Levelized cost of energy (LCOE) method is a frequently used approach to determine the economics of an energy project. However, the approach have faced a lot of criticism due to the lack of transparency in costing along with some additional drawbacks. Although the refinement of the LCOE method has led to its improvement, but there are still some concerns in the form of considerable benefits that may produce unreliable results. In order to provide the solution of drawbacks associated with LCOE method, this research work focuses on presenting an alternative costing approach. The adoption of benefit-to-cost ratio analysis (BCRA) method for the decision-making of energy systems is proposed in this work. A comprehensive assessment between LCOE and BCRA methods was carried out with a purpose to observe their influence in determining the success or failure rate of an energy project by considering the associated benefits. For this purpose, two case studies were considered; Chena Geothermal Power Plant (Alaska, United States) and Quaid-e-Azam Solar Power Project (Bahawalpur, Pakistan). The assessment was carried out on the basis of different scenarios, which were developed according to the obtainable benefits from a particular project. The results show that, compared with the LCOE method, the BCRA method is more feasible and practical in energy project decision-making process. Moreover, it was noticed that the BCRA method can provide better and useful insights to help maximize the economic benefits of the project.

The damages of different drilling modes to reservoirs are different in types and degrees. In this paper, the geologic characteristics and types of such damages were analyzed. Then, based on the relationship between reservoir pressure and bottom hole flowing pressure corresponding to different drilling modes, the experimental procedures on reservoir damages in three drilling modes (e.g. gas drilling, liquid-based underbalanced drilling and overbalanced drilling) were designed. Finally, damage simulation experiments were conducted on the tight sandstone reservoir cores of the Jurassic Ahe Fm in the Tarim Basin and Triassic Xujiahe Fm in the central Sichuan Basin. It is shown that the underbalanced drilling is beneficial to reservoir protection because of its less damage on reservoir permeability, but it is, to some extent, sensitive to the stress and the empirical formula of stress sensitivity coefficient is obtained; and that the overbalanced drilling has more reservoir damages due to the invasion of solid and liquid phases. After the water saturation of cores rises to the irreducible water saturation, the decline of gas logging permeability speeds up and the damage degree of water lock increases. It is concluded that the laboratory experiment results of reservoir damage are accordant with the reservoir damage characteristics in actual drilling conditions. Therefore, this method reflects accurately the reservoir damage characteristics and can be used as a new experimental evaluation method on reservoir damage in different drilling modes