CNOOC Limited

Horizontal wells only: 231 of the 231 wells in these cohorts. Average daily production per well, for wells grouped by when they first produced. Includes every well of the cohort that is old enough at each month. Wells that are shut in or have stopped producing count as zero, so the average reflects the full cohort, not just survivors. Rates are calendar-day (volume ÷ days in month). The cumulative axis accumulates those same monthly averages at the average month length. Months not yet fully reported are excluded. The 2010-2014 curve draws those years as one group. The chart opens on average daily rate against months on production, the rate on a log scale. The view control switches to rate against cumulative production per well, on the same log rate scale, or to cumulative production per well against months on production, on a linear scale. Every view draws the same cohorts from the same production history. Each cohort is solid through the last month all the wells in its curve sit inside fully reported data. Past it the dashed curve carries the same wells forward, on our forecast where a well’s own record ends, for up to five years. A dashed curve runs as far as at least nine in ten of its wells are accounted for. A well that is old enough but shut in still counts, as zero. The measured months are what these wells reported. In the forward months each well counts its own reported figure for each month it has one, our forecast for each month it has only that, and zero for the rest. The forward average counts every well in the curve. The drawn forecast runs up to five years past the measured months. Line thickness tracks the size of each cohort.