Note: Descriptions are shown in the official language in which they were submitted.
7~
~ SE OF M~NETIC SEP~R~TION IN SCAVENG~G Ery~oGEN ~SULFIDE
~hn; C.~1 Field:
This invention relates to scavenging ~lyclrogen sulfide, as enc,ountered
in well ~rill;ng or in waste or geothermal water or hy~Lv~dLLv~l oil~ by
use oE an ex~ess c~Jantity of m-agnetic iron oxide particles; the excess
is m-agnetically separa-ted for re-use.
Background Art~
~ dL~y~l sulfide is often present in drilling ~orma-tions and is a
by-~Lu~L of sane ~hPm;c~l processes. ~ L~V~L en~vw,LeL~d, it is a
la contaminate that must be Pl;m;n~P~
~ y~L~3~1 sulEide en~ L~L~d in drilling oil or cJaS wells may be
dangerous or even deadly. It may be s~dv~y~d by additives -to the
~rill;n~ mud. Cne such additive and the process of using it is dis-
closed in U. S. Patent ~o. 4,008,77S. i~Irther, in my U. S. Patent No.
4,344,842, it is ~;~cl~d ~hat such an additive may be added directly
to hydroc~rhnn oil c~nt~min~t~ by h~drogen sulfide, the scaven~ing
taking place in the oil without any other medium.
The additive so ~1~11;7~ is a umc~ue iron oxide particle character-
ized by an Fe304 crystalline phase but ;n~ in~ an Wl~L~ ~ Fe203
moiety; on reac,~ion with hydrogen sulficle an enviLu~ ,Lally safe reaction
~LV~t iS formed which is substantiall~ acid stahle. The reaction
p,roduct is non-masnetic, whereas the u~reacted particles are a-ttracted
--2--
to a magnet. When used as a drilling mud additive, the extent to which
the particles have been exhausted has been monitorecl by magnetic differen-
tiation.
~ 1Osure of the Invention:
The present invention is a process util;7;ng the described iron
oxide particles to scavenge hydrogen sulfide by suspension in contaminated
liquids such as water, hydro~rhnn liqlids or drilling mud. Utilization
of this process provides effective, safe and speedy hy~l~y~l sulfide
scavenging without accumulation of partic~late matter in the liquid and
10 without wasting the reactive particles.
The reactive iron oxide particles employed are onnq;~red to be
ferri-magnetic, in the sense that, while they are attracted to a magnet,
they retain little r~m~n~nt magnetism. Thus, once magnetically separated,
they do not attract one another and may be readily re-sn~pPn~P~. Uniquely,
these ferri-magnetic iron oxide particles react ~th llydl~y~il sul:Eide to
form a s~sk~lLially non-magnetic envlL~)rl"~"l~11y safe particulate
product of reaction. ~hus, an excess quantity over that required for
scavenging is used in the suspension and the unreacted particles are re-
used in a sll~pPn~;~n after being magnetically separated.
These characteristics make the described iron oxide particles
~qpPc;~11y useful in ~1im;n~tin~ l1YdLOY~11 sulfide from ~r;11;ng muds.
Typically, the iron oxide particles æe s1l~r~n~Pd in a water based
drilling l~ud in a quantity subs~n~1~lly in excess over that required to
react the H2S expected to be en~v~l~L~dO The mud with its s1-~rPn~d
particles is circulated through the ~r;ll~ formation, reacting with
hydlu~l sulfide encountered, and returns laden with non-magnetic pc~rticu-
late product of reactio~ as well as the abrasive solids such as sc~nd and
~rill;n~ cuttings. Thereafter, substantially all of the particulate
matter is con~e~ d~ed onto a first portion of the drilling mud; while
the rPm~;n;n~, subst~nti~lly particulate-free portion of the m~d (herein
referred to c~s the "second portion"] is retained for re-use. me first
~ c~lLl~Led portion of the ~r;ll;ng m~d is then passed through a magnetic
separator. Subst~n~;~lly all, or at least a greater portion, of the
excess unreacted iron oxide particles are separated out fro~ the mud and
are collected for re-use. The part;~ll~tP product of reaction and other
abrasive solids are next separated fro~ the first portion of ~he mud by
'7~'~
3~
a ~ullv~linn~l solids separator. The now substr~ntially particulate-free
first portion of the drilling mud is recombined with the second portion,
above referred to, in r~;n~q~ for re-cir~-l~t;~n. T~le magnetically
separated iron oxide particles are re-suspended in the mud toyether
5 with a quan~ity of new reactive ferri-magnetic iron oxide particles, in
order to restore -the drilling mud's hydroyen sulfide scavenginy ability.
To scavenge onnt~min~ting H2S from oil, an excess quantity of the
described iron oxide particles is mixed into suspension, for reaction.
Next, the hydrocarbo~ liquid containin~ the excess iron oxide particles,
10 which remain unreacted, the partic~late product of reaction and any
other solids, is passed Lllr~Llyh a magnetic separator. These unreacted
iron oxide particles so separated by the magnetic separator are collected
for re-use. Electrostatic precipitation ~l;m;n~tes the r~m~;n;ng particu-
late matter from the hydrocarbon liquid. The oil is now s~dvr~llyr~d,
15 par~ te-free and ready for ut;l;~t;~n.
'rO scavenge waste water or geothermal water, an excess quantity of
the described iron oxide particles is sl1~prPn~rPd in it. A conr~llLlc~Lion
step follows; for example, the water may be diverted to a settling pond
equipped with a weir; so ~hat on settling, subs-tantially all particulate
matter is cnn~"l ~lP~l into a first portion of the water. This portion
is passed through a magnetic s~drdLr~L, and, by it, the excess unreacted
iron oxide particles are sep æated from t~e water, ~or re-use of these
particles. If the water is to be used, the particulate product of
reaction and any other solids are then separated out by llfil;~ing a
25 c~llv~r~ n~l solids separator. Likewise, the second substantially particu-
late~ree portion of the water may ke used or ~ h~rged.
Best Mbde for Carrying Out the In~entio~:
The particle lltili~ in practicing this in~ention are ~1~Eelcbly
the synthetic Fe304 particles disclosed in U. S. Patent No. 4,008,775.
'rheir average size is approximately six to eight microns. 'rhough identi-
fied by X-ray ~iffra~tion as erystalline Fe304, ESCA/AUGE~ s~ectrosc~py
analysis indieates a surface coating of am~rphous Fe203; this ~nm~n~ition
along with the extraor~in~rily large effeetive surface area of the
synthetic particles may aecount for their exceptional reactivity~ Such
partieles are re~erred to in this disclosure as Fe304.
The ~p~rihed synthetic Fe304 particles are onn~ red to be ferri-
4--
magnetic, in the sense that while they are responsive ~o a r~gneticforce they do not become pern~nently magnetized by it. Thus, after
being magnetically separated and collected, the parti.cles separate
readily from each othex^ and are readily re-suspended in a liquid.
As disclosed in said Patent No. 4,008,775 these iron oxide particles
react with H2S to form a par~ lAte product of reaction which is envi-
lullls~lLally safe. mis particulate pLuLluL_L of reaction is also substan-
tially non-mdgnetic.
In the process of the present invention, speedy and sa~e scavengin~
10 is effected by employing in suspension an excess quantity of the particles,
and then effectively di:fL~I~ltiating between the unreacted excess parti-
cles, which remain magnetic, and -the reacted non magnetic particles. As
shown in the issued patent LL-LeLLL~d to, the particulate product of
r~ n is principally FeS2 and may ;n~ other non-magnetic substan-
15 tially stable iron-sulphur ~....~-~lds, all of which reaction products are
generally L-~f~ d to in this disclosure as FeS2. me reaction with H2S
may initiate within the amorphous Fe203 and proceed into the crystalline
core portion; the prin.~ l reaction o~ 7rr;ng in the core appears to be
essentially
3 4 6H2S ---73 FeS2 + 4~2 ~ 2~2-
Tests of magnetic recovery of the ~-~f;n~ iron oxide pc~rticles were
made by an ;nLlP~Pn~ nt test la~-ciLoLy, which reportecl as follows:
The equiF~ t used was an Eriez (-trademark) Lc~bOLdLUL~ l~et Drum,
~del L-8~ cadjusted to give equivalent recoveries of a 1,000 gauss high
25 gradient wet drum and an Eriez (LLdd~l~Lk~ Labo-dLoL~ ~.Tet High Tn~nC;ty
Magnetic Separator (WHIMS), Mcdel Lr4~ equipped with medium e~anded
metal oollection matrix.
Ihe -test procedures were as follows:
About 2kg of sample iron oxide particles were ~ rri~ in water and
30 passed through the l~l~n,~lo,y wet drun. The slurry was about 10~ solids.
The non-~agrletics were filtered and then washecl LI~U~I1 the Lr4 with the
ba~hy~ d field set to 8,000 gauss. All final p.roducts were filtered,
dried and ~e;~hP~
r~he tests were evaluatecl as follows:
At standard ~u~lc~lLLaLions, this sample sh~wed a 9S 3~ recovery on
the wet drum. mis ;n~ t~ that the recovery curves for n~re dilute
slurries will follow a SL~1dd1d recovery curve for wet drums. I'he
37
standard recovery curve shows an 85% to 88% recovery in the concentra
tion range of 9 grams per gallon (1 pound per 50 gallons). rrhis curve
also shows that the recovery w~uld be less than 5% when the ~ LLd-
tion drops to 0.54 grams per gallon (1 po~nd per 840 gallons).
Use in ~r; 11; n~ muds:
One of the dangers of drilling wells is that l~xpectedly large
concr~lL~dLions of hydrogen sulfide may be en~lLeL~d. These concen-tra-
tions are sometimes deadly. rme pos~ih;l;ty such a concentration mdy be
encountered warrants the llse, in the ~r;lling ~d, of a quantity of the
10 s~d~ly~r much greater than may actually be reacted. The described iron
oxide particles have ~x~ nt rhRol~ l properties so that they may
serve, in whole or in part, as the weighting agent.
~ or use in drilling mud the described iron oxide particles are
s~pPn~7~ in ~he drilling mud in amounts r~n~inr3 normally up to twenty
15 pounds per ~harrel. The ~r711;n~ mud, containing the excess guantity of
iron oxide particles, is circulated U~uuyll a drill bit and carries
th~-~fr~ll abrasive solids such as sand and drill cuttings, the particu-
late ~ u~L of reaction with hydrogen sulfide, generally l~Ll~d to as
FeS2 and the excess ~u~si~"li lly unreacted iron oxide particles, Fe304.
20 The quantity o~ FeS2 formed is greater in weight than the quantity of
reagent Fe304 particles; and since the abrasive solids were not there-
tofore present in the mud, the weight composition and rhP~ ;c~l prop-
erties of the ~7r;11;n~ mud may be altered on circulation and use.
Drilling mud ~ erLies are r~n~ red critical to the ~rilling
25 process. By the following extractions and additions, the circulated
used ~r;llin~ mud may be substantially freed of sand, drill cuttinygs~
and particulate pl~u~L of reaction and restored to its orlginal ccm-
position and rheolcgy, again containing the chosen quantity of reactive
iron o~ide par~iclesO
Qn rising to the surface, the used drilling mud is first passed
Ll~lv~yh a screen of conveni~nt size, roughly between 35 mesh and 100
mesh, to ~l;m;n~te the larger drill cuttinys, etc. The mud is then
preferably passed Ll~uyl~ a cyclcn~ type sep æator; ~y subjecting the
drilling mud to a c~n~rifugal force, substantiall~ all of the particu-
35 late matter is con~lLLdted into a first portionl for example la% or
less, of the drilling mud. Ihe second particulate-free ~ortion of the
~r;ll;ng ~d, ;n~ln~;ng any colloids used, is retained for re-use. This
extraction and con ~ l~ld~on reduces the volun~ of liql1d and particulate
kZ~3~7
--6--
matter to be passed through the next ~gnetie separation step, which may
make f~;h]~ the use of a smaller capaclty magnetic s~al~lLv~ or increase
its effectiveness.
On p~sing the cnnc~n~rated first portion of the used drilling mud,
5 contaim ng the partieulate matter, t~rough the magnetie s~dLrlLu~/ at
least a greater portio~ of the suhstantially unreaeted iron oxide parti-
cles will be separated out of the ~7r;11;ng mud. These partieles so
extracted are collected for re-use. rrhe extent of the extraetion is
dependent upon sueh faetors as the Pff;~i~nry with whieh the drilling
10 mud is L~uyhL into eontact with the magnetic sep æ ator; practical
ennr;iA~r~-tions are the eapaeity of the separator and the flow rate and
viscosity of the liquid.
After the magnetie separation, there are furthQr separated from
this first portion of the drilling mud the abrasive solids and the
15 particlllate product of reaction formed; any c~lv~llLional solids separa-
tion process may be used, sueh as s~;m~ntation or eQntrifusing. ~is
last extraction renders the first portion of the drilling mud substan-
tially free of partle~ t~ matter. The retained seeond portion of -the
drilling mud, ~nnt~;ning sueh eoll~ir7~ as were used, is re-~nmhin~fl with
20 the first portion of the ~7rill;~ mud. m e salvaged iron oxide particles
are then returned to the re-c~mh;n~ 7r;11;n~ mud, and a quantity of new
iron oxide particLes i~ also added~ restoring the ehosen quantity of
magnetie iron oxide particles to -the ~r;ll;ng r~wd, and thus restoring
i-~s ahilit~ to S~dv~lly~ hydro~en sulfide. The fluid is now ready for
25 re-use; and this process is r~peated upon continuing re cir~ll~t;~n.
The reacted partieles, as well as any of the fluid not re used, are
envi~ .taLly safe and may be diseharged or disposed of by conveying
to a simple waste heap.
V~ hle ~ ls of ~r;ll;n~ muds are sometimes salvaged after
30 ~7r;17;ng is eompleted, for re-use ~ wh~re. Tb do so is especiall~
worthwhile where as here, an exeess of reaetive partieles is used. On
eompletion of ~r;ll;ng~ the excess unreaeted iron oxide particles may be
magnetically s~p~r~ as above descrihed and salvaged for re-use else-
where. ~ccordingly, although the reactive particles are employed in an
35 excess amount during drilling, to provide a margin of safety in the
event of unexpected large ~m;~ n.~ of hydrogen s~ide, the prooess
is ec~n~m;~1 because the unreacted particles are separated from all
sand and drill cuttings and salvaged for re-use.
-7
Vse in hydrocarbon lic~uids:
If the cont~m;n~t~d liquid is a hydrocarbon liquid, this process
will provide effective scavenging, whether the hydrocarbon licruid is
crude or refined oil.
A quantity or ferri-magnetic iron oxide particles ,lre ~us~lded in
the c~nta~;n~ted hydrocarbon liquid. rrhis q~ntity is in excess over
that required to react the hydrogen sulfide, thus speeding the reaction
time.
Scavenging of hydrogen sulfide cnn~;31nP~ in anhydrous non-ac~eous
lic~uids is described in my co-pPn~in~ arrli~ation, abcve referred to,
and the considerations given to mixing and agitation are appl;c~h1
here.
After reaction of the hyclrogen sulfide has occurred, the hydrocarbon
liquid~ cnnt~;n;ng the exoe ss unreacted ferri-magnetic iron oxide particles,
the non-magnetic particulate product of reaction and any other solids,
is passed Ll~uyh a magnetic S~r~a~. Su~statl~ially all, c)r at least
a greater portion of the unreacted iron oxide particles is separated out
of the hydrocar~on liquid and collectea for re-use.
r~he non-p~r~ t~ product of reaction and any other solids are
next separated out of the hydrocarbon liquid by use of any conventional
solids separation process, such as se~;mPntation or centrifuging, or,
for even greater effectiveness, ele~Ll~sLaLic precipitation. These
enviL)""~"I~l1y safe solids may be ~;r~rnse~ of simply, as on r~n open
waste heap. After this last e~traction, the hydrocarbon liquid is -thor~
ou~hly scavenged, envil~l",~tlLally safe, substantially particulate-free
and is ready for 1lt;~ tion.
Use in water:
If the conta~unated liquid is water, such as industrial waste water
or ~nn~nced geo~h~rm~l steam, the described ferri-magnetic particles
are sl3~Pn~ in the water containing the hydrogen sulfide. I~e quantity
of iron oxide particles so added to the contaminated water is in excess
of that required to react the hydrogen sulfide present, ~hus to assure
glLick and effective scavenging. The hydrogen sulfide particles are
contacted and reacted by the described ferri-m~gnetic iron oxide parti-
cles, formin~ the non magnetic particulate product of reaction. Inorder to speed the reaction time the water may be agitated.
After effective scavenging has occurred, all the particulate may be
con~ L~ed in a first portion of the water small enough to be processed
~jlq ~ ,rr~
J ~ r ~ O
--8--
b~ an ec~n~m;~11y sized magnet.ic separator. For such concentration any
process may be used; for e~a~lple, the water may be allowed to sett.le in
a settling pond equipped with a weir. 'rhe rPma;n;ng or second po.rtion of
the water, substantially particulate-free, will flow over ~he weir. Gn
5 pA-~s;ng the first con~ LLdLed portion of the water through the magnetic
sep æator, all or at least a greater portion of the unreacted ferri-
magnetic iron oxide particles will be separated. ~rhe iron oxide particles
so separated are collected for re-useO
If the water is to be then use , the non-particulate product of
rPArt;~n and any other solids are then sep æ ated frcm this first portion
of the water by any ~vl,vr~r~ nA1 solids separation process, as by diversion
into a settling pond. Both po.rtions of the water are then usable. Alter-
natively, the water, itself envi~ k~ lly saFe and containing the
envi~ "~ 11y safe reaction product and other solids, rnay merely be
discharged.
Even though some o~ the magnetically separated iron oxide particles
may contain some reacted FeS2 m~lP~11P.~ the correlation between reactivity
of the particles and their magnetic characteri~stic is so great a~s to
warrant the reference, in this disclosure and clairns, to magnetically
separable particles as being subst~nt;~11y unreacted
V æ iations from the processes above described will be app æent to
those s]cilled in the art. For example, if the present ferri-rnagnetic
particles are u~sed in a drilling fluid in cnmhin~ti~n with a conventional
non-magnetic weighting agent ~such as barite, the descr~bed process will
nevertheless be useful For salvaging and re-using the unreacted ferri-
magnetic particles, as well as the c~11O;~ The barite, being non-
magnetic, will be separated out along with o-ther non-magnetic particles,
that is, the reacted particles, sand and drill cuttings. If i.t :is
de~Prm;nP~ that these non-magnetic particles taken together are not too
ahrasive to serve as a wP;~ht;n~ agent along with a replP.n;~hPd quantity
of unreacted particles and colloids, they may he so re-used; otherwise,
such all separated non-magnetic solids should be discarded
Industrial ~pp1;~h;1;ty:
A prinr;~l use of the present invention is ~n s~dv~n~in~ L~
sulfide from ~r;11;n~ m~ds ~y the use of a quantity of the particulate
iron oxide .~;gn;Fi~ntly in excess of that required to actually react
Z ~3'7
the hy~rogen sulfide, so as to provide a margin of sa~ety. ~l~agnetic
recovery of the excess L~ld~L~ the p~.ocess ec~n~ nc~ther justi~i-
cation for use of an exc~ess is tha~ the particles serve at least in part
as a ~ hting agent.
.....
