Abstract

Unconventional hydrocarbon resources, which are only marginally economically explored and developed by traditional methods and techniques, are different from conventional hydrocarbon resources in their accumulation mechanisms, occurrence states, distribution models, and exploration and development manners. The types of unconventional hydrocarbon are controlled by the evolution of the source rocks and the combinations of different types of unconventional reservoirs. The fundamental distinction between unconventional hydrocarbon resources and conventional hydrocarbon resources is their non-buoyancy-driven migration. The development of the micro- to nano-scale pores results in rather high capillary resistance. The accumulation mechanisms of the unconventional and the conventional hydrocarbon resources are also greatly different. In conventional hydrocarbon resources, oil and gas entrapment is controlled by reservoir-forming factors and geological events, which is a dynamic balance process; while for unconventional hydrocarbon resources, the gas content is affected by the temperature and pressure fields, and their preservation is crucial. Unconventional and conventional hydrocarbons are distributed in an orderly manner in subsurface space, having three distribution models of intra-source rock, basin-centered, and source rock interlayer. These results will be of great significance to unconventional hydrocarbon exploration.

Highlights

  • Unconventional hydrocarbon resources are becoming increasingly significant in global energy structures

  • Oil and gas entrapment is controlled by reservoir-forming factors and geological events, which is a dynamic balance process; while for unconventional hydrocarbon resources, the gas content is affected by the temperature and pressure fields, and their preservation is crucial

  • According to the relationship between source rock evolution and reservoir formation, we clarify the relations of various unconventional hydrocarbon resources, propose the identification marks and distribution models for unconventional hydrocarbon resources, and compare the differences between unconventional and conventional hydrocarbon in terms of types, characteristics, distribution models, and accumulation mechanisms, which provide important guidance for unconventional hydrocarbon exploration (Zou et al 2015)

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Summary

Introduction

Unconventional hydrocarbon resources are becoming increasingly significant in global energy structures. Unconventional hydrocarbon resources (including tight oil/gas, shale oil/gas, and coal bed gas) are becoming a significant component of world energy consumption (Jia et al 2012; Zou 2013). Unconventional hydrocarbons in tight reservoirs show characteristics distinct from those of the hydrocarbon sources hosted in structural and stratigraphic traps. According to the relationship between source rock evolution and reservoir formation, we clarify the relations of various unconventional hydrocarbon resources, propose the identification marks and distribution models for unconventional hydrocarbon resources, and compare the differences between unconventional and conventional hydrocarbon in terms of types, characteristics, distribution models, and accumulation mechanisms, which provide important guidance for unconventional hydrocarbon exploration (Zou et al 2015)

Generation of unconventional hydrocarbon resources
Identification marks of unconventional hydrocarbons
Key reason of non-buoyancy-driven accumulation
Mechanisms of non-buoyancy-driven accumulation Increase
Characteristics of unconventional hydrocarbon accumulation
Coexistence of unconventional and conventional hydrocarbon
The intra-source rock model
The source rock interlayer model
Conclusions
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