Heliometric Data measured at producer wellheads proved to be successful in the evaluation of the areal sweep efficiency

PRODUCER WELLHEAD MONITORING

Many reservoirs have been under waterflooding for over 50 years. Waterflooding is quite an old and successful method applied for secondary recovery, although there is still oil that has been bypassed and waiting to be recovered.

The areal sweep efficiency seems to be a critical factor for a successful recovery, in particular the high values for the mobility ratio are quite a concern.

In addition to existing classical numerical reservoir simulation used to calculated expected oil and water production rates, Actual Geology offers helium gas monitoring in associated gas measured at the producers wellhead. This method proved to be successful in the evaluation of the areal sweep efficiency in many basins.

Heliometric data provides the forecast of oil flow rate at each producing well and potential for increase of oil flow rate from the well indicating the lowest possible water cut at each producing well. This forecast is based on trend dependence, demonstrated by the below -mentioned graph.

Correlation of helium concentration at the wellhead and oil production rate

Measurement of helium concentration at producing wellheads was carried out in two stages. The first monitoring stage consisted of 6 cycles of observations on 287 wells. The second monitoring stage consisted of 3 measurement cycles at 329 wells.

The graph shows dependence between helium content in associated gas at the wellheads of production wells at the field and oil flow rates:

1) High levels of helium in associated gas are evidence of intensive degassing of the oil pool, causing lower amounts of gas in the pool (amounts of gas dissolved in the oil);

2) Lowering of gas content in the pool raises viscosity of the oil;

3) Greater viscosity of the oil makes the oil less mobile, lowering its speed of movement in strata, i.e. reducing well flow rates;

4) A explanatory chain consisting of the opposite phenomena is also valid: low helium content in associated gas – low degassing of the oil pool – higher gas content in the pool – low viscosity of the oil – high mobility and oil flow rates.