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

t_t = trip time, hour

t_c = core recovering time, hour

t_rc = 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