Fracture Contribution in Tight Sandstones Reservoirs of Sirte Basin, Libya Lessons Learnt from Characterization to Simulation

Abstract Belhedan Field, located in the Sirte Basin, is a brown field facing significant challenges related to production. The primary reservoir of interest is the Cambro-Ordovician Gargaf sandstone, described as a tight sandstone formation with variable fracture intensities. Besides tightness, the productive layers are characterized by natural fractures that serve as pathways connecting reservoir fluids to the wellbore. The distribution of fractures varies greatly throughout the field. In certain areas, the matrix contributes significantly, whereas in others, only fractures with direct access to the wellbore are influential. This paper presents a comprehensive study focused on understanding the role of fractures in the tight sandstone reservoirs of Belhedan Field. The study integrates detailed fracture characterization with advanced reservoir simulation techniques, including discrete fracture modeling (DFN). Geological, geophysical and production data, including borehole images, core analysis, well logging and pressure transient analysis, were utilized to characterize fracture orientation, intensity, and connectivity across the reservoir. Reservoir simulation model was then developed to simulate fluid flow dynamics considering the complex fracture network identified during characterization. The history matching process included calibrating well test data and conducting a regional analysis of fracture characteristics by tuning fracture intensity and geometrical properties. The simulation results were validated against production data and revealed the significant influence of fractures on well performance and their role in controlling water movement within the reservoir, providing insights into optimizing hydrocarbon recovery strategies. Lessons learned from this study are: (1) The importance of considering the distance to the faults while locating the infill wells especially in the southern area of the field. (2) Careful integration of production, geological and geophysical data proved crucial for accurate fracture characterization. (3) Acquiring more borehole images, core and production logging data will enhance the precision of simulation model.