东营凹陷古近系泥页岩中存在可供开采的油气资源

Feasibility Analysis of Existing Recoverable Oil and Gas Resource in the Palaeogene Shale of Dongying Depression

利用地球化学、岩石矿物、测井及录井等资料系统研究东营凹陷古近系沙河街组泥页岩,认为东营凹陷古近系沙三下亚段—沙四上亚段泥页岩厚度大,有机质丰度高、类型好、成熟度分布范围广,与北美地区已发现页岩气系统地质地球化学参数具有一定的可比性,具备形成页岩气的物质基础:东营凹陷沙三下亚段和沙四上亚段泥页岩全岩矿物组成具有较高石英和碳酸盐含量,粘土矿物含量低于50%,具有一定的脆性特征,且普遍发育微裂隙,有利于页岩油气的开采;东营凹陷古近系湖相泥页岩气测资料的调查发现,钻至沙三下亚段、沙四上亚段2套泥页岩发育段的探井气测显示均表现为高异常,钻井过程中频繁发生井涌和井漏现象,预示着气体的存在;2套泥页岩罐顶气轻烃(C1—C4)丰度随埋深增加而增加,在3 400m以深重烃/轻烃值较低,一般低于0.15,结合对2套泥页岩气油比的研究认为,东营凹陷针对泥页岩的勘探应采取油气兼探的方针。3 400m以浅以勘探泥页岩油藏为主,页岩气的勘探应在3 400m以深。研究表明,东营凹陷古近系泥页岩中存在可供开采的油气资源,是一个值得关注并投入风险勘探的新领域。

The exploration practice in the North America suggests that shale gas as an unconventional natural gas resource,is a kind of current alternative energy resource. According to measured data of geochemis try,mineral, logging, drilling and seismogram on the Palaeogene strata in the Dongying depression, the shale in the lower Esa and upper Es4 is characterized by large thickness,high abundance of organic matter, favorable types and wide range of thermal maturity. It has similar geological and geochemical characteristic comparing with the gas-generated shale in the North America. The shale in this area has high content of quartz and carbonate as well as less than 50% clay content. In addition, the shale has the brittleness and generally developed microfractures, which are useful to exploration of shale gas. The gas logging analysis on the shale of lower Es3 and upper Es4 shows the abnormal phenomena. The well kick and leak occurred frequently during well servicing, indicating the existece of gas. The light hydrocarbon abundance in the two setting of head space gases increase with depth,with C_5-7/C_1-4 value less than 0.15 while the depth is more than 3 400m. According to correlation of light hydrocarbon composition of head space gases and gastooil ratio as well as buried depth, the exploration of the shale gas reservoir in the Dongying depression should be oil and gas concurrent exploration,when the buried depth is less than 3 400m,in contract that the exploration should give priority to shale gas reservoir if it is more than 3 400 meters. Therefore,we proposes that it should be a remarkable notable and risk invest in new exploitation field since the Paleogene shale in the Dongying depression exists great recoverable oil and gas resource.