BERLIN–German oil and gas company Wintershall Dea AG, one of the investors in the now frozen Nord Stream 2 pipeline, said it would write off its 1 billion euro, or $1.1 billion, financing in the project and won't pursue new energy ventures in Russia. Germany last week halted the $11 billion Nord Stream 2 project that would have doubled the capacity of an existing pipeline traveling along a similar route and linking Russian gas fields directly to Germany. The project was backed by a number of Western energy players, including Shell PLC, which said on Monday that it would end...