The success rates for exploratory wells below 15,000' has steadily increased since the early 1980s, but there are significantly greater individual well risks and costs involved in them. The potential of success cannot be outweighed by undue cost and risk if deep drilling is to occur. Deep drilling is very expensive and costs increase exponentially the deeper you go. For wells below 15,000' two-thirds of their costs are incurred in the last quarter of drilling. Round trips to change a bit can take an entire 24 hour day.
Any trouble is magnified by depth.
A problem at 8,000' that takes hours to correct, takes days at 18,000'. Significantly high temperatures and pressures require special drilling and completion fluids and stimulation techniques, all adding significantly to the bottom line. Drilling costs are similar in most states, but we have additional cost endemic to Oklahoma. We are well known for having extremely severed and fragmented mineral interests which create a complex land situation. The legal and administrative costs this causes are more burdensome in Oklahoma than in competing states.