Abstract

Shale reservoirs, with huge oil and gas resources in place, play an important role as energy resources in the world. In the meantime, widely-distributed organic-rich shales are being considered as one of the important carbon sequestration targets. Some studies have been done to characterize rockfluid properties, and flow mechanisms in the shale reservoirs. Most of these studies, through modifying methods used for conventional reservoirs, fail to capture dynamic features of shale rock and fluids. In confined nano-pore space in shale reservoirs, interaction between the wall of shale and the contained fluid significantly affects fluid properties. The incapability to model capillarity with the consideration of imperative pore size distribution characteristics using commercial software may lead to inaccurate results for Carbon Capture, Utilization, and Storage (CCUS). This paper presents a novel formulation that consistently evaluates capillary force in the light of using pore size distribution (PSD) directly from core measurements, and develops an adsorption model to achieve a realistic representation of CO2 storage mechanisms. The assumptions in Langmuir isotherm model affect the validity when it is applied to unconventional reservoirs, especially CCUS. An adsorption model was developed to incorporate adsorption behavior using a local density optimization algorithm. Our advances were also designed for multi-component interactions to adsorption sites for a full spectrum of reservoir pressures of interests. This feature allowed us to fully understand the storage and sieving capabilities for CO2 system with remaining reservoir fluids.

Introduction

It is widely regarded that the increasing emission of CO2 and other Greenhouse gases can cause Greenhouse effect and CO2 has been a major challenge to the global climate change. Carbon capture and storage is one of the options under investigation to reduce CO2 emissions in the atmosphere (House et al., 2006; Stefan, 2008). The options for CO2 geological sequestration have been widely investigated and the technical papers and reports are well-documented for almost every aspect of CO2 geological sequestration. Geologic formations have attracted much attention for the purpose of reducing of emission of carbon dioxide to the atmosphere through storing and sequestration process in recent years.

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