Predicting and Tracking the Value of Injection Wellwork for WETs..

Danielle Ohms, Milne Point Unit, Alaska Well Management Masterclass, Oct 30-Nov 3, 2006

Value of Water InjectionInjector Wellwork often takes backseat to Producer Wellwork because difficult to place a value on it.

With understanding of which producers an injector supports and simple calculation, can place a value in terms of Oil Rate on Injector wellwork.

Also use calculated Value of Water to track Injector Wellwork benefits in WETs.

Value of Water InjectionExample: New Injector F-88i was drilled in early 2004 in an area not being efficiently swept.

Well Management Masterclass, Oct 30-Nov 3, 2006 Actually realized to a 920 bopd increase associated with 2600 bwpd injection into F-88i (value of water = 0.35 bo/bw).

The F-88i pattern includes 67% of F-45 production (as it receives weak support from another injector) and 50% of F-53 (as it receives clear support from another offset injector).

Simple Value of Water Calculation

For Depletion:Inj. Water Value =Secondary RecoveryEst. Ultimate RecoveryOil Cut *For Steady State:Injection Water Value = Oil CutUsing the Value of Water calculation for pattern F-88i, from the equation with reservoir depletion get a pattern value if 0.34 bo/bw. This yields a loss of 911 bopd due to under-injection of 2600 bwpd, using the current pattern values.2H 04 F-88i Pattern Parameters:Qo = 975 bopd Qw = 490 bwpdBw = 1.02 Bo = 1.15RF secondary = 20%RF total = 35%BwBo*Plug in

SummaryIn summary, this approach to calculating the Value of Water achieves similar results to that of material balance in Injection Choke model which are both very close to the actual production impact. This method has a defined value of water, independent of the time period. It does, however, decline gradually with pattern maturity, as expected. This method is simple to implement and reasonably accurate when compared with actual production performance. This Value of Water method makes it simple to determine the incremental oil rate (IOR) benefits of injector wellwork in WETs.

Value of Injector Wellwork

IOR = 100 bopdQo = 300 bopTF = 1250 bwpdBw = 1.02 Bo = 1.15RF secondary = 20%RF total = 35%Value of Water = 0.12 bo/bwFor 800 bwpd increased injection

Injector J-13i was SI during planned July field shutdown thus reduced rate for that month.

Value of MPU WaterMPU sought a Value of Water calculation method that would be consistent whether viewed over a month, a quarter, or a year period and be representative of losses actually realized in the field.

Note that it is not a typo to have Bw in the numerator of the above equation. It comes from converting water injection rate into oil and water production rate under steady state conditions.

The oil recovery curve is generated by a finite difference numerical simulator under steady state conditions. The derivative of the recovery curve (d[cum oil]/d[cum injection]) represents the true value of water injection which is a function of cumulative water injected. Before water breakthrough, one barrel of injected water is almost worth one (actually Bw/Bo) barrel of oil. As the reservoir matures, oil cut (Qo/(Qo+Qw)) decreases and so does the value of injected water. Oil cut is also plotted in Figure 2 to show how closely it approximates the injected water value.

If reservoir depletion is allowed, the value of water injected can be modified to account for the primary recovery that could have been produced if injection were to stop completely. A simple way to do this is to multiply the above calculated Value of Water by the ratio of secondary recovery to total expected recovery.

These equations are reasonably accurate in estimating the value of injected water yet simple enough to use in spreadsheet calculations.

Value of MPU WaterWhere Reservoir Depletion is allowed:These equations are reasonably accurate in estimating the value of injected water yet simple enough to use in spreadsheet calculations.

The F-88i pattern includes 67% of F-45 production (as it receives weak support from another injector) and 50% of F-53 (as it receives clear support from another offset injector). SummaryIn summary, this approach to calculating the Value of Water achieves similar results to that of material balance in Injection Choke model which are both very close to the actual production impact. This method has a defined value of water, independent of the time period. It does, however, decline gradually with pattern maturity, as expected. This method is simple to implement and reasonably accurate when compared with actual production performance. This Value of Water method makes it simple to determine the incremental oil rate (IOR) benefits of injector wellwork in WETs. Injector J-13i was SI during planned July field shutdown thus reduced rate for that month.Note that it is not a typo to have Bw in the numerator of the above equation. It comes from converting water injection rate into oil and water production rate under steady state conditions.

The oil recovery curve is generated by a finite difference numerical simulator under steady state conditions. The derivative of the recovery curve (d[cum oil]/d[cum injection]) represents the true value of water injection which is a function of cumulative water injected. Before water breakthrough, one barrel of injected water is almost worth one (actually Bw/Bo) barrel of oil. As the reservoir matures, oil cut (Qo/(Qo+Qw)) decreases and so does the value of injected water. Oil cut is also plotted in Figure 2 to show how closely it approximates the injected water value.

If reservoir depletion is allowed, the value of water injected can be modified to account for the primary recovery that could have been produced if injection were to stop completely. A simple way to do this is to multiply the above calculated Value of Water by the ratio of secondary recovery to total expected recovery.

These equations are reasonably accurate in estimating the value of injected water yet simple enough to use in spreadsheet calculations.