| Author's Name: GONG Qingshun, LIU Zhanguo, LONG Guohui, ZHU Jun, HUO Peng,
LI Zhaoqi, ZHU Chao, WU Jin, SONG Guangyong |
| In Qaidam Basin, the Kunlun piedmont zone is an important area of oil and gas exploration, and the lower
section of Paleogene Lower Ganchaigou Formation is its main oil-bearing layer. Controlled by the differences in the
development of sandstone reservoir, the degrees of oil and gas enrichment showed differences in different belts of Kunlun
piedmont zone. In order to clarify the difference and formation mechanism of reservoir of the lower section in Lower
Ganchaigou Formation, by using core, wireline logging data and experiment data, this paper analyzed the reservoir
characteristics and controlling factors in different belts of Kunlun piedmont zone, such as Qie6 block, Wunan slope belt,
Dongchaishan area and Wanxi structural belt. It is believed that the reservoir characteristics in the lower section of Lower
Ganchaigou Formation are significantly different in time and space. In Kunlun piedmont zone, the lower section of Lower
Ganchaigou Formation develops clastic pore-type reservoirs, and the reservoir’s storage space is mainly the primary
intergranular pore. There is five genetic types of sandbody in this study area, namely distributary channel, underwater
distributary channel, estuarine bar, sheet sand in braided river delta facies, and beach bar in shore-shallow lake subfacies.
The dual superposed effects of sedimentary facies and diagenesis result in significant differences in the development of
reservoirs in Kunlun piedmont zone. There are average porosity and permeability values of 14.1% and 32.76×10-3 μm2 in
Qie6 block, 13.4% and 36.48×10-3 μm2 in Wanxi structural belt, 6.7% and 2.38×10-3 μm2 in Wunan slope belt, and 3.1%
and 0.1 × 10-3 μm2 in Dongchaishan belt. Under the same burial depth, the differences of sedimentary structure and
sandbody scale, are the main reasons for reservoir physical properties’ differences in different sedimentary microfacies,
and underwater distributary channel had the best reservoir physical properties, followed by estuarine bar and distributary
channel, and the physical properties of beach bar and sheet sand are relatively poor. Under the different burial depth
conditions, the differential compaction caused by factors such as maximum paleoburial depth and paleogeothermal
gradient, is the main factor controlling the reservoir physical properties’ difference in Kunlun piedmont zone. The
reservoir physical properties in Qie6 block and Wanxi structural belt are the best, followed by Wunan slope belt, and it is
poor in Dongchaishan belt. |
