Reservoir evolution and property prediction of the Paleogene Apollonia Formation, Western Desert, Egypt

Abstract

The shallow-burial Neo-Tethys Cenozoic reservoirs host significant hydrocarbon resources. However, a limited understanding of the Paleogene Apollonia Formation, north Western Desert, Egypt, hinders further exploration and development. Here, RZK, WD33 and JD blocks were analyzed using a combination of petrological observations, petrophysical analysis, well logging analysis, machine learning, and deep learning. Five types of limestone and two types of dolostone were identified. Planktonic and benthic foraminifera (e.g., Nummulite) are well-developed. The sedimentary facies consists of grain shoals, shallow to deep ramp and deep-water slope facies. Grainstone and packstone from high-energy sedimentary environments yield high primary porosity and permeability. Dolomitization and bacterial sulfate reduction further enhance reservoir properties. Framboidal and granular pyrites are well-developed here. The reservoir spaces consist of framework pores, inter-granular pores, intra-granular pores, moldic pores, inter-crystalline pores, and fractures. The sedimentary facies and diagenetic history indicate that WD33 and RZK (esp. ERZK & MRZK) blocks exhibit promising reservoir performance. Drilled cores of three wells from different sedimentary facies served as the training dataset for machine learning and deep learning, while two core wells were utilized as the test group. Using XGBOOST, Random Forest, and Long Short-Term Memory algorithm, the predicted porosity values closely match core-measured values, with R² (coefficient of determination) values of 0.72, 0.58, and 0.61, respectively. The permeability prediction results also yield similarity to the measured values. The Jurassic and Cretaceous source rocks generated hydrocarbon for the overlying Paleogene Nummulite carbonate reservoirs in the Neo-Tethys domain. This study provides valuable insights into carbonate reservoirs in the north Western Desert and holds significance for global Cenozoic carbonate exploration and development.