# 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 4th 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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