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Advanced Mud Logging (AML) aids formation evaluation and drilling, and yields precise hydrocarbon fluid composition

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While traditional mudlogging techniques provide largely qualitative data, the prime objective of Advanced Mud Logging (AML) is to provide quantitative real time measurements in aid of a complete formation evaluation. To achieve this, wellsite mudlogging technologies have been enhanced, and various techniques which historically were limited to laboratories, have been adapted for well site usage. AML well site techniques thus include: (1) high frequency, improved accuracy monitoring of drilling parameters; (2) enhanced cuttings image acquisition and processing; (3) direct measurements on cuttings, including graindensity, spectral GR, NMR, XRD, XRF; and (4) sophisticated mud gas analysis capabilities. We describe the main system components developed and present some results of the first pilot tests done in Saudi Arabia with AML techniques and a dedicated AML unit. Examples in the four areas mentioned above illustrate and confirm the potential of AML. On one special technology test well, different systems, from two different companies, were run in parallel to establish the merits and possible limitations of especially the hydrocarbon analysis systems. One of the most striking examples of the quality of AML is a perfect match between the hydrocarbon fluid composition determined from mud gas returns, and those subsequently obtained from PVT measurements on wireline fluid samples. To achieve this, AML technology developers in the industry advanced across the whole process chain affecting such quantification. First and foremost, improving sample extraction and handling, combined with enhanced calibration procedures, to convert from in situ to surface conditions. Second, in addition to sampling both the return mud flow and the inflow, a more precise tracking of flowrates and system volumes was made possible with modern operating systems. Third, adding a mass spectrometer to the gas chromatograph, improved the final measurement potential.
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SPE 141277
Advanced Mud Logging (AML) Aids Formation Evaluation and Drilling, and
Yields Precise Hydrocarbon Fluid Composition
Ton Loermans
1
, Charles Bradford
1
, Farouk Kimour
2
, Reda Karoum
2
, Yacine Meridji
1
, Pawel Kasprzykowski
2
,
Karim Bondabou
2
, Alberto Marsala
1
/
1)
- Saudi Aramco,
2)
- Geoservices
Copyright 2011, Society of Petroleum Engineers
This paper was prepared for presentation at the SPE Middle East Oil and Gas Show and Conference held in Manama, Bahrain, 25–28 September 2011.
This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been
reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its
officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to
reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright.
1. Abstract
While traditional mudlogging techniques provide largely qualitative data, the prime objective of Advanced Mud Logging
(AML) is to provide quantitative real time measurements in aid of a complete formation evaluation. To achieve this, wellsite
mudlogging technologies have been enhanced, and various techniques which historically were limited to laboratories, have
been adapted for well site usage. AML well site techniques thus include: (1) high frequency, improved accuracy monitoring of
drilling parameters; (2) enhanced cuttings image acquisition and processing; (3) direct measurements on cuttings, including
graindensity, spectral GR, NMR, XRD, XRF; and (4) sophisticated mud gas analysis capabilities.
We describe the main system components developed and present some results of the first pilot tests done in Saudi Arabia with
AML techniques and a dedicated AML unit. Examples in the four areas mentioned above illustrate and confirm the potential
of AML. On one special technology test well, different systems, from two different companies, were run in parallel to establish
the merits and possible limitations of especially the hydrocarbon analysis systems.
One of the most striking examples of the quality of AML is a perfect match between the hydrocarbon fluid composition
determined from mud gas returns, and those subsequently obtained from PVT measurements on wireline fluid samples. To
achieve this, AML technology developers in the industry advanced across the whole process chain affecting such
quantification. First and foremost, improving sample extraction and handling, combined with enhanced calibration procedures,
to convert from in situ to surface conditions. Second, in addition to sampling both the return mud flow and the inflow, a more
precise tracking of flowrates and system volumes was made possible with modern operating systems. Third, adding a mass
spectrometer to the gas chromatograph, improved the final measurement potential.
2. Introduction.
Several years ago, in Saudi Aramco, a clear business need emerged for additional petrophysical techniques in cases where
traditional formation evaluation technologies were unable to provide all the necessary answers with sufficient certainty.
Interpretation of tight gas formations in particular was challenging, because the formation properties typically were right at the
edges of the operating envelopes of normal logging tool measurements and interpretation technology. With a perceived
potential for AML technologies to aid in several of those challenges, an AML research area was set up. The mission was to
expand and improve existing mudlogging technologies, and introduce and develop new ones. The vision had two related, but
distinct elements. Firstly, also labeled as “ARCHIE’S DREAM”
1
, a complete, albeit preliminary, as a “first aid”, formation
evaluation, based solely on AML data, including mineralogy, fluid contacts and fluid characterization, porosity and even
saturation, permeability and other parameters normally derived from conventional electric logging and coring. Secondly, a
process monitoring system to allow optimization of the drilling process (Loermans & Touati, 2003). Note that the potential of
measurements on cuttings has long been recognised in the industry (e.g.: Marsala et al, 1997).
As part of the mission, specific tasks to evaluate and further develop specific technologies with AML potential, such as direct
measurements of permeability on cuttings, and X-ray CT scanning (Touati, Siddiqui et al, 2004), were undertaken. It is
interesting to note that, partly because of the confirmation of potential of cuttings image analysis through such tasks, a major
1
ARCHIE’S DREAM = Advanced Rock Characterisation and Hydrocarbon Indication and Evaluation, through Systematic
Determination with Rock and Elemental Analysis Methods.
2 SPE 141277
research area in Saudi Aramco, Pore Scale Physics, evolved. At present, across the industry, image analysis with X-ray CT
scanning to obtain a whole range of key petrophysical analysis, even when not yet fully well-site suitable, almost appears an
established element for petrophysical measurements and data acquisition.
Having thus gauged the actual capability of some techniques, and benefitting also from several ongoing activities in the mud
logging industry, such as development of improved operating and data processing systems, the objective of a single integrated
AML unit, came within reach (Loermans, Kanj & Bradford, 2005).
In the following we will first briefly describe the main components of an integrated AML system and confirm, with laboratory
tests, that the necessary quality of the measurements should be achievable on the well site. The complete mud gas analysis
processing chain, as probably the most challenging development the mudlogging industry has tackled, obviously will get some
extra attention.
Next we will illustrate, with some examples from pilot test runs made in some Saudi Aramco wells, the potential in each of
the main four areas being addressed. Testing the merits of various mud gas analysis systems is particularly challenging. Thus
on one special test well, we had two mud logging systems, provided by two different companies, running in parallel. While
such set up might be relatively unique, and with some obvious special operational challenges, that is the only practical way to
really have identical operating and well conditions to test and compare different mud gas analysis systems.
Finally, a review of the current status leads to the conclusions that we, i.e.: the industry as a whole, are well on the way to reap
significant added value from AML, that significant parts of “ARCHIE’S DREAM” are being realised already and that even a
direct quantification of total hydrocarbon volume (i.e.: a continuous log of porosity * hydrocarbon saturation) from only AML
data is already getting within reach.
3. Description of main AML components.
3.1. Rig sensors and computing operating system.
While there are sufficient commercially available sensors available for most of the required measurements, including mud
flow rate and mud weight, developing a system to properly handle and process all the data, and turn those into information, is
a significant task.
First there are (a) the fact of dozens of sensors scattered around the well site, from mud pits to bell nipple, (b) the need for
quality control, and thus amongst others (c) the desire to do analogue to digital signal conversion as close as possible to the
sensors, and (d) have manufacturer’s sensor calibration schemes incorporated. Next there is the need for a computing system
which can handle and track e.g. fluid volumes across time and the surface and well bore spaces, process all the acquired data,
and provide outputs and displays which give the desired insights for real time decision making. Finally, in order to be able to
monitor drill string vibrations, the sampling frequency needs to be increased significantly from a few Hz, as done traditionally,
to around 50 Hz. (Figure 1)
SPE 141277 3
3.2 Cuttings measurements process
Given that a large number of separate measurements are to be made on the cuttings, typically requiring even significantly more
time for sample preparation than for the measurements themselves, the logistics and process chain for all of these activities
need special attention and development efforts. A comprehensive flow chart and operating procedures thus were developed.
Catching cuttings, partly because it is such a vital element in the process, is still done ‘by hand’, with the best possible industry
practice, obviously geared for the subsequent measurements to be done in terms of sets of cuttings, quantity and initial
washing and sieving. Depth lagging similarly is done with the aid of the mud flow and drilling tracking system, and occasional
spot checks.
Space, for all of the instruments, and the well site staff to perform all the tasks, including mud gas analysis and overall system
processing, even for land based units, is scarce. The ultimate objective is to have only a single large (40 ft) container for all of
the services. In the testing and development phases, more staff are useful and even necessary, and some double sets of
equipment still need to be catered for. Hence initially two smaller, conventional units were employed in addition to the one
large dedicated AML unit; at present one extra unit is still used.
3.3 High resolution video microscope.
The traditional microscope and digital camera add-on, have been replaced with a high resolution digital microscope, with an
outstanding depth of field (almost 1.5 mm at a magnification of 100, which is around 20 times typical industry standard), a
2.11 Mpixel CCD matrix, 3 CCD for enhanced colour reproduction, a high performance zoom lens (x20 - x200), a high
intensity light source and high optical aperture allowing iris reduction. Advanced image processing features and a full
integration into the operating system allow maxium usage, not only on site, but also real time in e.g. an Operator’s office based
operations centre.
With the image processing system available, many quantification tasks can be done much faster and with higher precision and
accuracy than possible with conventional methods. See figure 2, where, in a laboratory test of the system, a quantification of
lithology fraction turned out to be perfectly correct.
3.4 Rock matrix density.
The rock grain density is measured with a gas displacement pycnometer. Washed, crushed and dried samples are weighed and
placed in a chamber which is filled with gas to a certain pressure. Release into a second chamber with a known volume allows
the calculation of total grain volume, and, with the total weight, the matrix/grain density.
3.5 Porosity.
Two methods to measure porosity on cuttings are used, one based on an called envelope density analyzer, sometimes referred
to as ‘powder pycnometer’, to establish total bulk cuttings volume, and separately determined grain volume, the other based on
total cuttings volume and NMR measurements. The NMR measurements also providing a quantification of both effective and
total porosity.
3.6 NMR.
When, in a measurement sample of cuttings, there is sufficient difference in pore-size between the inter-cuttings ‘porosity’ and
the intra-cuttings (“real”) porosity, NMR measurements on cuttings suspended in a liquid should be able to yield a robust
porosity. When the cuttings are more closely packed and large pores are present, a careful removal of adsorbed, excess liquid,
like in conventional core plug measurements for electric properties, is required. We employed the latter method.
4 SPE 141277
Two NMR systems have been used. The first, commercially available, system, while simple to use in some respects, required a
relatively large volume of cuttings and, while laboratory tests on many samples had yielded good results, the first pilot showed
the system to be less sutiable for our field operations where more flexibility in acquisition and processing parameter setting
were required. Hence a new system was developed.
The second system, now used in the AML operations, includes a thermo-regulated magnet and integrated electronics. It is
driven by a laptop and specific software which also allows display of the results after the measurement is performed. Total and
effective porosity are derived from relaxation curves by applying appropriate cut-offs. Sample preparation consists of washing
and volume determination of the cuttings. Only a very small amount of cuttings is required. Thus hand picking of individual
cuttings is practical.
A significant advantage such small cuttings volume is that for very thinly laminated formations, such as turbidites, this NMR
instrument should be able to measure the properties of those very thin laminations, when neither electric logging
measurements, nor even normal core plug measurements, can resolve those directly.
The porosities produced by the two different methods (‘pycnometers’ and NMR) compare well, as illustrated in Figure 3,
corroborating that the measurements and the procedures for both, in principle, are robust.
3.7 Gamma-ray.
A spectral GR instrument has been developed, with a NaI detection crystal, special shaped sample holders (marinelli beakers
of about 250 cc), and shielding geared especially towards well site cuttings measurements. A typical measurement takes 15
minutes and displays gamma ray activity in API units. Laboratory tests proved a remarkably good signal to noise ratio and an
excellent match with measurements done on large rock pieces with conventional tools, also in terms of absolute value of the
GR readings, as distinct from only a good correlation with a (systematic) offset. More importantly even: results from a
laboratory test done with real cuttings collected from a well in Saudi Arabia and a conventional GR show a good correlation
(Figure 4).
SPE 141277 5
3.8 X-ray diffraction (XRD)
Laboratory work with various elemental and mineral quantification systems showed that, while initially the expectations for a
system based on spectral analysis from laser induced rock fragment breakdown were very high, with advances made in
commercially available portable XRD/XRF instruments, these latter had more potential for our purposes. Hence the focus was
shifted to these and several different instruments were tested in the laboratory.
Cuttings mineralogy is determined by XRD. Each mineral diffracts x-rays differently according to its crystallographic
structure, thus creating a unique diffraction pattern which is characteristic of the mineral. Moreover the signal produced by a
mineral in X-ray diffraction is proportional to the quantity of that mineral. This enables a quantitative approach after
appropriate calibration of the instrument with mixture of minerals of known quantities.
Table 1 below, from one of the laboratory tests done, this one on a well known mixture, confirms the accuracy and
reproducibility of the measurement being around 2 %.
Table 1. Test results XRD on 5 phase mixture
Phase Actual weight % weight % from XRD
Quartz 5 4
Dolomite 5 7
Anhydrite 42 42
Siderite 32 33
Calcite 16 14
For our field application, quantified minerals are quartz, calcite, dolomite, anhydrite, feldpars (K and Na), and clay minerals.
Sample preparation consists of washing, drying and manually crushing the cuttings. The analysis itself takes 12 minutes.
3.9 X-ray fluorescence (XRF)
Elementary composition is determined by ED-XRF (Energy dispersive X-ray diffraction), which yields a reliable
quantification of practically all elements of interest, even when present only as traces. Sample preparation consist of fine
grinding (to below 100 µm) of the cuttings, which is achieved with an automatic electrical grinder. The powder is then
pelletised with a hydraulic press. The measurement takes 5 minutes and is performed under a helium atmosphere.
Tables 2 and 3 below give some results from some of the laboratory tests done to confirm the reliability of the instrument for
some elements.
Table 2. Test results XRF on major elements
SiO2 TiO2 Al2O3 Fe2O3 CaO
(%) (%) (%) (%) (%)
Measured 47.45 1.03 17.33 6.63 1.33
Actual 51.95 0.85 16.76 6.33 1.13
MgO Na2O K2O BaO P2O5
(%) (%) (%) (ppm) (%)
Measured 1.71 0.96 2.51 544 0.24
Actual 1.53 1.37 2.51 580 0.18
6 SPE 141277
Table 3. Test results XRF on minor elements
MnO Cr Pb S
(ppm) (ppm) (ppm) (%)
average 723.4 162 14.8 0.07
σ (st.dev.) 4.04 6.96 0.84 0
actual 710 120 16 0.05
Co Zr V Cu
(ppm) (ppm) (ppm) (ppm)
average 7.33 194 149.4 56.8
σ (st.dev.) 0.58 1.41 6.35 0.84
actual 18 180 140 52
3.10 Complete mud gas analysis processing system.
The total mud gas processing system has two separate parts: (i) a real time, continual measurement gas extraction and analysis
system and (ii) a near real time fluid facies interpretation, evaluating the previously obtained data and grouping those into
interpreted clusters of separate sub reservoir units.
Compared to the traditional mud gas analysis systems, in order to be able to move to the goal of (a) quantified hydrocarbon
composition, and thereafter even to (b) a direct quantification of total hydrocarbon pore volume from mud gas readings only,
major steps forward across the whole process chain for the mud gas extraction and analysis were necessary.
Extraction of hydrocarbon from drilling mud under constant high temperatures and controlled thermodynamic conditions
makes it independent of environmental factors such as (variations in) mud temperature at the flow line and the mud flow rate.
The sampling point for this extraction from the return mud flow is best placed as close as possible to the bell nipple and the
apparatus for this, a major development in itself, obviously should be close to the sampling point. Also: in order to be able to
correct for gas still in the mud being pumped into the well, an identical gas extraction system is to be employed on the mud
flow going into the well. Note that there are some well documented cases of still significant gas left in the mud going into a
well, even in cases with seemingly normal and adequate surface degassing; also in some of our recent tests we’ve seen some
examples of this.
An exact knowledge and precise quantification of the extraction efficiency for the various hydrocarbon components,
continually checked and calibrated in the field, because these extraction efficiencies will vary sufficiently to affect the final
compositional calculations, is a crucial part of the whole process, which required significant R&D efforts during the past ten
years.
Given the distance between gas extraction points and the (advanced) mud logging unit even in the best rig lay outs, special
efforts are required to prevent any drop out of (heavier) HC components. A special gas transfer line which is under partial
vacuum to allow transfer of the heavier components in the gas phase is sufficient and necessary for that.
The extracted hydrocarbon is analysed in the gas chromatography/mass-spectrometry unit. After a quick, real time processing
of the data, the final fluid composition obtained provides precisely quantified downhole fluid composition in the C1-C5 range,
with a little less precise indication of some higher components. Qualitative information on long chain n-alkanes and light
aromatics are efficiently used as markers.
The fluid facies identification process used employs a number of peak gas selections and gas ratios for fingerprinting, typically
displayed in star/spider diagrammes.
4. Illustration of AML potential with early field pilot test examples.
In the early field pilot testing stages of a total system like this, where we are now, rather than immediately striving for a
complete and perfect formation evaluation, the first focus is of course on testing and adjusting the various separate elements,
confirming that laboratory performance is repeated in the field, and that the devised operating procedures really work in a
normal well site setting. Yet we have already had some nice examples illustrating the potential value from a fully operational
AML system.
SPE 141277 7
4.1 Tuning of drilling parameters to eliminate vibrations and extend bit life.
An excellent example of the potential to influence drill string vibrations was obtained when coring long sections of a special
technology test well. The AML drilling monitoring system detected clear vibrations (Figure 5), while the conventional system
did not. Rather than reacting on the AML indications, continuing operations as if no AML information was available, just as
one has to do in many scientific experiments, albeit a little risky of course, eventually led to a badly worn bit.
On subsequent runs, whenever vibrations were observed, only a slight adjustment of the drilling parameters, was necessary to
eliminate the vibrations (Figure 6), resulting in the bits coming out in a still excellent condition, allowing several re-runs.
4.2 Easier measurements on cuttings.
However simple it might seem, the ease of fast, accurate measurements of e.g. grain size under a microscope and other
cuttings metrics, is helping well site geology staff to improve on cuttings descriptions and ease on the amount of work required
for documentation.
With the quality of cutting images available, now routinely provided with the cuttings descriptions and included as part of the
logs available in real time to office based operations staff (Figure 7), the need for oil company well site geology staff on
location might be reduced, c.q. those tasks being shifted from well site to an operations centre covering several rigs at the same
time.
8 SPE 141277
4.3 XRD for reliable lithology indication.
In many cases where there is a conflict between indications from different systems, e.g. cuttings description suggesting one
lithlogy, a wireline density neutron suggesting another, but some uncertainty in the interpretation, no firm conclusion can be
drawn. We had an illustrative case like that on an appraisal well, where the initial geological description suggested an almost
100% dolomite lithology and there seemed little doubt about that. The wellsite XRD system however showed a roughly 50/50
dolomite anhydrite mixture (Figure 8), and only subsequent re-examination, showed the formation to consist of anhydrite
grains, fully covered with a thin layer of dolomite.
4.4 Close match between AML and wireline GR and grain densities.
The good performance of the spectral GR in the laboratory tests was measured also demonstrated in an exploration well, with a
strikingly small difference between GR-values from fully corrected wireline logs and the in real time obtained GR values from
the cuttings (Figure 9). Also, there was a good comparison for the individual elements (Th, Ur and K).
SPE 141277 9
A comparison between grain densities from the direct cuttings measurements and those determined after elaborate multi
mineral analysis of a full wireline logging set, including elemental spectral logs, shows encouraging results (Figure 10).
4.5 Comparison between AML and wireline NMR.
The newly developed NMR system on a very first field test already showed clear trends in formation porosity in line with
those from final evaluation based on an extensive wireline data set, even when the actual porosity values appeared to be biased
(higher), confirming that some more R&D work is to be done in this area before the porosity values can be readily used.
4.6 Trace elements correlate with HC presence.
Correlations between trace elements and hydrocarbon presence are relatively well known. We also found a remarkably good
correlation between mud gas readings and some trace elements (Figure 11).
This very good correlation corroborates the quality of both the mud gas analysis system and the XRF sample preparation and
instrument. Hence we may expect various application of trace element analysis to assist e.g. rock properties qualification in
gas shale reservoirs, to special hydrocarbon typing.
10 SPE 141277
4.7 AML HC composition compares well with PVT results.
All the efforts put into finetuning the whole acquisition and processing chain for the compositional analysis of the mud gas
stream were proven effective when the composition, determined real time and continuously obtained from this system
appeared to match perfectly with results from full PVT analysis on wireline fluid samples obtained subsequently (Figure 12).
This perfect match was one of the results obtained in a more elaborate test of two distinctly different advanced mud logging
systems from two different companies on a special technology test well. As mentioned before, having several (advanced) mud
logging units operating in parallel while drilling, is about the only realistic way in which mud gas analysis systems really can
be properly compared. If two systems were tested on two different wells, and the match with PVT results on one were not
perfect, the question would remain whether or not the other would have done better.
The results of the other system employed, while very good on any absolute scale one may use, and significantly better than
many would have expected only a few years ago, were a little less in terms of a perfect match than the results of the system
presented in Figure 12.
The potential business value of such compositional information, as precise and reliable as this, in real time and continuous, is
obviously enormous. The first benefit being an optimization of the subsequent (wireline or LWD) formation fluid sampling
programme. E.g.: Taking more subsequent samples in a case where unexpected variations in fluid composition are encountered
across a reservoir section, assist in delineation of separate reservoirs, and economise on further sampling activities when the
information already obtained is adequate.
4.8 Correlation and geosteering with AML HC fluid facies.
Given the quality of the fluid characterisation above, it becomes possible to do reservoir correlation and even geosteering
based on AML fluid facies. In the example given below (Figure 13), two distinct reservoirs, labeled “A” and “B” had different
fluid types as per the star diagramme given. Having penetrated zone/reservoir A, easily established from normally available
data, was confirmed with the determined fluid facies on a few smaples in that A-zone. Having penetrated zone “X” in this new
well, even with conventional electric logs, it was not clear whether or not this zone X was in reservoir B, or whether B was
still deeper. The fluid facies analysis clearly indicates that zone X does not belong to reservoir B, or that reservoir B is split in
distinct units/blocks with different fluids, type B and type X.
SPE 141277 11
5. Conclusions.
Given the still early stages of AML development, there are still several challenges to be tackled. E.g.: a further reduction in the
total well site footprint, including the number of staff required for the full operation; a further refinement of sampling and
sample cleaning procedures; improvement of accuracy and precision of some of the measurements on cuttings. Hence further
R&D AML efforts will be required to achieve the ultimate goals.
Yet, based on the foregoing, we may conclude the following:
AML is established.
We have developed an Advanced Mud Logging system, including instruments and processes (a) in aid of formation
evaluation, as a complete ‘first aid’, and (b) to assist, optimise and improve drilling operations. Measurements which hitherto
were limited to large laboratories are now possible with portable, well site suitable systems. Improved sensors and operating
system allow an enhanced monitoring and further optimization of drilling operations. Unlike conventional electric logging
tools AML does not have any reservoir temperature or pressure limitations, and is hardly, if at all, affected by adverse hole
conditions which often affect wireline and LWD electric logs.
AML may resolve properties of the thinnest laminae.
Interestingly enough, it appears that one of the largest traditional concerns related to mud logging: an intrinsically low depth
resolution linked to the manner in which even the best cuttings sample catching can be done, might be at least partially
compensated by the ability to measure very small rock fragments. Thus opens the possibility of directly measuring properties
of very thin laminae, well below the resolution of normal electric logs and even core plug measurements.
Clear illustration of AML potential from first field trials
The first results of field trials being done with this system are very encouraging. In all four areas, i.e.: (1) high frequency,
improved accuracy monitoring of drilling parameters; (2) enhanced cuttings image acquisition and processing; (3) direct
measurements on cuttings, including graindensity, spectral GR, NMR, XRD, XRF; and (4) sophisticated mud gas analysis
capabilities, clear illustration of the value and potential of AML has already been given with field examples.
AML HC fluid compostion compares well with PVT analysis.
The quality of hydrocarbon compositional analysis obtained perfectly matches PVT analysis results on wireline fluid samples.
AML provides the results in real time and continuously across the whole well, with formation fluid samples only after logging,
at only (few) selected intervals, and requiring further time and laboratory effort to be analysed.
Potential of geosteering with AML fluid facies.
Given the quality of the fluid composition analysis, reservoir correlation and even geosteering based on AML fluid facies
becomes possible.
Spectral GR, XRD, XRF for challenging mineralogy.
The spectral GR, XRD and XRF functionalties might turn out to be very effective and cost efficient elements for an adequate
evalution for challenging environments shuch as very tight / shale gas reservoirs.
Total HC volume quantification within reach.
Given the demonstrated precision obtained with hydrocarbon compositional analysis, a next R&D target: a reliable, direct, real
time, continuous quantification of total hydrocarbon volume, i.e., a continuous log of the product of porosity and hydrocarbon
saturation from mud gas readings, seems within reach. This, obviously, might be particularly useful for situations where
traditional methods face serious challenges, such as possibly in low porosity and tight, e.g. shale gas, formations.
12 SPE 141277
References
Loermans, Kanj & Bradford. “Advanced Mud logging: from Archie’s dream to reality.” SPE Technical Symposium of Saudi Arabia Section,
June 2005; SPE93726.
Loermans & Touati. “Archie’s dream …. and beyond: Advanced Mud Logging (AML).” SPE Technical Symposium of Saudi Arabia
Section, June 2003.
Marsala, A. F., Meazza O., Rossi E., Brignoli M., Santarelli F.J., AGIP S.p.A. “Petrophysical Characterization of Reservoir Rocks by
Measurements on Cuttings” - OMC ‘97 - Offshore Mediterranean Conference' - Ravenna, Italy, March 19-21, 1997
Touati, Siddiqui, Funk, Loermans and Kanj; Porosity measurements on cuttings from X-ray CT scans: study highlights; SPE Technical
Symposium Dhahran, Saudi Arabia; May 2004.
6. Acknowledgements
The results achieved in this project would not have been possible without significant efforts from many colleagues and continuous support
for several years for all related activities in both Geoservices and Saudi Aramco. In particular we would like to thank Omar Amoudi,
Mohammed Arakzeh, Lee Cockram, Johan Edso, Abdulaziz Al-Kaabi, Mathieu Naigeon, Maneesh Pisharath, Nezar Talhah, Eric Villard and
Hilal Waheed for their contributions.
... Mudlogging traditionally utilized qualitative data, but it recent years has benefited from quantitative mineralogy, onsite which is provided by pXRD (Loermans et al., 2011). Conventional petroleum exploration typically utilizes a range of quantitative measurements, but quantitative mineralogy onsite is rarely available. ...
... Numerous studies have been conducted to ensure that pXRD is a viable method for qualitative and quantitative mineralogical assessment of geological materials (Loermans, 2011;Uvarova et al., 2014;Burkett et al., 2015;Turvey et al. 2017). Preliminary studies on the qualitative and quantitative capabilities of pXRD for mudlogging and mineral exploration were undertaken by Loermans et al. (2011) and Uvarova et al. (2014), respectively. ...
... Numerous studies have been conducted to ensure that pXRD is a viable method for qualitative and quantitative mineralogical assessment of geological materials (Loermans, 2011;Uvarova et al., 2014;Burkett et al., 2015;Turvey et al. 2017). Preliminary studies on the qualitative and quantitative capabilities of pXRD for mudlogging and mineral exploration were undertaken by Loermans et al. (2011) and Uvarova et al. (2014), respectively. Burkett et al. (2015) explored the quantitative capabilities more fully through the analysis of a larger suite of synthetic mixtures of natural minerals, and a variety of field sourced samples with pXRD, laboratory XRD and verification with laboratory XRF. ...
Article
X-ray diffraction (XRD) is a well-established technique in the earth sciences as it can be used to identify and quantify minerals and is particularly useful for fine-grained sedimentary rocks. Due to the capital cost, environmental requirements and significant sample preparation, XRD instruments are generally confined to laboratories. Recent advances in XRD sample holders and X-ray sources have allowed for the development of portable XRD (pXRD) devices where the sample preparation is simpler and does not require regular calibrations by a technical expert. This technology was initially developed by NASA for the Mars Science Laboratory rover Curiosity, to perform mineralogical analysis of the Martian surface. Due to its portability, minimal sample preparation, fast collection times, and excellent correlation with laboratory-based XRD devices, pXRD has been shown to be of great use to petroleum geologists and engineers by providing rapid, quantitative mineralogical data. For mudlogging quantitative mineralogy is being used to guide directional drilling towards the target formations and to ensure lateral drilling stays within the target formations. Quantitative mineralogy from the target formation and overburden rock also provides important information regarding the engineering properties of these rocks (e.g. fracturability), and can help determine the most appropriate acid for acid-fracturing stimulation. For conventional petroleum exploration quantitative mineralogy onsite, can be used to understand geophysical responses, and as a screening tool for selecting samples for more detailed analysis.
... First of all, the spectral GR calculated from the concentration of Th, U and K could be used to correlate cuttings related data with wireline or LWD information. This confirmed the good depth match of the analyzed cuttings [14]. Additionally, traces elements could be used for geochemical fingerprinting, for stratigraphy studies and to determine of the depositional environment of the drilled formation [15]. ...
Conference Paper
Full-text available
Direct combustion of cuttings collected at the rig site can help identifying the presence and assess the variation of organic matter into a drilled rock, with minimum sample preparation and signal processing. This near-real-time data provides key information to optimize and de-risk critical decisions such as selection of sidewall coring points, wireline logging programs and sweet spots identification. The method is based on the isothermal oxidation of the sample, done directly at the wellsite and with field deployable equipment. Extensive lab tests have been done to validate both the measurement and the full workflow. Samples have been measured both with this wellsite dedicated equipment and with advanced lab devices. The results between the different methods have been compared and showed good agreement. The workflow has been applied several times to actual wellsite analysis. The results of one of these cases have been illustrated in this paper, together with the integration of the well site TOC with different datastream (i.e. advanced surface fluid logging and continuous isotope logging).
Conference Paper
Full-text available
During a drilling operation, rock cuttings are often sampled off a shale shaker for lithology and petrophysical characterization. These analyses play an important role in describing the subsurface; and it is important that the depth origin of the cuttings be accurately determined. Traditionally, mud-loggers determine the depth origin of the sampled cuttings by calculating the lag time required for the cuttings to travel from the bit to the surface. These calculations, however, can contain inaccuracies in the depth correlation due to the shuffling and settling of cuttings as they travel with drilling fluid to the surface, due to unplanned conditions like drilling an overgauge hole, and due to other unforeseen drilling events, especially critical in horizontal sections. We therefore aimed to remedy these inaccuracies by developing a series of styrene-based nanoparticles that tagged the cuttings as they were generated at the drillbit. These “NanoTags” were tested while drilling in Q4, 2019; and the results indicated that the NanoTags did in fact have the potential to identify some systematic errors compared with traditional mud logging calculations.
Article
Evaluating the formation quality by deriving porosity, pore size, and permeability from cuttings instead of drill cores is a promising and challenging field of research established in the past decade. Challenges with cuttings are their small and irregular size rendering them unsuitable for e.g. standard permeability measurements. Permeability can be estimated from nuclear magnetic resonance (NMR) measurements. NMR measurements on cuttings are especially challenging 1) because the total NMR signal is very low due to small sample sizes and 2) because the high ratio of outer surface to volume leads to a significant contribution of interstitial water to the NMR signal, which thus distorts the informative NMR signal from within the pore space. The aim of the study is to evaluate the use of NMR in combination with micro computed tomography (μCT) as a method to determine the pore space characteristics of small drill cuttings from the Bückeberg Formation (German Wealden). After accurate removal of interstitial water and a CT based sorting, it was possible to measure NMR signals representative for the individual pore sizes. The representiveness of the measured values was verified by simulations of the NMR signals in pore spaces determined via μCT. Porosity, relaxation time distributions, and permeability were calculated for cuttings assemblages with large, medium, small, and very small pores.
Petrophysical Characterization of Reservoir Rocks by Measurements on Cuttings " -OMC '97 -Offshore Mediterranean Conference
  • A F Marsala
  • O Meazza
  • E Rossi
  • M Brignoli
  • F J Santarelli
Marsala, A. F., Meazza O., Rossi E., Brignoli M., Santarelli F.J., AGIP S.p.A. " Petrophysical Characterization of Reservoir Rocks by Measurements on Cuttings " -OMC '97 -Offshore Mediterranean Conference' -Ravenna, Italy, March 19-21, 1997
Loermans and Kanj; Porosity measurements on cuttings from X-ray CT scans: study highlights; SPE Technical Symposium Dhahran, Saudi Arabia
  • Touati
  • Funk Siddiqui
Touati, Siddiqui, Funk, Loermans and Kanj; Porosity measurements on cuttings from X-ray CT scans: study highlights; SPE Technical Symposium Dhahran, Saudi Arabia; May 2004.
Petrophysical Characterization of Reservoir Rocks by Measurements on Cuttings
  • A F Marsala
  • O Meazza
  • E Rossi
  • M Brignoli
  • F J Santarelli
  • P Agip S
Marsala, A. F., Meazza O., Rossi E., Brignoli M., Santarelli F.J., AGIP S.p.A. "Petrophysical Characterization of Reservoir Rocks by Measurements on Cuttings" -OMC '97 -Offshore Mediterranean Conference' -Ravenna, Italy, March 19-21, 1997