Bu Hasa field in Abu Dhabi was the first giant oil field in the Arabian Gulf to produce from the Lower Cretaceous Shuaiba Formation (Aptian). The field has a productive area of about 155,673 ac (63,047 ha.) and 12.6 billion bbl of oil reserves. The formation is composed mainly of rudistid and algal sediments, rudistid mounds having overlain and built up the topography of an algal platform. The position and elevation of the platform edge, combined with rising eustatic sea level, created a tendency toward both vertical and lateral growth, and regulated the form and distribution of the rudist accumulation.

The Shuaiba Formation has good reservoir quality ranging in porosity from 18-25% and with average permeability exceeding 100 md. Nine reservoir units (A-I), classified by their porosity, permeability, and lithology, can be clearly defined from the logs.

Eleven main lithofacies have been defined in the Shuaiba from detailed core descriptions. These lithofacies were deposited in three main phases. The earliest phase consisted of chalky mud-supported sediment with some algal colonies, followed by a middle phase characterized by a thick algal platform. During this stage of deposition, a shallow-water carbonate platform developed over the south and central part of the field, grading into deeper, open-marine sedimentation toward the north. The late phase was characterized by rudistid buildups (mainly caprinids and caprotinids). The growth of the thick algal platform in the south and central areas controlled the initial distribution of the main rudistid buildup; toward the north, small rudistid reefs are sparsely developed and present only n the latest stage on high-energy shoals.