AU2017201518B2

AU2017201518B2 - Low resistance core sample marking system and method for orientation of a marked core sample

Info

Publication number: AU2017201518B2
Application number: AU2017201518A
Authority: AU
Inventors: Lars A. Eriksen; Rune Lindhjem; Arnstein Lovo
Original assignee: Devico AS
Current assignee: Devico AS
Priority date: 2016-03-04
Filing date: 2017-03-06
Publication date: 2021-11-18
Anticipated expiration: 2037-03-06
Also published as: NO343894B1; CA2959881A1; AU2017201518A1; NO20170322A1; CA2959881C

Abstract

Low resistance core sample marking system and method for orienting a core sample retrieved by a wireline-operated drill, where core orientation is achieved by the use of a reference marking device (110) and a data logger for recording geospatial/environmental data in an instrumentation unit (200), where the geospatial/environmental data registered by the data logger is related to the reference scribe mark on the core by the reference marking device (110) 3/3 10010 110 111 f10 102b A iA 112 100 101 112 110 102a SECTION A-A 103 Figure 4.

Description

3/3

10010 110 111 f10 102b

A iA

112 100 101 112

110

102a SECTION A-A

103

Figure 4.

Low resistance core sample marking system and method for orientation of a marked core sample

The present invention relates to a low resistance core sample marking system for wireline

operated core barrel drill enabling continuous marking of a core sample entering an inner

tube, according to the preamble of claim 1.

The present invention is also related to a method for orientation of a marked core sample

according to the preamble of claim 12.

The invention provides an accurate, time saving and easy way to assemble the core

sample accurately.

Background

Core samples are obtained through core drilling operations by using wireline-operated

drills as described in e.g. NO 168962, NO 316286, NO334083, WO2013028074, WO2013028075, WO2011056077, all in the name of the applicant. In e.g. NO 316286 it is disclosed a wireline-operated directional core barrel drill for rock drilling, especially for

rock drilling of curved holes with a predetermined path, having an outer drilling tube with a foremost rotatable drill bit and a part connected behind arranged for being locked

against rotation. In the drive shaft it is arranged an inner tube for receiving core samples when drilling, as the upper end is provided with space for a survey instrument to be able to measure and log data, such as inclination, direction and angle of rotation central

section of the main body, incl. high side of the eccentric bushing. The inner tube with the

core sample is brought to the surface and the core sample can be removed and subjected

to analysis.

For analysis purposes, there is a need to assemble the core sample correctly after it has been removed from the inner tube, and further to have an indication of the orientation of

the core sample relative to the ground, accordingly means for identifying the orientation

the core sample had within the ground prior to it having been brought to the surface.

Core marking, and further orientation of the marked core, has been solved in different

ways over the years, which will be discussed below.

Prior art solutions for marking core samples have traditionally been used in softer rock

formations for oil and gas exploration drilling, using a scribe shoe with multiple fixed

markers that scribes the core as it enters the inner tube. These solutions uses three or more markers often positioned nearly 120 degrees apart to provide an equal pressure on

each side of the core as it is scribed. The markers generally consists of one main/master blade, which is mechanically aligned with a survey instrument, and two or more blades

fixed at known angles from the master blade. Multiple types of survey instrument have been used, including gyroscope, accelerometer and magnetometer, arranged in different

positions in the drill string.

The prior art solutions with multiple markers causes high friction as the core enters the

inner tube, and can especially in harder rock formations result in the core breaking or

crushing, or the core blocking leading to grinding of the core and premature termination of the drilling run. This is especially relevant when drilling smaller diameter core samples

as is common in the mineral and geotechnical drilling industry, as the smaller diameter core sample is more prone to breaking than larger diameter samples.

Prior art solutions generally have fixed blades that are prone to wear and damage, especially in rapidly fluctuating geology. Often, one or several of the blades will stop marking, leading to difficult or impossible alignment of the core on surface, and

impossible subsequent orientation.

The multiple and fixed blades of prior art solutions can make it difficult to remove the core

sample from the scribe shoe and the core sample may easily break due to the friction from the blade. The mark in the core sample may then be lost in this section, which may further lead to loss of orientation data.

Other prior art systems for orientation of core samples traditionally used in hard rock

formations only orientate the rear and/or the front of the collected core. This means the remaining core sample (often 3 or 6 meter long) will need to be carefully inspected at each fracture joint, and then assembled to transfer the orientation data from one end to the other. This is often challenging, especially in broken formations.

Further, these prior art solutions are not arranged for recording the orientation at several

stages during the drilling process. Especially, in formations prone to core blocking, prior

art have drawbacks, as core blocking causes destruction of the fracture joints and relative rotation to occur between various parts of the core.

Further, prior art making use of the core catcher to perform orientation requires the core to be fixed to the formation before the core is broken off. In cases where the drill run ends

in a fracture or low quality formation there is a significant risk the core rotates relatively to the inner tube and survey instrument, and lead to a false core orientation reading. Also

in higher quality formations there are risks that the core comes loose and rotates in the core catcher, for instance due to operator mistakes, which again leads to false orientation

data.

Object

The main object of the present invention is to provide a low resistance core sample marking system for wireline-operated core barrel drill and method for orientation of a

marked core sample, which solves the above mentioned problems with prior art.

It is further an object of the present invention to provide a core sample marking system and method for orientation of a marked core sample, which results in low resistance

between a reference marking device and the core sample as the core sample enters an

inner tube during a drilling operation.

It is further an object of the present invention to provide a core sample marking system and method for orientation of a marked core sample, which results in low resistance between a reference marking device and the core sample as the core sample is removed

from the inner tube.

It is further an object of the present invention to provide a core sample marking system

and method for orientation of a marked core sample, which enables continuous marking and orientation.

and method for orientation of a marked core sample, which enables recording of orientation at several stages during a drilling process.

An object of the present invention is to provide a core sample marking system and method for orientation of a marked core sample, which simplify the analysis of a retrieved

core sample.

Further objects will appear from the following description, claims and attached drawings.

The invention

A low resistance core sample marking system for a wireline-operated core barrel drill

according to the present invention is disclosed in claim 1. Preferable features of the core

sample marking system are disclosed in the claims 2-11.

A method for orientation of a marked core sample is disclosed in claim 12. Preferable

features of the method are disclosed in the claims 13-15.

The invention is related to a wireline-operated core barrel drill for rock drilling, especially

a core barrel drill where one desires to retrieve core samples without retrieving the core barrel assembly.

The key component of the present invention is a reference marking device arranged in a

scribe shoe between an inner tube and core catcher sleeve, arranged in a core catcher

sleeve or arranged in an inner tube.

According to a first aspect of the low resistance core sample marking system according to the present invention the reference marking device arranged in the scribe shoe, core catcher sleeve or inner tube is arranged for continuously marking a core sample entering

the inner tube.

According to a second aspect of the low resistance core sample marking system according

to the present invention the reference marking device is projecting inside the scribe shoe, core catcher sleeve or inner tube and is a destructive type, e.g. a blade made of hard

metal, polycrystalline diamond composite (PDC) or similar.

According to a third aspect of the low resistance core sample marking system according to the present invention the reference marking device is projecting inside the scribe shoe,

core catcher sleeve or inner tube and is a non-destructive type, e.g. a pen or similar.

According to a further aspect of the low resistance core sample marking system according

to the present invention the reference marking device is a laser marking the core sample without projecting into the scribe shoe, core catcher sleeve or inner tube.

According to a further aspect of the low resistance core sample marking system according to the present invention the reference marking device is arranged to a resilient device

acting as a spring/damper reducing the friction created on the core sample by the

reference marking device, thereby reducing the risk of core blocking and breaking.

to the present invention the resilient device is a longitudinally extending lip, where rear part thereof is fixed to the scribe shoe, core catcher sleeve or inner tube.

According to a further aspect of the low resistance core sample marking system according to the present invention the resilient properties of the resilient device and thus reference marking device can be adjusted by changing the length of the lip or moving the position of

the reference marking device forwards or backwards on the lip, i.e. in longitudinal

direction of the lip.

According to another aspect of the low resistance core sample marking system according to the present invention the reference marking device comprises multiple marking devices aligned on the same line to ensure a continuous line is marked in varying rock formations

and reduce rotation of the inner tube during drilling.

According to a further aspect of the low resistance core sample marking system according to the present invention the reference marking device(s) is/are surrounded by multiple additional marking devices unevenly distributed circumferentially inside the scribe shoe, core catcher sleeve or inner tube, to separate them form the reference marking device for subsequent orientation.

to the present invention the scribe shoe, core catcher sleeve or inner tube has an inner diameter similar to the maximum diameter of the core sample and is provided with

longitudinal channels or recesses at least on a part of an inner surface thereof. The smaller diameter gives support to the core sample, while the channels allow water to pass by the

core sample as it enters the inner tube. If using only one marking device, the force from the marking device will decentralize the core sample, which may increase the risk of core

blocking. The channels according to the present invention will support and centralize the core sample as it is being marked, preventing the decentralization effect.

to the present invention there is arranged a window or slot behind the reference marking device in the scribe shoe, core catcher sleeve or inner tube. By this one can view the mark

on the core sample and use this to orient the core sample while it is still in the inner tube. Usually the mark on the core sample and the reference marking device will be on the

same line, but operator mistakes can cause the core sample to rotate relative of the core catcher sleeve. In other core orientation systems such rotation could not be detected and would cause a false orientation reading.

Geological analysis of the core sample benefits from the core sample being relatively

oriented over its full length. This means the remaining core sample (often 3 or 6 meter

long) will need to be carefully inspected at each fracture joint, and then assembled to transfer the orientation from one end to the other. This is often challenging, especially in broken formations.

With the present invention the reference marking device provides a continuous

mark/scribe on the core sample, making it far easier to assemble the core sample accurately.

to the present invention the orientation of a marked core sample can be found when combining the reference marking device with recordings from an instrumentation unit

comprising a data logger for recoding geospatial/environmental data arranged at rear end

of an inner tube, i.e. in front of, within or behind a head assembly.

The instrument unit comprises at least one of the following sensors: accelerometer,

magnetometer or gyroscope; for providing at least a portion of the geospatial/environmental data to the data logger.

According to the low resistance core sample marking system according to the present invention one or multiple extensions of the outer tube with equal total length of the

instrumentation unit and scribe shoe are assembled to the core barrel assembly to accommodate for the increased length of the inner tube assembly when a scribe shoe is

used.

By the present invention it is possible to record the orientation at several stages during the drilling process. This is especially useful in formations prone to core blocking as

multiple sections of competent core samples can be independently oriented and marked. Core blocking causes destruction of the fracture joints and relative rotation to occur

between various parts of the core sample, in many cases making it impossible to assemble the sections of core sample correctly to transfer the orientation data.

A method for orientation of a marked core sample according to the present invention will

include the following:

- arranging an inner tube assembly, with an instrumentation unit and at least one

reference marking device arranged in a scribe shoe between an inner tube and a core catcher sleeve, in a core catcher sleeve or in an inner tube assembled, horizontally and rotate the inner tube assembly until the reference marking device

is at the top/high side, or optionally the low/bottom side;

- in this position, log geospatial/environmental data of the instrumentation unit, and

implementing a correction factor that will electronically and automatically correct the subsequent geospatial/environmental orientation data to zero with the at least one reference marking device positioned at the top/high side, or optionally the low/bottom side;

- arranging the inner tube assembly in a core barrel assembly and perform

coring/drilling;

- marking a core sample continuously as it enters the inner tube by means of the at

least one reference marking device of the scribe shoe, core catcher sleeve or inner tube;

- at known depths, any time during the drilling process, perform measurements of the

geospatial/environmental data of the instrumentation unit and record and store

measurements in a data logger of the instrumentation unit.

For the rotation of the inner tube assembly for positioning the at least one reference

marking device at the top/high side, or optionally the low/bottom side, an external bubble

level might be used for best accuracy.

The geospatial/environmental data of the instrumentation unit in the mentioned initial

position will be displayed as zero. If the scribe shoe, core catcher sleeve or inner tube is replaced with a new, the same procedure must be repeated to obtain a new correction

factor.

There is no limit to the amount of measurements, but at least one must be recorded.

The method according to the present invention can further comprise a final recording

done when the core barrel assembly rotation is stopped at the end of the run. Contrary to

the prior art methods it has no effect on the orientation if the core barrel assembly is

rotated before or during the core break, or if the core barrel assembly is pushed down to touch the bottom of the hole after the core break. The latter is often performed to make it

easier to remove the core sample from the core catcher sleeve when on surface, but will result in false orientation data with prior art orientation systems.

The method according to the present invention further comprises a step of retrieving the

inner tube assembly with a core sample from the core barrel assembly.

The method according to the present invention further comprises connecting the

instrumentation unit to a master unit and transfer of the recorded data. The recorded

data indicates the orientation of the reference marking device, and thereby the at least one mark on the core sample, at the recorded depths in the borehole, i.e. not in relation

to the inner tube which is the case of prior art solutions.

The method according to the present invention further comprises rotating the reference

mark on the core sample according to the recorded orientation angle so that the orientation of the core sample is the same as it was down the borehole.

Recording of measurement data at the necessary depths may be performed in multiple ways. One solution is to send a command from the master unit instructing the

instrumentation unit to store measurement data at an indicated frequency. Each data

sequence is then stored in the instrumentation unit with an index number, while also the master unit keeps count of the number of the stored measurements. When the

instrumentation unit is in a position of interest the user indicates this in the master unit and the belonging measurement number is stored in the master unit. Once the

instrumentation unit is retrieved from the core barrel assembly it is connected to the master unit, the specific measurement number is requested and the data sequence transferred and processed.

Another possibility is to detect the quality and stability of measurement data as the

instrumentation unit is held stationary over a set timeframe, and use this to trigger a

recording. During insertion of the inner tube assembly and during drilling the instrumentation unit will continuously change position, and the measured orientation will not be stable over subsequent recordings. When drilling is stopped the core barrel

assembly, and thereby also the instrumentation unit, may be held stationary over a

certain duration of time, and this data be filtered out by a master unit after download or in the instrumentation unit before download. The time when drilling is started, after

drilling is stopped and/or before the overshot is lowered into the borehole may be noted and used to reduce the amount of data needing to be analysed and filtered.

Another option is to detect acoustic signals sent down from surface through the core

barrel assembly or inner tube assembly. An acoustic sensor recognizes the acoustic signal and triggers the instrumentation unit to perform a recording of its current orientation.

Accordingly, the present invention provides orientation by the use of at least one

reference marking device and the use of an instrumentation unit, where the orientation of the core sample is related to a reference scribe mark. The present invention further

enables multiple measurements to be taken during a run and used for orientation.

Further, the present invention enables optional configurations for taking measurements.

Further details and preferable features and advantageous details of the present invention will appear from the following example description, claims and attached drawings.

Example

In the following the present invention is described in more detail with reference to the

accompanying drawings, where:

Figures 1-2 are perspective drawings of core barrel assembly and inner tube assembly of a prior art core barrel drill,

Figures 3a-b are principle drawings of core barrel assembly and inner tube assembly provided with a low resistance core sample orientation system according to the present invention, and

Figure 4 show principle drawings of a scribe shoe according to the present invention,

Reference is now made to Figure 1 which shows a wireline-operated core barrel drill according to prior art. In Figure 1 it is shown a core barrel assembly 11 which is assembled

of several parts in the longitudinal direction. The core barrel assembly 11 comprises in order from below and up, a drill bit 12 with a reamer 13 and an outer tube 14.

In Figure 2 it is shown an inner tube assembly 20 having a lower core catcher sleeve 21

attached to an inner tube 22 having space for receiving a bore core which at the upper end is connected to a head assembly 23. Further, it is arranged a spear head 24 for

connection of the inner tube assembly 20 to a wireline with a quick snap connection (not

shown).

Further details of such a core barrel drill is well known for a skilled person and it is not

necessary to discuss this in further detail herein, as it is disclosed in the mentioned prior art publications.

The above described apparatus makes it possible to retrieve core samples from a core barrel drill.

Reference is now made to Figures 3a-b and 4 showing an inner tube assembly 20 provided with a scribe shoe 100 according to the present invention adapted for being arranged

between the inner tube 22 and core catcher sleeve 21, the scribe shoe 100 being arranged

for continuous marking of a core sample entering the inner tube 22.

The scribe shoe 100 is formed by a tubular casing 101 provided with threaded ends 102a-b

for connection with corresponding threaded ends (not shown) of the inner tube 22 and core catcher sleeve 21, respectively.

The scribe shoe tubular casing 101is provided with a through opening 103, arranged close to the end facing the core catcher sleeve 21, in which through opening 103 is arranged at least one reference marking device 110 projecting inside the tubular casing, arranged for

continuous marking of a core sample entering the inner tube 22.

The reference marking device 110 can be a destructive type in the form of a blade made of

hard metal, PDC or similar, or a non-destructive type, such as a pen or similar.

In a preferred embodiment, as shown in Figure 4, the reference marking device 110, in the form of a blade, is arranged to a resilient device in the form of a longitudinally extending

lip 111, arranged in the tubular casing 101 by that rear part thereof is fixed to the tubular

casing 101, acting as a spring/damper, reducing the depth of the mark/scribe applied to a passing core sample, as well as reducing the wear of the blade and friction caused by the blade on the core sample. The length of the lip 111 may be adjustable or the position of the reference marking device 110 can be adjustable forwards or backwards in longitudinal direction of the lip 111, to account for ground conditions and rock hardness requiring different damping effect.

In a further preferred embodiment of the scribe shoe 100, the tubular casing 101 has an inner diameter similar to the maximum diameter of the core sample and is provided with

longitudinal channels or recesses 112 at an inner surface thereof, at least at a part thereof, facing the core catcher sleeve 21, for allowing water to pass by the core sample,

while the smaller diameter offers support of the core sample for stabilizing it as it is marked by the reference marking device 110.

The above description of the reference marking device 110 arranged in a scribe shoe 100 can also be used for implementing the reference marking device 110 in the core catcher

sleeve 21 or the inner tube 22 (in a lower part thereof).

An instrumentation unit 200 is according to the present invention arranged at rear end of the inner tube 22, in front of, within or behind a head assembly 23, wherein the

instrumentation unit 200 comprises a data logger for recoding geospatial/environmental data. The instrumentation unit 200 according to the present invention further comprises

at least one of the following sensors: accelerometer, magnetometer or gyroscope; for providing at least a portion of the geospatial/environmental data to the data logger.

The instrumentation unit 200 can further comprise at least one acoustic sensor for detecting acoustic signal(s) sent down from surface through the core barrel assembly 11

or inner tube assembly 20. The acoustic sensor, when recognizing the acoustic signal, is

arranged to trigger the data logger to perform a recording of its current orientation.

It should further be mentioned that one or multiple extensions 15 (as shown in Fig. 3a) of the core barrel 14 with equal total length of the instrumentation unit 200 and scribe shoe

100 are assembled to the core barrel assembly 11 to accommodate for the increased

length of the inner tube assembly 20.

Modifications

The instrumentation unit according to the present invention can be provided with several data loggers for redundancy, or the sensors can be separately arranged in separate data

loggers.

The method according to the present invention can further comprise the use of high accurate sensors for calibrating the sensors of the data logger(s) when the

instrumentation unit is in a position outside the borehole.

Claims

1. Low resistance core sample marking system for a wireline-operated core barrel drill, especially for rock drilling, consisting of an instrumentation unit (200) comprising a data logger for recoding geospatial/environmental data and at least one reference marking device (110) arranged in an inner tube assembly (20) of the core barrel drill by arrangement in a scribe shoe (100) between an inner tube (22) and a core catcher sleeve (21), arranged in a core catcher sleeve (21) or arranged in the inner tube (22), wherein the reference marking device (110) being arranged for continuously marking of a core sample entering the inner tube (22), wherein:

- the reference marking device (110) is arranged to a longitudinally extending resilient device (111) acting as a spring/damper reducing the friction created on the core by the reference marking device (110), thereby reducing the risk of core blocking and breaking, and

wherein the recordings of the instrumentation unit (200) are related to the reference mark on the core sample made by the reference marking device (110).

2. Low resistance core sample marking system according to claim 1, wherein the longitudinally extending resilient device (111) is a longitudinally extending lip, where rear part thereof is fixed to the scribe shoe (100), core catcher sleeve (21) or inner tube (22).

3. Low resistance core sample marking system according to claim 2, wherein the resilient properties of the reference marking device (110) is adjusted by changing the length of the lip (111) or moving the position of the reference marking device (110) forwards or backwards on the lip (110), i.e. in longitudinal direction of the lip (110), to account for different ground conditions and rock hardness.

4. Low resistance core sample marking system according to claim 1, wherein the reference marking device (110) is formed by:

- a single reference marking device (110) that minimizes the resistance as the core sample enters the inner tube (22), or

- multiple reference marking devices (110) aligned on the same line to further secure a continuous mark in varying rock formations and reduce rotation of the inner tube (22) during drilling,

5. Low resistance core sample marking system according to claim 4, wherein the reference marking device(s) (110) are surrounded by multiple additional marking devices unevenly distributed circumferentially inside the scribe shoe (100), core catcher sleeve (21) or inner tube (22), to separate them from the reference marking device (110).

6. Low resistance core sample marking system according to any one of the preceding claims, wherein the reference marking device (110) or additional marking devices is a destructive type in the form of a blade made of hard metal or polycrystalline diamond composite.

7. Low resistance core sample marking system according any one of the preceding claims, wherein the reference marking device (110) or additional marking devices is a non-destructive type in the form of a pen or a laser.

8. Low resistance core sample marking system according to claim 1, wherein tubular casing (101) of the scribe shoe (100), the core catcher sleeve (21) or inner tube (22) has an inner diameter similar to the maximum diameter of the core sample and is provided with longitudinal channels or recesses (112) on at least a part of an inner surface thereof, for support of the core sample as it enters the inner tube (22) and to allow water to pass by the core sample.

9. Low resistance core sample marking system according to claim 1, wherein a window or slot is arranged behind the reference marking device (110) in the scribe shoe (100), core catcher sleeve (21) or inner tube (22) to detect if the core sample has rotated in the core catcher sleeve (21) after drilling was stopped.

10. Low resistance core sample marking system according to claim 1, wherein the instrumentation unit (200) is provided with an acoustic sensor arranged for activating the data logger to perform a recording of its current orientation by means of sensors arranged in the instrumentation unit (200) providing at least a portion of geospatial/environmental data.

11. Low resistance core sample marking system according to claim 1, wherein the instrumentation unit (200) can be implemented with a correction factor that electronically and automatically correct subsequent geospatial/environmental orientation data to zero with the at least one reference marking device (110) positioned top/high side, or optionally low/bottom side.

12. Method for orientation of marked core sample from a wireline-operated core barrel drill, especially for rock drilling, by using at least one reference marking device (110) arranged in an inner tube assembly (20) and an instrumentation unit (200) arranged at rear end of an inner tube (22), in front of, within or behind a head assembly (23), wherein the instrumentation unit (200) comprises a data logger for recording geospatial/environmental data, wherein the method comprises:

- arranging the inner tube assembly (20), with the instrumentation unit (200) and at least one reference marking device (110) arranged in a scribe shoe (100) between the inner tube (22) and a core catcher sleeve (21), arranged in the core catcher sleeve (21) or arranged in the inner tube (22), horizontally and rotate the inner tube assembly (20) until the reference marking device (110) is at top/high side, or optionally low/bottom side;

- in this position, log geospatial/environmental data of the instrumentation unit (200), and implementing a correction factor that will electronically and automatically correct the subsequent geospatial/environmental orientation data to zero with the at least one reference marking device (110) positioned at the top/high side, or optionally the low/bottom side;

- arranging the inner tube assembly (20) in a core barrel assembly (11) and perform coring/drilling;

- marking a core sample continuously as it enters the inner tube (20) by means of the at least one reference marking device (110) arranged to a longitudinally extending resilient device (111) in the scribe shoe (100), core catcher sleeve (21) or inner tube (22); and

- at known depths, any time during the drilling process, perform measurements of the geospatial/environmental data of the instrumentation unit (200) and record and store the measurements by means of the data logger.

13. Method according to claim 12, wherein further comprising a final recording done when the core barrel assembly (11) is stopped at the end of the run to enable detection of whether the core sample has rotated relatively to the core catcher sleeve (21) following the final recording.

14. Method according to claim 12, wherein recording of measurement at necessary depths:

- when drilling is stopped, the core barrel assembly (11), and thereby also the instrumentation unit (200) is held stationary over a certain duration of time, which data be filtered out by a master unit after download or by the instrumentation unit (200) before download, or

- by detecting acoustic signals sent down from surface through the core barrel assembly (11) or inner tube assembly (20) by means of an acoustic sensor arranged in the instrumentation unit (200) recognizing the acoustic signal and triggering the instrumentation unit (200) to perform a recording of its current geospatial/environmental data.

15. Method according to claim 12, wherein recording of measurement at necessary depths:

- by sending a command from the master unit instructing the instrument unit (200) to store measurement data at an indicated frequency,

- by storing each data sequence in the instrument unit (200) with an index number, while also a master unit keeps count of the number of the stored measurements,

- when the instrument unit (200) is in a position of interest the user indicates this in a master unit and the belonging measurement number is stored in the master unit,

- once the instrument unit (200) is retrieved from the core barrel assembly (11) it is connected to a master unit, the specific measurement number is requested and the data sequence transferred and processed.