Domestic drilling for petroleum took a big drop.

A total of 4,088 wells--1,889 oil, 623 gas and 1,576 dry--were completed in the first three months of 1987, compared to 7,525 in the first quarter of last year, for a 45.7% drop, according to the Petroleum Information Corp. Oil companies were cautious because of uncertainty about whether OPEC oil prices will hold at $18 per barrel, decline or even rise modestly by the end of the year, said P I analysts, who track drilling statistics worldwide.