Summary Solubility and diffusivity of gases in heavy oils, quantified by Henry's constant (Hij) and the diffusion coefficient (D), respectively, are essential properties for the design of recovery processes that require the injection of gas or vapor solvents into the reservoir. Data, obtained from various experimental procedures such as the pressure-decay technique (PDT), are used to estimate these two parameters. The PDT uses a pressure/volume/temperature (PVT) cell where the gas-phase pressure declines as gas diffuses into heavy oil following an early- and a late-time regime. Current approaches to analyze data from the conventional PDT are either graphical techniques based on early-time data or full numerical simulation. Early-time data, when the diffusing gas has not reached the bottom of the PVT cell, do not provide enough information to simultaneously estimate both the diffusion coefficient and Henry's constant. Hence, existing graphical procedures are limited to diffusion-coefficient estimation. In this paper, we propose a novel graphical technique to estimate the diffusion coefficient and Henry's constant by use of the late-time data from pressure-decay experiments. Our method is derived from the modeling of gas-phase pressure decay by use of Fick's second law and gas-phase mass-balance equations. We use the integral method to provide an approximate analytical solution to the set of equations. In addition, by use of the resultant solution, we develop a simple graphical method to directly estimate both the diffusion coefficient and Henry's constant. The estimated parameters through the proposed technique for methane/bitumen and carbon dioxide/bitumen experiments are in close agreement with those reported in the literature.

The pressure-decay technique is used to determine the diffusivity and solubility of methane and carbon dioxide in pure hydrocarbons and bitumen at temperatures of 0, 15, 20 and 25 °C and pressure of 3.5 MPa. An analytical-graphical technique is implemented to extract the related mass-transfer parameters, i.e., diffusion coefficient and Henry's constant, from the pressuredecay data. The results reveal that the diffusion coefficient of methane and carbon dioxide in both, pure hydrocarbons and bitumen, decreases as the temperature decreases. On the basis of the Henry's constants, the effect of the temperature on the solubility of the gaseous solvents in bitumen and pure hydrocarbons is also determined. As expected, the solubility of both gases in the studied pure hydrocarbons increases as the temperature decreases. In addition to confirming the known trends, this study provides new experimental data for low temperature gas-hydrocarbon diffusion process.

The objective is to present a matrix to identify environmental and social aspects which may impact the initiation, assessment, approval of final investment decision and implementation of oil and gas projects in Mexico. The matrix is applied to 19 blocks. The results demonstrate the usefulness in ease of identification of key elements which may be focus of attention to project feasibility. This may be used as tool for resource classification, and thus adapted to other countries. The Agency for Safety, Energy and Environment (ASEA) with collaboration from the Energy Ministry (SENER) were involved while the project selection was integrated by the National Hydrocarbon Commission (CNH). CNH selected 19 blocks for review with 75 oil and gas projects. SENER and ASEA developed a matrix with clear identification of environmental and social aspects which may have an impact on the potential implementation of each project. The traffic light and multivariate analysis methods were adopted to colour code the environmental and social elements. This coding allowed quick identification of key areas which need to be addressed for project feasibility. The selected blocks were located both offshore and onshore with different environmental and social issues. Unconventional and conventional resource developments were covered in the projects. The use of the matrix provided a consistent tool for better identification and understanding of the social and environmental aspects interacting in each block. It also emphasized the main sources of information and the best way to evaluate systematically the social and environmental aspects. The application of the matrix on real blocks exposed the social and environmental aspects that must to be addressed for the oil industry to develop from a sustainable vision. The evaluation of diverse blocks allowed for the identification of common characteristics and the subsequent classification of the blocks. The developed matrix may be used as a tool for making energy policy decisions. At the national level, it may also assist in understanding and meeting some of UN Sustainable Development Goals (SDG's). This paper presents a novel matrix to identify environmental and social elements relevant for the development of any oil and gas project. It also proposes a useful traffic light and multivariate analysis methods for the evaluation of these elements. The matrix allows quick and easy reference for identification of the key elements which may be focus of attention to oil and gas project feasibility. This approach may benefit the decision-making process within an integrated sustainability perspective.