Variability and Main Controlling Factors of Hydrocarbon Migration and Accumulation in the Lower Paleozoic Carbonate Rocks of the Tazhong Uplift, the Tarim Basin, Northwest China

Qifei Fang,Qingzhou Yao,Yongqiang Qu,Min Zhang,Lisha Yang,Shan Fan,Xiaoxue Wang,Weiping Zhu,Huizhen Li,Youlu Jiang,Dongdong Dai,Jianhui Yang

doi:10.1155/2021/6693658

Abstract

Hydrocarbon migration patterns and pathways were studied on the basis of three-dimensional seismic interpretation, drilling, geochemistry, production performance, and other data. Using these findings, the main factors controlling hydrocarbon migration and accumulation in the Lower Paleozoic carbonate rocks of the Tazhong Uplift were discussed. The spatiotemporal relationship between the hydrocarbon kitchens and pathway systems of the Tazhong Uplift and the spatial pattern of pathway systems were considered the main factors causing differences in hydrocarbon enrichment. Results also revealed that the Lower Paleozoic carbonates of the Tazhong Uplift have two hydrocarbon accumulation systems (inside and outside the source rocks). For the accumulation system within the source rocks, hydrocarbon migration and enrichment are vertically differentiated. Middle Cambrian gypsum salt rocks serve as the boundary, above which thrust and strike-slip faults mainly allow vertical transport of hydrocarbons. A multistage superposition pattern of strike-slip faults controls the differences in hydrocarbon enrichment on the periphery of the fault zone. Beneath the gypsum-salt rocks, hydrocarbon migration and enrichment is controlled by the topography of paleostructures and paleogeomorphology. For the hydrocarbon accumulation system outside the source rocks, hydrocarbon migration and enrichment are restricted by the layered pathway system, and the topography of the paleostructures and paleogeomorphology is the key factor controlling hydrocarbon enrichment. The Tazhong No. 1 Fault is the main vertical pathway system in the area underlain by no source rocks, and hydrocarbons are enriched at the periphery of the Middle-Lower Cambrian and No. 1 Fault Zone.

Highlights

The ultradeep ancient carbonate rocks of the Tarim Basin, with an abundance of hydrocarbon resources, are an important field with the best exploration prospects [1, 2]
The following conclusions are drawn: (1) Our proposed source pathway transport characteristics of the carbonate rocks in the Tazhong Uplift provide a new basis for detailed investigation of hydrocarbon migration in carbonate rocks
After determining the sources of marine carbonate rock hydrocarbons in the Tazhong Uplift, this paper studied the distribution, activity, and classification of various pathway systems

Summary

Introduction

The ultradeep ancient carbonate rocks of the Tarim Basin, with an abundance of hydrocarbon resources, are an important field with the best exploration prospects [1, 2]. The average matrix porosity is less than 2%, permeability is less than 5 × 10−3 μm2 [3, 4], and the compactness and high heterogeneity greatly impair the free flow of oil and gas. In these rocks, pathway elements occur as faults, fractures, and unconformity surfaces. Secondary dissolved pores participate in modifying the rock properties, enhancing reservoir porosity and permeability, and providing the necessary conditions for hydrocarbon migration, adjustment and accumulation in carbonate rocks [5, 6]

Results

Discussion

Conclusion