CONTROLLING FACTORS AND DEPOSITIONAL MODE OF'SLOPE SEDIMENTARY ROCKS' ON THE BURIED HILL INTHE SOUTHERN JINZHOU 25-1 OILFIELD

摘要

Buried hill oil reservoir is a special type of oil reservoir, which are protruding oil-bearing bodies ofolder strata located below the regional unconformity. With the continuous progress of oil drilling, buried hill oil reservoirs with industrial exploitation valuehave attracted more and more attention. In this paper, taking the buried hill reservoir of southern Jinzhou 25-1 Oilfield as an example, we have analyzed the distribution of slope sendimentary rocks in detail, and established the deposition mode of the overlyingslope sendimentary rocks on the buried hill, using a large amount of core, drilling, logging and seismic data. The research results show that the southern Jin- zhou 25-1 area is a buried hill-cladding anticline structure. The reservoir type is massive bottom water reservoir. The overlying slope sendimentary rocks on the buried hill are mainly sandstone and mud- stone, which can be further divided into slope sedi- mentary sandstone, slope sedimentary mudstone and beach bar sandstone. Slope sedimentary sandstone and mudstone are mainly formed by accumulation on the hillside due to the weathering of the mountain top. The beach bar sandstone is mainly formed by normal deposition. The controlling factors for the formation of slope sedimentary rocks include struc-tural and sedimentary factors. A large slope is not conducive to the accumulation of slope sedimentary rocks. Only when the slope is slow, can there be slope sediments in the uplift area with higher alti- tude. The fault activity in the Bohai Bay promoted the formation of joints and intensified deep leaching, which promoted rock ruptures and weathering, thereby providing a reliable source for the formation of slope sedimentary rocks. The deposition control factor is mainly the change of the tolerance space. Finally, the deposition mode of the slope sedimen- tary rock was established. That is, weathering occurs in the bedrock at the original high place, and the rock is carried along the slope and moved to the relatively low-lying accommodating space to form slope de- posits. Slope sediments are a set of near-source de- posits, which are poorly sorted and rounded, and their composition is basically the same as that of the bedrock. During the accumulation of slope sedi- ments, there is almost no effect of water flow, and the gravity component along the slope is its main transportation power.