Its Control To The Sandbodies On The Both Sides

This paper is instructed by the sequence stratigraphy, sedimentology, petroleum geology, in the way of comprehensively utilizing datum from the seismology, geology and drilling. I have carried out the sequence stratigraphy research with the main line of palaeogeomorphology in the central of Liaohe shallow sea region, with the conclusion that the palaeogeomorphology controlled the source pattern, stratigraphy structure, sedimentary system and sandbody distribution.On the basis of the research on the seismology, drilling logs and palaeontological datum, I have established the sequence-stratigraphic framework on Paleogene of Liaohe shallow sea region. I have divided the Paleogene into 4 second-order sequence, 11 third-order sequence, and analyse the features of the sequence. The centre of sedimentation in shallow sea region has developed in the eastern region during the long term, who has a strong inheritance and the sequence thickness changes of which are controlled by the depression structure. The central uplift zone are totally exposed during the in the sand three times with a total exposed during the E₂s³ period, who didn’t undertake sedimentation. During the early period from E₃S¹⁺² to E₃d², the exposed area contract to the south, while the north part undertook sedimentation. Then, E₃d² generally undertook sedimentation.In the way of bedding flattening of the palaeogeomorphology, I have restored the pre-sedimentary palaeogeomorphology of E₂s³, E₃s¹⁺² to E₃d³ from the central uplift zone in Liaohe shallow sea, and have analysed the features of palaegeomorphology and source. The studied area located in the transition zone of land and sea, who has a long-term NE source supply. Meanwhile, the central uplift zone provided a short-axis source supply, and formed a multi-period and multi-sendimentary-source-region providing sources to the region.In the way of identifying the palae-uplift, palae-slope, palae-vally, and so on, I have analysed the sand-controlling mechanisms, and come to conclude that the palaegeomorphology has a controlling effect on the source pattern, sequence structure, sedimentation system and sand distrubutuion. Overall, the "uplift" is a source area, and the "slope and valley" provide the channels and accumulation sites for the sediments transport. "Uplift - valley - slope - sequence boundary", the four of which are the key to develop the sand bodies if they have an effective configuration. The distribution of sand bodies are controlled by the fault slope in plane and by the system tract in vertical distribution. Sand bodies of lowstand system tract （LST） present aggradational superposition pattern, sand bodies of transgressive system tract（TST） present retrogradational superposition pattern, sand bodies of highstand system tract（HST） present progradational but the sand strata is thin, and the whole is based on the principle of lowstand sand bodies .By the analysis of oil-gas distribution and controlling factors of oil-gas reservoirs, the favorable zone evaluation has been carried out. The oil-gas reservoirs from central part of shallow sea have the features of widely distributed in plane and more oil-bearing in vertical section. Hainan-Yuedong draping structure are the main place of oil-gas, who has a more younger oil-gas strata and a shallow burial depth. Predominant regional tectonic location, abundant oil source conditions, multiform trap types and long-term successive developed oil-resource faults, all of which have controlled the regional oil-gas enrichment. Hainan-Yuedong draping structure belt, Eastern Hainan overlap structure belt and Xianghe-Yueya fault-nose structure belt, all of the three sub-tectonic zone have the extremely favorable petroleum geological setting.