# Decline Curve Analysis-Calculating EUR

**Question description**

If you have a given decline curve that has production rate versus time, how would one find the EUR (Estimated ultimate recovery) and reserves? Is it the area under the decline curve? If so, how would you find the area under a curve? Excel does not have a built in integral function.

I just need a step by step approach to solve the below problem basically:

**"The
oil reservoir has been under production for 12 years, and started to exhibit a
decline in the production rate after the 4 ^{th} year of production. The
oil production data of the 25 wells drilled in this oil reservoir is available
in the attached Excel spreadsheet. Select an appropriate method of estimation of
reserves and state any necessary assumptions to apply the method. Estimate the
Ultimate Recovery (EUR) for each well and for the reservoir, using an economic
limit of 30 STB/day of oil. Estimate the oil recovery factor using the OOIP
obtained with the volumetrics method"**

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