Matching the History

History matching is one of the important part in Reservoir Engineering. In conducting the task, as an engineer we would need to be very objective on the requirement. We need to ask first:-

1) What type of result we're expecting and for what purpose the result will then used for
2) Always talk to your boss, how much time do we have? so that we could have an agreement on when would be the delivery due. Also to prevent any unnecessary works especially when we know that it couldn't be delivered in time
3) Amount of data available and the confidence level we have on the data.

Only after considering all these checks then we could start doing the matching.

What is history matching basically & why do we run the history matching in the first place? Just like the stocks market, if we assume that not much parameters is changing through a period of time, we could estimate its future trend. Thus if the field operating condition got not much change throughout a period of time, we could use our observation until to date to predict the future performance of the reservoir. This is actually where the management will put most of their concern on especially when we're talking about the future recovery or the company future revenue.

Material balance or numerical simulation method are used for the matching of the pressures and production rates. Most of the time taken by the engineers is basically trying to experimenting with several reservoir and fluid parameters. In order to do the process efficiently, one would need to do it in a systematic way, or otherwise we could be stuck in the middle wasting much time trying to match every parameters. In my opinion, we should do it bottom up, doing the investigation of parameters starting from the reservoir to the surface. These are the recommended sequence of matching.

1) Bottomhole static reservoir pressure (BHP)
2) Oil rates
3) Water cut / the producing Gas-Oil Ratio
4) Tubing head pressure

Bottomhole pressures is more reliable to be used as a guide for the matching instead of trying the rates first, if enough data are available. This is because of we can rely on pressure measurement (most of today's pressure gauge is using the quartz gauge). But if we're talking about rates, there's possibility of measurement errors especially when measuring at the low production. That's why field data QC is important. We should be able to questioning its reliability when observing the anomalies by eyeballing through the profiles.

At the end of the day, when all the task was done and has been reviewed, we should be able to do economic analysis on our predicted profile and come out with a solution to improve the recovery through various possible methods (infill drilling, putting some injectors, Enhance Oil Recovery).