US 3100525 A
Description (OCR text may contain errors)
Aug- 13, 1963 A. w. SMITH ETAL 3,100,525
CEMENTING Filed Feb. 6, 1961 3 Sheets-Sheet 1 A@ 25 im@ 1li /7 4 /fbf/VI BYMF/QL Aug. 13, 1963 A.w.sM1TH ETAL CEMENTING 5 Sheets-Sheet 3 Filed Feb. 6, 1961 anw?? er INVENTUM BY/f AfoHA/fy d United States Patent O Texas Filed Feb. 6, 1961, Ser. No. 87,208 7 Claims. (Cl. 16o- 21) This invention pertains to the cementing of oil and gas wells, and in particular to the cementing of pipes disposed in such wells. It is customary in oil and gas petroleum Wells that at least some of the pipes in the well be cemented over at least a part of their length in order that they will be held firmly in place in the well. The cement also serves the purpose of sealing ofi the well at the position of the cement so that egress or ingress of fluids between the well and the earth structure surrounding the Weill be reduced or eliminated.
A principal object of the nventionuis to provide methods for cementing oil or gas wells.
Anotherobject of the invention is to provide such methods which are safe, economical, simple to perform, and yet are dependable.
A further principal object of the invention is to provide cementing methods for oil or gas wells which provide superior cementing thereof.
Briefly, the invention contemplates gasifying or aerating drilling fluid mud =in a well with an inert gas such as nitrogen or carbon dioxide so that the weight of the mud is reduced. The mud may be any type of drilling fluid known in the art. With the mud weight decreased, cement may be run into the well behind the mud more eliiciently and with less chance of breaking down of the formation around the well due to a high weight or pressure of mud or cement thereon. Less pressure must be imposed on the cement slurry while it is being pumped into the well in order to displace the mud and move the cement slurry to the proper position in the well, usually around the exterior of the lower end of a casing or tubing. The mud of lighter weight than normal is displaced by the cement slurry more readily so that excessive pressure does not act on the formation surrounding the `zone to be cemented.
Other objects and advantages of the invention will appear from the following detailed description of preferred embodiments thereof, reference being made to the accompanying drawings, of which:
FIGURE 1 is a verticalcross-sectional View in schematic representation `showing a well adapted for employment of the invention, with the apparatus shown in use during one stage of performance of the method; and
FIGURES 2-6 are each similar to 'FIGURE 1 showing different stages during performance of the method.
Referring now to the drawings in detail, and first to FIGURE 1, there is shown a well 10 having therein an `upper casing 11, usually called the surface or conductor casing. As, is customary, the casing 1,1 may be replaced by a plurality of outer casings of different lengths extending down into the well to different depths. 'Each of these casings may be treated for cementing purposes in accordance with the description herewith presented for the innercasing 12. Casing 12 is received through any suitable surface` apparatus which may be provided to perform the described functions of the well head members hereinafter mentioned. The well head members shown in FIGURE l of the drawings are casing head 13 supported at threadedconnection 14 at the upper end of "casing 11 above the elarths surface 15, tandem blowout preventer devices 16, 17, and adapter body 18 connected to the upper end of inner casing 12, for example `at a 3,100,525 Patented Aug. 13, 1963 "ice threaded socket form-ation (not shown) within enlarged lower portion 18a of body 18, or in other suitable manner. A lubricator device 18h seals the upper end of body 18, or other seal means may be employed.
Body 18'.l has side outlet 19 to which is connected a pipe 20 or other conduit means including a valve 21 and a gas jet or nozzle 22. A branch line 23, including valve 24, leads from a cement supply source 25 into line 20 between body 18 and valve 211 at T connection 26. Nozzle 22' has side inlet 27 into which drilling mud or fluid may be introduced through line 29 controlled by valve 30. Line 29 has connection with the outlet of a mud pump 32 and the inlet side of mud pump 32 is connected to a mud source (not shown), for example, a mud pit or tank adjacent the well head. Lateral outlet 35 of casing head `13 is connected through valve 36 and line 37 with the same or another mud source or reservoir.
As shown in FIGURE l, inner casing string 12 extends up through the blowout preventers 16, 17 to be sealed around thereby. Before commencing cementing of the well 10, drilling mud or fluid is pumped by pump 32 from the source thereof with valve 30 open so that the mud enters the gas jet or nozzle 22. Gas control valve 38 is open to permit flow of inert gas under high pressure through the nozzle. The gas is delivered from a suitable source of high-pressure inert gas such as that shown in copending United States of America patent application Serial No. 85,288, tiled January 27, 1961, and entitled Gas Method and Apparatus. Said application SN. 85,288 shows a supply of inert gas such as nitrogen or carbon dioxide which may be transported at low pressure to ua Well site and which will deliver inert gas at high pressure and at controlled temperature at the well site. `The gas supply according to that application is not limited by transportation regulations pertaining to highpressure limitations of pressure vessels and a supply of inert gas such as nitrogen gas may be delivered at pressures of 10,000 p.s.i.g. or higher, as desired. The gas is delivered through valve '38 to nozzle 22 where the mud is introduced therewith through lateral inlet 27 of the nozzle. The drilling mud or fluid is aerated or gasiiied to contain a very large proportion of gas in small-size bubble form. Because of the solubility characteristics and inertness of nitrogen, or the like, nitrogen remains mainly in small-bubble form, a proportion of the nitrogen being in solution, whereas air, or the like, having different solubility characteristics than nitrogen, or the like, will tend to break down the mud into its various constituents. Nitrogen does not break down the mud in this manner. The mud aerified with inert gas thereby becomes of appreciably lighter gravity or weight and this condition of the mud is maintained by maintenance of thehigh pressure thereon.
Gas-mud mixture concentrations may be conveniently expressed in the form of solution ratios, :solution ratio being dened as the ratio of volume of standard ygas at gallon barrels. The solution lratio `for practicable operationm-ay be of -a magnitude up to about 4000 scf. of gas `to `one t2-gallon barrel of mud. p
The aerated mud -is circulated through body 18 and Idown through string 12 to be discharged from the open lower -end of string 12 into the annular space :surrounding the casing in the well hole. The lower end of casing 12 fits more or `less loosely within the bore of well 10, the casing being somewhat smaller in diameter than the hole drilled toreceive the casing. Aerated mud fills the `annulus exterior of the casing wall and Within the well bore, ydisplacing unaerated mud the-retofore present and causing the unaerated mud to be circulated out of the well 'through Ithe annularA spaces between casing 12 and the well hole and between casings y11, 12, and line 37.
vOnce substantially all of the unaerated mud has been replaced by aerated mud, the mud circulation may be terminated by closing valves 30, 3S or valve 21. Valve 346 is left open so tha-t cement slurry may be introduced following the aerated mud.
The well is now in condition for cement slurry introduction at relatively low pressure. The rnud therein is aerated, as described, to be of light weight.
Referring now to FIGURE 2 `of the drawings, cement lslurry 40 is introduced into the well bore around the lower end of casing `12 by opening valve Z4connected to the cement source 25 and by closing valve 2'1 to shut off gas ilow while cement is introduced. 'Cement is pumped through line 23 into line 20 and thence downwardly through casing 12 into the well to the lower end of casing 12 Where the cement is discharged around the lower end of the casing, pushing the aerated mud upwardly th-rough the annulus provided and being discharged thro-ugh lateral outlet 35 of basing lhead 14 and through open valve 36 and line 37 to the mud supply or reservoir. The amount of cement pumped in is deter-mined by -the extent that it is desired Ifor the `cement to rise around the outside of casing 12 -at cement-mud interface 41. The casing can be cemented all the way or only part way Afrom its lower end up to the lower end of casing 11.
After the desired amount of cement slurry has been pumped into the well through casing 1210 bring the mudtcement interface 41 "(of FIGURE 2.) to the desired level after the cement in the interior of casing 12 :has been discharged from the lower end of casing 12, a displacing fluid, liquid or gas, is introduced above the cement in casing .'12 to displace the cement Idownwardly therefrom. The inert gas from nozzle 22 is convenient .for this purpose. lln view of the `fact that the gas-is inert and dry, it does not contribute to corrosion in the well apparatus, but instead minimizes corrosion. The `gas is supplied at pressures suicient :for the displacement without additional pressuring thereof being necessary. However, other fluids may be employed for the displacement, if ldesired.
After sufcient pressured gas (or other fluid) has been introduced to bring gas-cement interface to the desired point 43, FIGURE 3, then valve 36, which lhas been open during the displacement to permit escape of aerated mud, is closed. The displacing inert gas I(or other duid) is maintained by closing of valve 21, and Itime for setting of the cement is allowed. The cement setting time is deter-mined by the type of cement used, by the .accelerators Y used, if any, and by the amount of nitrogen introduced into the cement to aerate the cement. The cement slurry, if aeried in the manner described tor the mud, has increased internal pore space and thereby requires less setting time. Fur-ther, aerication of the cement slurry decreases cement loss into the formation because aeiied cement resists channeling Iflow into the formation. Still further, aerication of the cement slurry minimizes internal separations of the cement slurry so that .the cement slurry remains of uniform properties throughout.V Also,
huid loss reduction decreases setting-up time of the cement.
In FIGURE 3 of the drawings, thereis also indicated a zone l44 .around well 10 where the wall of the well hole is inclined to slough off or collapse, or is porous tending to become open to passage of -uid under pressure laterally out of lthe well. Because the cement is normally introduced under pressure and the pressure exerted by normal weighted mud above the cement is added to the cementing pressure, the pressure is often sufficient to cause mud or cement to be carried ijnto formation 42 andlost. However, with .the mud weight decreased due to aeration of the mud, the pressure is decreased to such an extent that cement will -not bypass or channel out of the well 4 to be lost in lformation I44 but instead will be retained in place to `seal oi formation `414 from .the well.
After the cement has been held in the Well for a sufilcient time tol set, the gas pressure or the pressure of other ldisplacement duid may be relieved. Lubricator 18b or any other type of device known in the fart through which Itools may be inserted into the well may be employed to insert a perforating apparatus 48 into casing 12. Apparatus 48 may, for example, be lowered by a :wireline 49 to a .point opposite oil or gas formation 50 at the cemented lower end of casing 1-2 where the same is desired to be perforated. Perforator 48 includes seal 52 therearound which is setto seal the perforating gun to the interior of casing l12. Inert lgas is then introduced in the manner described above the perforating gun which is then actuated to perforate the casing yas indicated at perforations 53. The pressure of gas above 4the per.- forator precludes the perforator from being blown up the hole by the well coming in or by force of explosive gases. Thus, the perforating of Ithe casing is carried out under safe conditions .and without chance of blowing out through the casing. Since the inert gas, such as nitrogen, is -at a high pressure of up to 10,000 p.s.i.g. or higher, as desired, the gas serves as a positive non-combustible check on the perfor-ating operation. T-his procedure is useful mainly only in the case of tubingless completions. After perforating has been completed, the gas pressure may be relieved by opening valve 24, the cement supply being disconnected therefrom, `and withdrawal of the pertorating gun from the casing accomplished through the lub-ricator 18h. This relief of Igas pressure may often -be util-ized to bring in the production lfrom the well. In this case, production may be controlled, for example, by introduction through lubricator w18b of a back-pressure valve (not shown) to seat at an appropriate point in the casing. The back pressure control apparatus may be, set lwhile the gas pressure lis still in casing 12, seal 52 being released to per-mit withdrawal of the perforator before the back pressure apparatus. is set.
In the case of completions other than tubingless completions, a diferent procedure is usually employed. Re.- 4ferrring now particularly to FIGURE S of the drawings, well 10 is shown after removal of all well-head equipment -above casing head :13, and after installation of' casing head 50, which :surmounts casi-ng head 13 and supports casing 12 inthe well, of tubing head 51, which surmounts casing head 50 and supports a tubing string 52 inside casing i12, and of master valve 53, which surmounts tubing head 51 and can be closed to control pressures within tubing 52. An adapter 18 is connected above master valve 53, and has a 4lateral outlet -55y Ito which line 20 is connected. Lubricator lSb, or a suit-able substitute, is connected above adapter 1.8 -for insertion of. tools into the tubing -in the well. 'y
A packer device 56 seals the annulus between Ytubing 52 and casing 12. A circulating sleeve 57, or any other suitable device Ifor valve-controlled flow between the tubing interior and the .annulus is provided above the packe-r. Such how may be instituted for the purpose of circulating inert gas into, and mud out of, the annulus above the packer, the mud exiting through one of the late-ral outlets 53 of tubing head 51, now through these being suitably controlled by valves, not shown. The mud may be Is0 circulated out, or not, as desired. Y
Perforator 59,;carried at the lower end of wire line 60 is lowered to the level of the Iformation where it is desired 'to perforate, valve 53 being open and lubricator 181) For testing the cement .after setting, the inert gas thereabove is released at the IWell head, so that any leaks may be detected and closed. More cement may be introduced through the casing or tubing, depending on the -form of the method employed, after which inert gas may be introduced to squeeze the cement into the leaks to seal them. Alfter setting, the cement may again -be tested for leaks in the described manner. The testing for leaks, is, of course, done before perforating.
While a preferred embodiment of the invention has been shown and described, many modifications thereof may be made by persons skilled in the art without departing from the spirit of the invention, and it is intended to protect :by Letters Patent Iall forms of the invention falling within the scope of the yfollowing claims.
1. Method for cementing in wells wherein the zone of the well to be cemented is iilled With a 'Weighted fluid, comprising, at the wel-l site, pumping a stream of iiquified inert `,gas to increase its pressure, heating the pumped iquied gas to vapor-ize the gas to form high pressure inert gas, gasifying a stream of said Weighted fluid drawn Vfrom a supply `thereof :at the surface with ysaid high pressure inert `gas prepared -at the Well site, circulating the gasiiied fluid into the well 'to displace said weighted fluid therefrom, circulating a volume of cement slurry into the Well to the zone [of the well to be cemented, and permitting the cement slurry to set in the well.
2. Method `according to claim 1, including directing 6 said cement slurry to the zone of the well lto be cemented by injecting said high pressure inert Igas prepared iat the well site behind the Icement slurry.
3. `Method `according to claim 1, Isaid `liquified inert gas being liquid nitrogen.
4. Method according, to c-l-aim 1, said liquiiied inert gas being carbon dioxide.
5. Method according to claim 1, 'said `gasification. of said Weighted uid .being `such that the `solution ratio, inert `gas/weighted fluid, kis in the range from about 50/ 1 to `about 400G/t1. f
6. Method according to claim 1, including `also gasifying said cement slurry 'With said high pressure inert gas prepared lat the Well site.
7. Method .according to claim 1, including running a .perforating ldevice into the well after said cement slurry is set, passing said inert gas prepared at the Weill site into the |vvell above ysaid perforating device to provide sa nonconrbustible condition in the Well, and operating the perforating device to open the Weil to production.
References Cited in the tile of this patent UNITED STATES PATENTS Hall Apr. 13, y1954 Bobo Apr. 7, 1959