Origin and
Distribution of Favorable Reservoir in Upper Triassic Feixianguan
Formation of Northeastern Sichuan Basin, China
Yang, Xiaoping1, Wenzhi Zhao2, Hong Cao3 (1) Geology
Department of RIPED, Petrochina, Beijing, China (2) PetroChina, Beijing, China (3)
Geophysics
Department of
RIPED, Petrochina, Beijing, China
In northeastern Sichuan basin, a great
achievement of petroleum
exploration
is to find a giant gas field in upper
Triassic Feixianguan formation in past few years,
which includes Luojiazhai, Dukouhe,
Tieshanpo pools. Moreover,
in early 2005 it is found another giant gas pool: Puguang
gas pool with an estimated reserve exceeding 3500×108m3. Therefore it is quite
significant to Study on origin and distribution of favorable reservoir for
them.
In the upper Triassic Feixianguan
formation of northeastern Sichuan Basin, it is mainly developed
three types of sedimentary facie, which are lagoon-tidal flat, oolitic bank of platform margin and slope. The favorable
reservoir mainly distributes in oolitic bank of
platform margin and consists of oolitic dolomite,
residual oolitic dolomite and sugary grained residual
oolitic mid-macro crystalline dolomite. With studying
on petrography, cathodoluminescence, scanning
electron microscopy, X-ray diffractometry, minor
element, and liquid inclusion for the reservoir, it is found that mixing dolomitization and dissolution are two key factors to form
effective reservoir. When the reservoir experienced post-sediment diageneses, it is happened four periods of dissolution
which are meteoric water dissolution, organic acid water dissolution during
shallow-buried, sulfuric acid water dissolution during deep-buried period and
meteoric water dissolution during the basin rising up. Moreover, it is also
found that the effective reservoir vertically interbeds
with sparry oolitic
limestone and literally distributes in oolitic banks
nearby lagoon-tidal flat.