Provenance types and controlling factors of the 4th member of the Xujiahe Formation in the Yuanba-Tongnanba area, northeastern Sichuan
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摘要: 近期勘探在川东北元坝-通南巴地区须家河组四段获得工业气流,揭示须四段具有良好的勘探前景,但其天然气富集程度差异较大,储层特征及主控因素尚待揭示。本文通过对大量钻井和分析测试资料的深入分析,明确了研究区须四段物源来自龙门山、米仓山和大巴山等多个构造带,研究区须四段可分为富钙屑砂砾岩、富石英砂砾岩和富长石砂岩3种类型储层。认为储层发育明显受到物源、成岩作用和裂缝等因素共同控制:物源体系控制储层岩石类型和空间展布,溶蚀作用改善了储层物性,而裂缝对致密砂岩渗透率的提高具有明显贡献,是该层段天然气高产的的关键因素。元坝东部富长石砂岩和元坝西部富钙屑砂砾岩叠合裂缝发育区是须四段勘探的最有利地区。Abstract: The industrial gas flows have been explored recently in the 4th member of the Xujiahe Formation in the Yuanba-Tongnanba area, northeastern Sichuan. Judged from drill cores and thin section examination, the sediments in the 4th member of the Xujiahe Formation may emanate from several structural belts in the Longmen, Micang and Daba Mountain areas. The reservoir rocks contain three types:calcium-rich sandstones and conglomerates, quartz-rich sandstones and conglomerates and feldspar-rich sandstones. The controlling factors include provenance types, diagenesis and fissure development. The types and spatial distribution of the reservoir rocks are constrained by the provenance systems. The dissolution facilitates the improvement of the porosity and permeability of the reservoir rocks. The fissures may contribute to the improvement of the permeability of the dense sandstones. The fissure development in feldspar-rich sandstones in eastern Yuanba and calcium-rich sandstones and conglomerates in western Yuanba is believed to be most favourable exploration conditions in the 4th member of the Xujiahe Formation.
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