DE1483772B - Process for the extraction of oil from an oil-bearing subterranean formation - Google Patents

Description

The invention relates to a method for extracting oil from an oil-containing underground formation, in the case of the flooding water through an introduction device, the at least one introduction borehole includes, is introduced into the formation and oil by a production facility that is at least a production well leading into the formation from which formation is produced.

The petroleum found in underground deposits, usually also as crude oil or simply as Oil, called production wells, is extracted from the reservoir through probes or boreholes are designated and are brought into the underground formations, mined and extracted. A large amount of the oil remains in the underground reservoirs when production or promotion is only carried out through primary extraction, d. H. if only the original Reservoir energy is used to extract the oil. When the original reservoir energy is insufficient or has been exhausted, supplementary measures are often used as secondary recovery measures are referred to, applied. Among the most successful and widely used Measures of this type becomes a medium through introductory devices, which one or more Introductory wells include, introduced, and directed into the formation. This causes oil in the Formation displaced, moved through the formation and out of production or production facilities that comprise one or more production wells, produced when the introduced medium is removed from the Introductory facilities to the production facilities flows. In a special extraction method of this type, water is used as the injection medium is used, and reservoir treatment is accordingly referred to as water flooding. The introduced Water is referred to as flooding liquid or flooding water to distinguish it from the formation or reservoir water already in the reservoir.

Flooding is a very useful extraction method, but it has two main features Disadvantages on. The first is their relatively poor microscopic displacement of the oil the cavities or pores of the subterranean formation. The microscopic displacement can be called microscopic flushing efficiency can be expressed; this is defined, in percent, as the ratio the amount of oil from the pore space of the portion through which the flooding liquid flows the formation has been displaced to the amount of oil originally located therein. The proportionate poor microscopic displacement is due to the immiscibility of the water; H. the Flooding fluid, with the oil it tries to displace. There is a relatively high one Interfacial tension between the water and the oil and, in some cases, an unfavorable one Contact angle of the interface between the two liquids with the solid surface. When the flooding fluid is miscible with the formation oil, d. H. with a mixable flooding, step these conditions do not apply. Accordingly, conventional water flooding does not lead to such high microscopic rinsing efficiency like a mixable flooding. It is generally to be admitted that a miscible flooding - although they have other disadvantages in special formations can - leads to the greatest microscopic flushing efficiency for any given Formation is possible.

The second disadvantage is known as premature breakthrough. The early breakthrough is promotion of the water introduced at the production well before that from inside the formation in the area Oil displaced before the flooding was produced. Premature breakthrough reduces the macroscopic or surface flushing efficiency of the water flooding in relation to the degree of Prematurity. The main reasons for premature breakthrough are permeability layers and the Tendency of the more agile flood water to form "fingers" through a subterranean formation, which contains less mobile oil, and thereby surrounds considerable proportions of the oil. Under Fingering is the development of inconsistent bulges or veins in the flooding front too understand which are advancing to the production facilities faster than the rest of the flooding front. Fingering leads to uneven insertion and uneven flow profiles.

The object of the invention is to create a method for improving the microscopic flushing efficiency a water flood used to extract oil from an underground reservoir is applied.

The invention provides a method for carrying out a water flooding, in which a microscopic Flushing efficiency is achieved that comes close to that of a mixable flooding. Another one Feature of the method according to the invention is that a premature breakthrough a Water flooding is avoided or reduced.

According to the invention is a method of extracting oil from an oil-containing underground Formation provided in the flood water through an introduction device, which at least an introduction well into which formation is introduced and oil from a production facility; which comprises at least one production well leading into the formation is produced, and which is characterized in that one of the following Introduces sufficient aqueous solution under such conditions into the formation and therein lets flow that its dimensionless displacement number

is during flow through a substantial portion of the formation at least 2 x 10 ~ ^5, wherein in the formula

₄ u _{s is} the viscosity of the aqueous solution (poise),

V _{s is} the Darcy speed of the aqueous solution (cm / sec) and

σ ₀ _ _{s is} the interfacial tension between the aqueous solution and oil with which the solution comes into contact in the formation (dynes / cm)

means and the specified dimensions for the flow parameters of one of the systems of suitable units represent.

The displacement number is a pure number and has no dimension. Accordingly, the units in which μ ₈ , V _s and ς ₀ _ _{s are} expressed must correspond to one another so that they do not cancel one another out. Suitable units for the links are, for example, the following:

μ _$ = poisen or g / cm see,
V _s = cm / sec and
o ₀ _ s - dynes / cm or g / sec ² .

According to the invention that the production of oil is improved when an aqueous solution is passed under such conditions through a formation that its displacement speed is at least 2 ■ 10 ~ ⁵ was found. When the aqueous solution flows through the formation under the aforementioned conditions, improved microscopic flushing efficiency is achieved. Obviously, the flow of the aqueous solution under these conditions causes a greater displacement of the oil in the voids or interstices of the formation. Furthermore, if a displacement number of at least 2 · 10 -4 ^{s is maintained} , in particular as a result of an increase in the viscosity of the aqueous solution in the manner explained below, premature breakthrough is prevented or reduced.

Flooding examples can be found in the literature in which numerical values for the three flow parameters a _o . _s , μ ₃ and V _{s have been} specified so that the associated value for the displacement number N _{d can be} calculated for these cases:

(1) J. K. Jordan, W. M. McCardell and R. C. Ho co tt, "Effect of Rate on Oil Recovery by Water Flooding "in" Oil an Gas Journ. ", Vol. 55 (1957), pp. 98 to 130.

^{The displacement figures 1.78 · ΙΟ- 8} , 2.54 · ΙΟ- ⁹ and 1.86 · 10 " ^{8 are} calculated from the flooding examples in this publication.

(2) F. M. Perkins, “An Investigation of the Role of Capillary Forces in Laboratory Water Floods ", Trans. AIME, Vol. 210 (1957), pp. 409-411.

^{A displacement number of 1.05 · 10 ~ 9 is} calculated from the flow parameters of the flooding example given in this work.

In the examples given, the displacement number lies between the values 1 · 10 ~ ⁹ and 2 · 10 ~ ⁸ . The present invention required minimum value of 2 × 10 ^-5 for the displacement speed is so even approached in any case, bearing in mind that it is in both publications to works that deal specifically with the optimal flow rate within the deposit.

When the aqueous solution is passed through the formation under conditions that their displacement number is greater than 2 x 10 ^-5, and the microscopic Ausspülwirkungsgrad is correspondingly greater. When flowing under conditions that the displacement number of the solution is as high as 3 × 10 ^-3 , the aqueous solution achieves a microscopic rinsing efficiency which is equal to or close to that of a medium which is miscible with the reservoir oil. Accordingly, it is preferred to flow the aqueous solution through the formation under conditions such that its displacement is at least 3 x 10 ^-3 . It is also possible to work with even higher displacement numbers. Usually, however, the increased cost of achieving a displacement number ^{substantially in excess of 3 x 10 -3} does not result in a comparable or adequate increase in microscopic rinse efficiency.

The invention is explained in further detail below.

ίο F i g. I is a top plan view of a 5 point pattern and illustrates in a schematic manner an embodiment of the invention;

F i g. II is a plan view of an arrangement for line ejection and explains a further embodiment the invention;

F i g. III is a cross section showing schematically the contact angle of the interface between Oil and water with a surface that is preferably water-wettable is illustrated.

The desired displacement number is achieved through mutual regulation of the three variables, each taking into account the others given in the above definition equation (1) of the displacement number. The creation of a desired viscosity of the aqueous solution is carried out by using a densifying agent for the water used in the aqueous solution. The creation of a desired interfacial tension between the aqueous solution and the reservoir oil is carried out by applying a surface-active one Agent in the aqueous solution. For any given viscosity and any given Interfacial tension of the aqueous solution can control the desired displacement number the rate at which the aqueous solution is passed through the formation can be achieved.

In practicing the invention, a

Minimum displacement selected that the flooding aqueous solution should have under normal operating conditions during the water flooding. The selection is made from the viewpoint that the displacement speed should be at least 2 ■ 10 ~ ^5, and preferably at least 3 × ^10-3. Then a range of Darcy velocities is determined that can be achieved during the water flooding. In particular, the highest minimum or minimum Darcy speed V _s that is achieved is selected. Darcy velocity is the velocity Q / A of the aqueous solution according to the Darcy equation of flow through porous media, where Q is the volumetric rate of introduction and A is the area perpendicular to the direction of flow at the point where the Darcy velocity V _{s to be} obtained means.

Since the actual flow occurs only through the pore space and not through the entire area A , the Darcy velocity V _{s is} less than the actual media velocity. Darcy speed is sometimes referred to as macroscopic speed or apparent speed. For a discussion of Darcy velocity from the point of view of macroscopic velocity, for both radial or cylindrical and spherical development, see the publication by John C. Cairboun, Jr., Fundamentals of Reservoir Engineering, J University of Oklahoma Press , Norman, Oklahoma (1955), pp. 75 ff.

The minimum darcy velocity can be selected after a calculation or estimate based on a general engineering comparison of the particular formation with other subterranean formations. In most subterranean formations, introduction of water at an introduction pressure at or near the pressure at which the formation ruptures will result in normal wellbore patterns such as those shown in FIGS. Illustrated I and II, minimum Darcy velocities in the range of about 3.5 x 10 ^-5 to about 3.5 x 10 ~ ⁴ cm / sec. By comparing the measurements of pressure decrease or build-up obtained in the course of normal surveys of wells drilled in the subterranean formation under consideration with similar values from other subterranean formations, a Minimum Darcy Speed can be estimated within this range.

Greater accuracy in choosing the highest attainable minimum Darcy velocity can be obtained by determining the maximum rate of introduction Q and dividing by the maximum area A that the expanding body of the aqueous solution will reach.

Any of the known methods of determining the maximum rate of introduction can be used. For example, the maximum induction rate can be calculated from an extrapolation of the pressure decrease or pressure build-up values obtained during normal testing of the wellbore designated as an induction well. Alternatively, a more accurate determination of Q can be made by empirically determining the sustained introduction rate of the aqueous solution or, as a satisfactory approximation, water which produces an introduction pressure closely approximating the pressure causing excessive rupture of the oil bearing formation.

The maximum rate of introduction can be achieved by localized cracking around the introduction borehole increase. On the other hand, the creation of larger fracture channels leads to a non-uniform Introductory profile; cracking to such an extent that connecting cracks or breaks cannot be generated between an introduction well and a production well be tolerated. Any localized cracking should be completed before empirical Values of the type set out above are determined for determining the maximum introduction rate will.

The area A of the expanding body of the aqueous solution is initially very small, peaks in an area slightly beyond the midpoint between the introduction well and the production well and then begins to decrease again when the developing flood front from an expanding sphere or expanding cylinder due to the strong pressure gradients in the vicinity of the production well. Area A can be calculated using standard engineering techniques for evaluating reservoirs for the particular borehole pattern to be applied and then used to calculate both the range of Darcy velocities and, in particular, the highest attainable minimum Darcy velocity.

Then an aqueous solution is chosen so that the ratio of its viscosity to its interfacial tension with the reservoir oil, taken in conjunction with the selected Darcy velocities, the selected displacement number results. For example, any aqueous solution is chosen at which the ratio of their viscosity to theirs

ίο interfacial tension with the oil reservoir at least in the range from 0.057 to 0.57 is, depending on a selected minimum-Darcy velocity within the range of 3.5 x 10 ^-5 to 3.5 x 10 ~ ^4, as mentioned above, to to achieve a displacement number of at least 2 · 10 ~~ ^5. Preferably, however, the aqueous solution selected should have a ratio of its viscosity to its interfacial tension with the reservoir oil in the range from 8.5 to 58.7, again depending on the selected minimum Darcy rate, by a displacement number of at least 3 · 10 ^-3 to reach.

Except for a ratio of their viscosity to their interfacial tension in the desired range the aqueous solution chosen should preferably have a viscosity suitable for flowing in the subterranean The formation is deep enough, but on the other hand is also high enough to allow its agility on one Value no greater than restricting the mobility of the oil in the subterranean formation.

The mobility of the aqueous solution and the mobility of the oil in a particular formation are related to one another with their corresponding viscosities according to the mobility equation below in relationship:

M ₀

K ₀

herein means

M _{s is} the mobility of the aqueous solution in the formation,

M _{0 is} the mobility of the oil in the formation, μ _{0 is} the viscosity of the oil,
μ _{3 is} the viscosity of the aqueous solution,

K _{s is} the relative permeability of the formation to the aqueous solution in the presence of any oil remaining after passage through the aqueous solution,

and

K _{0 is} the relative permeability of the formation for the oil in the presence of the formation's own water

As is apparent from the equation (2), the mobility of the aqueous solution is increased by increasing it the viscosity of the aqueous solution is reduced. If the mobility of the aqueous solution is not greater than that of the oil in the formation becomes a favorable condition called stability of flow is achieved. This stability of the flow reduces the formation of fingers to a very low level and prevents or diminishes premature breakthrough. It causes the oil that has been displaced from the formation by the aqueous solution at the same rate how the aqueous solution flows through the formation.

Accordingly, maximum oil recovery is achieved for any given displacement.

In the case of the aqueous solutions used as flooding liquid in the method according to the invention it can be Newtonian fluids, shear hardening fluids, or shear thinning fluids Trade liquids. A Newtonian fluid has a viscosity that is not of depends on the rate of shear. A shear hardening liquid, on the other hand, has a range of Shear rates in which the viscosity increases with increasing shear rate. Conversely, has a shear-thinning fluid has a range of shear rates in which the viscosity increases with Rate of shear decreases. Accordingly, there is a determination in the selection of the aqueous solution their viscosity under flow conditions in the underground reservoir is very significant.

Any known method can be used to make this determination. For example, viscosity can be calculated using Darcy's equation for flow through porous Media from the pressure differential that for a given flow rate through one withdrawn from the formation Core sample is required to be calculated. The other hand is usually from the practical point of view a technical approximation of the viscosity of an aqueous solution under flow conditions in the Formation satisfactory.

An engineering approximation of the viscosity of an aqueous solution under flow conditions in the formation can be made with the aid of a Couette-type viscometer using concentric cylinders with relative rotation with respect to one another. With such a viscometer, the rate of shear can be regulated. To simulate the low shear rate encountered at Minimum Darcy Velocity, the shear rate used when measuring viscosity should be low. For example, if a Brookfield Synchro-Lectic LVT Couette-type viscometer is used using concentric cylinders with outer and inner radii of 1.2573 and 1.3805 cm, respectively, the shear rate should be between 0.1 and 10 sec ^ Be ^1. In most cases a suitable rate of shear for determining the viscosity of the aqueous solution is that obtained at 1 sec " ¹ .

The same applies to the choice of the aqueous solution to be used as the flooding liquid a measurement of their interfacial tension with formation oil is very important. It can be any known one Method for measuring the interfacial tension can be applied. When the interfacial tension is low, the method using a modified dropper without a handle is suitable or approach is used. The modified handle-less dropper is a conventional handle-less dropper, except that an appropriately calibrated optical magnifier is used to measure the dimensions of the small droplets that form at low interfacial tensions. In the Carrying out measurements of the interfacial tension must take into account that the Interfacial tension of an aqueous solution with oil approaches an equilibrium value with the lapse of time. When performing these measurements, care must therefore be taken that the equilibrium value has been achieved.

The aqueous solution, taking into account its viscosity and its interfacial tension with the oil in the formation to produce the desired displacement in the range of achievable Darcy velocities is introduced into the formation. The adoption rate is controlled so that the Darcy speed of the aqueous solution on passage through the formation to the production facility is large enough to produce the desired displacement to achieve. For each part of the formation between the introduction facility and the production facility in the flow path of the aqueous solution, where the desired displacement number is reached, is achieved an improvement in oil recovery. However, it is about the greatest possible improvement in oil production To achieve otherwise under the same conditions, the aqueous solution should preferably be allowed to flow under such conditions that the desired displacement number for the reached the entire distance between the introduction facilities and the production facilities will. On the other hand, in some cases such operating conditions can also exist that an achievement the desired displacement number for the entire route is not practical. In any case the aqueous solution should travel a substantial part of the distance between the introduction well and the production well at the desired displacement along the flow path of the aqueous Solution can be passed through the formation.

The term "considerable part" as it precedes it used is to be understood in the usual sense. Accordingly, it designates a part of the Formation large enough to have a significant impact on the total amount of drainage from the formation to have extracted oil. This part of the formation is to be distinguished from the part of the formation which surrounds an introductory borehole at a distance of a few feet or meters and which is not an adequate one Size has to have some significant effect on the total amount of out of the formation to have extracted oil. Although high Darcy velocities and accordingly high displacement numbers achievable in these few feet or meters due to high local pressure gradients these represent a few feet or meters in general less than 1% of the distance along the flow path of the aqueous solution from the introducer to the production facility and contain less than about 1% of the oil in one technical oil well pattern. In contrast, the term "considerable part" denotes greater than about 10% of the distance along the flow path of the aqueous solution from the introducer to the production facility.

The aqueous solution can be introduced into the formation in a volume sufficient that it covers the entire flow path between the introduction facilities and the production facilities occupies. For economic reasons, however, a smaller amount of the aqueous Solution can be used. In addition, a smaller amount of the aqueous solution is desirable, since the pressure required to produce the aqueous solution at the required Darcy speed

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to pass through the formation in an amount sufficient to take up the entire flow path between the introduction facility and the production facility sufficient, may be excessively high. Accordingly the aqueous solution can be introduced into the formation in the form of a buffer and this buffer by a propellant medium, e.g. B. common flood water, through the formation to the production facility to be driven.

As the aqueous solution buffer flows through the formation, it tends to spread or Dispersion by leaving parts of it in the formation and not with the rest of the buffer advance through the formation. Although the use of any size buffer improved Brings about oil extraction, maximum extraction is achieved under otherwise identical conditions, if the buffer is of such a size that it can be removed from the introducers through the formation goes as far as the production facilities without being completely dispersed or dispersed. When the buffer has a volume equal to at least 1% of the pore volume of the formation in the flow path between the introductory facility and the production facility, it will normally retain their uniform character. However, it is preferred that the volume of the buffer be about 5% of the pore volume of the formation. If desired, the volume of the buffer can be also be bigger. Usually, however, the volume of the buffer does not need to be greater than about To be 20% of the pore volume of the formation.

The use of a buffer of the aqueous solution followed by a propellant medium is also useful from the standpoint of reducing the pressure required on the introducer to maintain the desired Dancy velocity of the aqueous solution as it travels through the subterranean formation to the production facility is allowed to flow. The pressure drop Δ P ₃ through a formatoin, which is caused by the flow of a buffer of the aqueous solution, is proportional to the product of the viscosity β _s and the natural logarithm of the ratio of the outer effective radius ^ _{1 of} the front edge of the buffer to the inner effective one Radius R _{2 of} the rear edge of the buffer. The effective radii ^ ₁ and R ₂ are measured along the same radial line from the introducer. The pressure drop can accordingly be expressed by the following equation:

Λ ρ - c (u ) In l —-1,
i R ₂ J '

here C is a constant of proportionality.

When the buffer is moved away from the introducer well by the propellant, this begins

Ratio (- _R -j to approach the value Ems, the

Loganthmus of proportion

R ₂

begins

Approaches zero, and accordingly the pressure drop caused by the buffer approaches the aqueous solution the value zero. When a buffer of the aqueous solution from the introducer through the Formation is advanced to the production facility, accordingly is the introduction pressure, required to maintain a desired Darcy speed is less than if the entire body of the introduced medium consists of the aqueous solution.

The use of a buffer from the point of view of reducing pressure requirements for maintenance a desired Darcy speed is particularly valuable when a high viscosity in the aqueous solution is required to achieve a favorable mobility ratio, i.e. H. no greater than one to be obtained between the aqueous solution and the oil. This is especially true in flat formations the case.

When using a buffer of the aqueous solution, it is preferred to use only one buffer. However, under certain circumstances, particularly when in the aforementioned manner high viscosities are required to achieve a desired mobility ratio, menrere Find buffer of the aqueous solution application. When using several buffers, it is preferred that at least one is of such a size that it is passed by the introducer the formation flows to the production facility without being completely dispersed or dispersed. Accordingly, at least one buffer will have a volume corresponding to at least 1% of the pore volume exhibit. On the other hand, however, the volume can also be about 5% of the pore volume of the formation or make more. The total volume of the plurality of buffers need not be greater than about 20% des To be the pore volume of the formation.

When a plurality of buffers of the aqueous

Solution is used, becomes a propellant medium is introduced into the formation between each of the buffers. The volume of the between each The propellant medium used to buffer the aqueous solution can be as desired in the individual case will. It is preferred, however, that the volume of propellant medium be between buffers and the aqueous solution is at least 5% of the pore volume.

Any materials can be used, as were previously used in water flooding to increase the viscosity of a flooding water have been used to increase the viscosity of the aqueous solution to be used. These materials include synthetic and naturally occurring compounds and polymers. For example, natural gums or mucilages, such as gum tragacanth, Soaps, cellulose esters, e.g. B. Carboxymethyldroxyäthylcellulose, partially hydrolyzed polyacrylamides and polystyrene sulfonates can be used.

I ⁿ a similar manner, any of the Malerialien as they have hitherto been used as surface active agents in water flooding, are used to reduce the interfacial tension between the aqueous solution and the formation of oil. These surfactants include anionic, cationic and nonionic surfactants. _{For example,} sodium dialkyl sulfosuccinates, alkyl aryl sulfonates, and polyoxyhydric alkyl aryl alcohols can be used. An aqueous solution suitable for use in the method according to the invention contains e.g. B. Oleate-type soaps in an amount sufficient to form a shear hardening solution, 0.01 to 5.0 percent by weight of a nonionic surfactant, and 0.01 to 1.0 percent by weight

percent of a soluble phosphate, e.g. B. sodium pyrophosphate, as an inorganic additive. As an an example for the oleate type soaps, in an amount sufficient to form shear hardening solutions be a substituted ammonium oleate in a concentration of 0.1 to 1.0 percent by weight called. As an example of the nonionic surfactants, let nonylphenol with average 4 to 10 moles of ethylene oxide combined with it.

Other suitable aqueous solutions include those solutions which the oleate-type soaps in an amount sufficient to form shear-hardening solutions, the nonionic surface-active agents Agents in an amount of 0.01 to 5.0 percent by weight and 0.01 to 1.0 percent by weight of one Contain alkylarylsulfonate. As an example of the alkylarylsulfonates, consider a commercially available one Called alkylaryl sodium sulfonate detergent, which consists essentially of 59 percent by weight inorganic Salts, 40 weight percent dodecylbenzene sodium sulfonate and 1 weight percent other compounds consists.

Other suitable aqueous solutions include those containing 0.2 to 1.0 weight percent ammonium hydroxide, 0.1 to 1.0 percent by weight oleic acid, ammonium chloride in an amount greater than 0.05 percent by weight and a nonionic surfactant, e.g. B. Nonylphenol with an average of 4 to including 10 moles of ethylene oxide combined therewith.

Other suitable aqueous solutions include those solutions containing 0.1 to 1.5 sodium di- (2-ethylhexyl) sulfosuccinate, 0.01 to 1.5 weight percent of a nonionic surfactant such as nonylphenol averaging 4 to inclusive 10 moles of ethylene oxide combined with it, and 0.13 to 2.0 percent by weight of an inorganic one Salt, such as sodium chloride.

Although the method according to the invention for improving the recovery of oil from any oil-bearing underground formation is advantageous, a particularly high effect is achieved when the oil-containing subterranean formation is preferably water-wettable. Under "water wettable" is an angle of contact α according to FIG. 3 of less than 90 °, measured by the water phase and formed of the interface between the water and the oil and the solid surface of the formation. In order to achieve particularly good results in such underground formations, the preferred are oil wettable, d. H. where the contact angle α is greater than 90 °, it is preferred before application of the method according to the invention to change the preferred wettability in such a way that the formation is preferably made water-wettable.

It can be made up of any of the known methods of converting a subterranean formation a preferred oil-wettable state in a preferably water-wettable state application Find. One such method is described in U.S. Patent 3,028,912.

The method according to the invention can be used in conjunction with any downhole arrangement such as conventionally in the production of oil from a formation using a flooding medium Find application, be carried out. For example, the method according to the invention can be carried out with a borehole pattern in which the flooding medium is in a central borehole is introduced and the oil is produced from boreholes surrounding the central wellbore will, or vice versa. 5-point or 7-point borehole grids are an example of the method according to the invention called. Furthermore, the method according to the invention can be used in the case of a borehole grid be carried out in which the displacement medium is simultaneously in a plurality of Boreholes is introduced, which are arranged in a line, and the production of a plurality occurs from boreholes provided in one or more parallel lines, d. H. where a Line output is achieved.

In FIG. 1 illustrates a 5-point borehole grid. An induction well 10 is surrounded by four production wells 12, 14, 16 and 18. The aqueous solution is introduced into the well 10 in the desired amount to form a buffer 20 in the preferred embodiment of the invention. The buffer 20 initially formed is shown in area A. The aqueous solution is introduced into well 10 at a rate such that the Darcy velocity of the aqueous solution in the subterranean formation is high enough to achieve the desired displacement. The aqueous solution is propelled through the subterranean reservoir by means of a propellant medium which is introduced into the introduction well 10. The rate of introduction of the propellant medium is chosen so that the aqueous solution has the desired displacement number.

With the continued introduction of propellant medium, the buffer of the aqueous solution advances through the formation. Area B schematically illustrates the location of the buffer approximately midway between the introduction well and the production well. In any such middle position, ie when the flooding front of the aqueous solution has covered about 45 to 65% of the distance from the introduction devices to the production devices in the manner indicated above, the minimum Darcy velocity is present, even if the invention is at maximum allowable rate is continued. During this period, the greatest volume of oil per unit distance of advancement of the aqueous solution through the subterranean formation is recovered. Accordingly, it is particularly desirable to maintain high displacement numbers during this section, ie high values of the product of the Darcy velocity F ₅ , calculated from (1) the rate of introduction of the partial medium at the surface and (2) the area for the position of the front of the aqueous solution, and the previously determined viscosity, M _{8 of} the aqueous solution, divided by the previously determined interfacial tension r _o ^ _s between the aqueous solution and the oil in place.

The Darcy speed then begins to increase somewhat, since the influence of the pressure gradient in Towards the production facility a deformation of the expanding cylindrical development caused. The speed reaches near the production facilities where the The pressure gradient and the deformation are strong, again a high value. Such a location of the

13 14

The buffer of the aqueous solution is shown schematically by Each core sample has been illustrated up to the point of Area C first. Although the buffer has been purged with carbon dioxide and the aqueous solution is then desirably saturated with water by preserving the water by continuity, in position C the sample has been allowed to flow. For this purpose, considerably thinner than in position B. In the case of still water, with the exception of position C, the aqueous solution has practically 3, where the water contained 1.4 percent by weight of sodium table the entire distance along the flow path of chloride . The flow of water through the introducer core sample to the production inlet was continued until an equilibrium pressure differential was passed through. reference was obtained. From this flow rate at this one

By applying a suitably high pressure differential, the liquid permeability was increased

displacement number is therefore (1) the high microscopic calculation using Darcy's law

Flushing efficiency equivalent to that of an extraction. It was an oil phase, namely hexadecane, in

driving with the introduction of a miscible medium each core sample by capillary desaturation with one

comes close, (2) the relatively high macro- pressure of 65 cm of mercury introduced, v / obei das

scopic flushing efficiency of a water flood 15 water displaced by the oil in a burette

and (3) the reduced fingering and that was measured to determine oil saturation. for

ringerte extent of premature breakthrough of each core sample was the oil saturation 77 ± 1 ⁰ Zo.

Reached flooding water of increased viscosity. Then a simulated water flooding was carried out with each

A recovery process was performed using one of the core samples.

Line exit is shown in FIG. 2 illustrates. The 20 In the simulated water flooding, the

Buffers 20 of the aqueous solution are loaded with a core sample of water under measured conditions.

guide bores 22, 24, 26 and 28 inserted. flow rate, pressure and volume. It

The development pattern is essentially the same except for using distilled water

as described above in connection with FIG. 1 is in Example 3, in which the water, accordingly

was written until the fronts of the buffers are equal to that used for saturation of the core sample

meet aqueous solution. Then, as in the water, 1.4 percent by weight sodium chloride is

ment D shown the development more linearly with one held. The flow rate was measured with a Ruska displacement

relatively constant area, regulated as a cylindrical ger pump; a pump rate of 1 cm ³ / h

with an expanding area. Accordingly, they are roughly equivalent to a Darcy speed of

after coincidence of the buffer of aqueous 30 1.42 · 10 ^-5 cm / sec. The water was through the

Solution flowed at higher Darcy velocities at the core sample applied until at the applied

A line exit pattern can be achieved when no more oil was produced at the flow rate. The ku-

a pattern with a single introductory drilling- mulative volume of oil coming out through the water

hole. the sample was removed was measured.

The following examples serve to further illustrate the core illustration of the invention. In this sample, a buffer of aqueous solution was determined, which was initially used to determine the amount of oil, the thickener and a surface-active agent contained from various core samples by flooding which could be removed by each of the core samples in the measured core samples with water. Since flow rates, measured pressures and in measured after, the further amount of oil was determined that passed from 40 volumes. The flow rates were controlled in the same way as the core samples by flooding them in a manner as the above in connection with aqueous solution under such conditions as described with the water. This flow rate was their displacement speed of at least 2 x 10 ~ ^5, were kept constant, except some could be removed. In each example, cases where the pressure required to maintain essentially the same operating method of flow rates constant, applied the pressure limits; if there were differences, these are exceeded by the apparatus. The aqueous solution was written. flow through each core sample until at the

In each example, a core sample was produced with the flow rate used and no more oil produced

know stratifications used to make the underground was. The cumulative volume of oil that

Imitate deposit. In the case of the core samples, the sample was removed by the aqueous solution,

if it were Berea sandstone cores, which was measured in this way.

were chosen so that they have porosity and permeabilities. The test results are summarized in the table within as narrow a range as is practical. The values for the simulated was possible, had. The gas permeabilities were flooding using distilled water-600 ± 60 millidarcy, and the porosities ranged from 55 ser and were practically the same for each core sample, they were 0.216 to 0.226. To avoid unnecessary repetition, the core samples had a length ^{of 31 + 0.07 cm, an area of 19.45 + 0.14 cm 2} in the table only once under the column above and a pore volume of 132.87 ± 3.67 cm ³ . Each writing "Comparative experiment, distilled water" on the core sample was stabilized beforehand by guiding it. The values for the simulated water flooding were treated with a sodium carbonate flux and then burned to 1300 ° C. with the use of sodium chloride, so that the water is listed under the column heading "Comparative properties of the core samples from the chemical test, salt water". Next, the point of view was essentially uniform. Table showing the extraction in terms of the total amount

In carrying out the examples, each was reported in terms of oil, expressed as a percentage of the in

Core sample placed in a Hassler line, with a 65 of the core sample before the simulated water flooding.

Cuff pressure of 17.0 kg / cm ^{2 was} applied essential oil, which by the simulated water

and the cell was placed in a box, in flood and through the aqueous solution from the nuclear

where the temperature was controlled at 25 ± 0.1 ° C. sample has been removed. The specified viscosity

of the aqueous solutions is that viscosity obtained from the pressure drop across the core sample under application of Darcy's law was determined. The value given as the interfacial tension is the was obtained by measurements using the modified drop method without a stem. The Media volume is the amount, expressed in units of the pore volume of the core sample, of the water, that used in the simulated water flooding under the two comparison or standard conditions was, or the aqueous solution used in the further flooding in the individual examples would. The stated Darcy velocity is the value obtained from the rate at which the water flows or the aqueous solution has been pumped in, has been determined.

example 1

In this example the fluid used was the fluid from a shear-hardening solution of 0.52 percent by weight ammonium hydroxide, 0.15 percent by weight oleic acid, 0.05 percent by weight Ammonium chloride and the rest water.

Example 2

The flooding liquid used in this example was that used in Example 1 similar except that it contained 5% by weight of a surfactant which of nonylphenol adducted with 9 moles of ethylene oxide per mole of nonylphenol.

Example 3

In this example, a shear-hardening solution was used as the flooding liquid 0.1 percent by weight of sodium di (2-ethylhexyl) sulfosuccinate, 0.1 percent by weight of a surface-active substance Means, consisting of nonylphenol, adducted with 6 moles of ethylene oxide per mole of nonylphenol, 1.4 weight percent sodium chloride and the remainder of water.

Example 4

In this example, a shear-hardening solution was used as the flooding liquid 0.07 percent by weight sec-butylamine oleate, 0.027 percent by weight Ethylamine hydrochloride and the rest of water. The solution had a pH of about 10.2.

Example5

In this example the same flooding liquid as in example 4 was used. The flow rate however, it was twice as large in this example as in example 4.

Examples 6 to 10

The flooding liquid used in these examples was a shear hardening solution made from 0.4 percent by weight of sodium di (2-ethylhexyl) sulfosucinate, 0.05 percent by weight of a surfactant By means of nonylphenol, adducted with 4 moles of ethylene oxide per mole of nonylphenol, 0.75 percent by weight Sodium chloride and the remainder water.

The flow rates used were 17.5, 160, 280, 400 and 560 cm ³ / h for Examples 6, 7, 8, 9 and 10, respectively.

In Example 10, were at the final flow rate, ie, 560cm ³ / h approximately 89.2% of the oil from the

3P core was recovered after 1.7 pore volumes of flooding liquid had been passed through the core sample. The flooding liquid was allowed to stand in the core sample for 2 days. A subsequent throughput of 1.3 pore volumes at 560 cm ³ / h increased the total recovery to 95.6% of the oil originally present in the core sample. The flooding liquid was then left in the core sample overnight. An additional pore volume of flooding liquid was then allowed to ^{flow through the core sample at 560 cm 3} /. The total oil recovery increased to 96.0% of the oil originally present in the core sample.

Comparative experiment, distilled
water

Comparative experiment, salt water

example 1 Example 2

Quantity, cm ³ / h

Darcy speed, cm / sec

Viscosity, cP

Interfacial tension, dyn / cm

Media volume, V ₁ ,

Displacement number

Extraction, ° / o

5.41 7.66 ΙΟ- ⁵

0.8911

27.5

1.5

2.5 · ΙΟ " ⁸ 39.4 5.41
1.42
1.0

32.5
1.5

5.2
34.2

ΙΟ- ⁴

ΙΟ " ⁸

560
7.95
3.17
1.4
1.5
1.8 ·
61.1

ΙΟ " ³

ίο- *

560
7.95
1.4
0.7
1.9
1.6-71.0

10 " ⁴

Example 3 Example 4 Example 5 Example 6

Quantity, cm ³ / h

Darcy speed, cm / sec

Viscosity, cP

Interfacial tension, dyn / cm

Media volume, V ₁ ,

Displacement number

Extraction, ° / o

560

7.95 x 10 ~ ³

1.0

0.084

1.5

9.5 ■ ΙΟ- "

84.8 280

3.98 ■ ΙΟ " ³
1.0
0.9
1.5

4.4 · ΙΟ " ⁵
55.5

560

7.95 · ΙΟ " ³
1.0
0.9
1.5

8.9 ■ 10-5
68.4

17.5

2.4 · ΙΟ " ⁴

3.64

0.11

1.5

8.3 · ΙΟ " ⁵
56.4

109 508/21

Example 7 example Example 9 Example 10

Quantity, cm ³ / h

Darcy speed, cm / sec

Viscosity, cP

Interfacial tension, dyn / cm
Media volume, V ₁ ,

Displacement number

Extraction,%

Claims (15)

Patent claims: 160 2.27 3.64 0.11 1.5 7.5 71.1 ΙΟ " ³ ιοί. Process for extracting oil from a oily subterranean formation, in which flooding water through an inlet device, which comprises at least one introduction wellbore into which the formation is introduced and oil produced from the formation by a production facility comprising at least one production well leading into the formation is, characterized in that one of the following by the introduction device Requires sufficient aqueous solution to be introduced into the formation under such conditions and lets flow therein that its dimensionless displacement number ^25th while flowing through a substantial portion of the formation is at least 2-10 " ⁵ , where in the formula 35 μ _Β the viscosity of the aqueous solution (poise), V _{s is} the Darcy speed of the aqueous solution (cm / sec) and σ ₀ _ _{s is} the interfacial tension between the aqueous solution and oil with which the solution comes into contact in the formation (dynes / cm), means, and the dimensions given for the flow parameters of one of the systems more suitable Represent units. 2. The method according to claim 1, characterized in that the solution is allowed to flow through 10 to 100% of the formation located between the introduction device and the production device with a dimensionless displacement number of at least 2-10 ~ ^3. 3. The method according to claim 1 or 2, characterized in that the aqueous solution in the form of a buffer with a volume of 1.0 to 100% of the pore volume of the formation applies. ■ 4. The method according to claim 3, characterized in that there is a buffer of the aqueous Solution, the amount of which is 1.0 to 20% of the pore volume, is used. 5. The method according to claim 4, characterized in that there is a buffer of the aqueous Solution, the amount of which is about 5% of the pore volume, is used. 6. The method according to claim 1 or 2, characterized in that at least one buffer 280
3.98
3.64
0.11 1.5 1.3
81.6 ΙΟ " ³ 10-3 400
5.67
3.64
0.11
1.5 1.9
86.7 ΙΟ " ³ ΙΟ " ³ ΙΟ- ³ 560 7.95 3.64 0.11 1.7 (3.0 to 4.0) 2.7 ΙΟ- ³
89.2
(95.6 to 96.0) the aqueous solution of 1 to 20% of the pore volume of the formation and at least one buffer of an aqueous propellant fluid of at least 5% of the pore volume of the formation introduces through the introduction device and thereby introduces the propellant fluid in a sufficiently large amount / time that the aqueous solution in the subterranean formation under conditions such flows that the dimensionless number displacement of the aqueous solution during the flow is at least 2-10 ~. ⁵ 7. The method according to claim 6, characterized in that there is more than one buffer of the introduces aqueous solution through the introducer. 8. The method according to claim 6 or 7, characterized in that there is more than one buffer introduces the aqueous propellant liquid through the introduction device. 9. The method according to claim 6, characterized in that the buffer or buffers aqueous solution and the buffer or buffers of the aqueous propellant fluid alternately and in in this order by the introduction device. 10. The method according to any one of claims 1 to 9, characterized in that the solution is allowed to flow ^{with a dimensionless displacement number of at least 3 · 10 -3.} 11. The method according to any one of claims 1 to 10, characterized in that one aqueous solution used with such a viscosity that its mobility in the underground Formation no greater than the mobility of the subterranean formation Oil is. 12. The method according to any one of claims 1 to 11, characterized in that as aqueous solution uses a shear-hardening liquid. 13. The method according to any one of claims 1 to 12, characterized in that one used aqueous solution containing a surfactant. 14. The method according to any one of claims 1 to 13, characterized in that an aqueous solution is used which has such a viscosity μ ₅ and such an interfacial tension with the reservoir oil T ₀ _ _s that the ratio Ms ^ os i ⁿ sec / cm is at least 0.057. 15. The method according to claim 14, characterized in that an aqueous solution is used with such properties that the ratio μ _$ / τ ₀ _ _{5 is} greater than about 8.5. 1 sheet of drawings