This study examines the role of the depositional environment for the final reservoir quality in four Lower Cretaceous sandstone reservoirs in the southwestern Barents Sea by linking facies to the distribution of primary textures, composition, and diagenetic alteration. Facies analysis reveals slope-to-basin-floor, distal shallow-marine, and deltaic depositional environments. The slope-to-basin-floor sandstone has the highest porosity of 3–19% (avg. 13%). It is attributed to good sorting, non-pervasive carbonate cementation that inhibited compaction and allowed for secondary porosity through later dissolution, and moderate clay infiltration that resulted in clay cutanes on grain rims and the precipitation of chlorite (which inhibited quartz growth). For the deltaic sandstone, moderate to fluctuating energy and sediment supply provided good conditions for mechanical clay infiltration and varying porosity of 2–18% (avg. 8%). The distal shallow-marine sandstone reservoir has the lowest porosity of 1–12% (avg. 7%). Based on its fine-grained and bioturbated character, deposition in a low-energy environment with low sediment supply seems likely. The combination of fine-grained lamina, interstitial matrix and bioturbation led to porosity reduction. Abundant mica and feldspar grains in the shallow-marine sandstone, partly a result of the provenance, and deep burial also resulted in extensive illitization. High mineralogical maturity, much monocrystalline quartz in the quartz-grain populations, and similar felsic chemical rock compositions for all facies associations and wells indicate similar source rocks with some variations. Abundant mechanically unstable mica makes the nearby Loppa High a plausible catchment, which is supported by the seismic geometries. This study demonstrates that the porosity evolution of the studied Lower Cretaceous sandstone reservoirs is determined mainly by the depositional environment despite minor provenance and major diagenetic variations.

本研究通过将相与原始构造、成分和成岩蚀变的分布联系起来，研究了沉积环境对巴伦支海西南部四个下白垩统砂岩储层最终储层质量的作用。相分析揭示了斜坡到盆地底板、远端浅海和三角洲沉积环境。斜坡到盆底砂岩的孔隙度最高，为 3-19%（平均 13%）。这归因于良好的分选性、非渗透性碳酸盐胶结抑制压实并允许通过后期溶解产生次生孔隙，以及适度的粘土渗透导致颗粒边缘粘土皮肤和绿泥石沉淀（抑制石英生长）。对于三角洲砂岩，中等至波动的能量和沉积物供应为机械粘土入渗和 2-18%（平均 8%）的孔隙度变化提供了良好的条件。远端浅海砂岩储层的孔隙度最低，为 1-12%（平均 7%）。基于其细粒和生物扰动的特性，在低能量环境中沉积物供应量低的情况似乎很可能。细粒层、间隙基质和生物扰动的结合导致孔隙率降低。浅海砂岩中含有丰富的云母和长石颗粒，部分原因是物源，深埋也导致广泛的伊利化。矿物学成熟度高，石英颗粒群中的单晶石英较多，所有相组合和井的长英质化学岩石成分相似，表明烃源岩相似，但有一些变化。大量的机械不稳定云母使附近的 Loppa High 成为一个看似合理的集水区，它得到了地震几何学的支持。本研究表明，所研究的下白垩统砂岩储层的孔隙度演化主要由沉积环境决定，尽管物源和成岩作用较小。