i know there must be the wellbore volume effect along the pressure record at the surface. but is it possible to analyze the shut in pressure recorded at well head to obtain the reservoir parameter? if it is so, it must be a cheaper way to know the reservoir parameter instead of running a downhole gauge.
Under the right conditions, yes. I think the chances of success are better for an injection well (falloff) than a producing well (buildup).
Based on the compressibility in the system, it may take very much longer than using a downhole gauge, even assuming you actually get to see the pseudo steady state region before encountering boundary effects. This means your well is shut in and production or injection deferred, which you'd expect would cost a lot more than using a downhole gauge and shut in tool. I mention shut in tool, because a downhole gauge alone will not help reduce wellbore storage (unless you can measure afterflow...) so you need to isolate the tubing volume from the test with a shut in tool. The main advantage of the downhole gauge without shut in tool is if it is in liquid it will have a reasonable response, as a surface gauge's response will be very heavily dampened and affected by any gas column movement in the tubing.
It´s possible but you will need to analyse the obtained data with other models that probably exist but are not valid as the known methods, because at wellhead you will have different conditions (pressure, temperature..etc.) , different kind of flow (and maybe different distribution of phases), and the most important thing that you will have to consider is that the data will be very affected by the wellbore storage effect.
If the parameter you are interested in is near wellbore parameters e.g. flowing bottom hole pressure (pwf) you can possibly estimate it from your wellhead pressure as long as your fluid column/densities in the wellbore is known (and this is always known in an injector well scenario like Ramon mentioned). However, if the parameters you are interested in are reservoir based, e.g. static reservoir pressures, the reservoir boundary effects and wellbore storage effects will be a challenge to overcome without a down-hole gauge and a shut-in device.
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