从滨里海盆地上古生界油气探讨中国海相碳酸盐岩油气勘探的科学思路

中国海相碳酸盐岩油气勘探“久攻不克”,其中碳酸盐岩有机质丰度和油气运移是两大难题。滨里海盆地上古生界油气储量的地质成藏条件分析提供了一种碳酸盐岩油气成藏模式,即碳酸盐岩油气生成与地幔流体以及与中地壳的低速、高导层有关。原油、沥青、干酪根的 Pb、Sr、Nd 同位素组成、碳酸盐岩矿物与含水矿物的高温、高压实验、热液条件下 HCO_3~-与 H_2的实验均证实了上述认识,油气可以通过无机反应生成。根据这一油气生成模式,应该重新审视中国油气勘探的方针。近期可在西部三大克拉通盆地(塔里木盆地、四川盆地、鄂尔多斯盆地)及南方海相碳酸盐岩地区以“碳酸盐岩—生物礁(白云岩化)—膏盐”的岩性结构为模式有望找到大型、超大型油气田,关键是对生物礁的勘探及识别技术的突破、白云岩孔洞、裂缝储层的识别、预测及膏盐层钻井技术的改进。

Petroleum Origin of Upper Paleozoic Marine Rocks in Pre-Caspian Basin: Enlighten on the Petroleum Prospect of Marine Carbonate Rocks in China

Why has not petroleum exploration for marine carbonate rocks made a great breakthrough in China till now?Causes are aspects.Two problems among them, at least,are the organic matter contents in carbonate rocks and the hydrocarbon migra- tion that are not favorable to petroleum accumulation.A new model of hydrocarbon accumulation in carbonate rocks is sug- gested by a review of the giant petroleum reserves and the ge- ological accumulation conditions of Upper Paleozoic marine rocks in Pre-Caspian Basin.The model indicates that hydrocar- bon generation in carbonate rocks is relative with the mantle fluids and the low-velocity and high-conduction layers in the middle crust.All the facts that deal with Pb,Sr and Nd iso- topic compositions in crude oils,bitumen and kerogen;the high temperature-pressure simulation experiment of carbonate min- erals and water-bearing minerals;and the hydrocarbon genera- tion experiment of HCO_3~- and H_2 under hydrothermal condition support the new model,that is,hydrocarbon can be generated by inorganic synthesis reaction.It is deemed that according to this model “Carbonate rocks-Reef(dolomitization)-Gypsum/ salt”,a new exploration strategy should be put forward and some giant and super-giant oil and gas fields may be discov- ered in the craton basins, such as Tarim Basin,Ordos Basin and Sichuan Basin,in western China and the marine carbonate Strata in southern China.The keys is to make great efforts in the exploration and recognition for reefs;the recognition of dolomite reservoirs;and the improvement of drilling technology in gypsum-salt strata.