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In case the bottomhole pressure data is not available it is considered constant over time.

Motivation

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Production rate in producing well depends on its productivity index 

qq^{\uparrow}(t)=J \cdot (p_e(t) - p_{wf})

and as such depends on how formation pressure is maintained 

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It keeps declining due to to the offtakes:

p_e(t) = p_e[q^{\uparrow}(t)]

and maintained by

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either aquifer or Fluid Injection

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One of the main purpose of injection wells is to maintain pressure in producers and correspondingly maintain production rates.

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 and in the latter case depends on injection rates:

p_e(t) = p_e[q^{\downarrow}(t)]

The combination of 

The ultimate purpose of CRM is to

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correlate the long-term (few months or longer) flowrate history and BHP history (recorded by PDG)

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The CRM is trained over historical records of production rate, injection rates and bottomhole pressure variation.

The major assumptions in CRM model are:

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