The Caspian Sea is in the process of establishing itself as a world-class producer of oil and gas. Massive reserves of both have been discovered over the last decade, including the world’s biggest oilfield discovery in the last 30 years (Kashagan), situated in the shallow waters of the north Caspian Sea.

Geology and Prospectivity

The Kazakhstan sector of the Caspian Sea can be divided into two distinct geological provinces from north to south — the North Caspian Basin and the Middle Caspian Basin.

— In the north, the mainly shallow water area forms part of the much larger North Caspian Basin which extends onshore some 400km to the north and east. The province, although only lightly explored, contains a large number of oil and gas fields including several super-giants such as the Kashagan.

From Devonian to Permian times, it was marked by carbonate deposition followed by salt; a winning combination of huge carbonate platform reservoirs overlain by an excellent seal. Where vertical migration has been made possible through areas of thinned salt, further Mesozoic reservoired fields are found in sandstones draped over the salt highs and sealed by shales to provide stacked pay.

— To the south of the Karpinsky Ridge — Mangyshlak Meganticline water depths increase dramatically and the geology also changes significantly. The area is structurally complex, being influenced by a number of tectonic events. The basin comprises a Late Permian-Triassic rift system which was affected by a late Triassic-Early Jurassic compressional event, uplifted and eroded and then overlain, partially unconformably, by a platform sequence of Jurassic through Eocene rocks. These were initially deposited in continental conditions becoming progressively more marine upwards.

The Eocene and younger section shows a marked change in depositional environment being dominated by the foreland basin which was forming to the north of the Great Caucasus foldbelt. A thick sequence of shales and sandstones was deposited, which includes the Lower Miocene Maykop shales; an important source rock.

Example data library section from Veritas Caspian llp Kazakh sector of the Caspian Sea survey.