赤水地区官南构造须四段气藏成藏条件分析
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摘要
2003年在赤水地区官南构造钻获上三叠统须家河组须四段气藏以来,针对赤水及邻区陆相碎屑岩领域进行了大量的地质综合研究及勘探工作,但大多侧重于地震资料的重新处理及解释、区带及圈闭评价、地层沉积及储层研究。为了进一步深化对该区须四段气藏成藏的认识并指导勘探工作,在系统总结上述诸多研究成果的基础上,重点通过对烃源岩、天然气组成与碳同位素特征及储层沥青等的研究,得出以下结论:须四段储层发育于辫状河河心滩亚相,为特低孔低渗的孔隙—裂缝型储层;须家河组烃源岩具有一定的生烃能力,须四段气藏是一个以海相为主、陆相为辅的上移新储型混源气藏;须四段气藏主要受气源输导体、沉积相、裂缝发育程度及适时的圈闭条件等的控制,气藏具有"多源混合,多期充注"的油气成藏特点。最后提出建议:该区下一步的勘探必须寻找大的断裂带(未断穿侏罗系区域优质泥岩盖层并与下部海相烃源岩沟通)及裂缝发育的部位。
Since the discovery of gas pools in the fourth member of Upper Triassic Xujiahe Formation in Guannan structure of Chishui area in 2003, comprehensive geologic study and exploration have been performed on the continental clastic rocks in Chishui and the adjacent areas. However, most the researches focused on reprocessing and reinterpretation of seismic data, evaluation of plays and traps, sedimentation and reservoirs. In order to deepen understandings of gas pooling in the fourth member of Xujiahe Formation in the study area and guide exploration in the next step, studies are carried out in respects of the source rocks, composition and carbon isotopic features of the gas as well as bitumen in the reservoirs. The following conclusions are obtained. The reservoirs in the fourth member of Xujiahe Formation are developed in river island subfacies of braided river and are of extremely low porosity and low permeability pore-fracture type. The source rocks in the Xujiahe Formation have certain potential of generating hydrocarbons. The gas pool in the fourth member of Xujiahe Formation is characterized by mixed gas sources, vertical migration, and accumulation of hydrocarbons in reservoirs younger than the source rocks, and the reservoirs are dominated by marine facies, with some terrestrial facies. The gas pool in the fourth member of the Xujiahe Formation is mainly controlled by gas source carrier beds, sedimentary facies, facture development and suitable trapping conditions, and is characterized by multiple sources and multistage charging. It is finally proposed to focus on large fault zone (not cutting through the regional mudstone seals of high quality in the Jurassic but cutting through the lower marine source rocks) and areas with well-developed fractures in future exploration.
Since the discovery of gas pools in the fourth member of Upper Triassic Xujiahe Formation in Guannan structure of Chishui area in 2003, comprehensive geologic study and exploration have been performed on the continental clastic rocks in Chishui and the adjacent areas. However, most the researches focused on reprocessing and reinterpretation of seismic data, evaluation of plays and traps, sedimentation and reservoirs. In order to deepen understandings of gas pooling in the fourth member of Xujiahe Formation in the study area and guide exploration in the next step, studies are carried out in respects of the source rocks, composition and carbon isotopic features of the gas as well as bitumen in the reservoirs. The following conclusions are obtained. The reservoirs in the fourth member of Xujiahe Formation are developed in river island subfacies of braided river and are of extremely low porosity and low permeability pore-fracture type. The source rocks in the Xujiahe Formation have certain potential of generating hydrocarbons. The gas pool in the fourth member of Xujiahe Formation is characterized by mixed gas sources, vertical migration, and accumulation of hydrocarbons in reservoirs younger than the source rocks, and the reservoirs are dominated by marine facies, with some terrestrial facies. The gas pool in the fourth member of the Xujiahe Formation is mainly controlled by gas source carrier beds, sedimentary facies, facture development and suitable trapping conditions, and is characterized by multiple sources and multistage charging. It is finally proposed to focus on large fault zone (not cutting through the regional mudstone seals of high quality in the Jurassic but cutting through the lower marine source rocks) and areas with well-developed fractures in future exploration.
引文
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[2]黄世伟,张廷山,谢刚平,等.赤水地区上三叠统须家河组沉积特征[J].天然气地球科学,2004,15(5):487-491.
[3]陈晓慧,张廷山,谢刚平,等.贵州赤水地区须家河组的储集特征及发育影响因素[J].天然气地球科学,2005,16(3):293-297.
[4]黄世伟,张廷山,王顺玉,等.四川盆地赤水地区上三叠统须家河组烃源岩特征及天然气成因探讨[J].天然气地球科学,2004,15(6):590-593.
[5]黄世伟,张廷山,王顺玉,等.赤水地区上三叠统须家河组源岩特征及天然气成因[J].地球科学与环境学报,2005,27(3):19-22.
[6]戴金星.天然气同位素特征和各类天然气鉴别[J].天然气地球科学,1993,4(2/3):1-40.
[7]王兰生,苟学敏,刘国瑜,等.四川盆地天然气的有机地球化学特征及其成因[J].沉积学报,1997,15(2):49-53.
[8]程付启,金强.四川盆地混元气藏形成的地质基础[J].天然气工业,2006,26(4):11-13.
[9]张庄,曾伟,杨西燕.蜀南地区上三叠统须家河组成岩相划分[J].西南石油学院学报,2006,28(6):13-15.
[10]胡明,秦启荣,李昌全.贵州赤水地区构造特征及与裂缝发育关系研究[J].西南石油学院学报,2006,28(1):13-17.
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