Copyright 2000, Offshore Technology Conference

This paper was prepared for presentation at the 2000 Offshore Technology Conference held inHouston, Texas, 14 May 2000.

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Abstract

The Kyurdashi structure in the South Caspian Basin is anelongated and pronounced structure associated with a NNW-SSE trending regional fault. Several onshore oil fields areassociated with this fault trend, i.e. Neftechala, Khilli,Babazanan, Qarabagli and Durovdag. The geologic setting forKyurdashi is very similar to these onshore fields with up to 20stacked reservoir zones within the Pliocene Productive Seriesand overlying Quarternary deposits.

Kyurdashi is an over 10 km long, faulted anticline withsteep flanks of 10-30 degrees. The center of the structure isintruded by a mud volcano which has pierced the structure andformed the Kyurdashi island. The structure is encompassed bytwo synclines modeled to be marginally oil mature withrespect to the Oligo- to Miocene Diatome Maikop sourceshales. On Kyurdashi island distinct oil seepage is observed.

The drilling of the first modern offshore exploration wellsin this area is scheduled in 2000 and 2001. It can be expectedthat drilling will confirm the prospectivity of this play typeand discover substantial amounts of hydrocarbons in thesouthwestern part of the South Caspian Basin.

Introduction. Azerbaijan has a long history of oilproduction and already more than 15 billion barrels oil wereproved during the last 150 years. However, explorationactivities until few years ago were confined to the onshore andthe shallow water areas close to the mainland.

Location. Seismic work and exploration studiesperformed during recent years indicate that the Bakuarchipelago is highly prospective for discovering new oil andgas fields. One of the most prospective areas is the Kyurdashiblock, located some 160 km south of Baku in a water depth of70-75 meters (Fig. 1). The study area is situated in thesouthern part of the Baku archipelago, in the delta of the KuraRiver, which drains large parts of the Caucasus Mountains.The Kyurdashi structure represents the offshore continuationof the Khilli-Neftechala anticlinal zone with two oil and gasfields producing from over 20 sand horizons within thePliocene Productive Series (Fig. 2).

Exploration History. The Kyurdashi structure wasdiscovered on the basis of seismic surveys performed the firsttime in 1948 and later in 1954-55. In 1988 additional 2D-seismic covered nearly the entire block and has provedKyurdashi as an elongated, well pronounced brachy-anticline(Fig. 3). On trend with Kyurdashi two more structures arelocated seaward, i.e. Araz-Sea and Shirvan. The block wasawarded in 1998 under a three year exploration contract to aninternational consortium.

Producing Analogs. So far no deep exploration well hasbeen drilled on Kyurdashi. Accordingly, the results of thegeophysical studies are to be compared with the onshoreKhilli-Neftechala anticlinal zone and equivalent productiveanalogs. There several valid structures have been proved byseismic and drilling. From the north to the south: Kyurovdag,Qarabagly, Babazanan-Durovdag, Khilli and Neftechalafields. The individual structures are separated by gentlesaddles. This prolific tectonic zone has its marine continuationin the Kyurdashi structure.

Neftechala as the closest analog is a brachy-anticline ofelongated shape oriented in a northwestern-southeasterndirection. Its areal extent at Apsheron level (Top Pliocene) is10x4 km. The fold is asymmetrical with a steep northern flank(dip of 25-300) and a more gentle southwestern flank (10-120).Numerous ruptures are observed, having different directionsand amplitude of displacement. In particular two largelongitudinal faults cut the crest of the fold on its whole length.

OTC 12199

Geological- geophysical summary of a typical offshore structure (Kyurdashi) in theSouth Caspian Basin, Azerbaijan.Dr. A. Javadova; E.P. Oehms, Wintershall Lenkoran GmbH, Baku, Azerbaijan

2 R. A. JAVADOVA OTC 12199

To the southeast the Neftechala fold gently submerges into thesea towards Kyurdashi.

A detailed study of all available geologic-geophysicaldata allowed a correlation of individual prospective unitswithin the Productive Series. The compiled geoseismic section(Fig. 4) passes from onshore to offshore through Neftechalaand Kyurdashi. Although the sequence consists predominantlyof shales with intercalated sands it is possible to discern foursedimentation complexes in the section representing thefollowing units: Quarternary deposits down to SH-1 (Seismic Horizon-1), U. Pliocene Apsheron-Akchagyl SH-1 to SH-2, Lower Pliocene including the main reservoirs Pereryva

SH-2 to SH-3, Miocene-Paleogene deposits down to SH-4.

Kyurdashi. A structure map was compiled (Fig. 5) forthe main target horizon (Suite Pereryva which is identicalwith horizon XX in the terminology used for the producingunits). In Kyurdashi it may be assumed that multiplereservoirs will be encountered, both in the Upper and theLower parts of the Productive Series. This will be analog toNeftechala and other onshore fields, both in the Lower Kuradepression as well as the Apsheron- and Baku oil and gasbearing areas.

The structure is a clearly defined anticline with steepdips and crestal faulting. The southwestern flank of thestructure is downthrown by some 100-400 meters incomparison to the northeastern part. A system of complicatedfaults is observed in particular on the crest of the structure areassociated with intensive mud volcanism and possible strike-slip movements. Accordingly normal and reverse faults areobserved in the data which are not likely to have breached thestructure due to the shale abundance and plasticity of therising mud. The faults however will have facilitated chargingof the structure from the nearby kitchens, which are modeledto be marginally mature for oil at the main source rock level,i.e the Maikop Formation.

Geologic and aeromagnetic results of the study show thatthe crater of the recent mud volcano is located in the center ofthe Kyurdashi uplift and has created the island of the samename. The rising mud volcano brought also significantquantities of oil to the surface together with mud. Signs ofother active mud volcanoes are also observed on individualseismic lines. The character of the seismic records shows thatplastic clayey rocks were compressed and evacuated up thesection. Possibly, the volcano, acting at the end Pliocene timeand buried by more recent deposits, is confined to this zonewith only few chimneys reaching the surface.

The seismic data show the presence of longitudinal andcross disturbances, i.e. normal and reverse faults in the

Kyurdashi area. For the first time it was also possible todistinguish obliquely laminated formations on the seismicrecords, associated with the Paleo-Kura deltaic deposits. Theauthor is convinced that modern 3D-seismic recently shot bythe present licence holder and special attribute processing willallow for identifying detailed sedimentation patterns in theKyurdashi area and possibly give direct hydrocarbonindications.

Conclusions. Kyurdashi according to all estimates is agood example for the numerous large undrilled structures inthe South Caspian Basin. The first exploration wells on theblock are planned in 2000 and 2001. It is expected that thesewells will confirm the onshore oil play also in the offshorepart. Accordingly these exploration wells will be of keyimportance for proving the southwestern part of the BakuArchipelago as a valid hydrocarbon play with potentially giantdiscoveries.

OTC 12199 GEOLOGICAL- GEOPHYSICAL SUMMARY OF A TYPICAL OFFSHORE STRUCTURE 3 (KYURDASHI) IN THE SOUTH CASPIAN BASIN, AZERBAIJAN.

4 R. A. JAVADOVA OTC 12199

OTC 12199 GEOLOGICAL- GEOPHYSICAL SUMMARY OF A TYPICAL OFFSHORE STRUCTURE 5 (KYURDASHI) IN THE SOUTH CASPIAN BASIN, AZERBAIJAN.

6 R. A. JAVADOVA OTC 12199

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