Method for extraction of deposits of high-viscous oil and bitumen. RU patent 2247830.

FIELD: oil extractive industry.

SUBSTANCE: method includes cyclic differently-directed forcing of air as oxidizer. This is achieved by changing oxidizer forcing pressure and its volume, changing position of air forcing points, extraction of high-viscous oil or bitumen. Appearance of sign-alternating pressures between beds of different saturation provides for acceleration of capillary counter-flow saturation with water of zones with oil or bitumen, forcing gases into portions with oil or bitumen along small porous channels and transfer of oil or bitumen from heated areas along large porous channels. Change of direction of flows of gas of oil or bitumen between wells strengthens process of increase of area of effect of bed by bed inside burning. In such a way, use of stagnant areas is increased and bitumen extraction coefficient is increased.

EFFECT: higher efficiency.

1 ex, 1 tbl, 2 dwg

The invention relates to the field of the oil industry, in particular to methods for the development of high-viscosity oil (BBH) or bitumen by in-situ combustion, and can be used to regulate the in-situ combustion (VG) using non-stationary modes of injection of air as oxidant in repression BBH or bitumen from raznoprofilnyh layers.

The known method for the development of high-viscosity oil by in-situ combustion, including the injection of air injection and the selection of products through the production wells. [Cm. Pat. U.S. No. 3179167, CL-11, published. - 1965].

The method involves the continuous injection of air to approach the high temperature zone to the producer, and then the transition to cyclic injection of air.

The disadvantage of this method is the low enrolment rate of burning and difficulty of movement of the combustion front in repeated cycles. This is because the combustion front moving through the more permeable areas to the producer covers the reservoir only a small thickness, because with repeated cycles of the combustion front will move primarily along the same layers as before. This is because after setting the front combustion or high temperature zone to the production well the heterogeneity of the reservoir, only amplified, as in the more permeable layers or cracking of high-viscosity oil has been replaced by more active agent (air or water).

There is also known a method of developing heavy oil or bitumen [see RJ "Mining", synthesis, 1969, No. 6, ind GP].

The method includes the cyclic injection through the injection well air with a constant flow and reservoir selection of products through the production wells. In periods stop pumping air into the reservoir through injection wells pump water to reduce the temperature of the reservoir is lower than the temperature of kikirevenge oil. After water injection produce oil extraction through production wells until such time as the temperature of the reservoir remains above the ignition temperature of the reservoir oil at the subsequent resumption of the injection of oxidant.

The main disadvantage of this method is the small coverage of bed combustion and consequently a low rate of recovery due to the fact that this method provides a constant rate of injection of air without regard to the temperature conditions in the reservoir and the rate of burning of fuel in time.

When pumping large volumes of air at the beginning of the cycle creates an excess of oxygen (in this period the rate of combustion is slowed down due to the lower temperature), which, breaking through the combustion front to producing wells, forms an explosive mixture with hydrocarbon gases. This leads to a forced termination of the development process of formation.

Thus, when the injection of air at a constant speed the burning process is unregulated, which ultimately reduces the main indicator of development - oil.

The closest in technical essence and the achieved result to the present invention is the method of development of deposits of heavy oil or bitumen [see U.S. Pat. RU # 1129986 from 15.07.83, CL E 21 In 43/24], which consists in injecting through the injection well air and the selection of produced products through production wells, injection of air in each cycle is carried out in an ever increasing pace, and after reaching the maximum possible air flow is injected with a constant rate, and the daily flow during periods of increasing the rate of injection is determined from the following relationship:

where q t is the daily flow at time t (nm 3 /day);

Δt - duration of period increase daily consumption of air in the cycle (day);

t - the current time (day);

q min is the initial air flow in the loop (nm 3 /day);

q max is the maximum air flow rate (nm 3 /day);

Cyclic injection of oxidant in increasing mode increases the coverage of bed combustion.

The disadvantage of this method is of limited use, since the change of geological and physical characteristics of the developed VG seams effectiveness drops sharply due to the lack of regulation of the process air injection. The technical objective of the proposed method of development of deposits of heavy oil or bitumen is the increased efficiency of the development of heterogeneous deposits due to the regulatory process in-situ combustion using nonstationary injection of air as oxidant and a combination of thermal and hydrodynamic stimulation.

The problem is solved by the described method development BBH or bitumen by creating in-situ hearth burning, including cyclic injection of air change rate of injection through the injection well and the selection BBH or bitumen through production wells.

What's new is that the optimal frequency of air injection is determined by the formula

t 1/2 t =L 2 /2χ,

where t 1/2 t - duration of politicla injection of oxidant into the reservoir, d.;

L is the characteristic length of the layer, m;

χ - the average piezo-conductivity of the layer,

χ=/μ c m,

μ - viscosity BBH or bitumen, PA·;

K - permeability layer, 2 μm ;

m - porosity reservoir, share units;

s - factor appointest reservoir, 1/MPa, (2÷5)·10 -4 .

The amplitude of the fluctuations of the flow rate of the injected air is measured as the ratio of the excess or reduce the discharge of air above average volume of discharge under cyclic in-situ combustion to the average rate of injection of air at the stationary injection by the formula:

B=(Q i3 Q 03 )/Q 03 ,

In the oscillation amplitude of the flow rate of the injected air.

Q 13 - maximum or minimum level of air injection, depending on the phase of the cycle, under cyclic in-situ burning (Q 13 min =0), nm 3 /day.;

Q 03 - average stationary air injection (Q 03 =Q 13 /2), 3 nm /d.;

  i is the cycle number (i=1, 2),

with the beginning of the cyclic injection of air is determined by the time of breakthrough of gas combustion in the operating well under steady-state pumping air through the interlayer with greater permeability, while periodically changing the location of the point of air injection and sampling BBH or bitumen, and the manifestation of the effect of cyclic exposure is determined in the form of additional production BBH or bitumen on sustainable integrated dependency of the volume extracted BBH or bitumen and pumped air:

Q(t)=f[Q hcpa. (t)],

Q(t) is the accumulated production volume, BBH or bitumen from the site by this time tracking, t;

Q hcpa. (t) is the accumulated amount of injected air at this point, m 3 .

The proposed method of development of deposits of heavy oil or bitumen in-situ combustion is based on the combination of thermal and hydrodynamic stimulation. Hydrodynamic effects is the periodic change in the amount of air injection and fluid extraction. Thermal effect that results as a consequence of air as oxidant.

With unsteady air injection between formation zones of different permeability and baumanagement are created by alternating the pressure gradient under the influence of which increases the process of capillary imbibition.

Due to the cyclic change of the volume of air injection and sampling BBH or bitumen in development come the periods of increasing and decreasing reservoir pressure, under the action of which increases the process of capillary imbibition.

During periods of increased injection rate of growth pressure in the gas-saturated high permeability and related bituminizing zones will differ due to the difference of their conductivity. All of this creates a positive pressure gradient, under the action of which the flow BBH or bitumen passes from bituminizing areas in gas-saturated.

Subsequent pressure increase BBH or bitumen will be displaced to areas of selection. Thus the cycle repeats. From cycle to cycle will increase the coverage of stagnant zones and to increase the ratio of bitumen producing.

Repeated jumps saturation resulting from uneven displacement of bitumen gases from heterogeneous reservoirs, create a nonequilibrium state of capillary forces at the contact zones with different saturation. The occurrence of alternating pressure between layers of different saturation accelerates countercurrent capillary impregnation water bituminizing zones, introduction of gases in baumanagement plots for small pore channels and the flow BBH or bitumen from heated areas, large pore channels. Changing the direction of the gas BBH or bitumen between wells enhances the process of increasing the coverage of the formation in-situ burning.

The process of changing the direction of the seepage is quite a long time. Depending on the permeability of the layers of the stabilisation process flows can last from a few tens of days to several months. Therefore, the manifestation of the effect of cyclic effects occurs with some delay. The effect of the additional production is determined by the integral volume of the extracted BBH or bitumen and pumped air as oxidant.

The mechanism of in-situ combustion in the reservoir determines the direct relationship between the volume of air injection and extraction BBH or bitumen. Differential dependencies between them due to the lag effect of unsteady air injection unusable. Therefore, it is necessary to use sustainable integral relation between the injected amount and selection BBH or bitumen.

The set of distinctive features can improve the development efficiency of heterogeneous deposits due to regulation of the VG process using nonstationary injection of an oxidant and a combination of thermal and hydrodynamic stimulation.

From available sources, the patent and scientific literature we are not aware of the claimed set of distinctive features. Therefore, the proposed method meets the criteria of the invention "inventive level".

The method is carried out in the following sequence (combined with a specific example).

On Mordovo-Karmelicka field of bitumen chose the number of wells to test the proposed method for the development of deposits. Wells arranged in accordance with the existing development project, in addition have set up a research platform, a pressure gauge, a thermometer and a device for the selection of the bitumen.

The initial baumanagement layer was not less than 40% of the pore volume, while the reservoir is characterized by the following parameters:

1) the depth of the layer, m - 120;

2) baumanagement thickness, m is at least 3;

3) the permeability of the reservoir, 2 μm is not less than 0.5;

4) the porosity, the percentage of units is not less than 0.18;

5) dynamic viscosity of the bitumen in situ, PA· - 3-10;

6) the coefficient of appointest layer-dependent saturation of the reservoir bitumen and gases, and characterizes the degree of compressibility of the reservoir unit pressure, which varies in the range - (2÷5)·10 -4 , 1/MPa, to find the optimal values from the point of view of achievement of a technical problem.

In the process of exploitation the proposed method, the discharge pressure of the coolant in the reservoir was not more than 4 MPa, the temperature is not above 250°C.

When testing the proposed method for the development of BBH and natural bitumens used equipment used in the oil industry:

stationary compressors type OECS-75-70;

mobile logging station type act-1 and act-2;

Control of the discharge pressure was carried out according to the indications gauges installed before and after fitting on the discharge lines.

Record of the amount of injection was performed by calculation depending on humidity and pressure of injection per unit volume of the reservoir (140-160 nm 3 /m 3 ).

When developing bituminizing layers or layers with BBH method VG technology provides stable heating of the reservoir, the optimum temperature at the combustion front is not higher than the ignition temperature of the reservoir (not higher than 250°C).

Before starting work, produced a revision of the wellhead equipment of wells leak, installed the gauges and thermometers.

Shot measurements of flow rate, reservoir temperature, static level, samples were taken of the gas and the liquid reactive wells.

The purpose of the discharge air is to maintain the fire burning in the bituminous layer.

The essence of the change of the blower is to regulate the combustion process of the bitumen in the reservoir and its promotion to the producer with a more full coverage heat developing section of the reservoir.

The estimated volume of air was determined based on the conditions of a particular well (element). The maximum rate of injection into a single well of 30-40 thousand nm 3 /day. (actual).

Let the well injection of air with the changed volume.

The amplitude of the flow rate of the injected air is measured as the ratio of the excess or reduce the discharge of air above average volume of discharge under cyclic in-situ combustion to the average rate of injection of air at the stationary injection by the formula

B=(Q i3 Q 03 )/Q 03 ,

where is the amplitude of the fluctuations of the flow rate of the injected air;

Q 13 - maximum (or minimum) level injection (depending on the phase of the cycle) when cyclic VG, nm 3 /day.;

Q 03 - average stationary air injection, nm 3 /day.;

(Q 13 min =0; Q 13 =2Q 03 ); i is the cycle number (i=1, 2).

Assuming the need to preserve the average volume of a cyclic injection of air equal to the volume under steady-state pumping "In" cannot be more than 1. This means that half of the increase in discharge pressure injected volume of air must be increased two times and a half time of reducing the pressure to decrease to 0 as a result of disabling injection wells. Measured temperature of the bottomhole zone injection wells. In the case of application of the method on the element was reduced or stopped pumping air into injection wells within 10-30 days, continuing the selection of bitumen from oil producing wells in the former regime. The optimal frequency of cycles obtained from hydrodynamic calculations, is determined by the formula

t 1/2 t =L 2 /2χ,

t 1/2 t - duration of politicla injection of oxidant into the reservoir, d.;

L is the characteristic length of the layer, m;

χ - the average piezo-conductivity of the layer,

χ=/μ m,

μ is the viscosity of the bitumen, PA·;

K - permeability layer, 2 μm ;

m - porosity reservoir, share units;

s - factor appointest reservoir, 1/MPa.

For Mordovo-Karelskogo field t 1/2 t =30 days. On the third day from the beginning of the injection, then periodically - once a week, took measurements of reservoir temperature, levels, samples were taken for gas and bitumen on reactive wells.

Rebuilt injection of air is increased to two times the volume of the injection well (with a daily consumption of 30-40 thousand nm 3 /day) for 10-20 days, simultaneously stopping the selection of bitumen from oil producing wells within 5-10 days. (Due to the time lag effect from the cyclical impact on observations about twice the time of the termination of the selection was changed accordingly).

If the production wells on the bitumen does not exceed the flow rate to air injection, carried out the next cycle by injection of air, since the start of well injection of air with the changed volume. When the excess production of reactive wells after the injection of air is continued operation of the reservoir before the termination of the receipt of the bitumen into the reaction wells.

In the absence of the influence of air injection on the layer selected and prepared another borehole injection of air.

The injection of air into the other hole was made in the mode of discharge in the main borehole.

The change of location of the discharge and the change of volume or pressure injection to modify the filtration flows produced on multiple items at the same time.

Evaluation of the effectiveness of the proposed method was made by comparing the flow rate and the water content of reactive wells before and after Cycling or building displacement characteristics (Fig.1-2).

Figure 1 shows the cumulative production of bitumen on the prototype. Figure 2 shows cumulative production of bitumen on the proposed method for the development of BBH or bitumen as a hatched area above the straight line extrapolation of the dependence between Q b (t) and Q the hcpa. (t).

For circular air injection was selected wells elements on which the current generation layer was 10-30%.

The rate of extraction of bitumen during the reporting period for each element of the field, where he held a cyclic injection of air, are summarized in table.

Table № item production Growth during the review period, kt 13 0,03 306 0,15 303 0,2 320 0,33 342 0,67 345 0,03 362 0,19 381 0,07 401 0,004 404 0,13 total 1,804

The analysis of the development of elements showed that the effectiveness of unsteady air injection on Mordovo-Karmelicka field of natural bitumen in the form of additional production in varying degrees was observed for all the considered elements, which is from 0.03 to 0.67 gg, and cumulative production of bitumen in the proposed method a total of 144 thousand tons against 142,2 thousand tons of the prototype.

Technical and economic efficiency of the proposed method is due to the increase of efficiency of development of heterogeneous deposits by regulation process in-situ combustion using nonstationary injection of air as oxidant in combination thermal and hydrodynamic stimulation.

The amount of additional production for the entire period of research and development projects amounted to 1.8 thousand tons.

The method of development of deposits of heavy oil or bitumen by creating in-situ hearth burning, including cyclic injection of air as oxidant with the change rate of injection through the injection well and the selection of high-viscosity oil (BBH) or bitumen through production wells, wherein the optimal frequency of injection of the oxidant is determined by the formula: