CA1210322A - In situ formation of sand control medium - Google Patents

Abstract

ABSTRACT

Substantially sand free oil is produced from an unconsolidated oil sand formation by a process characterized by: first forming a zone of consoli-dated permeable sand containing medium extending from a well bore radially into the formation by injecting substantially oxygen free hot aqueous fluid into the formation containing cokeable oil from the well bore at a rate, temperature, and pressure sufficient to heat the zone to a temperature at least sufficient to form coke binder for the sand grains therein, and then producing the substantially sand free oil through the thus formed consolidated permeable medium into the well bore from the oil sand formation. The process is presently viewed to be particularly useful for producing sand free oil from heavy asphaltic oil or tar sand formations by steam drive.

Description

03~ ~

IN S~TU FO~ATION OP S~ND CONTROL M~nIUM

Back~u ~ oe 5he Invention ~ield O~ The Invention ~ ..

The invention relates to recovery of oil. In one aspect, the invention relates to establishment of a zone of consolidated permeable medium extending from a well bore into an oil sand reservoir in a generally radial direction. The invention is viewed to have particular utility ~or recovery of sand free heavy asphaltic oil or tar from oil sand formations by steam drive.

Brief Desciption O~ the Prior Art Production of sand containing oil ~rom incompetent formations, (that is, formations which are insufficiently consolidated that particulates are produced concurrently with the oil) is a common problem in the oil industry.
It is often a particularly di~ficult to solve problem in the production of heavy asphaltic oil or tar from oil or tar sand ~ormations by steam stimulation.

Various means are currently used to mitigate this problem. For example, sand screens of a wide ~ariety oF de~ig~s are employed~

In another approach, particulate materials, either coate~
with a semi-cured adhesive or impregnated with a curable adhesive, are emplaced or positioned near the well bore to mitigate the problem. U.S. 2,625,287, U.S.
3,g29,191, U.S. 3,285,339, U.S. 3,625,287, U.S.
3,443,637, and UOS. 3,498,880 constitute exemplary disclosure of successful commercial proc~sses ~or sand control. Those in the industry may be more familiar with the names "SANCHECK", "SLURRY PACK", "SUPER SAND'~
and others for these types o sand control processes. i 3;22 . . ",.~

- 2 -The Problem of sand production concurrent wi~h oil is particularly of concern in produc~ion of heavy oil~;
or tars from oil sand or tar sand for~ations. Curren~
methods of sand con~xol, though quite useful in other circumstances, have limited applicability in such circumstances. The temperatures involved with thermal stimulation methods to recover such heavy oils or tars degrade many of the materials employed for conventional sand control.

Heavy oil deposits or oil sands or tar sands of the Athabasca type in which this invention is very useful can generally be described with reference to the ~thabasca deposits as an example. The Athabasca oil or tar sands are described as sands saturated with highly viscous heavy crude oil not recoverable in its natural state through a well by ordinary petrole~
recovery methods. The oil is highly bituminous in chaxacter with viscosities up to millions of centipcise at formation temperature and pressure. The API gravity of the heavy oil ranges from about 6 degrees to about 10 degrees in the Athabasca region and on down to negative numbers in other deposits such as the Maverick County, Texas, deposits. At higher temperatures, such as temperatures of about 200 degrees F. (~3C), this 2~ heavy oil or tar becomes mobile, but at such temperatures the heavy oil deposits are incompetent or unconsolidated.
One of the striking differences between such deposits and more conventional petroleum reservoirs is the absence of a consolidated matrix. ~hile the sand grains are in a grain-to-grain contact, they are not cemented together, except by the heavy oil or tar.

Heavy oil is conventionally produced from oil sands by the so called "huff and puf~" process. That process involves injecting steam into an oil sand formation L2~03~

3 --for a period of time, ~nd then reducing the pressure and producing oil ~hich flows back into the well bore. However, applicants are not aware of any disclosure involving injecting steam at the high 5 rates, temper~tures, and pressures needed to form coke binder for the sand grains in the locus, raise the temperature to a~ least 450F, and produce back substantially sand free oil. Indeed, sand production problems are often quite severe with conventional "huff and puff" operations.

U.S. 3,280,909 is ~iewed to be exemplary of one of the closest prior art reference types. It discloses forminy a hydraulic fracture from a well~ (and before the fracture can close) injecting steam, soaking, and producing a ~ell penetrating an oil sand reservoir.
However, there is no disclosure that the steam was injected at a sufficient rate, tempera~ure, and pressure to form a consolidated permeable zone, form coke binder in the permeable æone, or heat the zone to a temperature of at least 450F. Neither is there a disclosure that sand production was prevented upon production of oil, the unobvious result obtained a~cording to the instant ln~ention. Indeed, there are a num~er of references to heating the tar suf~iciently to reduce viscosity in the immediate vicinity of the fracture~, but no disclosure of ~mploying sufficient rates, temperatures, and pressures to form the binder and e~fact sand control.

U.S. 3,292,701 is viewed to be exemplary of the other closest prior art'reference type. It discloses fracturing an oil bearing formation by injectlon of an oxygen containing gas, and then increasing the temperature of the gas so as to coke oil present in the forma~ion to bond particles of the ~ormation ~ ",, ;

lZ~L032Z!

together, as a preferred embodiment. However, in Column 7, line 54 et al, it also discloses that the coke can a~so be produced by injection of "hot inert gases" under a pressure and rate adequate to fracture ~he incompetent form~tion and maintain the formation open during the deposition of the cokeO
Such, "inert gases" are de~ined to designate gases ha~ing an oxygen content below about one percent and are disclosed to be obtained by combustion of a carbonaceous material. Steam is not disclosed to be employed.

RE 26,466 and U.S. 3,250,328 disclose forming a fracture by applying heat and pressure by means of injecting a liquid phase reactant or oxidant which reacts exothermically with the oil in the adjacent formation. Examples of reactants include hydrogen peroxide, nitric oxide, sulfur trioxide, and the like.
However, there is no disclosure that sand is controlled upon subsequent production of oil or that the process would be useful to effect sand control or form a zone of consolidated permeable medium suitable ~or production of substan~ially sand free oil. Indeed, beginning on line 60 of Col~mn 5, it is stated that the method does not cause sufficient heat to even cause cracking or distillation of oil in the reservoir.

U.S. 3,4~,639 discloses consolida~ing unconsolidated sand in the region of a well bore (by sintering) by ! treatment with a plasma jet stream. While this process may be useful in many circumstances, it resembles the process of the invention only insofar as a consolidated sand zone is found near the w~ll bore.
This process of the invention avoids the use of special plasma jet equipment.
.

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U.S. 3,072,188 discloses conso]idating unconsoliclated sand in the reyion of a well bore by passing a fire front throu~h the region. In Colu~n 1, it is disclosed to be prior art to consolidate sand by heating the sand to coke oil in place to form a bond ~etween sand particles to form a structure of increased stability around the borehole of a well. Repeated passes of the fire front are disclosed to be useful to obtain the desired effectO The process of that patent resembles the process of this inYentiOn only in that the utîlity of a sheath of consolidated sand around a well bore for sand control is recognized, but no suggestion of the invention proçess steps for forming it are disclosed.

U.S. 3,974,877, U.SO 3,254,716, and U.S. 3,147,805 di~close forming a similar sheath by injection of steam and air or an oxygen containing gas in a controlled ratio to cause a low temeprature, controlled oxidation to occur and hydrocarbon coke like material to form. Field Exa~ple II of U.S. 3,97~,877 in Column 8 is exemplary of t~at process and the problem addressed. Fitzgerald et al, "Warm Air Coking Sand Consolidation-Field Results in Viscous 0il Sands", Journal of Petroleum Technoloyy, P 35-42, January, (196~, discloses a similar process.

U.S. 3,134,435 employs pyrophoric material and reverse combustion to form a permeable coke structure in a hydrocarbon containing formation. U.S. 3,182,722 also employs reverse in situ combustion to form consolidated zones for sand control.

U.S. 4,265,310, and references cited therein provide substantially more discussion involving heavy oil or tar sand reservoirs and methods of production there~rom.

6 12~ 32;~

German Offenlgungschrift 2,9~9,493 having an Offenlengungstag of 17th April 19~0, corresponds to .S~ 4,265,310. That patent discloses a ~ery advantageous ~ethod for economic recover~- of oil from such oil sand deposits. In particular, a method is very particularly described beginning in Column 21 ~or carryin~ out a mode of the process which is particularly advantageous in recovering tar from tar sand deposits. However, no disclos~re of prevention of sand production concurrent with oil production or of forming a consolidated permeable zone is made therein.

The process of the instant invention recovers t~r or oil from incompetent formations without concurrent production of substantial quantities of sand or other particulates. This invention relates to a new and unexpected result serendipitously discovered in further carrying out of one embodiment of the process described in V.S. 4,265,310 beginning in Column 21.
However, this invention is believed to have much more general applicability, in accordance with the disclosure and claims of this applicationO

Objects O The Invention An object of the invention is to provide a process for production of oil from an incompetent oil contain-ing for~ation wi~hout concurrent substantial production of particulates. In a more particular aspect, an object of the inven~ion is to provide a process for recovery of substantially sand free heavy bituminous oil or tar from an incompetent oil sand ~ormation wherein production is stimulated by injection of steam from an outlying well.

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- ~ 6)322 . - 7 -Summar~ Of The_Invention In a process for production of oil from an incompetent oil containing formation through a well bore, production of particulates concurrent with the oil is inhibited by: (a) first forming a zone of consolidated permeable medium extending from the well bore into the formation in a generally radial direction by injecting substantiall;~
oxygen free hot aqueous fluid into the formation from the well bore at a rate, temperature, and pressure suf-ficient to heat the zone to a temperature at least su~ficient to form coke binder therein from cok able oil therein, and then, (b) producing substantially particulate free oil through the thus formed consolidated permeable medium into the well bore from the incompetent oil con-taining formation.

In one a~pect, the incompetent oil containing formation is an unconsolidated oil sand formation, the hot aque~us fluid is steam, and the steam is injected into the well bore at a rate and pressure sufficient to reach a temperature in the zone of at least 450F.

According to another aspect, a horizontal hydraulic racture is formed into the oil sand formation rom the well bore prior to step (a), and then the zone o consolidated permeable medium is formed at a locus adjacent to the fracture.

In accord with another aspect, the steam is injected at a rate "Qs" expressed in cubic meters of water per day which is greater than or equal to 0.02174A/H
exp (0.02739XTERH), wherein A is the area to be substantially heated between the wells expressed in square meters, wherein H is the thickness of the reservoir to be substantially heated e~presse~ in meter~, and wherein TE~I is a rational positive member in the range of 40 to 100.

Brief Description Of The Drawin~s _ Fiy. 1 illustrates in semischematic fashion, a cutaway section of a tar sand reservoir in which a presentl~ pre-ferred mode of the invention is under way, employing an in~erted 5-spot configuration at a point n time following hydraulic fracturing and steam stimulation Of the left foreground well, and notching in preparation for hydraulic fracturing of the right foregrollnd well of the inverted 5spot.

Fig. 2 illustrates a semischematic cutaway cross section illustrating the process at a point in time followinq lS fracturing and steam stimulation of the outlying wells of the inverted S-spot to form coked sand production control zones.

Fig. 3 illustrates a semischematic cutaway cross section of the inverted 5~spot at a point in time in the process after the center well is fraced into fluid communication with the outlying wells and after conduction heating steam flooding is initiated through the ~racture system at a pressure sufficient to float the formation.

Fig. 4 illustrates a semischema~ic cutaway cross section ~5 of the inverted 5-spot at a point in time in the proces~
when conduction heating steam ~looding is well under way through the fracture system under pressure sufficient to float the formation, that is, to maintain the fractures in an open posi~ion. A zone of fluid mobility and increased hea~ is also shown progressing from the - center well to the outlyin~ wells.

2~32;~ ~
g Fi~. 5 illus~rates a semische~ati~: cutaway c~oss se~
of the inverted S-~pot at ~ point in time follc,wing establishment o-f the coked sand control zone and a zone of fluid mobility and incr~ased heat; and it illustra~s the beginning of sweeping of the heated zone of enhanced mobility by a matrix ~low steam flood progressing fro~
the injection well to the outlying production wells;
with sand control in the produc~ion wells by the coked sand control zone.

Descri~tlon Of The Dxawings Figs. 1 through 5 illustrate stages of one presently particularly preferred embodiment of the invention wherein sand fre~ tar is recovered from a subterranean tar sand containing formation, as is noted in the "Brief Description Of Drawings" section. Similar numbers are employed to refer to similar features in these Figs. 1 through 5.

Thus, referring to Fig. 1, terrain 1 comprisi~g over-burden 2 shown with break line 3 and overburden 4 lie over the tax sand formation 5 which is underlain stratum 6.

The overburden and tar sand formation 5 are vartically traversed by an inverted 5-spot pattern o~ well bores comprised of center injector well 7 and outlying pro-duction wells 8, 9, 10, and 11. Each well traversing the tar qand formation comprises casing 13 cemented to the formation by cement 12, and having tubing 14 com-municating to external facilities via outlet 21 through wellhead 20, and forming annulus 22 between the tubing and the well casing, which communicates to external faciIities through outlet 19. The wells are set through the tar sand formation and cemented to the underlying strata by cement 12 and 15.

L03Z2 ~ , According to a presently preferred mode now describ~d, each of the outlying production wells is first notched by rotating a h~draulic cu~ting tool to form notch 16 and then hydraulically fractured to fGrm horizontal hydraulic fracture 17. Well 9 is shown at completion o~ notching preparatory to hydraulic fracturing in Fig 1. Fracturing can be accomplished by either injecting an aqueous fluid through outlet 21 and tubing 14 or through outlet 19 and through annulus 22 into the n~tch previously formed. Well 8 is shown subsequent to injecting steam at a rate, temperature, and pressure sufficient to heat an adjacent zone to a temperature at least sufficient to form coke binder therein from cokeable oil therein and at a pressure sufficient to maintain parting of the hydxaulic fracture. A zone of consolidated permeable medium which is consolidated with coke binder therein, for short, the coked zone 18, is shown near well 8, and shows the extent of coked consol-idation of the tar sand formation by the steam treatment step. The heated zone 22, as shown near well 8, shows the extent of substantial heating of the tar sand formati by the steam treatment step. At ~he point in time shown in Fig. 1, well 8 has been fractured and steam txeated and shut in for a soak period. Well 9 has just been notched preparatory to hydraulic fracturing. Wells 10 and 11 are yet to be treated in sequence.

Fig. 2 illustrates the process emodimen~ at a point in time following treatment o the outlying production wells by hydraulic fracturing and st~am followed by perforation. Coked zone 18 is shown extending adjacent to the wells and perforations, as is heated zone 22.
Such extension along the well bore within the formation is effected by both conduction and by steam flow into ~L%~Il 322 the formation adjacent to th~ we~l b~re throuyh th~
perforations 24. Thu~, the coked zone protects the outlying well bores from sand production.

Fig. 3 illustrates the process embodiment at a point in time following notching and then hydraulically fracturing of the center well into communication with the outlyin~ production wells via horizontal ~racture 25. The outlying ~roduotiorl wells are back pressured as needed to distribute the hy~raulic horizontal fracture over the pattern covered by the inverted 5-spot. Also, ko arrive at the stage shown in Fig. 3, s~eam is immed-iately injected ;nto a horizontal hydraulic ~racture either through outlet 21 or ou~let 19 or both of the injection well 7 and through the fracture system at a sufficiiently hiyh rate, at a sufficient pressure, and for a sufficient time to float the formation along at least a major part of the fracture system between the wells formed by hydraulically fracturing the center injection well and the outlying production wells, to form coked zone 18 as shown adjacent to well 7 and adjacent to fracture 25 and 17, as shown in Fig. 3, further to effect channel flow of liquids ~hxough the floated fracture formation, and to effect conduction heating of substantial reservoir volume vertically ~5 perpendicular to the channel flow, as shown in Fig. 3.
.
Per~orations 24 are made in ~he casing and cement o the prodùction wells, as with a conventional perforation gun o~
~etting tool. Fluids are produced from the production wells. Back pressure is held on the production wells as needed to distribute ~he flow evenl~ oYer the pattern as fluids are produced from the corner production wells.

FigO 4 illustrates the process embodiment at a point in time after which steam at high rates and pressures has been injected through injection well 7 for a period of ~2~ 32~ ( " ~ j .

time. Zone 22 is conduction heated by steam passing from injection well 7 through the floated horizontal fracture system 17 and 25 toward pxoduction wells 8, 9, 10, and 11. Some fluid flow is ~eginning to occur in this zone 22 as well as in more intensely heated zone 23 outside of the coked zone 18. At thi.s point, the fracture system 17 and 25 is filled with steam and som~ mobilized-tar and condensate out to the point indicated by the leading edge of zone 23. From that point on through the fracture system channel, the makeup of the moving fluids graduates ~o higher proportions of pxoduced tar and condensate as ~he steam gives up its heat and condenses. Though there is matrix flow and interchange of fluids between the frac~ure channel and adjacent heated matrix, fluid flow i8 predominately through the floated fracture channel, as illustrated.
Of course, it is to ~e understood that the zones in the reservoir do not have the regularity and sharply defined limits shown in the drawinys, which represent an idealized ~o description for the sake o illustration and clarity.

Fig. 5 illustrates the process at a time well advanced into the high rate steam injection step. Fluids pass as generally shown by the arrows through the floated channel and adjacent thereto effecting conduction heating of the formation as generally shown by zones 22 and 23, and both hot tar and hot water are produced from the production wells by interchange of 1uids from the fracture channel into the more stron~ly heated zone 23 and, to a lesser extent into the less heated zone 22. Back pressure is held on the production wells sufficient to maintain the,racture system in the floated or parted position, at least until the tar near the fracture communication channel is sufficiently heated to permit free communication of fluids between the injection well and the production wells.

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., As can be seen from Fig. 5, the coked zone 18 protects the production wells from sand production.

As injection rates of steam and reservoir pressures are decreased, allowing collapse of the fracture system, the production wells continue to be protected from sand production by the coked zone 18.

Preferred Embodiments of The Invention Some presently preferred embodiments of the invention have been particularly described in the preceding section in connection with the Detailed Description of The Drawings. Other presently preferred modes are hereinafter described and further elaboration is provided.

An example of a successful demonstration of the process of the invention is described in SPE Paper 10707 entitled "The Street ~anch Pilot Test of Fracture Assisted Steam Flood Technology" by two of the inven-tors and others.
That paper was presented at the 1982 California regional meeting of the Society of Petroleum Engineers held in San Fxancisco, California March 2~~26, 1982.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
Claim 1: In a process for production of oil from an incompetent oil containing formation through a well bore; the improvement comprising inhibiting production of particulates concurrent with the oil by:

(a) first forming a zone of consolidated permeable medium extending from the well bore into the formation in a generally radial direction by injecting substantially oxygen free hot aqueous fluid into the formation from the well bore at a rate, temperature, and pressure sufficient to heat the zone to a temperature at least sufficient to form coke binder therein from cokeable oil therein, and then, (b) producing substantially particulate free oil through the thus formed consolidated permeable medium into the well bore from the incompetent oil containing formation.

Claim 2: The process of Claim 1 wherein the incompetent oil containing formation is an unconsolidated oil sand formation wherein the hot aqueous fluid is steam, and wherein the steam is injected into the well bore at a rate and pressure sufficient to reach a temperature in the zone of at least 450°F.

Claim 3: The process of Claim 2 wherein the oil is an asphaltic heavy oil or tar.

Claim 4: The process of Claim 2 wherein a fracture is formed into the oil sand formation from the well bore prior to step (a) and then the zone of consolidated permeable medium is formed at a locus adjacent to the fracture.

Claim 5: The process of Claim 4 wherein the fracture is a horizontal hydraulic fracture extending radially into the oil sand formation from the well bore.

Claim 6: The process of Claim 5 wherein the oil is an asphaltic heavy oil or tar.

Claim 7: The process of Claim 5 wherein the particulate free oil is produced through the consolidated permeable medium into the well bore by means of injecting a hot aqueous fluid into a second outlying well bore.

Claim 8: The process of Claim 7 wherein the oil is an asphaltic heavy oil or tar.

Claim 9: A process for production of substantially sand free oil from a well bore penetrating an unconsolidated oil sand formation comprising:

(a) first injecting substantially oxygen free hot aqueous fluid into the formation from the well bore at a sufficient temperature, rate, and pressure to heat the zone to a temperature of at least about 450° F such as to form a permeable consolidated sand filter medium in the zone, and then (b) producing substantially sand free oil from the oil sand formation into the well bore through the medium.

Claim 10: The process of Claim 9 wherein a fracture is formed into the oil sand formation from the well bore prior to step (a), and then the permeable consolidated sand filter medium is formed at a locus adjacent to the fracture.

Claim 11: The process of Claim 10 wherein the fracture is a horizontal hydraulic fracture extending radially into the oil sand formation from the well bore.

Claim 12: The process of Claim 11 wherein the oil is an asphaltic heavy oil or tar.

Claim 13: The process of Claim 12 wherein the sand free oil is produced through the permeable consolidated sand filter medium into the well bore by means of injecting a hot aqueous fluid into a second outlying well bore.

Claim 14: The process of Claim 13 wherein a horizontal hydraulic fracture is established between the outlying injection well and the production well, steam is injected into the injection well, and fluids are produced from the production well; the steam being injected into the outlying injection well at a very high rate, at a sufficient pressure, and for a sufficient time, while simultaneously producing substantially sand free fluids from the production well such as to: maintain parting of the formation along the fracture system between the wells, to effect channel flow of liquids through the parted fracture system between the wells, and to effect conduction heating of substantial reservoir volume perpendicular to the channel flow between the wells: wherein the steam is injected at a rate "Qs" expressed in cubic meters of water per day which is greater than or equal to 0.02174 A/h exp (0.02739 X TERH), wherein A is the area to be substantially heated between the wells expressed in square meters, wherein h is the thickness of the reservoir to be substantially heated expressed in meters, and wherein TERH is a rational positive number in the range of 40 to 100.