An integrated high-resolution image log, sequence stratigraphy and palynofacies analysis to reconstruct the Albian - Cenomanian basin depositional setting and cyclicity: Insights from the southern Tethys

Borehole image logs are used to overcome the lack of core samples and other conventional open-hole logs in many subsurface reservoirs around the world, significantly reducing the likelihood of petroleum resource exploration. These image logs can provide high-resolution data to visualize sedimentary structures, facies types, lithofacies, geomechanical characteristics, and depositional trends. Sedimentologists recognize the Bahariya Formation of the North-Western Desert of Egypt as the typical coastal-shallow marine depositional model that emphasizes a typical heterogeneous sandstone reservoir with many obstacles in production profile. One of the most significant issues related to the heterogeneous Bahariya reservoir that confronts hydrocarbon producers is the loss of productive target zones due to spatial facies changes. This research aims to overcome the exploration and development challenges of the complex and heterogeneous sandstone reservoir of the Albian - Cenomanian Bahariya Formation that lies in the Abu Gharadig Basin, Southern Tyths, Egypt. In this work, we used integrated image logging in conjunction with palynofacies, core samples, and sequence stratigraphy to provide high resolution information that can aid in better resource exploitation. Furthermore, we utilized the integrated work in the definition of the high-resolution para-sequences, sequences boundaries, lithofacies characteristics and paleocurrent analysis of each facies association. The interpretation of coastal shallow marine facies from four BHI-logs was established and calibrated with two core sets in order to define the best hydrocarbon reservoir intervals and focus on improving the development plan of the study area. Our findings show that the Bahariya Formation is characterized by eleven facies associations which have been interpreted based on the integrating of the twenty-seven electrofacies extracted from the FMI images, wireline logs, and core photographs. The identified facies associations were classified into five depositional sequences and their boundaries were determined using dipmeter patterns and extracted lithofacies from BHI. The LST and MFS deposits in both the fourth and fifth depositional cycles, respectively, whereas the HST deposits are found only in the third depositional cycle. According to our findings, the development of the shoreface sandy facies of cycles three and five represents the maximum rate of sea-level rise, as well as the development of the offshore sand bar system, which represents high-quality sandstone reservoirs. This case study demonstrates how image logs can be used to better understand the spatial distribution and geometries of sandstone bodies in the Bahariya Formation. Furthermore, it provides a reference imaging fingerprint of high-resolution coastal shallow marine, high-frequency sequences analysis, sedimentary structures, and extracted electrofacies analogues that can be used in the basin and elsewhere.

Automated summary

This research aims to overcome the exploration and development challenges of the complex and heterogeneous sandstone reservoir of the Albian - Cenomanian Bahariya Formation, and provides high resolution information that can aid in better resource exploitation through integrated image logging, palynofacies, core samples, and sequence stratigraphy techniques.