When an exploration drilling is initiated, nothing is certain.
In the past, only one exploration well in seven finally ended up as a productive deposit. Today, evaluation methods have been refined and little known zones are much more rare.
So the average is rather one success in three or four exploration wells.
In the case of success, certainly one is encouraged a lot! But, nevertheless, it is not the case that the field is going to be put into production immediately. Even if some of the uncertainties have been removed (there is oil and gas, there is a reservoir …), it is still necessary to drill several wells so that the deposit can be very well defined and the uncertainties further reduced. These complementary wells, which allow the deposit to be better understood, constitute the
appraisal.
As soon as the exploratory well is finished, a full study of the prospect, now called a discovery,
is re-launched and a programme of appraisal is established. |