Geological- geophysical summary of a typical offshore structure (Kyurdashi) in the South Caspian Basin, Azerbaijan.

Abstract

Abstract The Kyurdashi structure in the South Caspian Basin is an elongated and pronounced structure associated with a NNWSSE trending regional fault. Several onshore oil fields are associated with this fault trend, i.e. Neftechala, Khilli, Babazanan, Qarabagli and Durovdag. The geologic setting for Kyurdashi is very similar to these onshore fields with up to 20 stacked reservoir zones within the Pliocene Productive Series and overlying Quarternary deposits. Kyurdashi is an over 10 km long, faulted anticline with steep flanks of 10-30 degrees. The center of the structure is intruded by a mud volcano which has pierced the structure and formed the Kyurdashi island. The structure is encompassed by two synclines modeled to be marginally oil mature with respect to the Oligo- to Miocene Diatome - Maikop source shales. On Kyurdashi island distinct oil seepage is observed. The drilling of the first modern offshore exploration wells in this area is scheduled in 2000 and 2001. It can be expected that drilling will confirm the prospectivity of this play type and discover substantial amounts of hydrocarbons in the southwestern part of the South Caspian Basin. Introduction. Azerbaijan has a long history of oil production and already more than 15 billion barrels oil were proved during the last 150 years. However, exploration activities until few years ago were confined to the onshore and the shallow water areas close to the mainland. Location. Seismic work and exploration studies performed during recent years indicate that the Baku archipelago is highly prospective for discovering new oil and gas fields. One of the most prospective areas is the Kyurdashi block, located some 160 km south of Baku in a water depth of 70-75 meters (Fig. 1). The study area is situated in the southern part of the Baku archipelago, in the delta of the Kura River, which drains large parts of the Caucasus Mountains. The Kyurdashi structure represents the offshore continuation of the Khilli-Neftechala anticlinal zone with two oil and gas fields producing from over 20 sand horizons within the Pliocene "Productive Series" (Fig. 2). Exploration History. The Kyurdashi structure was discovered on the basis of seismic surveys performed the first time in 1948 and later in 1954-55. In 1988 additional 2Dseismic covered nearly the entire block and has proved Kyurdashi as an elongated, well pronounced brachy-anticline (Fig. 3). On trend with Kyurdashi two more structures are located seaward, i.e. Araz-Sea and Shirvan. The block was awarded in 1998 under a three year exploration contract to an international consortium. Producing Analogs. So far no deep exploration well has been drilled on Kyurdashi. Accordingly, the results of the geophysical studies are to be compared with the onshore Khilli-Neftechala anticlinal zone and equivalent productive analogs. There several valid structures have been proved by seismic and drilling. From the north to the south: Kyurovdag, Qarabagly, Babazanan-Durovdag, Khilli and Neftechala fields. The individual structures are separated by gentle saddles. This prolific tectonic zone has its marine continuation in the Kyurdashi structure.