| Author's Name: ZHANG Benjian, ZHONG Yuan, ZHOU Gang, YAN Wei, LI Kunyu, HE Yuan,
ZHAO Like, LONG Hongyu, Lü Wenzheng, QIAO Yanping |
| The great breakthrough and centralized evaluation results of the second member of Dengying Formation
(Dengying Member 2) in PT1 Well Block confirmed the development of high-quality marginal platform porous-vuggy
reservoir and the favorable conditions of lithologic gas reservoir in the northern slope zone of central Sichuan paleouplift.
In order to further describe the characteristics of the mound-shoal lithologic gas reservoir in Penglai area and evaluate its
exploration potential, this paper analyzes the microfacies characteristics and sedimentary evolution process of the
Dengying Member 2 in PT1 Well Block by making comprehensive use of drilling, logging and seismic data. The results
show that: (1) High-energy mound-shoal deposit of typical marginal platform is developed in the Dengying Member 2,
the lithology is dominated by clotted dolomite and micrite-very finely crystal dolomite, and mound core, mound flat and
inter-mound microfacies can be identified, presenting the characteristics of multiple facies sequence combination. (2)
Based on carbon isotope, resistivity curve and well-seismic calibration results, the Dengying Member 2 can be divided
into three submember, the thickness and microfacies of which presents the differential characteristics of different degrees
in vertical and lateral. (3) Based on the correlation between the microfacies and time thickness and internal amplitude
energy of submember, the distribution characteristics of sedimentary microfacies in three stages (early, middle and late)
are clarified and the sedimentary evolution model of the Dengying Member 2 in PT1 Well Block is established. (4) Under
the control of structural morphology and uniform gas-water interface, the main gas reservoir of the Dengying Member 2
in PT1 Well Block is mainly distributed in submember 3 of Dengying Member 2 and is differential to some extent due to
the constraint of sedimentary facies internally. Accordingly, this lithologic gas reservoir is evaluated comprehensively
based on multiple factors and it is divided three types of exploration area, in which class I and II areas have large water
avoidance and gas column height, and are the best dessert areas for the next concentrated exploration. This proposed
evaluation method can further provide important support and reference for the subsequent exploration of lithologic gas
reservoirs of Dengying Formation in the slope zone of central Sichuan paleouplift. |
