| Shajingzi fault belt in the northwest of Tarim Basin has achieved exploration breakthrough, showing a good
exploration prospect, but the study of oil and gas geological conditions in this area is relatively weak. Based on the
comprehensive use of the latest drilling, seismic and field outcrop data of Shajingzi fault belt, the segmented structural
characteristics and evolution process of Shajingzi fault belt are described in detail. Combined with the evaluation of oil
and gas geological conditions, oil and gas accumulation models of multiple sets of strata are proposed, and favorable
exploration directions are pointed out. It is shown that Shajingzi fault belt can be divided into east section, west section,
middle section and Aqia section according to the difference of structural features and derived faults. The Shajingzi fault belt
has the characteristics of multi-stage activity and late finalization. It has been in the position of structural slope for a long
time and has developed many types of traps. It is a favorable area for oil and gas migration and accumulation. At the same
time, the source-reservoir-cap is well configured in time and space, and the conditions for oil and gas accumulation are
available: (1)Two sets of high-quality source rocks, the Lower Cambrian Yuertus Formation and the Lower Ordovician
Sargan Formation, are developed, which have been proven to be the main source of oil and gas in this area. (2)Three sets of
reservoirs are developed: dolomite reservoir of the Cambrian subsalt mound-shoal facies, tidal channel sandstone reservoir
and shore bar reservoir of tidal flat-shore composite sedimentary facies of the Silurian Kepingtage Formation, fan delta
sandstone reservoir of the Triassic Ohoborak Formation and braided river delta sandstone reservoir of the Triassic Karamay
Formation. (3)Three sets of caprocks are developed, including the Middle Cambrian thick layer gypsum salt rock, the
Silurian Tataelta Formation’s mudstone interlayer and Yimugantawu Formation’s thick layer mudstone, and the mudstone
interlayer of the Triassic Ohoborak Formation and Karamay Formation. (4) The oil and gas filling shows the characteristics
of multi-stage filling and late stage dominated. Two oil and gas reservoir models of "structure dominated, multi-stage filling
and late stage reservoir formation" in Silurian and Triassic and "structure dominated, continuous filling" under the Cambrian
salt are established. It is considered that the Silurian system, Triassic system in the footwall of Shajingzi fault belt and the
Cambrian subsalt of Aqia section in the upper wall are favorable exploration areas. |
