As global crude prices plunged earlier this month, Venezuela’s foreign minister asked to see Saudi Arabia’s top oil official at a climate-change conference on Margarita Island, off the South American coast. Ali al-Naimi, the Saudi oil minister, was expecting a plea to reduce oil output and bolster markets. In anticipation, according to people familiar with the matter, he brought a message to Venezuelan Foreign Minister Rafael Ramirez : Saudi Arabia won’t cut production on its own. Mr. Naimi is expected to repeat the message to delegates at a meeting of the Organization of the Petroleum Exporting Countries in Vienna later this month, according to Saudi officials and fellow OPEC officials.