04/02691 Some thoughts on petroleum exploration in marine sedimentary basins of China: Zhang, J. and Wang, D. Shiyou Kantan Yu Kaifa, 2003, 30, (2), 9–16.(In Chinese)

Abstract

Based on the analyses of discovered oil and gas fields generated in the marine sedimentary strata of China, the prescribed minimum amount of total organic carbon (TOC) in efficient source rocks should be at least higher than 0.5%, and the coal measures formed in littoral facies could be an important contributor to hydrocarbon generation. The efficient reservoir space within carbonate rocks should be mainly fracture, cavities, and secondary porosity. Karstification would be also a very important factor for generation and development of these types of reservoirs. In terms of the degree of porosity and permeability development (from weaker to stronger), the carbonate reservoirs can be classified as Naxi (irregular and independent reservoir), Tahe (net like transitional type), and Weiyuan Renqiu (horizon like and block like type, which are well connected reservoir). Within the net like reservoir, there are extremely uneven characters and the reservoir lacks a unified basal water and pressure system. The controlling and key factors for alteration of the marine sedimentary reservoirs are most likely tectonic cycles with multiple opening closing. The retention conditions should be a direct controlling factor for guiding explorations to find commercial oil and gas traps and reservoirs within marine deposits. On the purpose of petroleum exploration, the targets should be selected by taking into consideration the relative activities of stable landmasses and their conditions for developing and generating of source rocks and reservoirs. It is important to double check the effective marine source rocks, based on the standard that the content of total organic carbon should be 0.5% or higher. The exploration in marine strata should start from shallow secondary oil traps and major petroleum reservoirs. It should attach importance to lithologic traps and exploration of gases. The conveyance and series exploration technologies, with the goals mentioned above, must be developed in near future.