Natural open fractures are present in sidewall cores and in whole-core samples from pre-salt reservoirs in the licence block BM-C-33 in the Campos Basin, Brazil. Open fractures are also observed in borehole image logs, and fracture densities are in general high. The highest density of open fractures is seen in the damage zones above and below larger cavities (amalgamated cavern damage zones (ACDZs)). Outside the ACDZs the fracture density is high in silicified carbonates, where it tends to increase with decreasing porosity. Clean dolomites are less fractured than the silicified interval, while the less brittle argillaceous dolomites have the lowest fracture density. Some fractures appear vuggy on borehole image logs, and fracture densities are high close to vugs and larger cavities. The positive correlation between fractures and vugs is caused by flow of dissolving fluids through open fractures, and fracturing at stress concentrations around vugs. Two major fault zones have been interpreted from borehole image logs that have damage zones with very high fracture density. The well-test permeability is much greater than the matrix permeability estimated from sidewall core and log measurements. This excess permeability is attributed to fractures, in combination with caverns and intervals with frequent vugs.

天然开放裂缝存在于巴西坎波斯盆地 BM-C-33 许可区块的盐下储层的侧壁岩心和全岩心样本中。在钻孔图像测井中也观察到开放裂缝，裂缝密度普遍较高。在较大空洞（合并洞穴损伤区（ACDZ））上方和下方的损坏区域中可以看到最高密度的开放裂缝。在 ACDZ 之外，硅化碳酸盐的裂缝密度很高，随着孔隙度的降低，裂缝密度趋于增加。与硅化层相比，清洁白云岩的裂缝较少，而脆性较小的泥质白云岩的裂缝密度最低。一些裂缝在钻孔成像记录上看起来是空洞的，靠近空洞和较大空洞的裂缝密度很高。裂缝和孔洞之间的正相关是由溶解流体通过开放裂缝的流动和孔洞周围应力集中的压裂引起的。两个主要的断层带已经从钻孔图像测井中解译出来，这些断层带具有非常高的裂缝密度的损伤带。试井渗透率远大于根据侧壁岩心和测井测量估计的基质渗透率。这种过度的渗透性归因于裂缝，以及洞穴和经常出现孔洞的间隔。试井渗透率远大于根据侧壁岩心和测井测量估计的基质渗透率。这种过度的渗透性归因于裂缝，以及洞穴和经常出现孔洞的间隔。试井渗透率远大于根据侧壁岩心和测井测量估计的基质渗透率。这种过度的渗透性归因于裂缝，以及洞穴和经常出现孔洞的间隔。