This book is based on the laboratory and field research on Langgak Field, operated by SPR Langgak as one of Province-Owned Oil Company. This book is written to be a guideline and to add knowledge related to enhanced oil recovery (EOR) activity, particularly CO2 Injection. The authors are aware that the information about EOR activity in Indonesia is still limited, so with the presence of this book, we hope it can be made as a reference, not only for students but also for engineers and other researchers who would like to carry out or perform EOR project using CO2 Injection. The authors realize that there are some flaws in the completion of this book. Nonetheless, the authors believe this book will serve as a foundation for other CO2 EOR projects in Indonesia and improve the readers' understanding of CO2 Injection activity. Special thanks are given to the Director of PT. SPR Langgak, Mr Ikin Faizal, who gave us excellent support in the making of this book.