New Insights Into Mechanism of Ring Structure and Its Implication for Hydrocarbon Exploration

Abstract

Seismic data from the north Pishan area in southwest Tarim Basin disclose that there have “a diapir structure” from basement to Paleogene with a low-amplitude structure in the upper part. Previous research considered such structure result from magma intrusions. But the newly drilled well P1, which to ensure the oil-bearing ability of weathering crust in the top of “magmatic intrusion”, confirmed that magmatic diapir structure does not exist at all.

Based on fine interpretation of 3D seismic data, core data and analysis of rock scraps, a new interpretation model of meteorite impact structure was proposed and it may be have a significant implication for understanding distribution of high quality reservoir and finding prospective traps in hydrocarbon exploration.

The ring structure have a structure-geomorphic feature of uplift in the central and collapse in the margin. It has a better symmetric structure except northeast area where dips of ring shape fault are slower. As far as structural deformation is concerned, it showed positive flower structural style in the central of ring structure which means such area experienced compressional process, while in the margin of ring structure, negative flower structural style is presented in the profile which indicated extensional movement. The formation thickness is change inside the ring structure accompanied by structural deformation. Core data from well P1 disclosed that the formation of the top of ring structure is upper Cretaceous which is composed of breccia dolostone and limestone. It can be divided in to 3 section vertically according to entirely different lithologic feature. Through the test analysis of samples that equidistantly acquired from core or rock debris in well P1, positive anomalies in Iridium appear in entire upper strata of breccia from the depth of 6873m and with the highest value of 0.41μg/g.

In conclusion, based on the above evidences, the ring structure in the north Pishan area is meteorite impact related structure. This is more reasonable than the viewpoint of diapir structure in that dome style is the feature of diapir structure in which the collapse should influenced by normal faults, furthermore, the central area of collapse in diaper structure was a depression instead of an uplift. The possible forming mechanism of ring structure thereby provide a new cognition for reservoir reconstruction which may be contribute to finding effective high quality reservoir in hydrocarbon exploration.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018