An abundance of fossil fuels combined with advances in technology to harness wind and solar power has sent energy prices crashing around the world. WSJ explains how it all happened at once. Photo illustration: Carlos Waters/WSJ Schlumberger Ltd., the world’s largest oil-field services company, is cutting about 21,000 jobs as oil producers slash spending in response to a historic drop in prices amid the coronavirus pandemic. Schlumberger said Friday that it recorded $3.7 billion in impairment charges in the second quarter, including about $1 billion related to the job cuts, which represent roughly one-fifth of its workforce. “This…