Galkanysh: A Tethyan Super-Gaint Gas Field

Abstract

The Galkanysh Gas Field is located in the Amu Darya Basin in Turkmenistan. The main gas-bearing reservoirs of the field (Upper Jurassic carbonates) were first discovered in 2006 and were initially known as the South Yoloten and Osman Fields, but were later realised to be a single accumulation. Earlier exploration drilling had failed to reach the Jurassic reservoir due to severe over-pressure being encountered in the overlying interbeded carbonates and evaporites.

The Upper Jurassic Carbonate reservoirs consist of massive limestones and dolomites in a stratigraphic / structural trap, which in parts of the field exceeds 600 metres in thickness. No significant siliciclastic intervals have been found within the carbonate reservoirs and the massive nature of the reservoir has provided a significant challenge to reservoir correlation and characterisation.

Initial exploration activity was undertaken by Turkmengeology (TmGeol) and its associates. Later work (during the development stage of the field) has been shared with Turkmengas (TmGas) and its affiliates.

The field was initially identified using 2D seismic data and the first well to penetrate the Upper Jurassic Reservoir (SY-10) encountered a fully gas-bearing interval with no identified Gas-Water Contact before entering non-reservoir sediments of Jurassic Age. The shooting of multiple 3D seismic datasets and the drilling of appraisal wells has allowed greater understanding of the reservoir, the size of the field and well tests have proved the gas-water contact, which has confirmed the status of this super-giant gas field.

GCA has for several years worked with geologists and engineers from TmGeol / TmGas to establish the size and ultimate potential of this super-giant field. This work has ranged from the interpretation of the seismic data, well log analysis, the construction of both static and dynamic reservoir models, to the generation / confirmation of production profiles based on the phased field development plans that are currently being executed.

The presentation will review the history of the exploration, appraisal and development of the Galkanysh Field, and the evolution of the understanding of the reservoir characterisation and resource estimation of the field. The presentation will provide an insight into the complex nature of the field, the challenges that had to be addressed to achieve the currnet understanding, the remaining uncertainties and challenges, and how the geologists of Turkmenistan have worked using international best-practise and local knowledge to develop a robust framework and understanding of the field that provides the basis for the on-going production and development of the field.

AAPG Datapages/Search and Discovery Article #90226 © 2015 European Regional Conference and Exhibition, Lisbon, Portugal, May 18-19, 2015