The Gas Huff-n-Puff PVT Experiment

The gas-based Huff-n-Puff (HnP) process is currently the dominating EOR process in tight unconventionals. This has happened as a result of operators looking to find new ways of increasing the production from their acreage, and several field implementations of the HnP process that have claimed success in doing so. Although the process has been studied largely the last years, there are still several aspects of the HnP process that are not yet fully understood, particularly its complex nature regarding the fluid phase behavior. To help increase the understanding of the HnP process from a fluid perspective, we suggest a novel PVT experiment that captures the key characteristics of the HnP process, and provide all relevant stakeholders with the key performance indicator (KPI) that we refer to as the gas HnP recovery efficiency, defined as “incremental volume of stock-tank oil (STO) produced per volume of surface gas injected” (which in field terms is denoted incremental STB of oil produced per MMscf injected) The proposed experiment is a hybrid of the traditional constant-volume injection (CVI) and constant-volume depletion (CVD) experiments, performed The paper outlines a detailed explanation of the experimental procedure, including what information is recorded during each period, and how to interpret the recorded data with relevance to a field implementation of the HnP process.