During deposition and subsequent diagenesis, reservoir rocks develop sediment texture and cement phases are formed during the precipitation of secondary minerals such as microcrystalline quartz, calcite and clay fibrous over-growths that contain secondary porosity. The grain size distribution and presence of secondary microporous material can influence the reservoir porosity and permeability. Using 3D X-ray microtomographic images we analyze the grains and pore space in Brae Formation sandstones from the South Viking Graben in the North Sea. The samples—derived from two cored wells (16/7b-20 and 16/7b-23), and located within the depth interval between 4,040 m and 4,064 m—display mean grain sizes between 315 and 524 microns (1.78–1.05 ϕ units), classifying them as predominantly medium-grained sands, with moderate to well-sorting (0.51–0.7 ϕ units). From our models we calculate the upper and lower bounds of the micropores on the pore connectivity and permeability. Our samples show total porosities between 10 and 18% of which 6 and 13% are effective, leading to a permeability range between 1 and 400 mD through the effective macropore network. We found that the fraction of effective porosity and effective permeability shows a non-linear reduction with increase in microporous cement volume fraction. Above a threshold cement volume of approximately 5.5% the effective pore network is disconnected and percolation is no longer possible. Based on our observations and modeling results we propose that cement precipitation can be a positive consequence of mineral trapping from sequestered CO₂, which can be important for reducing reservoir quality and ensuring efficient long term storage.

在沉积和随后的成岩过程中，储层岩石会形成沉积物质地，并且在次生矿物（如微晶石英，方解石和含有次生孔隙的粘土纤维过度生长）的沉淀过程中会形成水泥相。粒度分布和次生微孔材料的存在会影响储层的孔隙度和渗透率。使用3D X射线显微断层图像，我们分析了北海南维京群岛Graben的Brae组砂岩中的晶粒和孔隙空间。这些样品取自两个有芯井（16 / 7b-20和16 / 7b-23），并且位于4,040 m至4,064 m的深度区间内，显示的平均晶粒尺寸为315至524微米（1.78–1.05 ϕ单位） ），将其归类为中等粒度至中等分类（0.51-0.7 ϕ单位）的主要为中粒砂。从我们的模型中，我们计算出微孔的上界和下界对孔连通性和渗透性的影响。我们的样品显示总孔隙率在10％到18％之间，其中有效孔隙率在6％到13％之间，通过有效的大孔网络，渗透率范围在1到400 mD之间。我们发现随着微孔水泥体积分数的增加，有效孔隙率和有效渗透率的分数显示出非线性降低。超过大约5.5％的水泥固结体积时，有效的孔隙网络将断开，并且不再可能发生渗滤。根据我们的观察结果和建模结果，我们认为水泥沉淀可能是隔离的一氧化碳捕集矿物的积极结果。₂，这对于降低储层质量和确保有效的长期存储很重要。