Lacq

a large gas field in southwestern France, located within the Aquitaine Basin. The field is part of the anticlinal structure of eastern-southeastern strike. The gas deposits are included in the Upper Jurassic and Lower Cretaceous fractured limestones and dolomites at a depth of 3,500–4,300 m. The gas consists of methane (69–70 percent), heavy hydrocarbons (up to 5 percent), hydrogen sulfide (up to 15–17 percent), carbon dioxide (8–9 percent), and nitrogen (up to 0.5 percent). The annual production is 5 billion cu m of purified gas and 1.4 million tons of sulfur. A large hydroelectric power plant and large chemical and aluminum plants are located in Lacq. Most of the gas is transported to Paris through a pipeline, which also has branches to several other cities.