鄂尔多斯盆地天然气勘探新领域、新类型及资源潜力

New fields,new types and resource potentials of natural gas exploration in Ordos Basin

鄂尔多斯盆地蕴藏多种类型天然气资源。随着勘探领域由常规到非常规、浅层到深层深入,鄂尔多斯盆地逐渐展现出一批新领域、新类型天然气藏。基于近年来的勘探成果,梳理出深部煤层气、太原组灰岩气和铝土岩气、奥陶系盐下气、海相页岩气和深层元古界气等新类型气藏,并从沉积构造背景、源-储配置、封盖保存条件等方面进行了深入分析。通过分析其生-储-盖配置关系,总结不同类型天然气的成藏特征与差异,认为这些气藏整体上具有近源成藏、自生自储的成藏模式。在落实气藏富集特征的基础上,评价了各领域天然气藏的有利勘探区,明确了其资源潜力和储量规模。深部煤层气的有利含气区面积为6.9×10^(4)km^(2),资源量预计为13.80×10^(12)m^(3),预计可落实万亿立方米储量规模;太原组灰岩气藏的有利含气区面积为1.5×10^(4)km^(2),初步估算资源量为1.6×10^(12)m^(3),储量规模达5000×10^(8)m^(3);太原组铝土岩气藏的勘探面积为7000 km^(2),天然气资源量超过5000×10^(8)m^(3);奥陶系盐下马家沟组四段天然气的有利勘探面积为2.5×10^(4)km^(2),预计储量规模超过7000×10^(8)m^(3);乌拉力克组海相页岩的有利含气区面积为9000 km^(2),天然气资源量预计为1×10^(12)m^(3),并落实了含气富集区2个;深层元古界优选出2个天然气有利区,勘探面积为5.71×10^(4)km^(2)。鄂尔多斯盆地天然气资源仍具有较大的勘探潜力。

Ordos Basin is rich in various types of natural gas resources.With the deep exploration from conventional to unconventional hydrocarbons and from shallow to deep strata,a set of natural gas reservoirs of new fields and new types are discovered in Ordos Basin.Based on exploration achievements in recent years,the paper summarizes the new types of gas reservoirs,including deep coalbed methane,Taiyuan Formation limestone gas and bauxite gas,Ordovician presalt gas,marine shale gas,and deep Proterozoic gas,and further performs an in-depth analysis from the perspectives of sedimentary-tectonic background,source-reservoir configuration,and sealing-preservation condition.By analyzing the deployment relationship of source-reservoir-cap assemblage and summarizing the differences of accumulation characteristics and various natural gas,it is believed that these gas reservoirs generally have the accumulation model of near-source,self-generation and self-reservoiring.Based on determining the enrichment characteristics of gas reservoirs,the paper evaluates the favorable exploration areas for natural gas reservoirs in various fields and clarifies their resource potentials and reserve scales.The favorable gas-bearing area of deep coal bed methane is 6.9×10^(4)km^(2);the resources are estimated to be 13.80×10^(12)m^(3),expected to achieve a reserve of trillions of cubic meters.The favorable gas bearing area of Taiyuan Formation limestone gas reservoir is 1.5×10^(4)km^(2),with preliminary estimated resources of 1.6×10^(12)m^(3),and a reserve scale of 5000×10^(8)m^(3).The exploration area of Taiyuan Formation bauxite is 7000 km^(2),with natural gas resources exceeding 5000×10^(8)m^(3).The favorable exploration area for presalt natural gas in the Member 4 of Ordovician Majiagou Formation is 2.5×10^(4)km^(2),with an estimated reserve exceeding 7000×10^(8)m^(3).The favorable gas-bearing area of Wulalik Formation marine shale is 9000 km^(2);the natural gas resources are estimated to be 1×10^(12)m^(3),and two gas abundance zones have been identified.Two favorable areas of natural gas in the deep Proterozoic are optimized,with an exploration area of 5.71×10^(4)km^(2).The natural gas resources in Ordos Basin still have large exploration potential.