USRE25682E

USRE25682E - Jacoby method of well completion

Info

Publication number: USRE25682E
Authority: US
Publication date: 1964-11-10

Description

Nov. 10, 1964 c. H. JAcoBY METHOD OF WELL COMPLETION 2 Sheets-Sheet 1 Original Filed April 20, Y1959 INVENTOR.' CHARLES H. JAcosy TTOENE' YS C. H. JACOBY METHOD 0F WELL COMPLETION y f E 2 R .w M@ m M 8 Y N u T... l IH. R e L L O E s n k2 L U, L m o m l A s H A ...1... 4 nu @w E?. a. 3 O .....,...f. C i -l.|-

Nov. 10, 1964 Original Filed April 2 0, 1959 x EMjNZj .j

SPL/TTING OR FRAcrus/NGAREA Reissue-d Nov. 19, 19t

25,682 METHD OF WELL CGMPLETIQN Charles H. Jacoby, Dearborn, Mich., assigner to The International Salt Company, Inc., Scranton, Pa.

Original No. 3,064,957, dated Nov. 20, 1962,'Ser. No.

807,449, Apr. 20, 1959. Application for reissue Jan.

22, 1964, Ser. No. 350,929

7 Claims. (Cl. 299-4) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue speeldcation; matter printed in italics indicates the additions made by reissue. 1

This invention relates to the mining of l1qu1d-solubre minerals from underground strata, and more particularly to the solution mining of salt. It is well known that soluble mineral deposits may be recovered by the drilling of wells into the mineral strata, fracturing the strata to open a passageway from one well to another and then circulating a mineral solvent through the opened underground system. Such a system of interconnected wells and cavities is referred to as a gallery. It is also well known in the art that the solution mining of salt has particular difficulties due primarily to the fact that when water is pumped into a well drilled into a salt formation the Jfresh water will tend to rise and the brine-saturated Water remains near the bottom of the cavity. As a result the formed cavity develops primarily upwardly and only secondarily laterally. This condition isY further developed by reason of the insoluble impurities in the salt deposit falling out of the brine solution and forming a semiporous insoluble blanket on the iloor and to some degree, the walls of the cavity. It is of course obvious that in order to obtain any worthwhile amount of salt under these circumstances it is necessary to drill the well to the bottom of the salt strata and even then a great deal of the deposit will be wasted` Because of the aforesaid conditions it was a natural development to utilize the gallery system for solution mining of salt, and this is discussed in a number of letters patents, examples of which are Patents 1,960,932 to Tracy, 2,487,202 to Pullen and 2,850,270 to Hanson.

It is a primary object of the present invention to provide an improved method for completing a well driven into and through an underground strata of mineral to be recovered by the dissolution mining process.

A specific object of the present invention is to provide an improved method of sealing oil a well that has been driven through a salt bed and into the strata therebelow so that the subsequent fracturing or splitting operation will be limited to within the salt bed while still being coniined to the lower level thereof.

Another object is to provide an improved method for sealing the well in relation to the strata above and below the bed to be mined, by means of an improved concrete sheath and seal.

Still another object of the invention is to so locate and complete drilled wells which are to be interconnected so as to secure improved results 4in the mining oper-ation by more efficient use of the liquid solvent circulated through the gallery system.

Other objects and advantages of the invention will appear inthe specification hereinafter and in the drawings wherein:

FIG. l is a diagrammatic vertical sectional view taken through strata including a salt bed to be mined by circulation of water/through an injection well and fractured strata to the production well;

FIG. 2 .is a fragmentary sectional view, on enlarged scale, taken as indicated at Il-II of FIG. l, showing the lower portion of the completed well in more detail.

Referring now to FIG. 1, a target well 12, and injection well 14 have 'been drilled into a salt strata and an und ground connection has been effected as by splitting a uplifting the salt bed as indicated at 15, thereby establi ing a gallery for the purpose of solution mining throt` interconnected well In accordance with my improi method, the Iinjection well 14 is drilled and completed follows:

I prefer to use a rotary drill for sinking the hole cause I believe it allows a better bond between the vv rock and the cement shea'di which is provided around well casing, as will be described hereinbelow, by lessen the possible number of air-and water entrapment vo created by a rough wall and eliminates a major port of the detrital Slough which is created by running cas in a rough-walled hole. Such Slough rock will tend follow the casing down the hole and will often fo partial or total blockages in the aunulus between the h wall and casing. Usually a l2 to l5 diameter holt desirable and the hole 14 will be started with the propriate rotary bit. As it is desirable to have accur knowledge of the location of the bottom of the salt str and the composition of both the salt strata and the jacent roclc formation, when a point approximately feet above the calculated top of salt is reached, may use a 6l/zl core bit to core through -all the ma salt stratum and into enough of the underlying str to determine its exact nature. Alternatively, it would less accurate but also less expensive if the normal h were continued and logged by some geophysical me such as gamma ray logging.

I have found that improved cavity and gallery fori tion is obtained by confining the well-interconnect split to the salt strata. This is because the roel: fori tions underlying sait deposits, although not necessa' soluble, are in general, much more permeable horizon ly than the salt. An uplift in these planes would al considerable and possibly total loss of injection ll. Accordingly, when the above mentioned coring is inisl the hole is drilled on down approximately three i into the rock underlying the salt and the hole is t plugged back, preferably with a suitable expand cement 24, to a point about two feet above bottom salt, as indicated at 25. This will effectively seal od hole from the underlying rock. The casing 26 is t run into the hole and set to within about two feet the top of the plug as shown in FIG. 2. The dimensi given are respesentative only. The specific measl ments will depend upon the actual rock and salt cor tions found at each particular well site. I select a zi within the lower portion of the salt strata which is pure and as free of insolubles as possible. The lo tensile strength of the pure salt and the greater solubi thereof will aid in the splitting of the bed and subsequ wash-through operations. In any case the gap betw the end of the casing and the plug in the hole bottom be kept as small as practicable because this will be point of application of the splitting fluid pressure. point of application of the splitting and uplifting press is confined to as small a vertical portion of the hols possible because this reduces the possibility of caus multiple horizontal fractures within the same salt bed. two or more independent partings occur, the volume iiuid required to complete a fracture to the point of in section with the target well will be greatly increased, proper development of the cavity during mining may impaired. Given a small wall area exposed to spliti pressure, salt deposits may be horizontally split and lifted much more satisfactorily than most rock fori tions because of the low tensile strength of the salt because its bed planes generally run evenly horizonta After the core hole l and main hole 14 have b plugged back and the casing set, the next step is v`tblish a cement sheath around the outside or" the ing to ill the annular space between the casing and hole wall. The cement sheath serves to reinforce casing, insulate the casing against corrosive inlluences l1 as ground waters which in many locations often .tain considerable amounts of hydrogen sulphide and monia together with other corrosive salts, and to seal the hole above the lower end of the casing against sible vertical tracturing when the splitting pressur ntroduced, and against vertical escape of injection :l alongside the casing during wash-through operations. n order to obtain the best possible sealing effect it lesirable to have the cement sheath devoid of any :ks or fissures and to have the sheath bonded to the 'ounding rock. l have found the following improved hod of cementing the well to provide an excellent ihed sheath. The cement is placed by pumping it t the casing and the cement reaching the bottom or well will be forced upwardly around the outside ot casing. Since the material iirst pumped into the ng will be that which ultimately fills the space been the casing and 'the wall rock around the upper or of the well as indicated at 28, the rst cement ined into the casing is preferably regular Portland .ent mixed with fresh water. The fresh water cement allowed by batch of brine-based cement which Will .fide an improved sheathing of the lower end of the ng in the salt strata as indicated at .'50, because water- :d cemento will not bond with salts whereas the e based cement will bond with the beds of salt and ydrite. Fine granulated salt is mixed with the brinerd cement in proper amounts depending on roel; peratures, the temperature of the brine at the mixing lt and the ground water conditions immediately above salt sections, to maintain the brine in the saturated At the linal stage of cementing, 2% by weight :alcium chloride is added to the cement which will .th the lower-most end of the casing as indicated at So as to cause this portion of the cement to setup harden before the major portion of the cement above As soon as the calcium chloride containing portion 1e cement sheath has set the cement in and under the of the casing is drilled out down to the expanded ent plug 24 i the hole bottom and an expansion 1er is used to remove the rest of the concrete from 1nd the hole wall, from the bottom point of the 1g to the top of the plug, thus leaving the salt Wall ased over this area as indicated at 34. This is the t to be subjected to splitting pressure.

lternatively, before cementing, water, gravel or other arial may be placed in the hole bottom to form a pad iacer. This pad will keep the cement from filling the 'e gap between the casing and the bottom plug and, 1 removed after cementing is completed, will leave lesired area of the salt wall exposed. f course any vn method may be used to expose desired areas of ialt deposit to the splitting media by perforating the ent sheath or the sheath and casing.

ie use of the quick setting cement mixture at the lower ,on of the Well provides two important advantages. I, by permitting the cement at the bottom of the casing z drilled out as described, while the rest of the cement f th is still plastic or semi-liquid, the sheath is not :ct to vibration cracks which often result when the th has hardened before the drilling-in takes place. is prevented by the hardened lower portion of :nt backing up the still plastic sheath. Secondly, a iderable amount of waiting time, and the attendant ng and personnel cost, is saved. :laim:

The method of completing a well driven through nirden into a salt deposit overlying a non-salt desaid method comprising backplugging the well with nding cement to the elevation of the bottom of the area to be subsequently split, running a casing into the well to the top of said area, pumping water-based cement into said casing in a quantity suicient to lill the space between the casing and said overburden, then pumping into said casing a supply of brine-based cement sufficient to lill the space between the casing and the upper portion of the salt deposit above said area, then pumping into said casing a supply of calcium chloride containing cement suicient to till the remainder of the space between the casing and the salt deposit, and then after said calcium chloride containing cement is set and before the balance of said cement is set roaming out the cement at the splitting arca to expose the salt strata thercat.

2. The method of completing a well driven through overburden into a salt deposit and an underlying non-salt deposit, said method comprising backplugging the Well with expanding cement to the elevation of the bottom of the salt section to be fractured, running a casing into the well to the top of said section, pumping unset cement into said casing in a quantity sufficient to ll the space between thc casing and said overburden, then pumping into said casing a supply of brine-based cement suliicient to lill the space between the casing and the upper portion of the salt deposit above said section, then pumping into said casing a supply of calcium chloride containing brinebased cement sutlicient to ll the remainder of the space between the casing and the salt deposit, and then reaming out the cement at the area to be split to expose the salt strata thereat.

3. ln a method ot completing a Well driven through overburden into a salt deposit for solution mining thereof, the steps o1 baci/plugging the well with expanding cement to the elevation of the bottom ol a salt area to be fractured, running a casing into the well to the top of said area, pumping unset cement into said casing in a quantity suilicient to lill the space between the casing and said overburden and the upper portion of said salt deposit, then pumping into said casing a supply of cement containing calcium chloride suilicient to fill the remainder of the space between the casing and the salt deposit, and then after said calcium chloride containing cement is set and before the balance of said cement is set rearning out the cement at the area to be fractured to expose the salt strata thereat.

4. {The method of mining a subterranean soluble salt deposit lying above a non-salt strata, which method includes driving a well through said soluble salt deposit and into the strata therebelow, plugging back the well to a point above the elevation of said non-salt strata and within a relatively pure salt layer, inserting a casing into said well which is of smaller diameter than the well and to a point just above the plug at the well bottom, forcibly introducing a quantity of cement through said casing suliicient to fill the annular space around the casing upwardly from said plug, in which the cement last introduced is quicker setting than the previously introduced cement, cutting away the quick setting cement immediately above said plug to expose a, small vertical portion of the salt deposit when the quick setting cement has hardened and while the cement thereabove is still in plastic condition, and then applying a splitting and uplifting pressure Within said casing after all of the cement has hardened, preparatory to introduction of a salt solvent lluid into the split area] 5. The method of mining a subterranean soluble [salt] mineral deposit, which method includes (a) driving a well through said soluble [salt] mineral deposit and into the strata therebelow,

(b) sealing the bottom of the well by plugging back the Well to a level within the region of the soluble [salt] mineral deposit,

(c) inserting a casing into said well which is of smaller diameter than the well and to a point just above the plug in the well bottom, (d) sealing between the casing and well by forcibly introducing cement through said casing to seal between the casing and well upwardly from said plug,

(e) cutting away the cement to expose a small vertical portion of said soluble lsalt] mineral deposit in an area thereof between said plug and the bottom of the casing after the plug and at least a lowermost portion of the cement around the casing has hardened and without disturbing the stated seals at areas either above or below the exposed portion,

(f) then applying a splitting and uplifting pressure to said [salt] soluble mineral deposit at said exposed portion thereof so that such force is confined solely at the exposed region, preparatory to introduction of a [salt] soluble mineral solvent iluid into the split area.

6. The method according to claim 5 wherein the in- Itroduction of cement is controlled so that (a) the cement last introduced is quicker setting than the previously introduced cement so that the quick setting cement is disposed Within the region of and extends upwardly from the plug,

(b) said [salt] soluble mineral deposit being exposed after the quick setting cement has hardened but while the cement thereabove is still in plastic condition,

(c) the splitting and uplifting force being applied after all the cement has hardened.

7. The method of solution mining salt] soluble mneral which includes the steps of (a) driving a well through a soluble {salt} mineral deposit and into underlying strata,

(b) sealing the well by introducing cement into said well to form (a) a solid plug upwardly from tht well bottom to a point Within said soluble salt] mineral deposit and (b) a casing-embracing shel above said plug and extending upwardly through a least a substantial extent of the [salt] soluble min eral deposit,

(c) cutting away the cement to expose a small vertica area of the [salt] soluble mineral deposit just abov the plug after the plug and at least a lower-most por tion of said shell has hardened and without disturb ing the seal in areas either above or below the posed portion, whereby the plug and shell are dis continuous only at said exposed portion,

(d) and thereafter applying a splitting and upliftin force within the well so as to be confined in its a; plication solely to the exposed portion of the [salt` soluble mineral deposit to the exclusion of region above and below said portions.

References Cited by the Examiner The following references, cited by the Examiner, are c record in the patented tile oi this patent or the origin:

patent.

UNITED STATES PATENTS 1,960,932 5/34 Tracy. 2,847,202 8/58 Pullen. 2,850,270 9/58 Hanson. 2,952,449 9/60 Bays. 2,961,644 ll/ Shell.

BENAMN HERSH, Primary Examiner.