US 11,815,646 B2
Drilling fluid activation correction methodology
Marie-Laure Mauborgne, Sugar Land, TX (US); and Christian Stoller, Sugar Land, TX (US)
Assigned to SCHLUMBERGER TECHNOLOGY CORPORATION, Sugar Land, TX (US)
Appl. No. 17/258,197
Filed by Schlumberger Technology Corporation, Sugar Land, TX (US)
PCT Filed Jul. 8, 2019, PCT No. PCT/US2019/040792
§ 371(c)(1), (2) Date Jan. 6, 2021,
PCT Pub. No. WO2020/014116, PCT Pub. Date Jan. 16, 2020.
Claims priority of provisional application 62/695,227, filed on Jul. 9, 2018.
Prior Publication US 2021/0230954 A1, Jul. 29, 2021
Int. Cl. G01V 5/06 (2006.01)
CPC G01V 5/06 (2013.01) 19 Claims
OG exemplary drawing
 
1. A method for making natural gamma ray measurements of a subterranean formation, the method comprising:
(a) circulating drilling fluid through a logging while drilling string deployed in a subterranean wellbore, the logging while drilling string including a neutron source and a natural gamma ray sensor;
(b) causing the neutron source to emit neutrons while circulating in (a);
(c) causing the natural gamma ray sensor to acquire a spectral gamma ray measurement while the neutron source emits neutrons in (b);
(d) fitting the gamma ray measurement made in (c) to standard spectra to determine a total drilling fluid activation count, at least one of the standard spectra being an oxygen activation spectrum;
(e) processing the total drilling fluid activation count to compute a first drilling fluid activation correction in a first time interval;
(f) processing a count of the gamma ray measurement above at least one predetermined energy threshold to compute a second drilling fluid activation correction in a second time interval;
(g) processing a weighted average of the first drilling fluid activation correction and the second drilling fluid activation correction to computing a third drilling fluid activation correction; and
(h) applying the third drilling fluid activation correction to the gamma ray measurement to obtain a corrected total natural gamma ray measurement.