Abstract The Bolshoi Karatau carbonates of southern Kazakhstan record development of a 4500-m (14,763-ft)-thick platform that evolved close to the North Caspian Basin of western Kazakhstan during the Late Devo-nian and Carboniferous (Cook et al., 1994). Carbonate facies in the Bolshoi Karatau mountains of south-ern Kazakhstan provide outcrop analogs for coeval reservoirs in supergiant oil and gas fields in the North Caspian Basin (Figure 1 ). The carbonate platforms in the Bolshoi Karatau and the North Caspian Basin are similar in several important ways. First, both the Bolshoi Karatau and the Tengiz oil-field carbonate platforms were initiated in the Upper Devonian and ended in the Bashkirian, a span of about 50–55 m.y.(Figure 2 ) ( Lisovsky et al., 1992 ). Second, the strati-graphic thickness of the Bolshoi Karatau and the Tengiz oil field is similar (Figure 3 ). Third, the proven oil reserves in Tengiz occur in the Visean through Bashkirian, and these strata are well exposed in the Bolshoi Karatau (Figures 2 , 3 ). The seaward margin of the Bolshoi Karatau carbonate platform was probably structurally controlled by the rifted edges of a passive continental margin. The overall geometry of the carbonate platform was controlled by thermal subsidence and local tectonics. Over a 50–55-m.y. period of time, this passive margin underwent thermal subsidence, normal faulting, and numerous sea level fluctuations of varying amplitudes. Sedimentation rates suggest that subsidence decreased exponentially. Sediment accumulation rates ranged from 185 to 285 m/m.y. (606 to 935 ft/m.y.) during the Late Devonian, 60–100 m/m.y. (196–328 ft/m.y.) during the Tournaisian, 35–50 m/m.y. (114–164 ft/m.y.) during the Visean, 15–30 m/m.y. (49–98 ft/m.y.) during the Serpukhovian, and 20– 50 m/m.y. (66–164 ft/m.y.) during the lower Bash-kirian. The net result was a carbonate platform that evolved from reef and sand-shoal-rimmed platforms in the Devonian to deep-water ramps and skeletal mounds in the Tournaisian to ramps with skeletal mounds and rimmed margins in the Visean, Serpu-khovian, and Bashkirian (Figure 2 ).

Abstract Ghawar, the world's largest oil field, is located in the Eastern Province of the Kingdom of Saudi Arabia. This giant field is formed by an elongate northeast to southwest trending anticline. Production comes from Arab-D Member carbonates of the Upper Jurassic Arab Formation, which consists of four geographically-widespread carbonate/evaporite members. The Arab-D comprises two major shoaling upward cycles deposited during a relative highstand in sea level. These cycles are composed of smaller scale upward shoaling cycles and are comprised of a variety of skeletal grainstones and packstones with ooid grainstones locally common in the uppermost Arab-D. The Arab-D is further subdivided into time-stratigraphic reservoir zones and subzones that are based largely on porosity log pattern correlation. The first cycle comprises Zone 3 of the Arab-D. The abundance of grain-supported textures (packstone, mud-lean packstone, and grainstone) stays fairly constant in Zone 3B, but increases upwards through Zone 3A. A second shoaling-upward cycle beginning near the base of Zone 2B resulted in the deposition of virtually mud-free shoal-water deposited sediments seen in Zone 2A and culminated in the deposition of thin subtidal to intertidal/supratidal cycles and sabkha evaporites of Zone 1 and the lower portion of the Arab-D Anhydrite. The overlying upper Arab-D Anhydrite comprises sabkha evaporites and subaqueous evaporites with thin carbonate interbeds that can be traced for hundreds of kilometers. The overall pattern of sedimentation seen at Ghawar is that of a thinning carbonate section and a thickening evaporite section going from north to south, even though the overall thickness of the Arab-D Member remains fairly constant. The major diagenetic processes active in the Arab-D include dolomitization, leaching and recrystallization, cementation, compaction and fracturing. In general, interparticle porosity is abundant and moldic porosity is common in the reservoir, whereas intrapraticle, fracture, burrow and shelter porosity are much less common or rare. Intercrystal pores are common in dolomites. Microporosity is present throughout the reservoir in limestones and dolomites. It occurs as microporous skeletal and non-skeletal grains, microporous matrix and micropores between cement crystals.