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Патент USA US2408965

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Oct 8, 1946.
w. E. wlNN ET A».
Filed Aug. 22, 1941
Patented Oct. 8, 1_946
' William E. Winn, Dallas, Tex., and Patrick F.
, Dougherty, Chester, Pa., assìgnors to Sun Oil
Company, Philadelphia, Pa., a corporation of
New Jersey
Application August 22, 1941, Serial No. 407,955v
3 Claims.
(Cl. 23-232)
The present invention relates to a method of
:drilling oil and gas wells and is particularly di
rected to a method of detecting the presence of
hydrocarbons in the strata traversed by adrlll
While a well is being drilled.
lt-has long been the practice in drilling to in
spect and examine the mud fluid returns from
a Well in order to determine the nature of the
2 f
of cuttings Ifrom-the drill, such an amount of
colloidal material that its viscosity will be sub
stantially increased. Conversely when the drill
passes throughla formation having a high> salt
content the drilling fluid will'become so saline
that the clay particles thereinl will be flocculated
and the viscosity of the drilling fluid will bede
creased materially. ~ Due to these and other
causes, among" which may be mentioned the delib
strata being traversed by the drill and also the
erate variations of the _properties and charact
character of the fluid contents, if any, of such 10 teristics of the drilling fluid, by chemicalfor
The present invention is directed to an
improvement in the method of detecting and de
termining the amount ofA hydrocarbons present
other treatment, to meet conditions encountered
in drilling, thevproperties and characteristics' of
the mud fluid issuing from the well, i.' e. at> the
in the mud fluid returned from the well and also
point> at which it is generally examined, aresub
the presence and amount of such hydrocarbons 15 ject to rapid and large variations, and in time the
in the strata traversed by the drill, and is par
entire'amountvof drilling fluid being circulated
ticularly directed to a method of detecting the
will be alteredin'character.
presence of low molecular weight hydrocarbons in
We have discovered that such variations in
the strata traversed by the drill.
the properties and characteritics of the drilling
In the drilling of oil and gas wells by the ro 20 fluid `will cause serious errors in analysis of the
taryvmethod it is customary to circulate a mud
4drilling fluid.`> Thus, a highly viscous mud con
laden fluid- down through the drill pipe, out
taining a certain amount of hydrocarbons, for in
through openings, generally called eyes, in the
stance gas, will, in- mostkmethods of analysis,
drill where the mud laden fluid exerts cooling and
show a different gas content from that of afthin
lubricating action on the drill and also picks up
mud having the same actual gas content.
and suspends cuttings formed Iby the action of
lIt is an object of this invention to provide an
the drill, the mud with the cuttings suspended
improved methodv for examining drillingfluids
therein then returning to the surface through the
and particularly for detecting and analyzing hy
annular space between the drill pipe and the wall
drocarbons in vdrilling fluidsobtained from a bore
of the bore hole or casing if casing has been set. 30
At the surface the stream of mud fluid is passed
s A more detailed object of thev invention is to
over a shale shaker, which is merely a vibrating
provide a method for analyzing`A and detecting
screen, in order to separate the coarser cuttings
the'presence of hydrocarbons in a drilling fluid
from the drill fluid. The fluid passes through the
which will materially decrease the errors in anal
shale shaker, flows to a mud pit where it is picked
ysis caused by variations in the properties'and
upvby the pumps, and is again forced down the
characteristics of the drilling fluid.
drill pipe.
Since it is the common practice to maintain
Other further objects will be apparent as the
description progresses.-
the drilling fluid at a specific gravity such that
-For better understanding of the present inven
the hydrostatic head of drilling fluid at the .bot 40 tion, reference should be made to the accompany
tom of the hole will be greater than any fluid
ing drawing, Fig. 1 of which is a diagrammatic
pressure apt to be> encountered in the formations
representation vof a well being drilled in accord
traversed by the drill there is very little, if any
inflow of ñuids from the formations rinto the
drilling fluid. Consequently the amounts of gases
or other hydrocarbons mixed with the drilling
ñuid from the formations traversed by the drill
are usually small,. andtheir detection at the sur
ance with the ¿present invention, while l5‘ig.12` is
, ’a representation of a slight modification of >our
face isr frequently accompanied with many diñ‘ì
50 bit 5. lThe mud issues through eyes 6 in the lbit
It is wellv known lthat theproperties and char
acteristics of the drilling mud are affected by
In the drawing I designates Áa mud pit, from
which mud is withdrawn, by pump 2, and forced
through line 3,4-"down the drill pipe 4 to the drill
and cools or lubricates the bit and picks up the
_The mud, with cuttings suspended
therein, ascends in the annular space between the
the nature of the material introduced to the
walls of the bore hole 1 Yand the drill pipe 4. The
drilling iiuid in the form of cuttings from the
55 lower portion of the drill hole 1 is shown as being
formations traversed bythe'drill.v Thus, when
uncased while a string of surface casing 8 has
the drill is passing through a formation having
been set'in the upper portion. ` At the surface the
a high content of colloidal material (for example
mud from the annular space between the drill
a stratum of bentonitic‘ clay) the mud fluid> which
pipe and surface casing, 4 and 8 respectively, flows
is circulated past thedrill while it is traversing 60 Vthrough line 9 to a shale. shaker Ill, themud pass,
such a stratum will'have added to it, in the form
ing through the shale shaker and being returned
to the mud pitfI while cuttings are separated out
indications as to variations in light hydrocarbon A
on the shale shaker and are removed therefrom.
We have discovered that by passing gaseous
A portion of the mud is withdrawn from the
stream of mud fluid issuing from the well prefer-ff
ably before the mud fluid realches. the shale
shaker, as illustrated in the drawing. This por
tion of the mud fluid is withdrawn through .line> ..
carbon dioxide through the mud fluid we are able
lmore readily to remove the light hydrocarbons
therefrom, so that the effect of variations in the
properties of the mud fluid, resulting in variations
in its ability to retain light hydrocarbons, is mini
mized. Since changes in relative amounts of hy
exchanger 23, wherein the' mud may Vbe either 10 drocarbons >in the‘mud iluid serve as well as ab
heated or cooled to a predetermined temperature.
solute amounts to indicate differences in the na
I I by pump 26 and passes therethrough-'to aiheat
Thence the mud fluid flows to a mixer I2 where
it may be chemically treated, as hereinafter more
ture of the strata penetrated, the use of carbon
dioxide as the stripping agent permits determin
ing relative amounts of light hydrocarbons in
dicative of the nature of the formations pene
trated, such determinations varying more in ac
cordance with the hydrocarbon content of the
formation and less in accordance with variations
in properties of themud than by methods hereto
fully explained, by adding chemical or other
treating agents thereto through line 24. Suitable
means (not shown) are provided in mixer I2 to
thoroughly agitate andrmix `the treating agents
_added through line `2l rwith the mudfiuid. From
the mixer I 2 the mud fluid passes to a stripper I3
wherein light hydrocarbons present in themud
fore employed.
fluid may be separated therefrom. ~ The mud
Certain other gases, for example, air, steam.
methane or ethane, may be employed for strip
ping out the hydrocarbons. However, it has been
fluid, stripped of light hydrocarbons, is Vdis
charged therefrom to a line I4,«either being dis
posed of `as waste or returned t0 .the mud pit I. A
found that these other gases are much less effec
suitable agent for removing hydrocarbons, which 25 tive in removing the hydrocarbons than carbon
will hereinafter generally be referred to as a gas,
dioxide. Accordingly, if such other gas is used
is introduced in the stripper I3 through linev I5
as the stripping medium, a muchlarger propor
and bubbled up through the mud fluid vvtherein
and is removed therefrom through line I 6. In
passing through the mud fluid the gas willistrip
tion .of gas is required to minimize variations in
the amounts of removed hydrocarbons caused by
changes in the properties of the mud than would
out hydrocarbon gases present in the mud flow
be the case if carbon dioxide were employed and,
and possibly also low boiling liquid hydrocarbons.
consequently, the time required for treating a
given amount of mud fluid is unduly prolonged.
It is not known precisely why, carbon ,dioxide is
The gas with hydrocarbons stripped from the
mud flows through line I6 to a caustic treating
tank I7 Where it is bubbled through a solution of
caustic soda or other suitable alkali, thence itv '
flows through line I8 to a dehydrator I9 and
thence vthrough line 20 to a gas detector or ana
lyzer 2I, whence it may be vented to the atmos
phere through line 22.
As heretofore stated, it is well known in the art '
that asdrilling progresses the character and
properties of the mud fiow‘are subject to wide
variations due both to the character of material
>mixed with the mud 4flowvfrom theformations
penetrated by the drill and also due to deliberate ’
variations in the character and property of the
mud` fluid by chemical or other treatment. » We
have discovered that’ when »a Ygas. is bubbled
through the mud fluid being analyzed for the r
presence of light hydrocarbons _the variations in
the characteristics ofthe mud fluid do notaf‘fect
the results obtained as greatly as _when other
methods for removing the gaseous or` other light
hydrocarbons from the mud flow are employed.
" There are three possiblemeans by which the
gaseous or other hydrocarbons may be held in
the mud fluid: (l) by suspension in the form of
minute bubblesv of free gas or oil droplets, l(2)
so much more efllcient in removing the hydrocar
bons than other gases, but among the possible .
reasons may be mentioned the following: (1)
the relatively high solubility of carbon dioxide
in Water which allows it to dissolve in the water
of the mud fluid and displace hydrocarbons dis
solved therein; and (2) the high adsorptive pow
er of clay or sand particles for carbon dioxide as
compared to other gases which results in the dis
placement,> by the carbon dioxide, of hydrocar
bons ,adsorbed by the solid matter in the mud
fluid. Perhaps, also,` the relatively high solubil
ity of` carbon dioxide in oil, even as compared to
gaseous hydrocarbons such as methane or ethane,
may play a part. It should be understood, how
ever, that these reasons are proposed only as pos
sible. explanations of the effectiveness ,of carbon
dioxide and that we do not Wish to be bound by
Carbon dioxide has another advantage over
most other gases that vmay be employed for strip
ping out the hydrocarbons in that it may easily be
separated from the hydrocarbons, subsequent to
their removalfrom the mud fluid,y by absorption
„in alkali, thus permitting the hydrocarbonsto be
by- absorption in the liquid portion of the,l mud
60 tested separately. Also, if it is desired to analyze
fluid, and (3) by adsorption on the surface of
the removed hydrocarbons without first separat
solid .particles dispersed in the mud fluid.- By
ing the stripping agent therefrom, as by the well
means of methods knownheretofore, such as
>known combustion analysis, carbon dioxide is
'methods employing heat and/or vacuum for driv
particularly satisfactory since it will vnot undergo
ing out the hydrocarbons, it has been very diffi 6. combustion to liberate heat interfering With the
cult to remove substantially all of the gaseous and
analysis. lFurther, if it is desired to use`known
light liquid hydrocarbons present in the various
spectral methods of analysis such as by the mass
forms and the amount of such hydrocarbons re
spectrograph or infra-red analysis, carbon diox
tained by the lmud has been subject to variation
ide will not interfere with such analysis so that it
depending on the properties of the mud fluid.
Thus, when the mud wasv relatively viscous, the
contentfof removable hydrocarbons -as deter
mined'by these known methods was substantially
need not be first removed.
, ,
It is therefore preferred‘to use carbon dioxide
kas'the gas which is introduced through line I5
into the stripper la. This carbon dioxide with the
hydrocarbons stripped from the mud fluid passes
methods are‘thus unreliable and give erroneQus , 7 `through line. IB vand may bey analyzed. in any
less than when the mud was more-fluid.
known or desired manner. As illustrated in the
drawing, it may be passed to caustic treating tank
I1 wherein it is bubbled through a solution‘of so
dium hydroxide or other alkali. The carbon‘di
the temperature of the mud fluid being` analyzed
substantially uniform. Thus, substantially uni
form conditions are maintained on the mud being
analyzed throughout the drilling operation or
changes in the properties and characteristics >of
oxide, by reacting with the alkali in caustic treat
the mud can be caused to occur gradually so that
ing tank I1, is removed from the separated hy
the results of the analysis of the mud vary only
drocarbons and hydrocarbons pass through line
in accordance with the amountsy of gaseous or
I8 to dehydrator I9 where they pass through a
other light hydrocarbons in the mud and not in
body of calcium chloride or other dehydrating
with variations in the aforesaid char
agents and thus only hydrocarbons are sent to the 10 accordance
acteristics and properties affecting the ability of
gas detector or analyzer 2 I, wherein their amount
the mud to retain hydrocarbons. In other words
and' cliaiiact'er may be determined. It is, of
predetermined substantially uniform hydrocar
course, to be understood that if some other gas or
bon-retentive properties are imparted to the mud
vapor is employed in place of carbon dioxide suit
prior to the stripping operation in stripper I3,
able means for separating the gas from the hy 15 thereby facilitating the determination of a light
drocarbons admixed therewith may be provided.
hydrocarbon content indicative of the nature of
For instance, if air is used as the stripping medi
formation penetrated regardless of variations
um, the mixture of air and hydrocarbons` passing
drilling in the properties of the mud which
from the stripper I3 through line I6 may be sub
its ability to retain light hydrocarbons.
jected to a step designed to separate the hydro 20 affect
While the present invention has thus far been
carbons from the air, for example, to a distilla
in connection with the* detection of
tion step. Likewise, if steam is employed as the
hydrocarbons in the strata traversed by a drill
stripping medium, the mixture of steam and hy
during the drillin-g Vof a well, it frequently is de
drocarbons issuing from the stripper I3 may be
to log the formations traversed bythe
passed directly to dehydrator I9 in which the
25 drill after a well has been completed. For in
water vapor is removed, the dry hydrocarbon va
stance, during the course of drilling the well 1,
pors passing out of dehydrator I9 through line 20
certain strata may have been passed through
to gas detector 2|. Incase hydrocarbon gas is
by the drill bit which showed promise of being
used as the stripping medium, the gas removed
from the stripper I3 through line I‘S is subjected 30 oil or gas producing formations and it may be
desired to obtain additional information con
to a type of analysis in which the various indi
cerning the strata; or an electric survey may
vidual hydrocarbon gases are determined. Thus,
be run in the well 1 which indicates that cer
if methane is introduced through line I5, the hy
tain strata werev passed through by the drill
drocarbon gases removed through line I6 will be
were not located by other logging means,
subjected to the analysis required to separately 35 which
and it is, therefore, desired to obtain cuttings
determine the amount of methane and the
from such formations in order to more fully de
amount of ethane and any higher members of the
termine their value. Regardless of the reason
series, the latter determination identifying hy
for which it is desired to obtain additional infor
drocarbons present in the mud. If it is desired to
mation concerning any particular formation, this
determine the amount of methane present in the 40 -information may be obtained in the following
mud fluid, ethane may be introduced through line
I 5 to gas separator I3 and the ethane and meth
The _bit 5 is replaced by an under-reamer 5’
ane removed through line I6, separated and the
(Fig.4 2), and the drill pipe Il with the under
amount of methane in the mud fluid determined.
reamer 5’ secured to the end thereof is lowered
However, it is distinctly preferred to use carbon
into the well 1 until the cutters 25 on under
dioxide since, as stated, this has greateffective
reamer 5’ are opposite the formation a: concern
ness in removing the light hydrocarbons from the
'Ying which information is desired. Drilling mud
mud fluid, and the apparatus for practicingv the
is circulated from mud pit I vby pump 2 through
illustrated embodiment of the invention has been
line 3 down drill pipe 4 and issues from'> openings
shown and described particularlyv for the use of .
or eyes 6’ in the under-reamer 5’ and *"near the
carbon dioxide.
cutters 25 thereon. The drill pipe is rotated- in
In order to still further reduce "the effect of
the usual manner so that the cutter 5' will under
variations in the properties and characteristics of
cut the walls of well 'I in the usual manner. The
the mud fluid on the detection of gaseous or other
drilling mud circulated down drill pipe 4 returns
light hydrocarbons therein, we have provided the 55 to the surface in the annular space between drill
treater or mixer I2 in the line II through which
-pipe 4 and the walls of well 1 carrying suspended
the mud passes. As the mud íiuid passes through
the treater I2 suitable and conditioning chemi
cals, or preferably solutionsthereof, may be add
in it the cuttings from the walls of well 1 at the
formation œ formed by the action of the under
'5'. The drilling _mud issues from the
ed thereto by introducing them through4 valved 60 reamer
well through line 9 and a portion thereof is with
line 24 and mixing them therewith. We are thus
drawn through line II. The treatment of the
able to control the viscosity, salinity and other
drilling mud' passing ~through line II will 'be the
characteristics and properties of the mud fluid
as that heretofore described, andthe Ymud
within a fairly definite or fixed range.. For in
to' analysis to >detect the'presence
stance, the visocity of the mud may be controlled
Vtherein from the cuttings from
by adding aqueous solutions of various alkali
formation a: obtained by the -action of under
metal phosphates in the well known manner, or at
reamer 5’. If desired, thecuttings A‘may be’nsep
arated from themud byV usual methods, for in
centrated solutions» of suitable salts the salinity
may, of course, be readily controlled. vNumerous 70 stance. by the Shale shaker lo, the cuttings
washedÍand subjected to detailed analy‘sisï" in
speciñc methods of controlling various properties
times merely by the addition of water or of con
and characteristics of the mud fluids used in
drilling are well known and such specific methods
do not form a part of the present invention. Also,
by means of heat exchanger 23 we can maintain
order to obtain additional information concern
ing the nature of the formation œ.
This method of operation permits the analysis
of mud returns from particular portions of the
-bore hole and thus makes it possible to make a
more fdetailedand careful study of the more
Apromising strata traversed by the bore hole, and
also permits a check to be made Von the survey
made during drilling in case there are Yany in
dications that such survey was not accurate for
Some reason, for instance, due to a partial break
down of the apparatus, or the like.
‘ At` times it may be desirable to use the latter
method of analysis exclusively. In this case an
electrical survey may be made of the well and
in. or'derto accurately determine the' depth at
which the'particular portion o'f the mud ñuid
under consideration passed the drill. However,
various methodsof determining and making al
lowance for this lag in the returns of mud from
the drill are well known and, since they form
no part of the present invention, they are -not
.herein described.
What we claim and desire to protect by Let
ters Patent is:
'1. The method of logging oil and gas wells that
are drilled with the aid of a circulating drilling
iluid in vorder to determine a light hydrocarbon
content of the drilling mud emerging from the
Well indicative of the nature of the formation
the most promisin-g formations under-roamed
and logged in accordance with the present in
vention, to thereby obtain the detailed infor
mation concerning the nature of the strata trav
ersed by the bore hole and their fluid contents.
penetrated regardless of variations during drilling
This method of operation frequently permits a
in the properties of the mud causing variations
substantial saving to be made in the cost of
in its ability to retain hydrocarbons, which com
drilling a well, since the special apparatus nec
essary for mud analysis and the trained oper 20 prises diverting a minor portion of the circulat
ing 'drillingiluid from the main stream, subject
ators and engineers required for its operation,
ing 'said minor portion to a treatment which com
needbe employed at any particular well for only
a limited time and thus a single crew can log
a number of'wells being drilled simultaneously
prises the addition thereto of materials which
will impart uniformv hydrocarbon-retentive prop
in contrast to the usual requirement of an ex
ert'ies to the minor portion under the same fixed
pensive crew for each well during the entire
course of drilling. Further savings are made
possible since it is unnecessary to conduct the
original drilling of the well in any special man
n'er in order to facilitate the analysis of mud
and the well may be drilled and completed in
the most economical and expeditious manner.
As thus far described, our invention relates to
standard external conditions of stripping, sub
jecting the thus treated drilling iluid to the strip
detecting and determining the hydrocarbons in
the mud fluid. However, it is recognized that
ping action of a gas to remove hydrocarbons,
separating the mixture of stripping gas and hy
drocarbons from the drilling fluid and subjecting
said mixture to further treatment including an
analysis to determine the amount of removed by
2. The method of logging oil and gas wellsthat
are drilled with the aid of a circulating drilling
fluid in orderto determine a light hydrocarbon
determining the viscosity and salinity and other
ontent of the drilling mud emerging from the
properties of the mud as it issues from the well,
well indicative of the nature of the formation
both by itself and also in conjunction with a
penetrated regardless of variations during drill
determination of these same properties of the 40 ing in the properties of the mud causing varia
same component of the mud as it enters the Well.
tions in its ability to retain hydrocarbons which
comprises diverting a minor portion of the cir
Therefore, it is contemplated that we may either
continuously or intermittingly obtain samples
culating drilling fluid from the main stream, sub
of the mud fluid issuing from the well through
jectng said minor portion to a treatment which
line 9 and determine the properties and char
comprises the addition thereto of materials
acteristics of this mud fluid before it is subjected
which will _impart _uniform hydrocarbon-reten
to any treatment hereinbefore specilied.- Also,
tive properties to the minor portion under the
much `useful information can be obtained by
samples of the mud from line 3 as it enters the
well may be continuously collected and subjected
to analysis to determine the properties and char
acteristics of this mud. Likewise the rate of
flow ofthe mud fluid should be noted and re
corded Yin order that in conjunction with the
same fixed, standard external conditions of strip
ping, subjecting the thus treated drilling fluid to
the stripping action of carbon dioxide, thereby
effecting ther removal, with the carbon dioxide,
_from the drilling fluid, of hydrocarbons, and sub
jecting the carbon dioxide with the hydrocarbons
admixed therewith to further treatment includ
depth cf the well the depth at which any com
ponent member of the mud fluid passes the bit 55 ing ananalysis to determine the amount of re
moved hydrocarbons.
5 may be determined. It is also to be noted that
much useful information cani be ascertained by
_3. The method of logging oil and gas wells that
determining the nature and properties of the
cuttings separated from the mud fluid by shale
shaker I0. However, we do not herein claim the
analysis of such cuttings since »this is a feature
of our co-pending application, Serial No. 407,956.
It is well known in the art of drilling wells, that
in determining the depth at which any material
are drilled with the aid of a circulating drilling
fluid in order Itordetermine a content of light hy
drocarbons inthe drilling mud emerging from the
well indicative of the nature of the formation
penetrated, which comprises diverting a minor
portion` of the circulating drilling fluid from the
main stream, subjecting said minor portion of the
drilling lluid to the stripping action of carbon
Ádioxidathereby effecting the removal, with the
carbon dioxide, from the drilling fluid, of hydro
from the drill to the surface, and the distance
carbons, and subjecting the carbon dioxide with
that the drill has advanced during the interval
the _hydrocarbons admixed therewith to ,further
that a particular portion of the mud fluid was
treatment including an analysisto determine the
travelling to the surface must be subtracted from 70 amount of removed hydrocarbons.
from the formations traversed by the drill enters
the-mud stream, allowance must be made for
the time necessary for the drilling mud to travel
the depth at which the drill is operating when
this portion of the mud fluid reaches the surface,
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