Sonatrach

About: Sonatrach is a company organization based out in Algiers, Algeria. It is known for research contribution in the topics: Hydraulic fracturing & Structural basin. The organization has 460 authors who have published 494 publications receiving 6339 citations. The organization is also known as: Sonatrach SPA.

Two novel combined systems for predicting the peak shear strength using RBFNN and meta-heuristic computing paradigms

Abstract: Effective prediction of the peak shear strength (PSS) is of crucial importance in evaluating the stability of a rock slope with interlayered rocks and has both theoretical and practical significance. This paper offers two novel prediction tools for the PSS prediction based on radial basis function neural network (RBFNN) and meta-heuristic computing paradigms. For this work, the gray wolf optimization (GWO) and ant colony optimization (ACO) algorithms were used to select the optimal parameters of RBFNN. Then, these two new models were compared with the gene expression programming (GEP) model. A total of 158 experimental data were used to train and test the proposed models using three input parameters, i.e., normal stress, compressive strength ratio of joint walls, and joint roughness coefficient. Finally, the computational result revealed that the RBFNN-GWO model, with the coefficient of determination (R2) of 0.997, produced a better convergence speed and higher accuracy compared with RBFNN-ACO and GEP models, with the R2 of 0.995 and 0.996, respectively. The RBFNN-GWO model was found an efficient predictive tool that can help rock engineers in the slopes design processes.

Henry Hub and national balancing point prices: what will be the international gas price reference?

Abstract: One of the lessons in the history of international trade in commodities is the emergence — sooner or later — of an international price reference, most commonly known as an international marker price. In the area of oil, West Texas Intermediate (WTI) plays the role of a marker for sour crudes traded in the Atlantic basin. Brent oil fulfils this function for sweet crudes traded in Europe. Another important aspect in the area of global commodities is that the emergence of a marker price is not always necessarily related to the relative share of production or exports of the commodity, but primarily to the existence of an organized market for this commodity. Today, while international gas trade is intensifying, we still lack an international price reference for this commodity. This is due to the fact that the international trade of natural gas is still highly regionalized. It is also due to the fact that most gas markets are still regulated. Nevertheless, deregulation efforts have been implemented in both developed (the United States, the United Kingdom, continental Europe, Korea) and developing countries (Brazil, Chile) and have led to new market structures based on more competition in all segments of the gas chain, except transportation. In the meantime, price structures based on supply and demand principles are supposed to have emerged in the US and UK markets in the 1990s as a result of the implementation of deregulation measures. Today, the US gas market, which represents more than 660 billion cubic metres per year of consumption and the UK gas market, which is close to 100 bcm annually, are considered mature enough to make the principles of supply and demand operate inside these markets. In fact, the Henry Hub (HH) price, which is determined at a physical location in Louisiana, US, and the national balancing point (NBP) price, which is determined somewhere inside the national transmission system (NTS), without any precise location, are considered as potential candidates to serve as a marker price in the international trade of gas. The objective of this paper is to examine some fundamental properties of the HH and NBP prices and assess which of them has the biggest potential to become an international price reference. Our main conclusions are: 1According to the relatively huge volume of gas traded on the US spot market, compared with the UK, and according to the experience accumulated by the New York Mercantile Exchange (NYMEX) in gas trading, the HH price has a bigger potential than the NBP to become an international price reference, particularly because the UK market is supposed to import more and more gas indexed to oil in the coming years. 2However, on the price fluctuation side, the NBP spot price seems to fluctuate more normally than the HH price in the short term, which can give a certain advantage to NBP prices. 3We cannot exclude the fact that in the coming years we will have two or even more reference prices in the Atlantic Basin: the NBP, the HH and also reference prices at other regional hubs.