Elsevier BV

Encouraged by the wide spectrum of novel applications of gas hydrates, e.g., energy recovery, gas separation, gas storage, gas transportation, water desalination, and hydrogen hydrate as a green energy resource, as well as CO2 capturing, many scientists have focused their attention on investigating this important phenomenon. Of course, from an engineering viewpoint, the mathematical modeling of gas hydrates is of paramount importance, as anticipation of gas hydrate stability conditions is effective in the design and control of industrial processes. Overall, the thermodynamic modeling of gas hydrate can be tackled as an equilibration of three phases, i.e., liquid, gas, and solid hydrate. The inseparable component in all hydrate systems, water, is highly polar and non-ideal, necessitating the use of more advanced equation of states (EoSs) that take into account more intermolecular forces for thermodynamic modeling of these systems. Motivated by the ever-increasing number of publications on this topic, this study aims to review the application of associating EoSs for the thermodynamic modeling of gas hydrates. Three most important hydrate-based models available in the literature including the van der Waals–Platteeuw (vdW–P) model, Chen–Guo model, and Klauda–Sandler model coupled with CPA and SAFT EoSs were investigated and compared with cubic EoSs. It was concluded that the CPA and SAFT EoSs gave very accurate results for hydrate systems as they take into account the association interactions, which are very crucial in gas hydrate systems in which water, methanol, glycols, and other types of associating compounds are available. Moreover, it was concluded that the CPA EoS is easier to use than the SAFT-type EoSs and our suggestion for the gas hydrate systems is the CPA EoS.

Immiscible water-alternating-gas (WAG) flooding is an EOR technique that has proven successful for water drive reservoirs due to its ability to improve displacement and sweep efficiency. Nevertheless, considering the complicated phase behavior and various multiphase flow characteristics, gas tends to break through early in production wells in heterogeneous formations because of overriding, fingering, and channeling, which may result in unfavorable recovery performance. On the basis of phase behavior studies, minimum miscibility pressure measurements, and immiscible WAG coreflood experiments, the cubic B-spline model (CBM) was employed to describe the three-phase relative permeability curve. Using the Levenberg–Marquardt algorithm to adjust the vector of unknown model parameters of the CBM sequentially, optimization of production performance including pressure drop, water cut, and the cumulative gas–oil ratio was performed. A novel numerical inversion method was established for estimation of the water–oil–gas relative permeability curve during the immiscible WAG process. Based on the quantitative characterization of major recovery mechanisms, the proposed method was validated by interpreting coreflood data of the immiscible WAG experiment. The proposed method is reliable and can meet engineering requirements. It provides a basic calculation theory for implicit estimation of oil–water–gas relative permeability curve.

To investigate the situation of conventional oil and gas, this paper examines the global oil and gas discoveries, proved reserves, production, consumption and price. All the influencing factors can be subjected to risk and opportunity analyses, so in the paper, we build upon a risk-opportunity analysis framework, which is a new train of thought. To forecast the peak time of oil and gas production, we used the methods of multi-Hubbert model forecasting and data forecasting. Our results showed that the world oil production will reach a peak between 2010 and 2015 and the gas production will reach a peak around 2030 Oil peak is coming and gas peak is on the way. The main purpose of forecasting oil and gas production peak is give people enough time for preparing mitigation and adaptation plans. This means taking decisive action well before the problem is obvious.

A finite element method is developed for simulating frequency domain electromagnetic responses due to a dipole source in the 2-D conductive structures. Computing costs are considerably minimized by reducing the full three-dimensional problem to a series of two-dimensional problems. This is accomplished by transforming the problem into y-wave number (K y ) domain using Fourier transform and the y-axis is parallel to the structural strike. In the K y domain, two coupled partial differential equations for magnetic field Hy and electric field Ey are derived. For a specific value of K y , the coupled equations are solved by the finite element method with isoparametric elements in the x-z plane. Application of the inverse Fourier transform to the K y domain provides the electric and magnetic fields in real space. The equations derived can be applied to general complex two-dimensional structures containing either electric or magnetic dipole source in any direction. In the modeling of the electromagnetic measurement, we adopted a pseudo-delta function to distribute the dipole source current and circumvent the problem of singularity at the source point. Moreover, the suggested method used isoparametric finite elements to accommodate the complex subsurface formation. For the large scale linear system derived from the discretization of the Maxwell’s equations, several iterative solvers were used and compared to select the optimal one. A quantitative test of accuracy was presented which compared the finite element results with analytic solutions for a dipole source in homogeneous space for different ranges and different wave numbers K y . to validate the code and check its effectiveness. In addition, we addressed the effects of the distribution range τ of the pseudo-delta function on the numerical results in homogeneous medium.