When several wells flow into one shared tank battery, their oil mixes in common vessels and leaves through a single sales meter. That is efficient to operate but it destroys the one thing accounting needs most: a per-well number. Central tank battery allocation is how operators rebuild that per-well number, dividing a single measured sales total back among the wells that fed the battery. This guide explains how the split is calculated from each well's tested rate and runtime, why the result must reconcile against the metered sales barrels, and how field data makes the whole allocation defensible.
Tank Battery Allocation in one line: Central tank battery allocation is the method of assigning barrels back to individual wells when many wells flow into one commingled battery measured by a single sales meter. Each well's share is estimated from its most recent tested rate multiplied by how long it ran, and those theoretical volumes are then scaled so their sum matches the actual metered sales total.
A central tank battery is a set of shared vessels - separators, treaters, and stock tanks - that gathers production from a group of wells so it can be measured and sold in one place. The economic advantage is obvious: one battery, one set of tanks, and one custody-transfer point serve a whole pad or field. The accounting problem is equally obvious. Once oil from Well A, Well B, and Well C mingles in the same treater and flows out through the same meter, there is no physical way to look at the sold barrels and say how many came from each well.
Yet a per-well number is exactly what everyone downstream requires. Royalty is paid on a well or lease basis, reserves and decline curves are tracked per well, and regulators expect production reported by well. The sales meter gives an accurate total for the battery, but that total has to be divided among contributors before it means anything to accounting. Allocation is the bridge between the one number the battery actually measures and the several numbers the business needs.
The measured sales figure is the anchor of the whole exercise. Whether the battery sells through a LACT unit that meters and samples oil automatically or through gauged tank tickets, the total leaving the battery is a hard number. Allocation never changes that total; it only decides how to split it. That constraint is what keeps the process honest, because the individual well figures, however they are derived, must add back up to what actually left the battery.
The split starts with a theoretical volume for each well. Every well is periodically routed to a test separator, where its oil rate is measured in isolation for a set period; that measured rate is the well's tested rate until the next test replaces it. To estimate a well's contribution over an accounting period, the operator multiplies that tested rate by the well's runtime - the hours it actually flowed, not the hours in the month, since wells cycle off for downtime, workovers, or high line pressure. A well that tested at a given daily rate but ran only part of the period contributes proportionally less.
Summing those rate-times-runtime products across all wells gives a total theoretical volume for the battery. That theoretical total will almost never equal the metered sales total exactly, because tested rates age, wells drift between tests, and measurement is imperfect. So the theoretical volumes are scaled by an allocation factor - the ratio of measured sales to total theoretical - applied to every well. If the wells collectively looked like they should have made more than the meter recorded, each well's allocated barrels are trimmed proportionally; if less, each is bumped up. The result is a set of per-well allocated volumes that, by construction, sum exactly to the sales total.
This is why runtime is as important as rate. A tested rate with no runtime is meaningless, and a runtime with a stale rate is misleading. The two together produce the theoretical basis for the split, and the accuracy of the allocation depends directly on both being current and correct. A well credited with full-period runtime when it was actually down for a week will be over-allocated, pulling barrels away from the wells that genuinely produced them.
The reconciliation step - comparing the sum of well theoreticals to the measured sales barrels - is where allocation earns or loses trust. A small allocation factor near one means the wells behaved close to their tests and the split is reliable. A factor that drifts well away from one is a warning: tests may be overdue, a well may be producing very differently than when it was last tested, or the measured sales figure itself may be off. Treating that factor as a health check, rather than just a plug number, turns allocation from a formality into a diagnostic.
The quality of the whole allocation rests on the quality of two inputs - runtime and the sales total - and both are exactly what a SCADA system captures natively. A cloud SCADA platform such as Merobix records each well's runtime continuously by watching the well's controller or a route valve, so the hours flowed are logged as they happen instead of reconstructed from memory or paper. On the measurement side, integrating the LACT unit's totalizer and proving data into the same platform means the sales barrels feeding the allocation are the meter's own figure, timestamped and traceable, rather than a manually transcribed ticket.
With runtime and LACT data living in one place, the allocation becomes something an operator can stand behind. Every well's contribution traces to a tested rate, a logged runtime, and a metered total that all reside in the same auditable record, and the allocation factor is visible period over period so a drifting well or an overdue test surfaces early. When a royalty owner or an auditor asks how a well's barrels were derived at a shared battery, the answer is a documented calculation from measured inputs rather than an estimate, which is the difference between an allocation that survives scrutiny and one that does not.
Each well's theoretical volume is calculated as its most recent tested oil rate times the hours it actually ran during the period. Those theoretical volumes are summed for the whole battery, then scaled by an allocation factor - the ratio of the metered sales total to the total theoretical - so the well volumes add up exactly to what the sales meter measured. The sales total is never changed; allocation only divides it.
The allocation factor is the metered sales total divided by the sum of all the wells' theoretical volumes. It is applied to every well to force the allocated barrels to reconcile with actual sales. A factor close to one means the wells produced near their tested rates; a factor far from one signals overdue well tests, a well drifting from its test, or a measurement problem worth investigating.
Because a well's contribution is its tested rate multiplied by runtime, an error in runtime directly distorts the split. A well credited with more runtime than it actually flowed gets over-allocated and steals barrels from wells that really produced. Capturing runtime continuously in a SCADA system, rather than estimating it, keeps each well's theoretical volume accurate and the whole allocation defensible.
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