This is from the Red Emperor pages of Interactive Investor - by preempt:

HRN are now only planning to drill SN to a depth of 2,400 Mt's to target the Jessoma deposit. This should reduce the cost of the well considerably and sure up reserves a lot quicker. With the reduced bore size in SN they will be able to wire line test any discovery straight away, so our wait may not be as long as some think. On success, any future wells will be de-risked considerably. I also understand the SN well is expected to have a thicker Cretaceous Jessoma target? In Yemen, most of the wells only flow from one zone, so given the positive view on the S1 Jessoma zone, they may have thought it better to sure up this zone first?

We are looking at an oil field, not just two wells total. If/when SN identifies a continuation of the Jessoma discovery, this will justify further wells in the basin to prove the extent of the resource. Success in SN which is looking far more likely now that we have discovered oil in S1 will underpin RMP at around recent highs with future development offering massive upside. The only enemy is our impatience. The six billion barrel Yemen fields were not proved up after drilling one or two wells.

The international interest demonstrates the level of confidence here.