US3815678A - Hydrocarbon sweep process - Google Patents

Abstract

This invention relates to a process for freeing hydrocarbons, especially heavy or immobile hydrocarbons (such as undriven hydrocarbons, for example those of high viscosity and gravity), from underground formations. More particularly, this invention relates to a process for bringing to the earth''s surface hydrocarbons trapped in an underground formation, as, for example, hydrocarbons remaining in the formation after primary recovery therefrom, and even after a water-flooding process has been accomplished in said formation, as a result of introduction into the formation of hot water at a point or points downstream from the producing well or wells.

Description

United States Patent Terry et al.

[ 1 June 11, 1974 HYDROCARBON SWEEP PROCESS [75] Inventors: Ruel C. Terry, Morristown, N.J.;

John A. Sutherland, Houston, Tex.

[73] Assignee: Allied Chemical Corporation, New

York, NY.

[22] Filed: Sept. 7, 1971 [21] Appl. No.: 177,978

[52] US. Cl. 166/272 [51] Int. Cl E2lb 43/24 [58] Field of Search 166/245, 272, 303

[56] References Cited UNITED STATES PATENTS 1,237,139 8/1917 Yeomans 166/272 X 3,276,518 10/1966 Schlicht [66/272 3,332,485 7/1967 Colburn 166/245 3,386,508 6/1968 Bielstein 166/272 3,500,915 3/1970 Fitzgerald 166/272 Primary Examiner-Robert L. Wolfe Attorney, Agent, or Firm-Patrick L. Henry; Jonathan Plaut [57] ABSTRACT This invention relates to a process for freeing hydrocarbons, especially heavy or immobile hydrocarbons (such as undriven hydrocarbons, for example those of high viscosity and gravity), from underground formations. More particularly, this invention relates to a process for bringing to the earths surface hydrocarbons trapped in an underground formation, as, for example, hydrocarbons remaining in the formation after primary recovery therefrom, and even after a waterflooding process has been accomplished in said formation, as a result of introduction into the formation of hot water at a point or points downstream from the producing well or wells.

4 Claims, 3 Drawing Figures PATENTEDJUN 11 197.4 313 1567 FIG. 1 3

o o o o o o IY o o o o o o O O 0 FIG. 2

11- o o o o o o RUEL c. TERRY JOHN A; 'SUTHERLAND INVENTORS.

HYDROCARBON SWEEP PROCESS BRIEF DESCRIPTION OF THE PRIOR ART The introduction of heat into a formation is well known in the prior art as a means of lowering the viscosity of hydrocarbons found within the formation in order to bring them to the surface. Such processes include the introduction of steam, as disclosed, for example, in US. Pat. No. 2,412,765, and the introduction of hot water into the formation, as disclosed, for example, in US. Pat. No. 3,465,826. Furthermore, it is known in the prior art to introduce a heating medium to lower the viscosity of the'hydrocarbon found in the formation into one well and to remove the hydrocarbon from another well removed from the first, as disclosed, for example, in US. Pat. No. 3,193,009.

However, none of the patents or processes of the prior art teach a process for treating wells in which primary recovery has been economically concluded, taking advantage-of the paths opened by that first recovery, and perhaps a water flood treatment, to continuously introduce heat to the producing formation and produce hydrocarbons from a second point of exit updip (in the incline of the producing formation, closer to the surface) from the previously producing well.

It is to accomplish production of hydrocarbons in such situations as just previously described that the processes of this invention have been devised. The invention will become more apparent with relation to the following description.

BRIEF DESCRIPTION OF THE INVENTION Generally, the invention relates to a process in which, preferably, hot water, or other hot liquid medium, is introduced into a formation below the point of the previously or at the time producing well. The formation is one in which at least primary recovery has occurred. That is, the first 25 percent, or whatever percentage of hydrocarbons are freed from the well during the first period of recovery, has taken place. Characteristically, production of hydrocarbons'from the well has declined as the period of primary recoverycomes to an economic end. i

In some cases, the formation in which the well just disclosed has been producing has been water-flooded. That is, cold or ambient water has been pumped through the formation in an attempt to increase productivity.

In any case, as a result of pimary recovery and/or water-flooding, channels of movement for the injected liquid and the hydrocarbons are found in the formation.

According to the invention, hot water, i.e., water in the temperature range of 300 to 700F., for example, is pumped down into the formation through a well located below (i.e., downdip of) the producing well. At a point updip of the producing well, even-hotter water is introduced into the formation, such water being in the temperature range of 400 to 8 5 QF., for example (higher temperatures required as you go deeper so there is a differential between injection and producing temperature), but in any event at a temperature hotter than that introduced at the lower point.

Hydrocarbons are removed at the point of production. Preferably a bleed well is located below (i.e., downdip of) the lowest or first point of introduction to remove excess water, and maintain a constant injection pressure.

According to the invention, the sweep of the hot water introduced at the first-mentioned well downdip of the producing well will be through the channels already found in the formation toward the point of greater heat updip therefrom. Heat introduced into the formation and the increased pressure found in the formation as a result of entry of water therein will lower the viscosity of'the hydrocarbons and free them, thus allowing them to be floated along by the movement of the hot water toward the point of egress. Since much of the hydrocarbon is disposed between individual sand particles in such formations, the movement of the water against each particle and the increased pressure, which causes a hydraulic gradient and fracturing, in addition to supplying the necessary heat, will result in a freeing of a substantial part of the hydrocarbons still trapped in the formation, perhaps as much as percent or more in some cases.

Still generally, as applied to the usual formation, the hot water is inserted at injection points at the lowest (downdip) pointof production in the formation theretofore. The next level of wells found updip therefrom is then used as the producing wells, with wells still one further level updip being the points of hotest water injection, as discussed. Because of the channeling already found in the formation from primary recovery and water-flooding, if it has been performed, the hydrocarbons freed by the injection of the hot water, the increase in pressure in the formation and the sweep of the water, will move updip toward the producing wells. When this series of producing wells is economically played out from its thus stimulated production, the process will be continued updip, by using the just described producing wells as the downdip injection wells, the wells of highest temperature as the new producing wells and the next series of wells as the new wells of highest temperature. Wells downdip may be used as excess pressure bleed wells. This process will thus continue progressing updip until the formation has been completely swept.

Now that the invention has been discussed in general terms, it will be discussed in more detail with reference to the following drawings.

FIG. 1 is a schematic showing ofthe invention with relation to an underground formation and individual wells for injection of hot liquid into the removal of liquids from the formation; and

FIGS. land 3 are embodiments showing the particular well pattern for applying the invention.

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1, a typical formation is shown wherein the trapping fault occurs, say along line AA. The oil or gas producing zone B in the formation has been operated for primary production previously through well 3, shown schematically. It is proposed to introduce downdip from the well 3 into a second well 4 hot water in the ing well 3 is found a second hot water injection well 5,

the water introduced into well 5 being hotter than that 3 introduced into well 4, say 400 to 850F., for example, once more depending on formation depth and conditrons.

The introduction of hot water into the formation at 4 and 5 results in a heating up of the formation and an increase in the pressure therein to lower the viscosity of the hydrocarbon to be produced and increase the pressure to free it from its immobile position so that greater amounts will flow up the producing well 3. Since the formation has already undergone primary recovery, and possibly even water-flooding, through channels of movement already established through which the hot water and the hydrocarbons will flow to the producing well 3.

A bleed well 6 may be introduced downdip from the two hot water sources (4), in order to remove excess water, if necessary. The increase of pressure as a result of the introduction of the water in the formation may also result in subsidiary, cracking of the formation, i.e., opening up further or clearing out of channels for greater hydrocarbon flow. Where pressures become too great, however, the bleed well 5 may be used to reduce the pressure situation.

The normal application of this invention may best be seen with relation to the well patterns in the typical field shown in FIGS. 2 and 3.

During the period of primary recovery, wells would have first been drilled typically at a higher depth in the formation B, and then at lower depths. Those lower depth wells are identified by I in FIG. 2 and are at a depth shown ml in FIG. 3. Further wells would have typically been drilled, for example, at II, III and IV, moving across the field laterally and updip. Primary hydrocarbon production would have occurred from such wells, with perhaps as much as 25 percent of the available hydrocarbons in the field produced.

Typically, water-flooding of the field might then have been undertaken to stimulate further recovery. Generally, the water would first be introduced at the depth of the wells downdip, i.e., at the wells labelled I, with pro- I, which are equivalent to the well 4 shown in FIG. 1. Hydrocarbons are produced through the producing wells at H, which are equivalent to the producing well in FIG. 1 indicated at 3. Hot water is further introduced updip from the producing wells at II through the wells at III, which are equivalent to the injection well 5 in FIG. 1. The downdip bleed well or series of wells may again be included. Movement of the hot water from the I wells to the wells at III, the added heat to lower the viscosity of the hydrocarbons in the formation, and the increased pressure in the formation result in a sweeping of immobile hydrocarbons out the producing wells at II.

It is contemplated that the introduction of the hot water and the removal of the hydrocarbons will be simultaneous and continuous after the preliminary buildup period of hot water and therefore heating of the formation is accomplished. Rather than introduce the hot water at all the wells of levels I and III and produce through all the wells at II, certain of the wells may be selected which from their. previous production histories would seem to be near the greatest areas of immobile hydrocarbons remaining in the formation. Furthermore, of course, where the wells do not lie in the pattern shown in FIGS. 2 and 3, additional well or wells may have to be dug in order to complete the desired ering through the wells of III. In this way the whole field duction had through the wells updip from those first 1 wells and at the level of II. When the wells at II watered out, i.e., started producing substantially all water or at least hydrocarbons at an uneconomic rate, the same water-flooding technique would have been had with the injection point being the wells at II and the production point of the wells updip at III. This technique of waterflooding would, perhaps, have been had across the whole field.

Applicants invention, as already discussed, involves the tapping of the field after it has substantially undergone economic primary production and, in some instances, water-flooding, and directing the hot water in the formation in the manner previously described to stimulate further economic recovery of hydrocarbons. The channels for movement of the hot water and the hydrocarbons are also established in the formation. The hydrocarbons that have not been removed are either of high viscosity or are otherwise rendered immobile within the formation. By introducing hot water thereinto. The viscosity of the hydrocarbons is lowered, the pressure within the formation is raised, as discussed, and the sweeping movement of the water all combine to free immobile hydrocarbons found in the formation. I

Specifically, in the field diagramatically illustrated in FIG. 2, hot water would be introduced into the wells at may be swept of a substantial portion of its insitu hydrocarbons.

We claim:

1. Method for stimulating a hydrocarbon producing field having a plurality of separate wells including producing wells extending into different areas of the field, comprising the steps of l injecting hot water through at least one of said wells into an area downdip of at least one producing well, (2) injecting relatively hotter water through at least one of said wells into an area updip of said at least one producing well, (3) flowing said hot water from said first injection area toward said second substantially through channels in the formation already existent as a result of earlier field production, (4) removing hydrocarbon from said at least one producing well, and repeating the steps set forth above with the at least one of said wells updip of said producing well being the at least one producing well, said at least one producing well being the at least one of said wells downdip of said last-mentioned producing well for injection of hot. water, and injecting relatively hotter into the field by at least one well further updip from the last-mentioned producing well.

2. A method as claimed in claim 1, further comprising removing water from said formation downdip of said first-mentioned area of injection.

3. A method as claimed in claim 1, said water at said first area of injection being in the range of about 300 to about 700F.

4. A method as claimed in claim 3, said water at said second area of injection being in the range of about 400 to about 850F.

Claims (3)

1. 2. A method as claimed in claim 1, further comprising removing water from said formation downdip of said first-mentioned area of injection.
2. 3. A method as claimed in claim 1, said water at said first area of injection being in the range of about 300* to about 700*F.
3. 4. A method as claimed in claim 3, said water at said second area of injection being in the range of about 400* to about 850*F.

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