Depositional Setting and History of the Red Series Reservoirs Block 1, South Caspian Sea, Turkmenistan
David Ince1, Gordon Yeomans2, and Kamarolzaman B. Yahya2
1Petronas Carigali Sdn. Bhd, Kuala Lumpur, Malaysia
2Petronas Carigali Turkmenistan Sdn Bhd., Ashgabat, Turkmenistan
Petronas Carigali Sdn. Bhd. has been actively exploring and developing the Block 1 area of the Central Caspian Sea, Offshore Turkmenistan for the past 10 years and to date has drilled 16 wells of which five have been cored, providing a near complete coverage of the Pliocene Red Series reservoir section.
The lowermost part of the RS8 reservoir interval in the Livanov area shows features considered to represent the results of large-scale slump and water escape processes. The overlying section shows structures that allow the recognition of large wave or dune-like bedforms. This facies type is predominant in the majority of sand dominated cores in the intervals including those from the Owez and Mashrykov wells some 50 km distant to the N.W. along the Apsheron structure and is interpreted as the deposits of lacustrine sand waves. The sequence passes abruptly upward into a thin, 8-10 cm, carbonate horizon comprising various carbonate grains and a crustose mat of probable algal origin indicative of oxygenated, clear water conditions and reflecting an abrupt cessation of sediment supply. The overlying mudstones appear to have been deposited under anoxic conditions for the most part, although TOC analysis shows them to be organically lean. The section then passes into a heterolithic succession, frequent lowering of lake levels and dessication of the lacustrine mudstones is indicated by shrinkage cracks and palaeosols. Analogues, at least in part, for the various facies may be found in the present day Caspian Sea and surrounding lake margins.
The availability of cores from these wells has revealed a complex geological history in a highly variable reservoir section. Further understanding of the reservoir will require extensive coring and integration of the data with seismic and well log interpretations.
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