Study On The Genesis Of The Archean Bedrock Reservoir In Dongying Depression

This Paper studies reservoir characteristics including types of reservoir rock, reservoir space, physical properties and pore structure of the buried hill of Archaeozoic in Dongying Depression, both quantitatively and qualitatively. Then it carries out reaches on mechanism of reservoir space formation, to find out relationships between reservoir characteristics and lithology, magmatic intrusion, migmatization, structure activity and physical weathering. Also it divides formation periods of reservoir space and compares main reasons effecting formation and distribution of the buried hill reservoir.Firstly, fissure-hole reservoir and crack-pore reservoir are main types of reservoir in the study area, based on which four classes of reservoir are divided. For the Class I reservoir, porosity is higher than10%and permeability is higher than1010-3μm2. In this area, granitoid and diorite account for60.1%and16.2%of reservoir rock, while all types of cracks, especially the high angle structure cracks with width from0.5mm to2mm and crack space smaller than2cm, form the reservoir spaces which have been filled with fillings such as calcite and crude oil. With porosity and permeability being lower than10%and1010"3(xm2separately, the researched reservoir is layer of low porosity and permeability in general.Secondly, magmatism, tectonism and weathering are main causes of reservoir formation in this area. The Archean crystalline basement, formed2.5billion years ago, had suffered a magmatic intrusion450million years ago, thus framing a granitoid basement of the Archean bedrock reservoirs in Dongying Depression. And in the north hurried hills of Dongying Depression, a few nearly east-west faults that being active since the Mesozoic to quaternary provide high reservoir space for hydrocarbon accumulation and migration. What’s more, weathering caused types of cracks and pores at the top of the Archean reservoir.Besides, the Archean rocks in the study area experienced a long geological evolution. Had been invaded and included by new Archean middle-late magma, palosome suffered more than other2magma intrusion and modified by regional metamorphism, tectonic crushing, weathering leaching, water dissolution, leaving a great amount of cracks as secondary reservoir space.Finally, according to the research of the formation mechanism and main control factors, the evolution of the reservoir model is summarized based on the fundamental factors like lithology, major controlling factor like structure, and broken and physical weathering, atmospheric fresh water leaching, deep dissolution as the secondary controlling factors.