Spiculitic cherts are uncommon reservoir rocks and their porosity evolution is poorly understood compared to sandstones and carbonates. In the Gohta oil and gas discovery on the Loppa High in the south-western Barents Sea, the reservoir is in brecciated, silicified, and dolomitized Permian spiculites below the Permian/Triassic unconformity. It represents the infill of several collapsed cave systems with spiculite clasts in a micritic matrix, separated by intact cave roofs of shale and spiculite facies. The cave collapse was related to dissolution of less resistant (?limestone and ?spiculitic) beds, due to percolation of freshwater during latest Permian – earliest Triassic emersion. During later transformation of opal-A to opal-CT, associated growth of silica concretions left the margins of spiculite clasts depleted in SiO₂ and thus highly porous. Subsequent transformation of opal-CT to quartz resulted in precipitation of texture-preserving quartz and chalcedony cements. The latter show a systematic decrease of δ¹⁸O from the first to last precipitated phase, implying crystallization under increasing temperatures during renewed Middle–Late Triassic burial. Later diagenesis includes in situ brecciation and fracturing, dolomitization affecting mainly the micritic matrix of cave-collapse facies, chemical compaction, and calcite cementation. The best reservoir properties are in cave-collapse facies (commonly 10–25% and 0.03–19 mD) where the pore system is dominated by (1) uncemented interspicule pores and central parts of spicule molds within clast margins, and (2) intercrystalline pores between dolomite crystals in the breccia matrix. The primary depositional facies have much lower porosity and permeability (rarely exceeding 10% and 1 mD, respectively). This study shows that porosity in the cave fill most likely formed by local redistribution of silica to form concretions and dissolution of the carbonate matrix to source the growth of dolomite crystals, while prolonged subaerial exposure only played an indirect role by isolating spiculite clasts and preventing their complete silicification during burial.

针状硅质cher石是罕见的储集岩，与砂岩和碳酸盐岩相比，它们的孔隙度演化了解得很少。在西南巴伦支海的Loppa高地的Gohta油气发现中，储层位于二叠纪/三叠纪不整合面之下的角砾岩，硅化岩和白云石化的二叠纪针状岩中。它代表了多个塌陷的洞穴系统的填充物，这些洞穴系统中的针云母碎屑形成了针状岩屑，被完整的页岩和针云母相洞穴顶隔开。洞穴倒塌与较难抵抗的（石灰岩和？spiculitic）床层的溶解有关，这是由于在最新的二叠纪-最早的三叠纪出现时淡水的渗透所致。在随后的蛋白石A转变为蛋白石CT的过程中，伴随的硅结石的生长使SiO _2中的针石岩屑边缘消失了因此高度多孔。蛋白石-CT随后转变为石英导致了保质石英和玉髓水泥的沉淀。后者显示δ的系统性下降¹⁸从第一个沉淀相到最后一个沉淀相都为O，这意味着在新的中晚期三叠纪埋葬过程中，在温度升高的情况下会发生结晶。后来的成岩作用包括原位造斜和压裂，白云石化作用，主要影响溶洞塌陷相的微晶基质，化学压实作用和方解石胶结作用。最佳的储层性质是在塌陷相（通常为10–25％和0.03–19 mD）中，其中的孔隙系统主要由（1）未胶结的孔间孔和在胶质边缘内的针状模子的中央部分以及（2）晶间孔组成。角砾岩基质中白云岩晶体之间的孔。一次沉积相的孔隙度和渗透率要低得多（分别很少超过10％和1 mD）。