Krom, although published in 2017, that report details what occurred with respect to the STP oil industry in 2015, including the payment described. However, in ERHC's annual report for 2016 they said this...
So, if the upside retained was 15% of the block, why not just say that?
With respect to the future value consideration on Block 11, we know that Kosmos shot seismic on that block and that they did not relinquish the block afterward which would imply that a decision was made to proceed "through seismic to drilling", meaning a payment could have already been due from Kosmos. I have speculated before that it is possible that ERHC was able to pay for some of their litigation expenses against Kosmos with proceeds received from Kosmos from the Block 11 agreement.