Data-Driven Quantitative Reservoir Characterization and New Insights in Pubei Field of Turpan-Hami Basin, Western China

Abstract

Turpan - Hami is a Mesozoic - Cenozoic intermontane basin superimposed on the Cambrian crystalline basement and Paleozoic folded strata in the far northwestern China. This basin is a W- E orientation and surrounded by the Tian Shan and the Bogda mountains in the south and north respectively; and about 50,000 km² consisted of Turpan Sag to the west and Hami Sag to the east. The sediment fill of the Turpan - Hami basin contains more than 9 km of continental sediments from Late Permian to late Tertiary age, in which the Jurassic strata is up to 2.2 km composed of eight 3rd – order sequences. Pubei field is in the SW of Turpan-Hami basin and was found in 1993. The Jurassic oil is considered as oil derived from coal. The reservoir is dominated by alluvial and fluvial and lacustrine sequences of sandstone and siltstone sealed by lacustrine shale. Tectonic, lithological changes and fault geometries controlled on hydrocarbon traps. Limited amounts of oil and gas were produced in two decades. Exploration challenges were raised from poor quality seismic imaging caused by gravels with thickness up to 1800 m in the surface as well as harsh environment, and thick coal-beds in the subsurface, both resulted in severe seismic wave absorption; whereas the complicated strata by thrusting in Cenozoic time increased the uncertainty of seismic data interpretation. In 2014, seismic low-frequency 3D survey of 304 km² was completed by BGP with a frequency spectrum of 6 octaves, ranging from 1.5 to 96 Hz. The embedded ultra-low frequency components greatly improve seismic imaging below the coal-beds and small faults as well as lithological changes. A high accurate data-driven quantitative seismic inversion and attribute analysis in sequence stratigraphic framework was achieved by input of high lateral fidelity new data. The combined maps of structure, sedimentary facies and seismic attributes provided the possibilities to conduct quantitative assessment; and the application of spectrum decomposition and reservoir fluid mobility offered an evidence to predict oil and gas within thin reservoirs. Reservoir prediction has been proven by industry oil and gas flow from a new well completed in August 2015. With the improvement of deep seismic imaging, it is possible to conduct seismic evaluation in Paleozoic strata below coal-beds in the near future. This case demonstrated that low - frequency seismic technology remains keys to unlocking the oil and gas resources in a matured basin.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016