Most companies have contracts which average the oil price over the last 30 days, which could be 25th of month or other agreed date. It is not the price on the exact date oil was picked up. The price could be posted price of the purchaser or a combination price. There are plus and minus factors such as distance to delivery point, quality of oil and Cushing demand. So an operator's price will be uniform for wells in the same area, despite the date of pick-up. Some companies sell to company picking up the oil and others pay transport for sale elsewhere. It could be possible to use Cushing price if that was in contract.