BECH AFD versus ICD’s

February 22, 2012: Extensive testing of the BECH AFD (autonomous flowcontrol device, which is also referred to as a self-adjusting ICD) and comparing this with a standard ICD has been performed, where we have learned that the AFD is performing as expected. In low to high viscosity fluid flow-through, we record significant higher flow rates through the AFD than the ICD when inflow pressure drops below initial choke setting (as it will in a wellbore). Hence, significant higher flow rates as well as stable production can be expected.

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More flow through the AFD

A simple comparison between the new autonomous AFD and the ICD can be given as follows. Assume the two valves are initially set at the same flow rate at initial reservoir pressure. Over time, the reservoir pressure drops due to depletion, and hence the pressure drop across both valves decreases.

The ICD  in simple terms is just a orifice that follows the law of Bernoulli. The flow will then decrease according to the square root of the pressure change. One example: If the flow is 36 l/hr at a differential pressure of 27 bars, the flow will reduce to 12 l/hr at 3 bar pressure across the ICD. The problem is that if the ICD is set optimally initially it chokes too much during depletion.

The autonomous ADC, on the other hand, is a device based on a hydraulic feedback principle that essentially maintains nearly constant flow through the depletion phase of the reservoir.    When pressure increases or decreases, the valve will change the choke function to maintain constant flow.

One simple way to visualize the AFD is like a nozzle that increase in size when pressure drops or decrease in size when pressure increases.

Reservoir engineering management - Quicker reservoir drainage

The autonomous valve can play an important role in the field economy as it can drain the field at nearly half the time compared to using ICD’s, with an improved performance. 

Both the ICD and the AFD can be termed “non-Darcy reservoir production”. This implies that it is no longer the inherent reservoir permeabilities that controls production but the outside tool called the ICD or AFD. This actually gives us a new tool to maximize reservoir recovery as discussed in the following.

Reservoir management is concerning optimizing production when parameters changes.  During production of an oil or gas field, unexpected events often occur. This can be due to changes  in relative flow between reservoir layers or water and gas coning. At any time period in a fields life, some  different optimal conditions exist. Of course, once the ICD is installed there is no way change these conditions.

The AFD will maintain constant flow regardless of varying reservoir conditions. There are several benefits such as:

1. •The AFD will increase flow in the depleted stages of the reservoir, thereby giving at higher recovery at  the late life of the field.
   

2. •The AFD will maintain constant flow that for example can lead to a parallel movement of the  water or gas contact, theoretically giving a waterfree production resulting in water breakthrough along an entire horizontal well.
   

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The AFD is a tool to optimize well recovery even if the  extent of the reservoir is not fully known. For a given well path a maximum recovery is therefore likely. To summarize, the two following benefits are:

1. •The AFD will provide a higher flow during depletion than the ICD, thus providing more income in the late phases of a field.
   

2. •The AFD may provide a higher total recovery by delaying water or gas coning.
   

Interested in seeing more video’s explaining the function, benefits, etc.? Click here.

This development project is funded under Statoil’s LOOP product development program, which supports new innovative technologies that enhance their business areas. Partial funding is being provided by Innovation Norway and Skattefunn, while also the share holders of BECH contribute with a substantial funding

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Contact

cindy@hansenenergy.biz
BECH Wellbore Flowcontrol AS