# Coring Cost Per Footage Drilled

Coring is a special process to recover wellbore rock in the well.

Figure 1 – Core from the well. Credit – Wikipedia

This article will demonstrate how to calculate coring cost per footage recovered.

Coring cost per footage recovered is expressed below;

Where;

Cc = coring cost per foot

Cb = cost of core bit

Cs = cost of coring service from a service company

Cr = rig day rate

tt = trip time, hour

tc = core recovering time, hour

trc = core barrel handling time, hour

L = length of core recovered, ft

Rc = percentage of core recover, %

Example – Geologist plans to do coring from 14,000 – 14,500 ft. The information for this operation is listed below;

Coring bit = 20,000 \$

Coring service price = 120,000 \$

Rig day rate = 100,000 \$

Expected trip in and out time = 24hours

Core recovery time = 12 hours

Core and tool handling time = 4 hours

Expected core recovery = 90 %

Determine the expected coring cost per foot.

Figure 2 – Coring Depth

Solution

Cb = 20,000 \$

Cs = 120,000 \$

Cr = 100,000 \$/day ( 4166.67 \$/hr)

tt = 24 hrs

tc = 12 hrs

trc = 4 hrs

L = 500 (14,500 – 14,000)

Rc = 90 %

Cc =681.5 \$/ft

Coring cost per footage drilled is 681.5 dollars.

Reference book => Formulas and Calculations for Drilling Operations

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