Research On Petroleum Geological Characteristics Of The Lower Cretaceous In Eastern Heilongjiang Province

The studied area is in the east of Heilongjiang Province with the fault of Kiamusze-Yitong-Luobei-Yilan bounding as the western border. It borders on Russia across the Wusuli River on the east and the Heilongjiang River on the north. The total area is about 13 square kilometers. Regional tectonics are composed of Mesozoic and Cenozoic basin groups, the Jiamusi block and terrain of Wanda Mountain. This thesis takes main basins of east Heilongjiang Province as research objects. Studying on the characteristics of lower cretaceous petroleum geology of east Heilongjiang Province, including the characteristics of sedimentary, source rocks, reservoir and cap rocks and their assemblage.Four sedimentary facies of lower cretaceous Chengzihe formation and Muling formation of east Heilongjiang Province were identified. During the sedimentary period of Chengzihe formation and Muling formation, fan-delta facies and coastal shallow-lake facies were mainly developed. Fluvial facies and semideep lake facies were locally developed, and some subaqueous fan deposition were developed in Muling formation. The climatic environment of the sedimentary period of Chengzihe formation and Muling formation in the studied area was warm and humid, and it was processed with shallow water body and sufficient source supply. Depositional area and lake basin continued to expand with the retreat of provenance. Two depocenters of Chengzihe formation are located around No.Bo-1 well of Boli basin and No.Wang-1 well of Tangyuan area. The water body deepened during the sedimentary period of Chengzihe formation. The two depocenters are located around No.Bin-1 of Suibin area and No.ZK2 and No.ZK3 well of Boli Basin.Dark mudstones are thick and wide spread, and they are the main hydrocarbon source rock series of lower cretaceous in the studied area. Abundance of organic matter indicates that hydrocarbon source rocks quality of Chengzihe formation and Muling formation are moderate and fine, the quality of Yunshan formation in Hulin basin is poor. Types of organic matter are mainly type Ⅲ kerogen and type Ⅱ2 kerogen. Type Ⅱ1 kerogen were also developed in Boli basin. Which indicates lower cretaceous is of great gas generating potential. Maturity of organic matter of most samplings are at lower mature state or mature state. Maturity of organic matter of Boli basin is of high evolution level, and it has entered into the higher mature state or over mature state.Reservoirs of lower cretaceous Chengzihe formation and Muling formation of east Heilongjiang Province are mainly composed of fan-delta sand body, underwater fan sand body and river sand body. The main type of sandstone is lithic arkosics. It has low content of quartz and is mainly composed of plagioclase. The lithic is mainly volcanic rock lithic, and metamorphic rock lithic and sedimentary rock lithic are also developed. The fillings is mainly muddy miscellaneous. The maturity of sandstone content and sandstone structure are low. Sandstone of Chengzihe formation is of strong diagenesis, which leads to the damage of primary pore, thus, the secondary pore dominates. This situation is on the contrary to Muling formation. Sandstone porosity and permeability of Chengzihe formation and Muling formation are poor. It is mainly ultra low porosity and ultra low permeability. On the comparison analysis of physic characteristics of sandstone in every sedimentary facies, this thesis concludes that the physic characteristics of braided river channel lag deposit sand body are the best, followed by distributary channel sand body and estuary bar sand body of fan-delta facies. The physic characteristics of underwater fan sand body is the poorest. Lower cretaceous sandstone of Hulin basin is poorly developed and it can not develop fine reservoirs. Comprehensive analysis, the reservoir properties of Muling formation is better than Chengzihe formation, but they are both poor reservoir.The mudstone of shallow lake facies were developed widely of Chengzihe formation and Muling formation. The mudstone had large thickness and lateral distribution stability. They were the two main sets of regional caprock of the lower cretaceous in studied area. The regional cap layer condition of Chengzihe formation is better than Muling formation. In addition, the thin layer of volcanic rock and mudstone of fan delta can be used as the local cap in study area.There are mainly three types of the source-reservoir-cap assemblage in the studied area. The mudstone of lake at the bottm, the sandstone of fan-delta and underwater fan at the central forms the self-generated and self-reserved type. The mudstone on the top of Chengzihe formation and the sandstone at the bottom of Muling formation forms the lower-generated and upper-reserved type. The mudstone at the bottom of Muling formation and sandstone on the top of Chengzihe formation forms the upper-generated and lower-reserved type.