| Author's Name: ZHANG Benjian, ZHOU Gang, SONG Zezhang, YAN Wei, WANG Hua, TAO Jiali,
TIAN Xingwang, DING Xiaoheng, ZHONG Yuan, MA Kui, YANG Dailin, LI Yong,
ZHANG Zili, CHEN Xi, SUN Yiting, XIANG Zhu, HUANG Maoxuan |
| In September 2022, the Well Dongba-1, deployed by PetroChina Southwest Oil & Gas Field Company on the
north slope of the central Sichuan paleo-uplift (Penglai gas area), achieved a significant exploration breakthrough in the
Longwangmiao Formation of Lower Cambrian. The breakthrough conform the multi-layers three-dimensional natural gas
accumulation in ultra deep and ancient marine carbonate rocks of Upper Sinian-Lower Cambrian in the north slope of
central Sichuan paleo-uplift. First, this article analyzes the sedimentary facies, lithofacies, and reservoirs of multiple gasbearing
layers of Upper Sinian-Lower Cambrian in Penglai gas area. Then, starting from three aspects: source rock and
source reservoir configuration, sedimentary facies and diagenesis, multi-layers gas bearing characteristics and traps, the
favorable conditions for multi-layers gas bearing in the slope area are dissected, and a three-dimensional reservoir
formation model is established. The results indicate the widely distributed thick and high-quality source rock such as the
mud shale of the Dengying Member 3 and the black shale of Qiongzhusi Formation, provides a good material guarantee
for multi-layers natural gas accumulation. The source-reservoir assemblages of upper generation-lower storage and side
generation-side storage ensures the efficient filling of natural gas into the reservoir. The Sinian Dengying Formation is
influenced by multiple cycles of Tongwan movement and sea level’s rising and falling, and thick stacked mound-shoals are
developed. The Cambrian Canglangpu Formation and Longwangmiao Formation are controlled by paleogeomorphology to
develop high-energy granular shoals of dolomitization. The mound-shoals and high-energy granular shoals form the
material basis for reservoir formation, and the widely developed karst process in the later stage further improves the
physical conditions of the reservoir, directly controlling the formation and distribution of high-quality reservoirs. Locally
developed small-scale structural traps, together with lithological traps and structural-lithological composite traps in the
slope background, control the multi-layers gas bearing. Exploration practice has shown that the Sichuan Basin is rich in
ultra-deep oil and gas resources. Continuously deepening the understanding of ultra-deep reservoir formation and
geological theory, emphasizing the simultaneous advancement and mutual promotion of geological theory and engineering
technology, and continuing to advance towards the 10 000 meter’s ultra-deep layer will inevitably open up new fields of
high-quality scale reserve and production. |
