Lipid-based drug delivery nanoparticles, including non-lamellar type, mesophasic nanostructured materials of lyotropic liquid crystals (LLCs), have been a topic of interest for researchers for their applications in encapsulation of drugs...

Perhaps as much as 50% of the oil-in-place in carbonate formations around the world is locked away in the easy to bypass microporosity. If some of this oil is unlocked by the improved recovery processes focused on tight carbonate formations, the world may gain a major source of lower-rate power over several decades. Here, we overview the Arab D formation in the largest oil field on earth, the Ghawar. We investigate the occurrence of microporosity of different origins and sizes using scanning electron microscopy (SEM) and pore casting techniques. Then, we present a robust calculation of the probability of invasion and oil saturation distribution in the nested micropores using mercury injection capillary pressure data available in the literature. We show that large portions of the micropores in Arab D formation would have been bypassed during primary drainage unless the invading crude oil ganglia were sufficiently long. We also show that, under prevailing conditions of primary drainage of the strongly water-wet Arab formations in the Ghawar, the microporosity there was invaded and the porosity-weighted initial oil saturations of 60–85% are expected. Considering the asphaltenic nature of crude oil in the Ghawar, we expect the invaded portions of the pores to turn mixed-wet, thus becoming inaccessible to waterflooding until further measures are taken to modify the system’s surface chemistry and/or create substantial local pore pressure gradients.

Summary Microporous carbonates contain perhaps 50% of the oil left behind in current projects in the giant carbonate fields in the Middle East and elsewhere. Pore geometry, connectivity, and wettability of the micropore systems in these carbonates are of paramount importance in finding new improved-oil-recovery methods. In this study, we present a robust pore-imaging approach that uses confocal laser scanning microscopy (CLSM) to obtain high-resolution 3D images of etched epoxy pore casts of the highly heterogeneous carbonates. In our approach, we have increased the depth of investigation for carbonates 20-fold, from 10 µm reported by Fredrich (1999) and Shah et al. (2013) to 200 µm. In addition, high-resolution 2D images from scanning electron microscopy (SEM) have been correlated with the 3D models from CLSM to develop a multiscale imaging approach that covers a range of scales, from millimeters in three dimensions to micrometers in two dimensions. The developed approach was implemented to identify various pore types [e.g., intercrystalline microporosity (IM), intragranular microporosity (IGM), and interboundary sheet pores (SPs)] in limestone and dolomite samples.

Permeability estimation based on image analysis is a good alternative when an intact core-plug is not available for laboratory measurement. While there is much research on permeability estimation from 2D and 3D images or models, accurately estimating permeability for carbonates, a type of rock with substantial heterogeneity, is still challenging. In this study, a method for permeability estimation based on thin-section image analysis and 2D permeability simulation is developed for grain-dominated carbonates based on semi-theoretical analysis of 2D and 3D permeability (K2D and K3D) relationship. The mathematical expression of the K2D/K3D is examined and validated with a grainstone carbonate sample, for which both K2D and K3D were obtained through permeability simulation based on micro-CT images. The method was applied to 24 grain-dominated carbonate samples collected from different locations with a large variation in rock textures and fabrics and a broad range of permeability from 0.1 mD to 3200 mD. Representativeness of the thin section and the correct determination of the effective pores are the key for accurate estimation. The estimated permeability was compared to the measured value, and 92% of the results are within a factor of ±5, and 46% are with a factor of ±2. Potential sources of systematic error are discussed both qualitatively and quantitatively.

Epoxy-pore casting is widely used to characterize geological samples. In this study, we present a robust pore imaging approach that applies Confocal Laser Scanning Microscopy (CLSM) to obtain high resolution 3D images of etched epoxy-pore casts of highly heterogeneous carbonates. In our approach, we have increased the depth of investigation for carbonates 20-fold, from 10 μm reported by (Fredrich, 1999; Shah et al., 2013) to 200 μm. In addition, high resolution 2D images from scanning electron microscopy (SEM) have been correlated with the 3D models from CLSM to develop a multi-scale imaging approach that covers a range of scales, from millimeters in 3D to micrometers in 2D. The developed approach was implemented to identify various pore types, e.g., the inter-crystalline and intra-granular microporosity, and the inter-boundary sheet pores in the limestone and dolomite samples.