*Article* **Patent Analysis on the Development of the Shale Petroleum Industry Based on a Network of Technological Indices**

#### **Jong-Hyun Kim and Yong-Gil Lee \***

Department of Energy Resources Engineering, Inha University, 100 Inharo, Nam-gu, Incheon 22212, Korea; kjhpov@gmail.com

**\*** Correspondence: leedomingo@inha.ac.kr; Tel.: +82-32-860-7555

Received: 2 November 2020; Accepted: 16 December 2020; Published: 21 December 2020

**Abstract:** This study investigated the technological developments in the shale petroleum industry by analyzing patent data using a network of technological indices. The technological developments were promoted by the beginning of the shale industry, and after the first five years, it showed a more complex development pattern with the convergence of critical technologies. This paper described progress in the shale petroleum technologies as changes in relatedness networks of technological components. The relatedness represents degree of convergence between technological components, and betweenness centrality of network represents priority of technological components. In the results, the progress of the critical technologies such as directional drilling, increasing permeability, and smart systems, were actively carried out from 2012 to 2016. Especially, unconverged technology of increasing permeability and the converged technology of directional drilling and smart system has been intensively developed. Some technological components of the critical technologies are more significant in the form of converged technology.

**Keywords:** shale gas; tight oil; shale petroleum; technological development; patent; network analysis
