CA2216388A1 - Sand-bearing water-soluble stick and methods of use - Google Patents
Sand-bearing water-soluble stick and methods of use Download PDFInfo
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- CA2216388A1 CA2216388A1 CA 2216388 CA2216388A CA2216388A1 CA 2216388 A1 CA2216388 A1 CA 2216388A1 CA 2216388 CA2216388 CA 2216388 CA 2216388 A CA2216388 A CA 2216388A CA 2216388 A1 CA2216388 A1 CA 2216388A1
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Abstract
A sand-bearing water-soluble stick is provided, which descends rapidly through a column of salt water in a well, allowing the efficient and accurate placement or a column of sand throughout a particular interval of downhole pipe. Methods of use are provided which include sand placement techniques utilizing the stick in typical oil and gas well applications.
Sizing and shaping options are provided which assist the user in correlating the sticks to the appropriate piping. In the preferred embodiment, the stick is formed from sand and polyethylene glycol, although the stick can be made with solid materials other than sand, and with other water-soluble bonding agents.
Sizing and shaping options are provided which assist the user in correlating the sticks to the appropriate piping. In the preferred embodiment, the stick is formed from sand and polyethylene glycol, although the stick can be made with solid materials other than sand, and with other water-soluble bonding agents.
Description
A SAND-BEARlNC WATER-SOLUBLE S~ICK ~ND MESHODS OF USE
By:
J~hn Donald Gray and Mattho~ M~cha-l Wald~n P~ ou~d Our inventio~ relates to the placemQnt of a column of sand in the wellbore of ~n oil, g~, or other fluid produ~ing well.
Such wellbore~ typicall~r have procluction casing which i8 perforated at depths ad~acent to producin~ formations. The convent~nal well completion wlll ha~e tubing within th~
production casing, although current practlce~ include completions w~ich UtiliZQ the casing without t~bing. Tubingless completions will typically use a sm~ller intex~al diameter pipe for the cas$ng.
In a number of applications, in the oil and gas industry, th~ operator will n~ed to plac~ a sand column over a particular interval in the wellb~e, e.g. i~olatin~ producing zone perforations in the production ~asing string, isolating and enhancing the i~tegrity o~ a bridge plug, temporarily abandoning "
~he well, an~ othex applic~tions. Such a sand column fills the well}~re from one dep~h ~o another. These ~pplications will typically i~volve ~ çolumn of salt water in ~he wellbore, the water being used to overcome the fo~m~tio~ pressure and k~ep hydrocaxbons from entering the wellbo~e ~uring the oper~tio~.
The salt water typically enco~ntered in ~hese situations include le~se water (produçed), he~y NaC1 brines, fresh wa~er with KCl ~dditives for formation pro~ection, ~nd o~her solu~ion~
wi~h var~ing de~sities. Altho~gh more exotlc solutions have higher densities, e.g. some calcium chlorides, zinc br~mides, and c21~ium Br~ide soluti~ns, it remains that, in the ~st majori~y of situations, the ~ellbore will con~ain saLt ~ater solutions with densi~ies ranging from t~at of fresh water to ahout twelve pounds per g~llon.
Curxent met~ods of placing the sand in the desired wellbore i~terv~1 p~imarily ~nvolve the use of san~ bailers, which are run lnto th~ wellbore ~y wireline. This can be a cos~cly and time-consuming process, depending on the depth of the well, the height of the desire~ sand ~olumn, and other factors.
Furthe~mo~e, it requires the tempora~y i~sertion of substantial ha~dwa~e into the well~ore, creating an 4pportunity for ~echa~i~al failu~e an~ the possi~llity of lost tools w~ich must be fished at high expense. Without the sand bailer, the operator ls limite~ to dropplng sand in~o the well~re, alt~ough this is very impractical ~u~ ~o possible ~bridging" of the sand whil~
descending, a~ well as, ~he ~ime ~equired for the unconsolid~ted sand to ~escend to t~e desired dep~h.
Another method involves pumping ~ high-viscosity, liquid slurry of sand and polymer, ~own the tubing into 2 pre~sure isolated area ad~acen~ to the production casing perforatlons.
The op~rato~ must first fill the tubing with a liquid, typically salt water, and thi~ vol~me o~ tubing liquid enters the formation before the slurry re~ches it~ desired position. Such foreign fluid entry intG the far~ati~n h~ po~entially undesirable e~fects. After the slurry rea~hes ~he desired location, it is allowed to set, and is then press~re test~d to see if the perfoxations are adequat~ly i~olated from flui~ flow, by the slurry.
~ no~her u~sati~factory method of placing sand is to ~rop uncon~olidated ~an~ into the t~bing or casing at the surface.
Thls is no~ feasi~le ~hen the well has sur~ace pres~ure, and is high}y conducive to "bridging" when the sand accumulates at locations higher than the effective bottom of the well.
The abillty to quickly pl~ce a column of sand in a wellbore, without u~ilizing the above m~thods, is ~ery desirable and is the subject of our invention.
Summary Of Th~ In~ention Our in~ention comprises a carefully con~tructed compc~ition which we refer to as a "sand stick," which is ma~e of sand, aggregate~, or othe~ solid materials, and a ~ater-soluble bonding agent, the water acting as the catalyst for dissolution. The sa~d stick is solid at standard te~perat1lre an~ pressure, a~d is sh~ped to be received by, and move through, the casing or tubing.
It will remain a solid during ordinary temperatures encountered at well sites. The stick falls through a column of salt water at a much greater rate than unconsoli~a~ed s~nd, in that the stick h~s a higher den~ity than the salt water solutions encounte~ed i~
such operations. As the stick falls, the incre~sing heat in the wellbore accele~ates the dissoluti~n pro¢ess. The stick wlll function in both typic~l and exotic salt water solu~ions.
Knowin~ well ch~rac~eristics, particul~rly the height of the colum~ o~ ~alt water in the well, allows the bon~ing a~ent to be chosen such that all, or substantially ~11, of t~e sand stick ~ill dissol~e before i~- reaches the bo~tom of the s21t w~te~
column. The ~issolution process occurs gradually, which ~llows the stic~ to descend rapidly through the column. ~eing wa~er-soluble the dissolved bonding agent goes into sclutlon with the salt water as the stick descen~.
Since the operations will ~sually involve piping o~ kn~wn a~d standardized internal diameters, the ~nd ~t~ck can also b~
constructed such that the sand volume per stick will flll a predetermined length of pipe. Various s~ick sizes can be m~de which pro~ e 'che appropriate volume to correspond with ~nerlcan Petrole~ Ins~i.tute Standard pipe sizes, ~s well as other , .
s~nd~rdi~ed sizes applicable at the tlme of use. In the cas~ of larger pipe, this ~oncept can be extended to sh~ping and sizing the sand stick such that an integer number of ~and stick~ will ~ill a linear foot, linear meter or other standard unit of length, of the lar~er pipe. In all such cases, colored dye~ or other product indicators can be utilized to enable the operator to ~atch the appropriately sh~ped and size~ sand ~ick to a parti~ular standardi~ed pipe size.
Furthermore, th~ sand thickness used in the stick can be va~ied depending on the require~ents of the operation. A very fine grained sa~d can be utilized such that, when released, it will 2ct ~ a low permea~iLity, low porosity cap on the top of a sand colu~n made of coarser sand. Conve~sely, a coarser sand mes~ may be chosen in situations where it is anticipated tha~ the sand column will be re~oved using a sand bailer.
T~pering or rounding one or more ends of the sand stick is ~n additio~al benefit, since the smoothe~ profile of the descen~ing sand stick may provi~e a more effe~tive descent in some applications.
With our sand stick, a new method for filling an interval of pipe with sand is available which will be useful in numerous oil and gas well operations. For example, an ope~ator will typically, need a column of s~nd to cover the productlon casing interval from ~epths below and above a se~ of perfora~ions. The sand column isolates the perforations while other activities, such as the addition of additional perforations, are con~ucted at hi~her locations in the wellb~re. In the new method 3~ placing the column o~ d, the operator places a number of sand sticks i~ the tubin~, or in casin~ if no tubing is present within the c~sing. The number of sticks will be chosen suc~ that ~he volume of the sand is sufficlent to fill the produc~io~ c~sing ~om the effective well bottom to a pre~etermined point abo~e the top of the perforatioxls. The effecti~e w~11 bottom Ca~ be the well's total dep~h, the well's total depth topped or plugged b~ck in previous activities by ~ormation san~, cement, etc., or a brid~e plug. As a prec~ution the operator may wait some length of time followin~ the lnsertion of the sand stick~, to ensure that substantially all of the sand has fallen into place. As a fuxther precaution, the operator can determine the exact ~oc~tion of t~e top O~ the s~nd column by "~gging" it with either 'che t~bing or a wireline device. This can also be done at the beginning of t~e operatio~ t~ confi~m the anticipated depth of the effective well ~o~tom. The bonding agent in the sand stic~
which is utili~d in this method will be cho~en su~h ~h~t ~he stick w111 dissolve prlor to reaching the effec~ive bottom of the well, ~hile the sand will descend to the desire~ depth significantly faster than unconsolid~ted sand, as a result of the hi~h initial ~e~sity of the san~ stick.
In this example, since the primary purpose of isola~ing the perfor2tions is to prevent fluid communic~tion between the perfor~tions and the wellbore ~nterval above the perforations, it is sometimes desixable to enhance the s~nd column effectiveness by "capping" the sand column with a relatively short in~erval of Piner mesh sand. The lower permeability and porosity in this interval will provide additio~al resis~ance to fluid ~ommunication through the column. When this is desired the method for isolating perf~rations would also include the step of ~ropping a small n~m~er of sand sticks containing ~ much finer sa~d, lmmediately or soon after the other ~ticks w~re droppe~.
Further industry uti~i2ation of our sand stick will oc~ur in those operations where a bridge plug's sealing integri~y i~
bolstered by placing a sand column on top of the plug. I~ the e~ent the plug is retrieva~le and ~n up-hole c~menting operatiGn is in~olved, the sand column also isolates the pl~g from the cement, making it much e~sier to remove after the up-hole operation~ a~e completed.
If applicable, the sand stick can be us~ with an~lo~ous results in fresh wate~.
In some operations ~he pressure in the wellbore at the surface will dic~ate the use of p~ocedures and e~uipment to c~ntrol ~uch pressure ~uring the placement of the sand sticks. A
sand stick i~sertion device is u~ilized, which has a top ~n~
bottom valve, the v~lves allowing the isolat-on of one or more san~ sticks from the atmosphere and the pressured plpe at the sur~ce. ~te~ the stick is isolated, the insertio~ de~ice bottom valve is opened allowing the sand stic~ to en~er the we~l pipe. We ha~e also pr~ided procedures and techn~q~es for t~e situation where the opening of the ins~rtion de~ice ~otto~ valve is complicated by a large pressure differential between the well and the insertion device interior. In this situation, a pressure ~qualization line establishes fluid communic~tion between the well and the insertion device interior, which allows the val~e to ~e open~d smoothLy. Once the stick has ente~ed the ~ell and the i~sertion ~evice bottom val~e has been closed, a pressure rele~se v~lve is provi~ed which reduces the p~essure within the insertion de~ice interior to ~tmospheric pressure.
De~cription of the Draw~ngs Fig. 1 is an oblique ~iew of the sand stic~.
Fig. 2 is an unscaled schematic repre~entation of a conventional well comp-letion, showing the tubing and packer within production casing, as well as, a set of per~orations, prior tc the placement of a sand column in the wellbore.
Fi~. 3 is an unscaled schematlc representation of the conventional well completion in Fig. 2, followi~g the pla~ement of a san~ ccl~unn in the wellbore.
Fig. 4 is an unscaled schematic repre~entation of a conventional well completion, showins~ the tubing and packer within producti~n casing, ~s well ~s, a bridge plu~ set beneath casing lea~, prior to the placement of a sand column in the we 1 lbore .
Fi~. 5 is an unscaled schematic representation of the co~ventional well compl~tion in Fig. ~, following the placement of ~ sand col ~n in the w~llbore.
Fig. ~ is an ~nscaled schematic representation of a ~ubingless well completion, showing the pxod~ction casing, as well as, a set of perforations, prior to the placement ~f a sand c~lumn in the well~ore.
Fig. 7 is an unscaled schematic representation of the tubingless well comple~ion, i~ Fig. ~, ~ollowin~ the p~acement of a sand column ~n the wellbore.
Fig. 8 is a schematic representatio~ of the san~ stick insertion ~evice, including means for press~re di~ferenti~l reduction.
Description The sand stick 20-is shown in Fig. 1. The dimensions, s~nd type and type of bonding agent can be adjusted or selected for the particular well application. O~r fiel~ experience has shown that ~ 2:1 volumetric blend of 20/40 mesh s~nd (Tyler) to polyethylene gly~ol of varylng molecular weights forms a sand stick which works effective~y in situations where the standing water column is as deep as 16, 000 ~eet. It is anticip~ted tha'c simil~r pe~fo~mance can bè obtained in deeper w~lls, as well. In these applications the sand stick preferred shape is circular along it~ longitudinal axis. T~e sand stick descended rapidly through much of ~he column, and completely, o~ substanti~lly dissolved befoxe re~ching the depth o~ ~he intended top of the sand colun~. The i~iti~l rate of descension of the ~nd stick was several times the anticipated descension rate of unconsoli~ted sand.
The molec~llar weight o~ the polyethylene ~lycol signi~lcantl~ affects ~he rate at which the sand stick ~alls through the column, with higher weights causing a more rapid desce~t. ~he abo~e field experience has shown that wells in ~he approxim~te ~ange of 8,000 to 16,00~ feet serve as appropriate applications for a sand stic~ using polyethylene gly~ol with apprcximately ~000 molecular weight (C~smetic, loiletry and F~agrance Association "PEG-150"). In the3e applications, w~ich involve~ approximately 2.44 inch inte~al diameter tu~n~, 3.5 inch i~ternal diameter:--casing, and 4.0~ inch internal dlameter casing, the s~nd stick diameter was 1.75 inches with a length of 24 inches. (Th~s~ dlmensLons provided approximatel~ one linear foot of sand column in the tubing application.~ In such applicatio~s, it was determined that the 1.75 inch sand stick diameter in the 2.44 inch internal diameter tubing, produce~ a~
ln~eased likelihood of unwanted accu~ulations of sand ~t depths less than the target. It is anticipated that the opti.mum sa~d stick ~iameter fo~ 2.4~ inch interna~ diameter tubin~ will ~e approximately 1.5 inches . When this diamet~r is used ~h~ sand stick l~ngth is incre~sed to appr~ximately 30 inches, in order to provide an equivalent sand volume.
Our field experience also i~cluded ~ san~ sticX c~mbining 20~40 mesh sand using polyethylene glycol wi~h approximately 33~0 molecula~ weight (Cosmetic, Toiletry an~ Fragrance Associatio~
"PEG-7~") in an approximately 8,000 foot well. In this application, t~e sand stick, performed satisfactorily, a~though the amount of ti~e necessary for the sand colu~n to stabil~e was significantly increa~ed, d~e to the stick's dissolut1cn at lesser depths than the heavier stick did undex similar circumstances, Other field experience indicates t~at using pol~ethylene glycol with approximately ~000 ~olec~lar weight lCos~etic, Toile~ry and Fragrance ~ssociation "~EG-100") performed satisfactorily in a 10,000 foot well.
From ~hese experienc~s we co~clude tha~ a well having an 8,000 foot s~lt water col~n with ordinary dow~hole te~peratuLe gradient5, is at the u~per e~d of the range in which PEG-75 }s desirable as the bonding agent, i.e. the u~e of a heavier polye~hylene glycol, wiLl produce desirable increaseS ln the ra~
~t which the sa~d stick descend~.
Although a theoretically infinit~ number of weights co~ld be chosen based on well dep~h, downhole temperat~re ~radients, operator p~e~erences and scheduling demands, etc., we have ~etermine~ that th~ ~eight selections offered by the s~nd s~icks utilizin~ PEG-75 an~ PEG-~50 ~olyethylene g~ycol will satis~actorily ad~ress all typical well ~pplications. ~he in~enti~n contempla~es, however, that a nu~ber of sand sticks 20 with bonding agents of varying molecular we~ghts, will ultimately be u~ilized to cover the needs of vaxious oil ~nd gas prod~cing geo~raphical areas.
The inv~ntion ~lso contemp~ates that other water-soluble bondi~g a~ents might be substituted, although polyethylene glycol appears optimum among curr~ntly ~nown materia~s. "NO~OX~NOL 100"
(non~lphenol), for exampl~, is w~te~-solu~le, howeve~, it is incompatible with certain hy~rocarbons which could, under certain circumstances, lead ~o unwante~ emulsification of downhole fluids.
current practice utilizing the sand sticks 20 indicates t~at, in a tubingless completion, it is ~ery useful to shape the sticX 20 such tha~ it will fall through 2-7/8" outsi~e diame$er tubing 76 ~2.441" internal diameter), ~nd to size the stick 20 such ~ha~ the bulk sand volume wlthin will fill one linear foot (or one linear unit of len~th) of such pipe 76. T~is assists the operator in making ~he de~ermina~ion a~ to the number of sticks 20 require~. Other stick 20 ~izes can be made which ~ill provide similarly useful correlations to American Petroleum Insti~ute ~tan~ard pipe sizes, as well as other stan~ardized ~iz~s, which might be in e~ect at the time of product application.
Furthermore, our invent1on includ~s sand sticks 2~ which will have a finer mesh sand in place of the sand which fo~ms the . ~
bulk of the sand column 34. A "cap" 37 of ~his finer ~esh sa~d will reduce the effective permea~ility and porosity of the sand ~olumn 34 with ~espect to fluid communication across the top 32 of the column 34. It is anticipated that silica f~our or 100 mesh sand will-provide appropriate reductions, although other size~ m~ be ~ppr~priate under the c}rcumstances.
It is fuxther antlcipate~ that 12/20 mesh sand, or larger, wi~l ~e u~eful in some applications, e.g. those in which a sand bailer i~ ~sed to re~ove the sand colwmn 34,54,74 a~ter the operation is completed. Si~ilarly, in som~ applications, variou~
aggregates or conglomerates c~n ~e su~stltuted for, or combine~
with, the s and.
An ad~iti~nal aspect o~ our invention is ~ reshaping o~ one or both en~s to pro~ide ~ tapered rounde~ profile as it enters the pipe 76. In some~applications, it is anticip~ed that the sand stick 20 w~ll desçend more e~ecti~ely i~ this is done.
The preferred methods of using of the sand stick 20 in va~ious downhole sand placement operations involve a downhole pipe 3~,56,76 (e.g. production or intermediate casing) w~ich the operator desires to fill with sand, in an interval exten~ing from a particular bottom de~th, i.e., th~ effective well bott~m 38,58,78, to a p~ticular ~op ~epth ~2,S2,72. This downhole pipe 36,S6,16 will be in ~luid rommunication with receivin~ pipe 81 at the surface 80, with no other pipe within it, or the downhole pip~ 36,55,76 will be in fluid co~munic~tion with receivirg pipe ~1,61 ~t the surface 40,6~ as a result of a co~tinua~ion pipe 4~,~2, such ~s tubing. In either case, t~e ~ontinuation piping 4~,62,7~ betwee~ the downhole pipe 36,56,76 an~ the receivin~
pipe 41,61,81 at the surface 40,6~,80, h~s an inside diameter which al~ows the sa~d stick 20 to be received into, and pass through and out of, all pipe from the receiving pi~e 41,61,81 at the surface 40,60,80 to the effective well bottcm 38,58,78.
FigQ. 2-5 schematically depict ~onventional well completions show~ng fluid communication from ~he downhole pipe 36,56 through the continuation pipe 42,62 to the ~urfa~e 40,60. Figs. 6-7 depict a tubingless completion where the downhole pipe 76 is co~tinuous to the ~eceiving pipe 81 at the surface 80.
Typical operations are xefiected in Figs. 2-3,6-7 wher~
.
perforations 44,84, through the downhole pipe 36,76 i~to the formation 46,86, ~xe covered and isolated by the s~nd column 34,74. Figs. 4-5 represent a remedial cementing operatio~
configuration where a bridge pl~g 64 i5 set bene~th ~ casing leak 66 an~ a sand column 54 is placed on the bridge plug ~4.
In either type of completion the sand column 34, 54, 74 is formed by placing the 5and sticks 20 in the receivi~g pipe 41,61,81 at the surface 40,60,80 and waiting for the sticks 20 to fall, dissolve and deposit the san~ on the e~ective well bottom 3~,58,78. Because the stic~ 20 has been ~onstructed in a manner that the linear foota~e ~illed by each sand stick 20 is known, the operator ~an ~al~late the number of stick~ 20 to be dropped which wi~l result in a sand column 34,54,74 of ~esired h4ight.
In some w~llbor~ situ~tions, portions of the sand m2y go into the formation 46,86 outside the downhole pipe 36,56,76, or ~hrough a casin~ leak 66. If this is anticipated by the op~rator, an addltional ~u~ber of sticks 20 can be dropped ~o offset the anounts lost.
The perfo~mance of the sand sticks 20 will be maximized wh~n the operator determines the height (fluid level) 48,68,88 of the salt water column 30,50,70, ~d ~hooses a sand s~i¢k 20 w~th a molecular weight which is compatible with that column height, such that the sand st~ck 20 is completely dissol~ed, or su~stantially dissolved, prior to reaching the depth desired for the top of the sand column 34,54,74. Simil~rly, the chos~n sand stick 20 wil~ not complete the dissol~tion process prematurely.
. In ~any sltuations, it will be desirable to attach a s~nd s~ick 20 insertion device 100 ~o the receiving pipe 41, 61, 81.
The important features of such an insertion ~evice lO0 a~e schematically ill~strated in Fig. 8. If wellbore 102 pressures r~ult in ~ pressurized recei~i~g pipe 41,61,81 at the surface 40,60,80, this attachm~nt should take place following the closin~
of ~ valve 104 at or nea~ the surface 40,~0,80 which will isolate the insertion ~evice 100 from pressures wlthin the recelving pipe 41,61,~1. Once the insertion devlce 180 is installed, the inSer~ion ~evice middle portion 106, shaped to hold one or more s~icks 20 i~ its interior, can be isolated from receiving pipe 41,61,81 p~essu~e by closing the insertion de~ice bottom val~e 108. Af~er the insertion ~evice top valve 110 is opened, on~ or more sand sticks ~0 can be placed in the insertion dev~ce middle portion 106 thro~gh ~he insertion device top valve 110. The ins~rtio~ device top valve 110 is then closed and the insertion device bottom valve 108 opened, whic~ ~llows the sti~k 2~ or stic~s 20 to fall from the inse~tion device middle portion 106 into the interior of the receiving pipe 41,61,81 at the surface 40,~0,80, at whiçh point the stlcks 20 ~egin the descent through continuous piping 42,62,76 to the do~nhole pipe 36,56,7fi inter~al to be fille~ by the sand release~ from the sticks 20 during the dlssolution pr~cess. This stick 20 insertion procedure is repeate~ until the desired number oX sand ~ticks 2~ ha~e entere~
the wellbore 102 through the receiving pipe 41,61,81.
If the pressure in the receivin~ pipe 41,61,81 is large ~noug~, it will crea~e a pre~sure differen~ial across the ins~rtion device bottom ~alve 108 which can make it di~ficult to ope~. Fig. 8 also ~pic~s pressure differenti~l re~uction means which equalizes the pressu~e acxoss the insertion deviGe botto~
valve 108, ~uch means comprises ~ pressure equali~ation line 112, which, by directly or indi~ectly connecting the insertion de~ice middle portion 10~ interiox to interior of the receiving pipe 41,61,81,- allows such equalization to occur. The equaliz~tion process be~ins when the sand stick 20 or sticks 20 have been inserte~ into the insertion ~evice middle portion 106 and the insertion device top valve 110 has been closed, at which point a pressure equaliza~ion v~lve 114 on the pressure eq~ali~ti~n Iine 112 is opene~, allowing ~luid communication between the ~nteriors of the recei~ing pipe 41,61,8~ an~ the insertion device middle portion 106. Once the pressure has e~ualized the pressure equalizatlon valve 114 is close~, and th~
inse~tion device bottom valve 108 can be opened and closed, as described above. ~ressure rewaining in the inser~ion device mlddLe portion 10~ interior can then be bIed off, preferably by use of a insertion de~i~e middle po~tion bleed valve 116 attached to the in~ertion device middle portion 106. Howe~er, it is also possible to release such pressure by opening ~he insertion device top ~Talve 110.
If th~ operator desires ~o ''cap" the sand column with a finer mesh sand, to reduce the effective permeabi~ity and porosi~y of the sand colwnn 34, 54, 7~, the operato~ places a second group of sand sticks 20, which have a flner mesh ~and, into the interior of the receiving pipe 41,~1,81 ~ollowing the ~irst gr~up of s~n~ sticks 20, using the same procedures, i.e.
with or witho~t an insertion device 100 ~ttached.
The molecular weights ~escribed can be approximate~ without s~verely alteri~g the per~ormance characteristic~ of the resulting s~nd sticks 20. They are also approximated to the extent tha~ polye~hylene glycol industry nomenclature and speci~ications are appr~ximate~. For example, the molecuLar weights ~ssigned by The Dow Chemical Company in its publication "The E~ol~glycol ~Iandbook" (Copyright, 1988; Form No~ 17 8 -10~6-885-AMS) have, ~n part, been used herein, and these are stated to be approximates in that publication. In accord~nce with tha~
publication, the average viscos~ty ~or polyethylene glycols ha~ing molecular weights from 3350 to 8000 should be from 93 to 800 ce~tistokes. Furthermore, Christianson Chemi~als, Inc., in ijts Materi~l Safe~y Da~a Sheet, in~icate~ that for 6000 molecular weight polyethylene glycol (PEG-6000), the avera~e molecular weight vaxieS from 5800-6800. For 8000 molecular ~eight (PEG-8000~ the rang~ stated th~rein is 7000 to 8600.
Our experience reveals that the best performance of the sand stic~ is achieved when the stick is ma~e by care~ully controlled blending tech~iques. Without such techniques the sand distribution wlthin the bo~ding agent will be uneven, which c~
result i~ loss o~ stick inte~rity, h~ndling difficul~ies and unsatisfac~ory dissolu~ion in a~ual use. Our manufacturing procedure includes a method of making the stick~ which enhan~es the even ~istribution o~ sand in the bonding agent. In this method, the bondin~ agent is heated to approximately 200~ F at w~ich point the sand is ad~ed, the ratio of sand to bonding ~gent volumes ~eing pxedetermine~. The bonding agent is bei~g ~gitated while the sand is being a~de~, and the re~ulting slur~y is ~ehe~ted to ~OC~ ~ prior to being pou~e~ into tubes of p~edeter~ined volume, where ~he slurry solidifies as it cools.
The temperatures ~epeIld on the molecular weights of the polyethylene glycol being used. Reasonable variations ~n such temperatures can be tolerated without jeopardizing the ~sic function of the sand stick, par~icularly in light of typica~
fluctu~tions in the mol~cular wei~hts of polye~h~lene glycol and ambient tempe~atures.
Although the present inventio~ has been dé~cribed in congiderable detail with reference to certain preferred an~
alternate embodiments thereof, other embodiments are possible.
Accordi~gly, the spirit and scope of the appende~ ~1 2ims shoul~
not be limited to the descri~tion of the embodimen~s contained herein, Furthermore, the claims submitted with this pro~isional applic~tion are in no manner intended by us to limit the scope of our invention zs otherwise disclo~ed b~ the remainder of this specification.
lg
By:
J~hn Donald Gray and Mattho~ M~cha-l Wald~n P~ ou~d Our inventio~ relates to the placemQnt of a column of sand in the wellbore of ~n oil, g~, or other fluid produ~ing well.
Such wellbore~ typicall~r have procluction casing which i8 perforated at depths ad~acent to producin~ formations. The convent~nal well completion wlll ha~e tubing within th~
production casing, although current practlce~ include completions w~ich UtiliZQ the casing without t~bing. Tubingless completions will typically use a sm~ller intex~al diameter pipe for the cas$ng.
In a number of applications, in the oil and gas industry, th~ operator will n~ed to plac~ a sand column over a particular interval in the wellb~e, e.g. i~olatin~ producing zone perforations in the production ~asing string, isolating and enhancing the i~tegrity o~ a bridge plug, temporarily abandoning "
~he well, an~ othex applic~tions. Such a sand column fills the well}~re from one dep~h ~o another. These ~pplications will typically i~volve ~ çolumn of salt water in ~he wellbore, the water being used to overcome the fo~m~tio~ pressure and k~ep hydrocaxbons from entering the wellbo~e ~uring the oper~tio~.
The salt water typically enco~ntered in ~hese situations include le~se water (produçed), he~y NaC1 brines, fresh wa~er with KCl ~dditives for formation pro~ection, ~nd o~her solu~ion~
wi~h var~ing de~sities. Altho~gh more exotlc solutions have higher densities, e.g. some calcium chlorides, zinc br~mides, and c21~ium Br~ide soluti~ns, it remains that, in the ~st majori~y of situations, the ~ellbore will con~ain saLt ~ater solutions with densi~ies ranging from t~at of fresh water to ahout twelve pounds per g~llon.
Curxent met~ods of placing the sand in the desired wellbore i~terv~1 p~imarily ~nvolve the use of san~ bailers, which are run lnto th~ wellbore ~y wireline. This can be a cos~cly and time-consuming process, depending on the depth of the well, the height of the desire~ sand ~olumn, and other factors.
Furthe~mo~e, it requires the tempora~y i~sertion of substantial ha~dwa~e into the well~ore, creating an 4pportunity for ~echa~i~al failu~e an~ the possi~llity of lost tools w~ich must be fished at high expense. Without the sand bailer, the operator ls limite~ to dropplng sand in~o the well~re, alt~ough this is very impractical ~u~ ~o possible ~bridging" of the sand whil~
descending, a~ well as, ~he ~ime ~equired for the unconsolid~ted sand to ~escend to t~e desired dep~h.
Another method involves pumping ~ high-viscosity, liquid slurry of sand and polymer, ~own the tubing into 2 pre~sure isolated area ad~acen~ to the production casing perforatlons.
The op~rato~ must first fill the tubing with a liquid, typically salt water, and thi~ vol~me o~ tubing liquid enters the formation before the slurry re~ches it~ desired position. Such foreign fluid entry intG the far~ati~n h~ po~entially undesirable e~fects. After the slurry rea~hes ~he desired location, it is allowed to set, and is then press~re test~d to see if the perfoxations are adequat~ly i~olated from flui~ flow, by the slurry.
~ no~her u~sati~factory method of placing sand is to ~rop uncon~olidated ~an~ into the t~bing or casing at the surface.
Thls is no~ feasi~le ~hen the well has sur~ace pres~ure, and is high}y conducive to "bridging" when the sand accumulates at locations higher than the effective bottom of the well.
The abillty to quickly pl~ce a column of sand in a wellbore, without u~ilizing the above m~thods, is ~ery desirable and is the subject of our invention.
Summary Of Th~ In~ention Our in~ention comprises a carefully con~tructed compc~ition which we refer to as a "sand stick," which is ma~e of sand, aggregate~, or othe~ solid materials, and a ~ater-soluble bonding agent, the water acting as the catalyst for dissolution. The sa~d stick is solid at standard te~perat1lre an~ pressure, a~d is sh~ped to be received by, and move through, the casing or tubing.
It will remain a solid during ordinary temperatures encountered at well sites. The stick falls through a column of salt water at a much greater rate than unconsoli~a~ed s~nd, in that the stick h~s a higher den~ity than the salt water solutions encounte~ed i~
such operations. As the stick falls, the incre~sing heat in the wellbore accele~ates the dissoluti~n pro¢ess. The stick wlll function in both typic~l and exotic salt water solu~ions.
Knowin~ well ch~rac~eristics, particul~rly the height of the colum~ o~ ~alt water in the well, allows the bon~ing a~ent to be chosen such that all, or substantially ~11, of t~e sand stick ~ill dissol~e before i~- reaches the bo~tom of the s21t w~te~
column. The ~issolution process occurs gradually, which ~llows the stic~ to descend rapidly through the column. ~eing wa~er-soluble the dissolved bonding agent goes into sclutlon with the salt water as the stick descen~.
Since the operations will ~sually involve piping o~ kn~wn a~d standardized internal diameters, the ~nd ~t~ck can also b~
constructed such that the sand volume per stick will flll a predetermined length of pipe. Various s~ick sizes can be m~de which pro~ e 'che appropriate volume to correspond with ~nerlcan Petrole~ Ins~i.tute Standard pipe sizes, ~s well as other , .
s~nd~rdi~ed sizes applicable at the tlme of use. In the cas~ of larger pipe, this ~oncept can be extended to sh~ping and sizing the sand stick such that an integer number of ~and stick~ will ~ill a linear foot, linear meter or other standard unit of length, of the lar~er pipe. In all such cases, colored dye~ or other product indicators can be utilized to enable the operator to ~atch the appropriately sh~ped and size~ sand ~ick to a parti~ular standardi~ed pipe size.
Furthermore, th~ sand thickness used in the stick can be va~ied depending on the require~ents of the operation. A very fine grained sa~d can be utilized such that, when released, it will 2ct ~ a low permea~iLity, low porosity cap on the top of a sand colu~n made of coarser sand. Conve~sely, a coarser sand mes~ may be chosen in situations where it is anticipated tha~ the sand column will be re~oved using a sand bailer.
T~pering or rounding one or more ends of the sand stick is ~n additio~al benefit, since the smoothe~ profile of the descen~ing sand stick may provi~e a more effe~tive descent in some applications.
With our sand stick, a new method for filling an interval of pipe with sand is available which will be useful in numerous oil and gas well operations. For example, an ope~ator will typically, need a column of s~nd to cover the productlon casing interval from ~epths below and above a se~ of perfora~ions. The sand column isolates the perforations while other activities, such as the addition of additional perforations, are con~ucted at hi~her locations in the wellb~re. In the new method 3~ placing the column o~ d, the operator places a number of sand sticks i~ the tubin~, or in casin~ if no tubing is present within the c~sing. The number of sticks will be chosen suc~ that ~he volume of the sand is sufficlent to fill the produc~io~ c~sing ~om the effective well bottom to a pre~etermined point abo~e the top of the perforatioxls. The effecti~e w~11 bottom Ca~ be the well's total dep~h, the well's total depth topped or plugged b~ck in previous activities by ~ormation san~, cement, etc., or a brid~e plug. As a prec~ution the operator may wait some length of time followin~ the lnsertion of the sand stick~, to ensure that substantially all of the sand has fallen into place. As a fuxther precaution, the operator can determine the exact ~oc~tion of t~e top O~ the s~nd column by "~gging" it with either 'che t~bing or a wireline device. This can also be done at the beginning of t~e operatio~ t~ confi~m the anticipated depth of the effective well ~o~tom. The bonding agent in the sand stic~
which is utili~d in this method will be cho~en su~h ~h~t ~he stick w111 dissolve prlor to reaching the effec~ive bottom of the well, ~hile the sand will descend to the desire~ depth significantly faster than unconsolid~ted sand, as a result of the hi~h initial ~e~sity of the san~ stick.
In this example, since the primary purpose of isola~ing the perfor2tions is to prevent fluid communic~tion between the perfor~tions and the wellbore ~nterval above the perforations, it is sometimes desixable to enhance the s~nd column effectiveness by "capping" the sand column with a relatively short in~erval of Piner mesh sand. The lower permeability and porosity in this interval will provide additio~al resis~ance to fluid ~ommunication through the column. When this is desired the method for isolating perf~rations would also include the step of ~ropping a small n~m~er of sand sticks containing ~ much finer sa~d, lmmediately or soon after the other ~ticks w~re droppe~.
Further industry uti~i2ation of our sand stick will oc~ur in those operations where a bridge plug's sealing integri~y i~
bolstered by placing a sand column on top of the plug. I~ the e~ent the plug is retrieva~le and ~n up-hole c~menting operatiGn is in~olved, the sand column also isolates the pl~g from the cement, making it much e~sier to remove after the up-hole operation~ a~e completed.
If applicable, the sand stick can be us~ with an~lo~ous results in fresh wate~.
In some operations ~he pressure in the wellbore at the surface will dic~ate the use of p~ocedures and e~uipment to c~ntrol ~uch pressure ~uring the placement of the sand sticks. A
sand stick i~sertion device is u~ilized, which has a top ~n~
bottom valve, the v~lves allowing the isolat-on of one or more san~ sticks from the atmosphere and the pressured plpe at the sur~ce. ~te~ the stick is isolated, the insertio~ de~ice bottom valve is opened allowing the sand stic~ to en~er the we~l pipe. We ha~e also pr~ided procedures and techn~q~es for t~e situation where the opening of the ins~rtion de~ice ~otto~ valve is complicated by a large pressure differential between the well and the insertion device interior. In this situation, a pressure ~qualization line establishes fluid communic~tion between the well and the insertion device interior, which allows the val~e to ~e open~d smoothLy. Once the stick has ente~ed the ~ell and the i~sertion ~evice bottom val~e has been closed, a pressure rele~se v~lve is provi~ed which reduces the p~essure within the insertion de~ice interior to ~tmospheric pressure.
De~cription of the Draw~ngs Fig. 1 is an oblique ~iew of the sand stic~.
Fig. 2 is an unscaled schematic repre~entation of a conventional well comp-letion, showing the tubing and packer within production casing, as well as, a set of per~orations, prior tc the placement of a sand column in the wellbore.
Fi~. 3 is an unscaled schematlc representation of the conventional well completion in Fig. 2, followi~g the pla~ement of a san~ ccl~unn in the wellbore.
Fig. 4 is an unscaled schematic repre~entation of a conventional well completion, showins~ the tubing and packer within producti~n casing, ~s well ~s, a bridge plu~ set beneath casing lea~, prior to the placement of a sand column in the we 1 lbore .
Fi~. 5 is an unscaled schematic representation of the co~ventional well compl~tion in Fig. ~, following the placement of ~ sand col ~n in the w~llbore.
Fig. ~ is an ~nscaled schematic representation of a ~ubingless well completion, showing the pxod~ction casing, as well as, a set of perforations, prior to the placement ~f a sand c~lumn in the well~ore.
Fig. 7 is an unscaled schematic representation of the tubingless well comple~ion, i~ Fig. ~, ~ollowin~ the p~acement of a sand column ~n the wellbore.
Fig. 8 is a schematic representatio~ of the san~ stick insertion ~evice, including means for press~re di~ferenti~l reduction.
Description The sand stick 20-is shown in Fig. 1. The dimensions, s~nd type and type of bonding agent can be adjusted or selected for the particular well application. O~r fiel~ experience has shown that ~ 2:1 volumetric blend of 20/40 mesh s~nd (Tyler) to polyethylene gly~ol of varylng molecular weights forms a sand stick which works effective~y in situations where the standing water column is as deep as 16, 000 ~eet. It is anticip~ted tha'c simil~r pe~fo~mance can bè obtained in deeper w~lls, as well. In these applications the sand stick preferred shape is circular along it~ longitudinal axis. T~e sand stick descended rapidly through much of ~he column, and completely, o~ substanti~lly dissolved befoxe re~ching the depth o~ ~he intended top of the sand colun~. The i~iti~l rate of descension of the ~nd stick was several times the anticipated descension rate of unconsoli~ted sand.
The molec~llar weight o~ the polyethylene ~lycol signi~lcantl~ affects ~he rate at which the sand stick ~alls through the column, with higher weights causing a more rapid desce~t. ~he abo~e field experience has shown that wells in ~he approxim~te ~ange of 8,000 to 16,00~ feet serve as appropriate applications for a sand stic~ using polyethylene gly~ol with apprcximately ~000 molecular weight (C~smetic, loiletry and F~agrance Association "PEG-150"). In the3e applications, w~ich involve~ approximately 2.44 inch inte~al diameter tu~n~, 3.5 inch i~ternal diameter:--casing, and 4.0~ inch internal dlameter casing, the s~nd stick diameter was 1.75 inches with a length of 24 inches. (Th~s~ dlmensLons provided approximatel~ one linear foot of sand column in the tubing application.~ In such applicatio~s, it was determined that the 1.75 inch sand stick diameter in the 2.44 inch internal diameter tubing, produce~ a~
ln~eased likelihood of unwanted accu~ulations of sand ~t depths less than the target. It is anticipated that the opti.mum sa~d stick ~iameter fo~ 2.4~ inch interna~ diameter tubin~ will ~e approximately 1.5 inches . When this diamet~r is used ~h~ sand stick l~ngth is incre~sed to appr~ximately 30 inches, in order to provide an equivalent sand volume.
Our field experience also i~cluded ~ san~ sticX c~mbining 20~40 mesh sand using polyethylene glycol wi~h approximately 33~0 molecula~ weight (Cosmetic, Toiletry an~ Fragrance Associatio~
"PEG-7~") in an approximately 8,000 foot well. In this application, t~e sand stick, performed satisfactorily, a~though the amount of ti~e necessary for the sand colu~n to stabil~e was significantly increa~ed, d~e to the stick's dissolut1cn at lesser depths than the heavier stick did undex similar circumstances, Other field experience indicates t~at using pol~ethylene glycol with approximately ~000 ~olec~lar weight lCos~etic, Toile~ry and Fragrance ~ssociation "~EG-100") performed satisfactorily in a 10,000 foot well.
From ~hese experienc~s we co~clude tha~ a well having an 8,000 foot s~lt water col~n with ordinary dow~hole te~peratuLe gradient5, is at the u~per e~d of the range in which PEG-75 }s desirable as the bonding agent, i.e. the u~e of a heavier polye~hylene glycol, wiLl produce desirable increaseS ln the ra~
~t which the sa~d stick descend~.
Although a theoretically infinit~ number of weights co~ld be chosen based on well dep~h, downhole temperat~re ~radients, operator p~e~erences and scheduling demands, etc., we have ~etermine~ that th~ ~eight selections offered by the s~nd s~icks utilizin~ PEG-75 an~ PEG-~50 ~olyethylene g~ycol will satis~actorily ad~ress all typical well ~pplications. ~he in~enti~n contempla~es, however, that a nu~ber of sand sticks 20 with bonding agents of varying molecular we~ghts, will ultimately be u~ilized to cover the needs of vaxious oil ~nd gas prod~cing geo~raphical areas.
The inv~ntion ~lso contemp~ates that other water-soluble bondi~g a~ents might be substituted, although polyethylene glycol appears optimum among curr~ntly ~nown materia~s. "NO~OX~NOL 100"
(non~lphenol), for exampl~, is w~te~-solu~le, howeve~, it is incompatible with certain hy~rocarbons which could, under certain circumstances, lead ~o unwante~ emulsification of downhole fluids.
current practice utilizing the sand sticks 20 indicates t~at, in a tubingless completion, it is ~ery useful to shape the sticX 20 such tha~ it will fall through 2-7/8" outsi~e diame$er tubing 76 ~2.441" internal diameter), ~nd to size the stick 20 such ~ha~ the bulk sand volume wlthin will fill one linear foot (or one linear unit of len~th) of such pipe 76. T~is assists the operator in making ~he de~ermina~ion a~ to the number of sticks 20 require~. Other stick 20 ~izes can be made which ~ill provide similarly useful correlations to American Petroleum Insti~ute ~tan~ard pipe sizes, as well as other stan~ardized ~iz~s, which might be in e~ect at the time of product application.
Furthermore, our invent1on includ~s sand sticks 2~ which will have a finer mesh sand in place of the sand which fo~ms the . ~
bulk of the sand column 34. A "cap" 37 of ~his finer ~esh sa~d will reduce the effective permea~ility and porosity of the sand ~olumn 34 with ~espect to fluid communication across the top 32 of the column 34. It is anticipated that silica f~our or 100 mesh sand will-provide appropriate reductions, although other size~ m~ be ~ppr~priate under the c}rcumstances.
It is fuxther antlcipate~ that 12/20 mesh sand, or larger, wi~l ~e u~eful in some applications, e.g. those in which a sand bailer i~ ~sed to re~ove the sand colwmn 34,54,74 a~ter the operation is completed. Si~ilarly, in som~ applications, variou~
aggregates or conglomerates c~n ~e su~stltuted for, or combine~
with, the s and.
An ad~iti~nal aspect o~ our invention is ~ reshaping o~ one or both en~s to pro~ide ~ tapered rounde~ profile as it enters the pipe 76. In some~applications, it is anticip~ed that the sand stick 20 w~ll desçend more e~ecti~ely i~ this is done.
The preferred methods of using of the sand stick 20 in va~ious downhole sand placement operations involve a downhole pipe 3~,56,76 (e.g. production or intermediate casing) w~ich the operator desires to fill with sand, in an interval exten~ing from a particular bottom de~th, i.e., th~ effective well bott~m 38,58,78, to a p~ticular ~op ~epth ~2,S2,72. This downhole pipe 36,S6,16 will be in ~luid rommunication with receivin~ pipe 81 at the surface 80, with no other pipe within it, or the downhole pip~ 36,55,76 will be in fluid co~munic~tion with receivirg pipe ~1,61 ~t the surface 40,6~ as a result of a co~tinua~ion pipe 4~,~2, such ~s tubing. In either case, t~e ~ontinuation piping 4~,62,7~ betwee~ the downhole pipe 36,56,76 an~ the receivin~
pipe 41,61,81 at the surface 40,6~,80, h~s an inside diameter which al~ows the sa~d stick 20 to be received into, and pass through and out of, all pipe from the receiving pi~e 41,61,81 at the surface 40,60,80 to the effective well bottcm 38,58,78.
FigQ. 2-5 schematically depict ~onventional well completions show~ng fluid communication from ~he downhole pipe 36,56 through the continuation pipe 42,62 to the ~urfa~e 40,60. Figs. 6-7 depict a tubingless completion where the downhole pipe 76 is co~tinuous to the ~eceiving pipe 81 at the surface 80.
Typical operations are xefiected in Figs. 2-3,6-7 wher~
.
perforations 44,84, through the downhole pipe 36,76 i~to the formation 46,86, ~xe covered and isolated by the s~nd column 34,74. Figs. 4-5 represent a remedial cementing operatio~
configuration where a bridge pl~g 64 i5 set bene~th ~ casing leak 66 an~ a sand column 54 is placed on the bridge plug ~4.
In either type of completion the sand column 34, 54, 74 is formed by placing the 5and sticks 20 in the receivi~g pipe 41,61,81 at the surface 40,60,80 and waiting for the sticks 20 to fall, dissolve and deposit the san~ on the e~ective well bottom 3~,58,78. Because the stic~ 20 has been ~onstructed in a manner that the linear foota~e ~illed by each sand stick 20 is known, the operator ~an ~al~late the number of stick~ 20 to be dropped which wi~l result in a sand column 34,54,74 of ~esired h4ight.
In some w~llbor~ situ~tions, portions of the sand m2y go into the formation 46,86 outside the downhole pipe 36,56,76, or ~hrough a casin~ leak 66. If this is anticipated by the op~rator, an addltional ~u~ber of sticks 20 can be dropped ~o offset the anounts lost.
The perfo~mance of the sand sticks 20 will be maximized wh~n the operator determines the height (fluid level) 48,68,88 of the salt water column 30,50,70, ~d ~hooses a sand s~i¢k 20 w~th a molecular weight which is compatible with that column height, such that the sand st~ck 20 is completely dissol~ed, or su~stantially dissolved, prior to reaching the depth desired for the top of the sand column 34,54,74. Simil~rly, the chos~n sand stick 20 wil~ not complete the dissol~tion process prematurely.
. In ~any sltuations, it will be desirable to attach a s~nd s~ick 20 insertion device 100 ~o the receiving pipe 41, 61, 81.
The important features of such an insertion ~evice lO0 a~e schematically ill~strated in Fig. 8. If wellbore 102 pressures r~ult in ~ pressurized recei~i~g pipe 41,61,81 at the surface 40,60,80, this attachm~nt should take place following the closin~
of ~ valve 104 at or nea~ the surface 40,~0,80 which will isolate the insertion ~evice 100 from pressures wlthin the recelving pipe 41,61,~1. Once the insertion devlce 180 is installed, the inSer~ion ~evice middle portion 106, shaped to hold one or more s~icks 20 i~ its interior, can be isolated from receiving pipe 41,61,81 p~essu~e by closing the insertion de~ice bottom val~e 108. Af~er the insertion ~evice top valve 110 is opened, on~ or more sand sticks ~0 can be placed in the insertion dev~ce middle portion 106 thro~gh ~he insertion device top valve 110. The ins~rtio~ device top valve 110 is then closed and the insertion device bottom valve 108 opened, whic~ ~llows the sti~k 2~ or stic~s 20 to fall from the inse~tion device middle portion 106 into the interior of the receiving pipe 41,61,81 at the surface 40,~0,80, at whiçh point the stlcks 20 ~egin the descent through continuous piping 42,62,76 to the do~nhole pipe 36,56,7fi inter~al to be fille~ by the sand release~ from the sticks 20 during the dlssolution pr~cess. This stick 20 insertion procedure is repeate~ until the desired number oX sand ~ticks 2~ ha~e entere~
the wellbore 102 through the receiving pipe 41,61,81.
If the pressure in the receivin~ pipe 41,61,81 is large ~noug~, it will crea~e a pre~sure differen~ial across the ins~rtion device bottom ~alve 108 which can make it di~ficult to ope~. Fig. 8 also ~pic~s pressure differenti~l re~uction means which equalizes the pressu~e acxoss the insertion deviGe botto~
valve 108, ~uch means comprises ~ pressure equali~ation line 112, which, by directly or indi~ectly connecting the insertion de~ice middle portion 10~ interiox to interior of the receiving pipe 41,61,81,- allows such equalization to occur. The equaliz~tion process be~ins when the sand stick 20 or sticks 20 have been inserte~ into the insertion ~evice middle portion 106 and the insertion device top valve 110 has been closed, at which point a pressure equaliza~ion v~lve 114 on the pressure eq~ali~ti~n Iine 112 is opene~, allowing ~luid communication between the ~nteriors of the recei~ing pipe 41,61,8~ an~ the insertion device middle portion 106. Once the pressure has e~ualized the pressure equalizatlon valve 114 is close~, and th~
inse~tion device bottom valve 108 can be opened and closed, as described above. ~ressure rewaining in the inser~ion device mlddLe portion 10~ interior can then be bIed off, preferably by use of a insertion de~i~e middle po~tion bleed valve 116 attached to the in~ertion device middle portion 106. Howe~er, it is also possible to release such pressure by opening ~he insertion device top ~Talve 110.
If th~ operator desires ~o ''cap" the sand column with a finer mesh sand, to reduce the effective permeabi~ity and porosi~y of the sand colwnn 34, 54, 7~, the operato~ places a second group of sand sticks 20, which have a flner mesh ~and, into the interior of the receiving pipe 41,~1,81 ~ollowing the ~irst gr~up of s~n~ sticks 20, using the same procedures, i.e.
with or witho~t an insertion device 100 ~ttached.
The molecular weights ~escribed can be approximate~ without s~verely alteri~g the per~ormance characteristic~ of the resulting s~nd sticks 20. They are also approximated to the extent tha~ polye~hylene glycol industry nomenclature and speci~ications are appr~ximate~. For example, the molecuLar weights ~ssigned by The Dow Chemical Company in its publication "The E~ol~glycol ~Iandbook" (Copyright, 1988; Form No~ 17 8 -10~6-885-AMS) have, ~n part, been used herein, and these are stated to be approximates in that publication. In accord~nce with tha~
publication, the average viscos~ty ~or polyethylene glycols ha~ing molecular weights from 3350 to 8000 should be from 93 to 800 ce~tistokes. Furthermore, Christianson Chemi~als, Inc., in ijts Materi~l Safe~y Da~a Sheet, in~icate~ that for 6000 molecular weight polyethylene glycol (PEG-6000), the avera~e molecular weight vaxieS from 5800-6800. For 8000 molecular ~eight (PEG-8000~ the rang~ stated th~rein is 7000 to 8600.
Our experience reveals that the best performance of the sand stic~ is achieved when the stick is ma~e by care~ully controlled blending tech~iques. Without such techniques the sand distribution wlthin the bo~ding agent will be uneven, which c~
result i~ loss o~ stick inte~rity, h~ndling difficul~ies and unsatisfac~ory dissolu~ion in a~ual use. Our manufacturing procedure includes a method of making the stick~ which enhan~es the even ~istribution o~ sand in the bonding agent. In this method, the bondin~ agent is heated to approximately 200~ F at w~ich point the sand is ad~ed, the ratio of sand to bonding ~gent volumes ~eing pxedetermine~. The bonding agent is bei~g ~gitated while the sand is being a~de~, and the re~ulting slur~y is ~ehe~ted to ~OC~ ~ prior to being pou~e~ into tubes of p~edeter~ined volume, where ~he slurry solidifies as it cools.
The temperatures ~epeIld on the molecular weights of the polyethylene glycol being used. Reasonable variations ~n such temperatures can be tolerated without jeopardizing the ~sic function of the sand stick, par~icularly in light of typica~
fluctu~tions in the mol~cular wei~hts of polye~h~lene glycol and ambient tempe~atures.
Although the present inventio~ has been dé~cribed in congiderable detail with reference to certain preferred an~
alternate embodiments thereof, other embodiments are possible.
Accordi~gly, the spirit and scope of the appende~ ~1 2ims shoul~
not be limited to the descri~tion of the embodimen~s contained herein, Furthermore, the claims submitted with this pro~isional applic~tion are in no manner intended by us to limit the scope of our invention zs otherwise disclo~ed b~ the remainder of this specification.
lg
Claims (36)
1. A sand-bearing water soluble composition, comprising;
sand, and a water-soluble bonding agent, the combination of the sand and the bonding agent being a solid at standard temperature and pressure, the combination being shaped such that it may be received into and through a length of pipe.
sand, and a water-soluble bonding agent, the combination of the sand and the bonding agent being a solid at standard temperature and pressure, the combination being shaped such that it may be received into and through a length of pipe.
2. The sand-bearing, water-soluble stick of claim 1, wherein the shape, solubility and density of the composition is such that the composition will descend through a column of fresh water in the pipe at a higher rate than the sand alone.
3. The sand-bearing, water-soluble stick of claim 1, wherein the shape, solubility and density of the composition is such that the composition will descend through a column of salt water in the pipe at a higher rate than the sand alone.
4. The sand-bearing, water-soluble stick of claim 1, wherein the molecular weight of the bonding agent is such that the composition will substantially dissolve before reaching the bottom of a column of fresh water in the pipe.
5. The sand-bearing, water-soluble stick of claim 1, wherein the molecular weight of the bonding agent is such that the composition will substantially dissolve before reaching the bottom of a column of salt water in the pipe.
6. The sand-bearing, water-soluble composition of claim 1, wherein the composition is in the form of a stick having a length and a generally circular cross-section perpendicular to the length.
7. The sand-bearing, water-soluble composition of claim 6, wherein the stick has a tapered end.
8. The sand-bearing, water-soluble composition of claim 6, wherein the stick has a rounded end.
9. The said-bearing, water-soluble composition of claim 1, wherein the bonding agent is polyethylene glycol.
10. The sand-bearing, water-soluble composition of claim 1, wherein the composition is sized such that the volume of sand deposited approximately fills a predetermined length of the piping.
11. The sand-bearing, water-soluble composition of claim 10, wherein the magnitude of the predetermined length of the piping filled is approximately an integer.
12. The sand-bearing, water-soluble composition of claim 1, wherein the composition is colored to correspond with a particular size or grade of the pipe.
13. The sand-bearing, water-soluble composition of claim 1, wherein the composition is marked to correspond with a particular size or grade of the pipe.
14. The sand-bearing, water-soluble composition of claim 1, wherein the composition is sized such that the volume of sand deposited approximately fills a linear foot of the piping.
15. The sand-bearing, water-soluble composition of claim 1, wherein the composition is sized such that the volume of sand deposited approximately fills a linear unit of measure of the piping.
16. The sand-bearing, water-soluble composition of claim 1, wherein the composition is sized such that the number of sticks dropped, multiplied by an integer, will provide a volume of sand sufficient to fill approximately one linear foot of the piping.
17. The sand-bearing, water-soluble composition of claim 1, wherein the composition is sized such that the number of sticks dropped, multiplied by an integer, will provide a volume of sand sufficient to fill approximately one linear unit of measure of the piping.
18. The sand-bearing, water-soluble composition of claim 1, wherein the sand bulk volume is approximately double that of the bonding agent volume prior to combination.
19. In piping having an interval of fresh water or salt water, a device for depositing sand at the bottom of the interval of water, comprising a sand-bearing water-soluble composition, the sand-bearing water soluble composition comprising sand, and a water-soluble bonding agent, the device being shaped such that the device may be received into and through a length of the piping.
20. The device of claim 19, wherein the molecular weight of the bonding agent is such that the device will descend through the water at a higher rate than the sand alone.
21. The device of claim 19, wherein the molecular weight of the bonding agent is such that the bonding agent will substantially dissolve before reaching the bottom of the interval of water.
22. In piping having an interval of fresh water or salt water, a device for depositing solid material at the bottom of the interval of water, comprising a solid material-bearing water-soluble composition, the solid material-bearing water-soluble composition comprising a solid material, and a water-soluble bonding agent, the device being shaped such that the device may be received into and through a length of the piping.
23. The device of claim 22, wherein the molecular weight of the bonding agent is such that the device will descend through the water at a higher rate than the solid material alone.
24. The device of claim 22, wherein the molecular weight of the bonding agent is such that the bonding agent will substantially dissolve before reaching the bottom of the interval of water.
25. In the method of filling a portion of a downhole pipe with sand, in a hydrocarbon or other fluid producing well, where the interior of such downhole pipe is in fluid communication with the interior of a receiving pipe at the surface, where fresh water or said water fills the portion of the downhole pipe which is to be filled and all or part of the well interval between the downhole pipe and the receiving pipe, and where an effective well bottom determines the lower depth of the portion of the downhole pipe to be filled, the improvement, comprising:
placing sand-bearing water-soluble sticks in the interior of the receiving pipe; and waiting for the sticks to descend, dissolve and deposit the sand on the effective well bottom.
placing sand-bearing water-soluble sticks in the interior of the receiving pipe; and waiting for the sticks to descend, dissolve and deposit the sand on the effective well bottom.
26. The method of claim 25, wherein the effective well bottom is the effective total depth of the well at the time the sand placement operation begins.
27. The method of claim 25, wherein the effective well bottom is the top of a bridge plug set in the downhole pipe.
28. The method of claim 25 further comprising the additional step of placing a second series of sticks in the receiving pipe following the first group, the second series of sticks having a substantially finer mesh sand.
29. The method of claim 25, wherein the shape, solubility and density of the sand-bearing water-soluble sticks are such that the sticks are completely or substantially dissolved before reaching the intended depth of the top of the pipe interval to be filled.
30. The method of claim 25, wherein the shape, density and solubility of the sand-bearing water-soluble sticks are such that the sticks will descend through a column of salt water at a higher rats than the sand alone.
31. The method of claim 25, wherein the sand-bearing water-soluble sticks are formed by combining sand with polyethylene glycol.
32. The method of claim 25, wherein the step of placing one or more sand-bearing water-soluble sticks in the receiving pipe further comprises:
attaching a stick insertion device to the well, the stick insertion device having a top valve, a middle portion having an interior for holding one or more sticks, and a bottom valve, the valves being sized for receiving the sticks when open, the insertion device being attached to the well such that the insertion device middle portion interior is in fluid communication with the interior of the receiving pipe when the bottom valve is open;
separating the interior of the receiving pipe from the insertion device middle portion by closing the insertion device bottom valve;
opening the insertion device top valve;
inserting one or more sticks through the insertion device top valve into the insertion device middle portion interior;
closing the insertion device top valve;
opening the insertion device bottom valve, allowing the stick or sticks within the insertion device middle portion to fall into the interior of the receiving pipe; and repeating all post-insertion device attachment steps until the desired number of sticks have entered the interior of the receiving pipe.
attaching a stick insertion device to the well, the stick insertion device having a top valve, a middle portion having an interior for holding one or more sticks, and a bottom valve, the valves being sized for receiving the sticks when open, the insertion device being attached to the well such that the insertion device middle portion interior is in fluid communication with the interior of the receiving pipe when the bottom valve is open;
separating the interior of the receiving pipe from the insertion device middle portion by closing the insertion device bottom valve;
opening the insertion device top valve;
inserting one or more sticks through the insertion device top valve into the insertion device middle portion interior;
closing the insertion device top valve;
opening the insertion device bottom valve, allowing the stick or sticks within the insertion device middle portion to fall into the interior of the receiving pipe; and repeating all post-insertion device attachment steps until the desired number of sticks have entered the interior of the receiving pipe.
33. The method of claim 25 wherein the step of placing one or more sand-bearing water-soluble sticks in the receiving pipe further comprises:
a. isolating pressure from the receiving pipe interior from the surface by closing a receiving pipe valve located on or above the receiving pipe, b. attaching a stick insertion device to the well, the stick insertion device having a top valve, a middle portion having an interior for holding one or more sticks, and a bottom valve, the valves being sized for receiving the-sticks when open, the insertion device being attached such that the insertion device middle portion interior is in fluid communication with the interior of the receiving pipe when the bottom valve is open;
c. connecting the insertion device middle portion interior to the receiving pipe interior with a pressure equalization line, the pressure equalization line having a pressure equalization valve whereby such connection is closed when the pressure equalization valve is closed:
d. closing the pressure equalization valve;
e. separating the interior of the receiving pipe from the insertion device middle portion by closing the insertion device bottom valve;
f. opening the insertion device top valve, if closed, g. inserting one or more sticks through the insertion device top valve into the insertion device middle portion interior, h. closing the insertion device top valve;
i. opening the receiving pipe valve such that a pressure differential is created across the insertion device bottom valve:
j. opening the pressure equalization valve such that the pressure differential across the bottom valve is substantially eliminated, k. closing the pressure equalization valve, l. opening the insertion device bottom valve, allowing the stick or sticks within the insertion device middle portion to fall into the interior of the receiving pipe, m. closing the insertion device bottom valve;
n. reducing the pressure within the insertion device middle portion to atmospheric pressure; and o. repeating steps f through n until the desired number of sticks have entered the receiving pipe interior.
a. isolating pressure from the receiving pipe interior from the surface by closing a receiving pipe valve located on or above the receiving pipe, b. attaching a stick insertion device to the well, the stick insertion device having a top valve, a middle portion having an interior for holding one or more sticks, and a bottom valve, the valves being sized for receiving the-sticks when open, the insertion device being attached such that the insertion device middle portion interior is in fluid communication with the interior of the receiving pipe when the bottom valve is open;
c. connecting the insertion device middle portion interior to the receiving pipe interior with a pressure equalization line, the pressure equalization line having a pressure equalization valve whereby such connection is closed when the pressure equalization valve is closed:
d. closing the pressure equalization valve;
e. separating the interior of the receiving pipe from the insertion device middle portion by closing the insertion device bottom valve;
f. opening the insertion device top valve, if closed, g. inserting one or more sticks through the insertion device top valve into the insertion device middle portion interior, h. closing the insertion device top valve;
i. opening the receiving pipe valve such that a pressure differential is created across the insertion device bottom valve:
j. opening the pressure equalization valve such that the pressure differential across the bottom valve is substantially eliminated, k. closing the pressure equalization valve, l. opening the insertion device bottom valve, allowing the stick or sticks within the insertion device middle portion to fall into the interior of the receiving pipe, m. closing the insertion device bottom valve;
n. reducing the pressure within the insertion device middle portion to atmospheric pressure; and o. repeating steps f through n until the desired number of sticks have entered the receiving pipe interior.
34. The method of claim 33 wherein the insertion device further comprises a middle portion bleed valve attached to the insertion device middle portion whereby pressure is released from the insertion device middle portion interior when the middle portion bleed valve is open, and further wherein the step of reducing the pressure within the insertion device middle portion to atmospheric pressure is accomplished by opening the middle portion bleed valve, followed by closing the middle portion bleed valve when the pressure has been so reduced.
35. The method of claim 33 wherein the connection made in the step of connecting the insertion device middle portion interior to the receiving pipe interior with a pressure equalization line, is indirectly made through other wellhead apparatus.
36. In the method of filling a portion of a downhole pipe with sand, where the interior of such pipe is in fluid communication with the interior of a receiving pipe at the surface, where the interiors of the downhole pipe and receiving pipe are connected by a pipe string, where water fills the portion of the downhole pipe which is to be filled and all or part of the connecting pipe string, and where an effective well bottom determines the lower depth of the portion of the downhole pipe to be filled, the improvement, comprising:
calculating the number of sand-bearing water-soluble sticks required to fill the desired interval in the downhole pipe;
adding one or more sticks to the calculated number, if desired, to accommodate for possible sand loss;
placing the above sum of sand-bearing water-soluble sticks in the interior of the receiving pipe; and waiting for the sticks to descend, dissolve and deposit the sand on the effective well bottom.
calculating the number of sand-bearing water-soluble sticks required to fill the desired interval in the downhole pipe;
adding one or more sticks to the calculated number, if desired, to accommodate for possible sand loss;
placing the above sum of sand-bearing water-soluble sticks in the interior of the receiving pipe; and waiting for the sticks to descend, dissolve and deposit the sand on the effective well bottom.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US2683596P | 1996-09-27 | 1996-09-27 | |
| US60/026,835 | 1996-09-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2216388A1 true CA2216388A1 (en) | 1998-03-27 |
Family
ID=21834060
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2216388 Abandoned CA2216388A1 (en) | 1996-09-27 | 1997-09-24 | Sand-bearing water-soluble stick and methods of use |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2216388A1 (en) |
-
1997
- 1997-09-24 CA CA 2216388 patent/CA2216388A1/en not_active Abandoned
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