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ALLUVIAL DEPOSITION AND IMPLICATIONS FOR RESERVOIR DEVELOPMENT, SHUANGYANG SANDSTONE, MOLIQING BLOCK, YITONG GRABEN, P. R. CHINA

John S. Sneider1, Andrew S. Harper2, Susan Cao2, and Haibin Zhou3
1 Sneider Exploration Inc
2 MI Energy Corp
3 ZPEB (PetroChina Zhongyuan)

Moliqing Field lies in the Yitong Graben, within the Moliqing Rift, at the southeastern margin of the Songliao Basin. The main reservoir objectives in the Moliqing area are the alluvial sands of the Eocene Shuangyang Formation, Member 2 (Sand Groups IV and V), which are at depth range of 2200-2900 meters. The Moliqing trap is interpreted to have a significant stratigraphic component, involving the discontinuous Shuangyang alluvial sands.

The primary geological risk factor at Moliqing is reservoir distribution, due to the fact that the main reservoir objective Shuangyang sands are discontinuous and quite variable in thickness and quality. Careful and comprehensive geological studies, including the integration of core data, well logs and seismic data will be crucial to successful development of the Shuangyang reservoir.

Since 2001, operator MI Energy and partner PetroChina, together with contractor ZPEB have drilled 6 wells to test the Eocene Shuangyang Formation Sandstones, which are the main reservoir objectives in Moliqing Field. Conventional core samples were taken in the Shuangyang interval in well Y41-2, which is a discovery well, with 51m pay and currently producing 200 BOPD.

Y41-2 Shuangyang Mbr 2

o Core Depth: 2660.6 – 2693.6m
o Porosity:  4.3 – 16.6%  6.8 – 18.4%
o Permeability:  0.07 – 33.8mD  0.08 – 651mD
o Unit Thickness:  6.5m  5m
o Lithology:  Sandy Siltstone  Gravelly Sandstone
o Facies:  Abandoned Channel Fill  Braided Channel

 

Y41-2 Shuangyang Mbr 1

o Core Depth:  2865.27 – 2890.0m
o Porosity:  5.5 – 11.5%  3.9 – 14.4%
o Permeability:  0.06 – 2.73mD  0.26 – 15.1mD
o Unit Thickness:  2.8m  3.2m
o Lithology:  F Silty Sandstone  F Silty Sandstone
o Facies:  Alluvial Fan Overbank  Alluvial Channel

The Shuangyang sands in Well Y41-2 are interpreted to have been deposited in alluvial environments adjacent to east- and northeast-trending, down-to-the-north graben-bounding faults. Specific facies observed in Y41-2 cores include braided channel and abandoned channel fill (Mbr 2), and alluvial channel and overbank (Mbr 1).