Various Techniques to Determine Absolute open Flow Rate of a Well & Pressure Drop in Pipelines
When a gas well is discovered, it undergoes a lot of tests to determine its parameters. The tests performed to obtain these parameters are known well testing. Well testing is performed at many stages of discovering a reservoir even while extracting hydrocarbon from it. At the initial stages of discovery of a reservoir, well testing is performed on the exploration & appraisal well. Parameters such as confirmation of hydrocarbon presence, well productivity, reservoir heterogeneity, reservoir connectivity etc. can be obtained. At the later stages of discovery of a reservoir, well testing is also performed. Parameters such as average permeability & thickness of a reservoir & also the skin factor of the reservoir can be determined. These parameters are later used during the continued production of hydrocarbon from the reservoir.
The main purpose of a gas well testing is to perform deliverability testing. Deliverability testing measures the production capabilities of a well against flow restrictions. Flow restrictions of a well can be due to backpressure, reduction in size of the wellbore, change in bottomhole pressure or increase in surface pressure. One of the factors used to determine the deliverability of a well is known as absolute open flow rate ( ). The is known as the maximum flow rate that a well can produce against a sandface pressure equivalent to only the atmospheric pressure (14.65 psia). This is only in theory as practically, the sandface pressure of the reservoir will never reach to the atmospheric pressure but, the calculated can be used to determine a maximum flow rate for the reservoir.
After performing flow-after-flow test &Rawlins-Schellhardt technique on the gas well the optimum parameters to produce the well was determined. The reservoir must be operated at a bottom hole pressure of 3000 psia. This pressure will provide a flow rate of 22196.13 Mscf/D. By operating the reservoir at this pressure, the pressure loss across the 10km transportation pipeline will be 2.72 psia.