This document analyses the effects of regulation and competition policy on the structure of the gas market. The natural monopoly features of transportation, added to the physical and technological features of gas as a commodity, allow this activity to be the focus of interesting regulatory procedures directed to increase the level of competition in the wholesale trading and supply segment. We will focus on the mandatory open access regime, and employ the most relevant analytical frameworks including the Ramsey pricing structure and the Efficient component Pricing Rule (ECPR). While presenting those schemes, we try to introduce the principles of nonlinear pricing (second-degree price discrimination) to take advantage of custome's heterogeneity in different dimensions as duration or reliability of the contracts. As is traditional in studies related to access pricing, we show that under specific conditions the ECPR yields the same results of a Ramsey structure.