Appraising Carbon Geological-Storage Potential in Unconventional Reservoirs: Engineering-Parameters Analysis

Abstract

Summary Most of the work focuses on the influences of reservoir parameters on carbon-storage capacity in depleted shales, and it is very useful for selecting good candidates as repositories. Undoubtedly, the engineering parameters in shales are also very important for carbon sequestration. However, little work has discussed their impacts on carbon dioxide (CO2) storing. To improve this situation, the objective of this work is to estimate the carbon-sequestration capacity under different engineering parameters. On the basis of a trilinear flow model, this paper studies the impacts of engineering parameters on carbon-storage potential. First, the methodology of appraising carbon-sequestration potential is introduced: (1) introducing the conceptual model, (2) developing the mathematical model, (3) obtaining the wellbore-pressure solution, (4) determining the injection time, and (5) appraising the carbon-sequestration capacity. In the conceptual model, the shale formation is divided into two subsystems and three regions: matrix subsystem, natural-fracture subsystem, hydraulic-fracture (HF) region, inner region, and outer region. With basic equations, a mathematical model is developed in these subsystems and regions. After that, on the basis of the mathematical model, CO2 storage potential in abandoned shales is investigated at different values of fracture conductivity, fracture number, fracture length, inner permeability, and wellbore length. Although much effort has been taken to estimate the carbon-sequestration potential, little work has considered the engineering parameters. This paper innovatively estimates the carbon-sequestration capacity under different engineering parameters, which provides a guideline to selecting wells and monitoring facilities for storing CO2 in the residual-depleted shale reservoirs.