What is well testing?
Test on oil and gas are performed at the various stage of drilling, completion and production. Reservoir engineers need to monitor the performance of every single well constantly in order to optimise production and the lifetime of the field.
For most large fields, decisions with a very high financial impact are based on well-test results, e.g. shutting down wells, drilling new wells, reducing production rate from the reservoir, etc.
Types of Well testing:
Conventional well testing:
Conventional test means the production from each well is done separately using a test separator. The stream from the well being tested is separated into two (or three) “phases”: high vapour-pressure oil and gas (and water).
The current of each of the previous phases is measured and sampled at the same time as certain parameters are recorded such as the choke opening, the flow pressure of the wellhead, the pressure of the separator and the temperature of the separator. (Other parameters can also be recorded, and samples cannot be taken in each well test.On production platforms, samples can only be taken at intervals of a few years).
After the test, the analyses and data recorded are combined mathematically in order to find the well contribution to the output streams of the production plant.
These flow rates are the main data of a well test and are determined for one or more choke configurations. The flow rates are plotted against the choke configuration, the spring flow pressure or some other parameter and are used until the next well test, to calculate the theoretical contribution made by each well to the output currents of the process plant.
Under normal operating conditions, The test separator measurement cannot be expected to give an uncertainty of better than +5 % to +10 % of reading of each phase volume flow rate.
Well testing by multiphase meters:
The multiphase meter may be installed in the same way as the test separator, see.
Multiphase metering replacing test separator and its meters:
Multiphase metering can be used to increase overall testing capacity (SM = single phase metering station):
Continuous monitoring of well performance:
As multiphase meters become available, it is possible to install them on the flow line of individual production wells. This offers the benefit of a continuous monitoring of each well, as well as eliminating some of the uncertainties in calculating the theoretical performance of the well.
Multiphase meters on each well’s flow line replacing test separator and its meters (MM = multiphase meter):