Mesozoic Clastic Source-Rocks and Carbonate Reservoirs of the Middle Caspian Petroleum System

Elmira Aliyeva¹, Dadash Huseynov¹, Haji-Murad Aliyev², Akper Feyzullayev¹, Ibrahim Guliyev³, and Ali Suleymanov^4
1Geological Institute of Azerbaijan National Academy of Sciences, Baku, Azerbaijan
²AZNiPineft, Baku, Azerbaijan
³Geology Institute of Azerbaijan National Academy of Sciences, Baku, Azerbaijan
⁴AzNiPineft, Baku, Azerbaijan

The depositional environments of the Middle Jurassic-Lower Cretaceous terrigenous-carbonate succession in the Middle Caspian Basin are represented by marine (Upper Aalenian-Lower Cretaceous) and continental (Lower Aalenian) settings with the existence of marginal facies in the Lower and Upper Aalenian as well as the Kimmeridgian-Tithonian and Valanginian (facies of lagoons in the north-west part of the region under study). Several orders of variation in stratal architecture have been recorded throughout the studied succession. The first-order fining upward trend detected in the Middle Jurassic – Lower Cretaceous section confirms the transgressive character of the basin. However, frequent environmental changes testify to rapid sea-level fluctuations expressed in short-term depositional cycles. An investigation of organic matter (OM) distribution demonstrates a strong depositional control. The highest amount of TOC in a continental environment was recorded in swamp sediments. In a marine setting the maximum concentrations of TOC were determined in the shelf zone. The amount of TOC in mudstones varies on average from 0,44 % in the upper shoreface to 0,96 % in lower shoreface; 1,47 % - 1,67 % - outer shelf and 0,9 % - deepwater part. Organic matter concentrations decrease upward through the Middle Jurassic succession. The type of organic matter in the studied sediments is in full agreement with the depositional environment interpretations - type III in the continental-marginal Jurassic succession and type II in Cretaceous sediments. The OM maturity degree strongly varies within the area under study. All the main oil-gas fields in the western flank of the Middle Caspian Basin are associated with fractured carbonaceous organogenic Upper Jurassic-Neocomian reservoirs.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece