PETROGRAPHY AND DIAGENESIS OF THE HAWAZ SANDSTONE FORMATION, MURZUQ BASIN, SW LIBYA

Abstract

Middle Ordovician Hawaz Formation represents the primary reservoir rocks in Murzuq Basin. In J Oil Field Hawaz Formation consists of a 550 feet thick succession made of fine-grained quartz-arenite displaying a variable degree of bioturbation. This J Oil Field study is an integration approach and it is based on 235 feet thick of slabbed cores photographs from well J4-NC186, with core samples, petrography, wireline log data, and conventional core analysis of the Hawaz siliciclastic sediments. The Hawaz Formation was deposited in wave-dominated shoreface and shelf environments. The stratigraphical and sedimentological characteristics of the Hawaz Formation in the study area in Murzuq Basin are attributed to shoreface and shelf facies associations within which some 9 facies have been distinguished. The lower part of the cored section of the Hawaz Formation is dominated by the outer and inner shelf facies associations. The outer shelf association is dominated by mudstone whereas, the inner shelf association is dominated by siltstone/sandstone. Petrographic analysis provides a means of assessing the composition of the sandstone and relating this to their
provenance, tectonic setting, diagenetic evaluation and economic potential (Pettijohn et al, 1987). Petrographic investigations show that Hawaz sediments can be divided into six categories: (a) rock fragments, (b) quartz, (c) feldspar, (d) micas and authigenic quartz, clay minerals and other constituents. Originated mainly from metamorphic rocks in humid climates.