US2591807A - Oil well cementing - Google Patents

Description

H. M. GREENE OIL WELL lCEMENTING April 8, 1952 Filed Aug. 23, 1947 \\Jllli I! asfazlm-Mr IN V EN TOR.

TJUP/yfy Patented Apr. s, i952 .l

. HaekeuM. Greene, Whittier, Calif'.

e Means for Cementing Oil, Gas and ApplieatienAugust 23,1947, serial Ne. 770,239

This invention has to do with systems for carrying out cementing operations in oil wells, and is directed particularly to improved methods and equipment for displacing` and compacting cement into a water shut-off or like zone by explosive force. The invention represents vvarious improvements over lthe practices described in Patent No. 1,734,670, issued November 5, 1929, on Water Wells.

According to the general method contemplated,

a vertically elongated body of cement is lowered in a cased or uncased well bore to the cementing zone, for example a cased location where the cement is to be displacedto and compacted about the outside of the casing. (The same general procedure is applicable to cavitating4 and cementing in open-hole.) By detonating an explosive charge in the cement mass, the resulting force tends to deform or cavitate the bore wall, and to displace the cement into the cavity with great 'force resulting in a densely compacted, strong binding and fluid impervious mass when set.

- One of my major purposes is to confine theexplosive force in a manner assuring its most ef- `ective application to the cement. -l'or this purpose I place in the well bore above the cementing zone a plug or 'barrier sufficient to confine the'xplosive force, at least to a substantial de-l gree, tothe cementing zone below. i Preferably,

formation of the barrier is eifected by virtue of Y and in closely timed relation to the creation of an explosive or'pressure generating force, so that .thereiect of that force is confined for the most part toadisplacement of the cement to the.' intended location. `Particularly contemplated is the provision in the cement container, of a mass of material which is caused by the explosion force to bridge across and plug the well bore.

1 VThe inventiongfurther contemplateseifecting the ultimate cement displacement by two explosiveforces,` the first actingrto rupture the fcement containencavitate the well and perforate thef'casing (Whenthe hole is cased) and to cause initial displacement ofithe cement into the cavity.k `Afsecondexplosive or pressure `generating force,` preferably of less vshock 4intensity and greaterjduration than the` rstis applied `to a topportion of the cement body to serve'the dual purposes, of forming the barrier and of generating a sustained pressure which continues ldise placement and compaction of the cement to the limit `of existing yconditions.k y Of advantage is a timedgor sequential relation in the `firing `of 7 claims. (01.,'1e6-5-1);

the two explosive charges, thefsecond being det# onatedlpreferably a fraction of a second following detonation of the first so that perforation, cavitation' and initial and finalv displacement `of Athe cement follow in the order stated. f

j Where casing is to be'opened to passthece-l ment into a space adjacent the formation, per'-v foration. of the casing may be accomplished by thesimple expedient of placing at the outside of orwithin the cement mass a number ofipro jectiles, .preferably bullet-like land placed in'prearranged order, whichare driven by the cement. displacing explosion force through the casing, all as will later appear. i

The abovementio'ned aswell as various additional `features and objects of the inventionwill be understood to better advantage from the fo1' lowing detailed description ofk certain typical procedures and equipment illustrated by thea-ccompanying drawing, in which:` f Fig. 1 isV a sectional view showing the equipment lowered to an intermediate cementingzone in the'well; g Y, :1 L Fig; 2 is a similar View illustrating the condition of the hole and cement at the instant followingexplosion ofthe rstcharge; and; Fig.,3 illustrates the formation of the plugand ultimate displacement of the cement afterjex` plosionof the second charge.- 1 q f As Y a typical environment,l the cementing equipment, generally indicated at l0, is shown to be lowered in a well containing the4 usual casing Il,A with the lower portion of the equipment brought opposite a zone l2 to be cementedas for shut-off of Water formation, or,V any other purpose. The apparatus comprises an elongated shellv i3, typically of aluminum baseor other ruptureable material, closed at its lower-guide endl i4 and open at the top.v The shell is suitably suspended, as by an electrical cable l5 attached to the ,bail I6. Thel shell contains anextended bodyof cement -Il sufficient inquantity for the particularcementing job.

l `,Ernestle@in the bottomlpormeh f th'cemrit isA a capsulet 3| 8 vcontainingan Aexplosive charge-1 9 toA befred by-:detonator 20 in Vthe capsulegheadf Where casing is to be perforated, the capsule may serve alsoas a support `for a plurality of radially positioned, 'bullet-like metal projectileszlye-- Ceived in barrelsor sleeves 2H and pointed-.outrwardlytoward Vthe casing,.-` The detonator electrically connected to aconductor i?YZ/ extenti-` ns: upwardlydntospace 23, and with a second'. Conductor t 24.,- extending'i upwardly .-through; the

shell toY connect 'at-,25 `with the `conductoratable,

I5. The charge I9 is a relatively high velocity charge, rated at a velocity of for example 7000 feet per second, capable of creating a more instantaneous or shock explosion for cavitation and-,1 perforation of the casing. Being of this type, the charge I9 lacks the capacity of the slower burning upper charge 26 for prolonged gas and pressure generation.

The second explosive charge 26 contained in space 23 which may be separated from the cement by a suitable medium 21, ty-pically is shown to be in the form of an explosion-type fuse connected to conductor 22 and at 28 to one of the casing-engaging springguides 29. The explosive 26 may be of any of the known types and compositions characterized by its tendency to ignite practically instantaneously throughout its length, and to have, with relation to the first described charge I9, more sustained pressure and heat generating qualities. For example, the charge 26 may have a rated explosive velocity of around 2600 to 2800 feet per second, which gives the charge, upon detonation, less shattering force than the lower charge, and a tendency for prolonged burning to create a relatively extended pressure surge. To promote sustained heating, the charge 26 may contain a substantial quantity of small metal particles which tend to hold heat acquired by the initial detonation. Where the claims refer to an explosive it is intended to include any material capable upon ignition or detonation of producing large quantities of gas. Similarly, the term explosive iorce refers to the force created by any such'gas generating material.

Above. the charge 26, shell I3 contains a barrier forming material 30, which in the broad contemplation of the invention may be of any suitable composition capable of becoming displaced by the explosive force to bridge across the well or casing bore, at least to the extent of largely confining the second explosion created pressure to the zone below. As illustrative, the material 30 is shown to comprise a mass of small gravellike and sand particles capable of expulsion from the shell and compaction by the combined effects of the force of the explosion below and the iluid column resistance above, to form a barrier or bridge mass in the casing.

Assuming the shell to be lowered to the position of Fig. 1 in a hydrostatic column 3 I, passage of current through the conductor cable I iirst fires the detonator to explode the charge I9, the eiect of which is to drive the projectiles 2| through the casing to form the perforations 32,

vsee Fig. 2, and to start the cement displacement through the perforations into a cavity 33 formed or enlarged by the explosive force. A portion of the cement may bridge the casing below the explosion zone, as indicated at 3 I I. The bottom extent of the container I3 is of course ruptured leaving the/upper extent oi the cement column free for downward displacement in the casing and out through the perforations. The burning qualities of the charge 26 are such that upon passage of the current through it, the fuse will explode a fraction of a second following explosion of the charge I9. The initial effect of the explosive force of the upper charge is to displace the material 30 upwardly and out of the shell into a barrier mass 34, in which the particles may become densely compacted into a substantially iluid imprevious body which plugs the casing as 'illustrated in Fig. 3. As will be understood, the upper portion of the casing I3 will at least be deformed, and frequently completely rupturedrby the internal explosive pressure. The relatively prolonged pressure generation resulting from burning of the upper charge, displaces the cement downwardly with great force so that it may be caused to completely ll the casing and cavity 33 at the zone I2, as an extremely dense and compact mass strongly bonded to the formation by reason of the transmitted pressures and condition of the cement. Thus the residual effect of the explosion of charge 26 and the closed condition at 34 of the hole above, is to apply to the cement a sustained pressure assuring its retention in place until the cement sets. Thereafter the barrier 34 and cement plug may be drilled through, or allowed to remain, depending upon the objectives of the particular operation.

I claim:

1. Apparatus for depositing cement in a zone rst to said high velocity charge and then to the lower velocity charge to ignite the charges in that order.

2. The method of depositing cement in a zone within a Well bore, that includes lowering in the Well to said zone a vertically elongated body of cement, creating an explosive force at the lower portion of said body, cavitating the bore wall adjacent said lower portion of the body and moving the cement into the resulting cavity both by virtue of said force, and creating a second explosive force above said body resulting in prolonged application of pressure, independently of the normal well pressure, to cause displacement and compacting of the cement downwardly and into the cavity.`

3. The method of depositing cement in a zone within a well bore, that includes lowering in the well to said zone a vertically elongated body of cement, creating an explosive force at the lower portion of said body, cavitating the bore wall adjacent said lower portion of the body by said force, creating above said body and below a location where said bore is to be plugged a second and sequential explosive force, and forming at said loca'- tion a plug across the bore and displacing and compacting the cement against the bore wall at said zone by virtue of said second explosive force.

4. The method of depositing cement in a zone within a well bore, that includes lowering in the well to said Zone a vertically elongated body of cement, creating at a lower portion of said body a relatively high velocity explosive force. cavitating the bore wall adjacent said lower portion of the body and moving the cement into the resulting cavity both by virtue of said force, igniting above 'said body and below a location where said bore is to be plugged a relatively slow burning charge, forming at said location a plug across the bore by the combustion force of said charge, and-com'- pacting the cement against the bore wall at said zone also by sustained application of pressure to the cement resulting from the burning of said charge. f

5. Apparatus for depositing cement in a zone within'a well bore, comprising a vertically elo'n gated container to be lowered to said zone and containing a. body ot cement, an explosive first chai-'gein a lower` portion of said container and serving-Y upon ignitionto cavitate the well bore at saidf'2one, a second'ignitable charge in the container'above'said first charge, radially expansible plugging means carried by the container above said second charge and adapted to be expanded against the bore wall by the force of said second charge to form a barrier across the well bore above said cavity, and means forigniting said charges. fuApparatus -fordepositing cement in a zone within a well bore,comprising a vertically elongated' containerI to be lowered to said zone and cont 'a ,i1`1in`gl a, body of cement, an explosive first charge in4 a lowerI portion of said container ,and serving upon ignition to cavitate the wellbore at saidzone, a second'ignita'ble charge the container above fsaid body of cement, radially expansible. plugging materialcarried bythe container above said second charge and ,adapted to be expanded againstthe bore wall by the force of said second charge to form a barrier in the well bore aboveI said cavity, and. means for sequentially igniting' said'charges in the order named,

`'1. The method ofdepositing cement in a zone within a well bore, that includes lowering in the well to said zone'a vertically elongated body of cement, creating aan explosiveliorce at the lower portion of said body. cavitating''the bore wa1ladjacent said lower portion of tlij body by virtue of said force, and creating a seco dffxplosive force above said body resulting in pro j'nged application of pressure, independently of the'w'normal well pressure, to cause displacemeiitfand' compacting of the cement downwardly and'intovthe cavity.

HasKnir. M..GREENE.

REFERENCES .oITEn The following references are ofrecord in the file of this patent: v

UNITED STATES PATENTS Number Name v Date Re.21,356 Pitzer. Feb. 13, 1940 1,588,643 Alexander June 15, 1926 1,594,448 Boynton Aug. 3, 1926 1,734,670 Greene Nov. 5, 1929 2,307,729 Foster Jan. 5, 1943 2,381,929 Schlumberger Aug. 14, 1945 2,418,486 Smylie Apr. 8, 1947 OTHER REFERENCES The on Weekly, July 3,1;1931, pp. 16 and 17.

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