Mechanical Properties as Predictors of Sand production: Case Study of the Mamuniyat Reservoir, Murzuq Basin-Libya

Sand production is one of the instability issues in oil reservoirs within the oil industry. This research paper seeks to establish a methodology for detecting sand production in the Mamuniyat Reservoir (Upper Ordovician) across multiple oil fields in the northwest Murzuq Basin, Libya. Well logging data from five oil wells (1, 2, 3, 4, 5) in Fields 1 and 2 have been processed to calculate the Sand Production Indicator (SPI), which is based on the estimation of petrophysical and mechanical properties. The Mamuniyat reservoir is classified in ascending order into Clayey Mamuniyat and Clean Mamuniyat sandstone, based on a 25% shale baseline. Montmorillonite and illite are identified as the dominant clay minerals, as recognised by natural gamma-ray spectrometry (NGS) in the Mamuniyat reservoir. Additionally, the reservoir is classified from very low strength (E) to high strength (B) based on uniaxial compressive strength (UCS). The shale content (Vsh) has noticeable changes in the UCS, cohesion (Co), and friction angle (Ф) of the Clayey Mamuniyat sandstone rather than the Clean Mamuniyat sandstone, which is about 70 MPa, not exceeding 30 MPa, and 20 degrees of the UCS, Co, and Ф, respectively. Whereas the Clean Mamuniyat sandstone is ranged from 80 to 110 MPa of the UCS, about 20 MPa of Co and close to 40 degrees of Ф. Accordingly, the studied reservoir does not meet the threshold criterion for sanding problems according to the standard shear to compressibility modulus ratio (G/Cb), which is less than 8×10¹¹ psi².