RU2087686C1 - Method for development of oil deposit - Google Patents

Abstract

FIELD: oil production industry. SUBSTANCE: this relates to oil deposit with separated break of different permeability. According to method, in deposit which is nonuniformly flooded with injected water, detected are flushed and oil-containing intervals, determined is character of distributing current oil resources, found are zones with various concentration of resources. Then beds and sections are selected for directed cyclic treatment of localized resources. Work is performed for levelling filtration properties of beds in wells to increase hydrodynamic resistance of high-permeable intervals in injection wells. Cyclic water injection is performed with increase of volumes pumped through injection wells of those rows towards which displaced are zones of higher oil saturation, thus moving oil towards producing wells and preventing its displacement to flooded sections. EFFECT: high efficiency. 2 dwg, 2 tbl

Description

 The invention relates to the oil industry, namely to the development of oil fields.

 There is a method of developing an oil reservoir by pumping water in a stationary mode [1] One of its drawbacks is that over time, stable filtration paths of the injected water are formed in the reservoir, and areas that the injected water bypasses. As a result, reservoirs with increased permeability are washed out, and zones with low permeability reservoirs are poorly drained. The oil recovery coefficient is not high enough. Additional capital-intensive technological measures are needed to recover oil reserves.

 Closest to the proposed invention in technical essence is a method of developing an oil field, including the selection of oil through production wells and pumping water in a cyclic mode through injection wells [2] The known method allows you to extract an increased amount of oil from the reservoir due to unsteady effects and changing the direction of the flow of displacing agent in the reservoir. However, it does not provide for oil extraction from all interlayers of a permeable section of the productive horizon.

 In the known method, it is necessary to ensure a simultaneous approach of the displacement fronts to the tightening row of the completion wells by taking into account zonal heterogeneity and creating different pressures in areas with different filtration properties.

 The solution of this problem by the proposed method is generally problematic, and for deposits that have been under development for a long time it is practically impracticable, since the formation of the displacement front is caused not only by the reservoir properties of the formations and the pressure change associated with taking into account zonal heterogeneity, but also by technogenic factors: prolonged shutdown and / or premature retirement of production and injection wells. The disruption in the interaction of the system of production and injection wells caused by these factors can lead not only to deformation, but also to complete reformation of the displacement fronts formed under the conditions of operation of all wells. As a result, the possibility of pulling oil pillars to a number of producing wells can generally be excluded. The manifestation of these and other technogenic factors in the known method is not taken into account. And this reduces the technological effect in its implementation.

 The effectiveness of the known method is also reduced due to the fact that the effect is not selective, but on the entire development object, without taking into account the degree of depletion of reserves and leaching of various intervals of the productive section, as well as without taking into account the nature of the distribution of current oil reserves in it. The cyclicity of the impact by known technology provides a change in the composition of the produced fluid, primarily due to changes in the filtration fields in highly permeable and more developed reservoirs. In areas of increased concentration of current oil reserves associated with less permeable formations, the change in the filtration fields is less intense and the effect of non-stationarity is manifested to a lesser extent.

 The factors noted above cause lower technological parameters of the known method, which are associated with the need to pump large volumes of water and produce a larger volume of liquid.

 The disadvantage of this method is not high enough current oil production.

 The aim of the invention is to increase current oil production and oil recovery.

 This goal is achieved by the fact that in the method of developing an oil deposit, including the selection of oil through production wells and pumping water in a cyclic mode through injection wells, according to the invention at a late stage of development, washed and oil-containing cut intervals are identified, their capacitive and filtration properties are evaluated, and their capacitive and filtration properties are evaluated, and the nature of the distribution of current oil reserves by constructing maps of current oil-saturated thicknesses and / or coefficient of current oil saturation, zones with different concentrations are revealed current oil reserves, map out reservoirs and areas for influencing the reserves localized in them, carry out work to level the filtration properties of the reservoirs in wells, and cyclically inject water with increasing volumes of injection through injection wells of those rows in which the increased oil saturation zone has shifted, providing the movement of oil to production wells and preventing its movement to waterflood areas.

 In the recommended method, targeted impact is thus provided, oriented mainly to areas with a high concentration of current oil reserves. The intensity of the effect on the washed areas is significantly reduced. The impact is targeted both through the section by reducing the filtration properties of high permeability and waterflood intervals and increasing them in low permeable oil-containing layers, and by area due to cyclic effects from injection wells.

 Work on the selection of intervals for regulating the filtration properties of reservoirs, and then for cyclic exposure, is based on the results of an analysis of the development of oil reserves from the development site. In this regard, washed and oily formations are identified, their capacitive and filtration parameters are determined, and the nature of the distribution of current oil reserves is determined. Reliable and informative results are obtained as a result of special field geophysical well surveys. For example, radioactive logging. Based on research materials, maps of current oil-saturated thicknesses characterizing the distribution of current oil reserves are built.

 A less expensive way to solve the problem is mathematical modeling of the process of developing a deposit or its section. Based on modeling materials, maps of the distribution of current oil saturation are constructed, which also characterize the distribution of oil reserves contained in the reservoir.

 Thus, the intervals of the productive section of the objects for regulating the filtration properties and cyclic effects are established on the basis of knowledge of the nature of the distribution of current oil reserves and the filtration properties of the reservoirs in which they are localized.

 The recommended method provides for a strictly defined sequence of work in the wells. So, work on regulating the filtration properties of the reservoirs, i.e. the use of bottom-hole treatment methods (BHP) should precede the cyclic effect. Only with this sequence, a greater degree of equalization of the volumes of the working agent entering the differently permeable formations is ensured, as well as a more uniform displacement front and less water cut of the produced oil than in the case of work in the reverse order (first cyclic impact, and then work on SCR).

 The mechanism for ensuring greater efficiency of the proposed technology is illustrated by the following example.

The development object is represented by two layers. The permeability of one of them is K ₁ 1000 μm ² • 10 ^-3 , the permeability of the other K ₂ is 100 μm ² • 10 ^-3 . The properties of the fluids and other geological and physical parameters of the reservoirs that determine the displacement of the displacement fronts are the same.

будет трехкратной.During cyclic exposure, the difference in the position of the displacement fronts, determined by the expression

will be three times.

500 мкм²•10^-3, а во втором увеличена до

200 мкм²•19^-3.The assumption is made that the work on the treatment of bottom-hole zones of formations has changed the initial permeability by half. In the first layer, it is reduced and amounted to

500 microns ² • 10 ^-3 , and in the second it is increased to

200 microns ² • 19 ^-3 .

.During cyclic impact after work on leveling the filtration properties of the reservoirs, the difference in the position of the displacement fronts in them, as well as in the volumes of incoming pumped water, will be determined by

.

 In the case of work on leveling the filtration properties of the reservoirs after cyclic exposure, during the stationary mode of water injection, the difference in the position of the displacement fronts, as well as in the volumes of water entering the reservoirs, will be determined by the ratio of the permeability of the reservoirs and will be almost 40% greater (500 / 200 2.5) than in the previous case.

 Thus, the combination of known technological operations in a strictly defined sequence, regulated by the proposed method, leads to a more uniform distribution of injected water across differently permeable formations and equalization in them of the velocities of displacement of the displacement fronts and, as a result, a greater technological effect, manifested in slowing down the rate of watering of the reservoirs, a decrease in current water cut in products, in an increase in current and total oil production relative to similar indicators, according to radiated in case of carrying out the same works outside the recommended technological cycle. The foregoing is illustrated by an example (figure 1).

 In FIG. 1 shows the position of the displacement fronts in the reservoirs of different permeability under different waterflooding conditions of the development object.

500 мкм²•10^-3 и

200 мкм²•10^-3). 3 и 4 нагнетательная и добывающая скважины.Legend:
1 and 2 reservoir layers with permeability K ₁ 1000 μm ² • 10 ^-3 and K ₂ 100 μm ² • 10 ^-3 . (Their permeability after SCR

500 μm ² • 10 ^-3 and

200 μm ² • 10 ^-3 ). 3 and 4 injection and production wells.

 5-5, 6-6, 7-7, 8-8 the position of the displacement fronts.

. Обводненность продукции при этом составляет 70%
б. Линии 6-6 характеризуют положение фронтов вытеснения при циклическом заводнении, определяемом выражением

. Обводненность продукции 62%
в. Линии 7-7 характеризуют положение фронтов вытеснения после проведения работ по регулированию фильтрационных свойств пластов после циклического воздействия, при реализации стационарного заводнения

. Обводненность продукции 40%
г. Линии 8-8 характеризуют положение фронтов вытеснения после проведения работ по регулированию фильтрационных свойств пластов и реализации после этого циклического воздействия, т.е. по рекомендуемому способу. Обводненность продукции 30%

.a. Lines 5-5 characterize the position of the displacement fronts during stationary water flooding, determined by the ratio of the permeability of the layers

. The water content of the product is 70%
b. Lines 6-6 characterize the position of the displacement fronts during cyclic flooding, defined by the expression

. Product water cut 62%
in. Lines 7-7 characterize the position of the displacement fronts after carrying out work on regulating the filtration properties of the layers after cyclic exposure, when implementing stationary flooding

. Water cut 40%
Lines 8-8 characterize the position of the displacement fronts after carrying out work on the regulation of the filtration properties of the reservoirs and the implementation after this of cyclic impact, i.e. by the recommended method. Water cut 30%

.

. Соответственно ведет себя и обводненность добываемой жидкости.In the considered example, the difference in the position of the displacement fronts in the case of the implementation of the technology adopted as a prototype is threefold, and in the case of the implementation of the recommended technology is half

. Accordingly, the water content of the produced fluid also behaves.

 In FIG. 2 shows a group of alternately operating injection wells according to the known method a and recommended b.

 An example implementation of the method.

 The method was tested in one of the fields of Western Siberia, in the area representing the development block, on four sides limited by rows of injection wells. The block dimensions are 2 x 2 km.

Production facility consists of AB strata $\genfrac{}{}{0ex}{}{\text{3}}{\text{one}}$ + AB $\genfrac{}{}{0ex}{}{\text{one}}{\text{2}}$ The upper horizon is represented by the alternation of thin layers of reservoirs and clays.

Horizon AB $\genfrac{}{}{0ex}{}{\text{one}}{\text{2}}$ represented by monolithic reservoirs and interbedded thin-layer reservoirs and clays. The permeability of monoliths is usually higher and amounts to 200-300 and sometimes 400 microns ² • 10 ^-3 , and finely-alternating collectors from units to several tens of microns ² • 10 ^-3 , and finely-alternating collectors from units to several tens of microns ² • 10 ^-3 .

At the site, 41 wells were drilled, including 25 mining and 16 injection. The number of wells during the experiment was: producing 25 and injection 16 wells. Pressure on the discharge lines 21.2 22.9 MPa. The pressure in the central part of the block, i.e. in the selection zone, 16.2-16.5-17.3 MPa. The initial pressure of 17.2 MPa. The water cut of the products before conducting field experimental work is 88.8%. Monthly oil, water and liquid withdrawals are 4394 tons, 36038 tons and 40432 tons, respectively. Monthly water injection 30805 m ³ . The current compensation ratio is 0.85.

 Cyclic flooding was carried out for three months. Unsteadiness was carried out by periodically stopping (for 15 days) a certain group of injection wells, while another group of injection wells was working during this period. Namely, in the same mode, the following elements of the injection system worked: wells in the northern half of the western row, wells in the western half of the northern row, wells in the southern half of the eastern row, and wells in the eastern half of the southern row. And the remaining elements of the RPM system: wells in the eastern half of the northern row, wells in the northern half of the eastern row, wells in the western half of the southern row, wells in the southern half of the western row worked in a different, opposite mode (Fig. 2a).

 With this geometry, the arrangement of alternately shut-down and working groups of wells provided the maximum change in the prevailing direction of fluid flows in the reservoir.

 Groups of alternately operating injection wells, their injectivity and monthly injection volumes according to the known and proposed technologies are given in table. one.

 According to field geophysical surveys of wells drilled at the underlying facilities 8 years after putting into development of the area under consideration, washed and oily intervals of the productive section were identified. According to field geophysical research of wells of the experimental section (ASOIGIS), taking into account the research materials of the above-mentioned group of wells, the capacitance-filtration properties of washed and oily interlayers were evaluated. Based on these data, we constructed a scheme for changing current oil-saturated thicknesses.

 Based on a complex of geological, geophysical and field data, a filtration model of the development object within the site was created. The model reproduced the history of its development and built a map of the calculated values of the current oil saturation.

 Using a range of materials, including maps of current oil-saturated thicknesses and maps of the current value of oil saturation coefficient and other materials for well research, we determined the nature of the distribution of current oil reserves in the development object.

Based on the totality of all the data, intervals were identified for aligning the filtration properties of the object collectors. As such, high-permeability monolithic reservoirs localized in the lower part of the AB section are taken as such. $\genfrac{}{}{0ex}{}{\text{one}}{\text{2}}$ in injection wells of the northern and western cutting rows. It was found that the zone with greater current oil saturation and large current oil saturated thicknesses turned out to be asymmetric and localized not in the center of the development block, but shifted to its southeastern part and elongated in the direction from southwest to northeast. This configuration is largely associated with prolonged inactivity of the injection wells of the eastern as well as southern cutting rows.

Based on the obtained results, in order to prevent oil being pushed into the marginal, southeastern zone of the block, the injectivity of the section was aligned in four injection wells (through one) of the western and northern cutting rows by ordering filterable gel-forming compounds (GOS), thereby increasing the hydrodynamic resistance lower highly permeable AB monoliths $\genfrac{}{}{0ex}{}{\text{one}}{\text{2}}$ (table 1). GOS-1 was used (carboxyl methyl cellulose 2.5% lignosulfonate-KSSB and sodium dichromate 1% each). The injection volume for wells 1, 3, 14 and 15 was 20, 30, 25 and 35 m ³ , respectively, in accordance with the thickness of the intervals of the reservoir AB $\genfrac{}{}{0ex}{}{\text{one}}{\text{2}}$ to be processed (RD 39-0147035-254-88P). Table 1 shows the injectivity of these wells before and after the SCR.

After the OPZ works, the site was developed for three months under steady-state waterflooding conditions, while the water cut of the product amounted to 73.6%. After that, they switched to a cyclical effect, but not according to the previous scheme, but according to the change in addressing current reserves. According to the new modified scheme, two groups of injection wells also worked in antiphase. So, when the wells of the first group of wells of the western and northern injection rows were operating, the wells of the second group were at the stop of the wells of the eastern and southern rows (Fig.2b). And when the wells of the second group were working, the wells of the first group were at a stop. The duration of the wells of the first group is 15 days, and the wells of the second group are 20 days. Accordingly, the stopping time was 15 and 10 days. This operating procedure ensured large volumes of injection and sides of the discharge rows, in the direction of which the zone of increased concentration of reserves shifted. The excess was 67% or 19540 m ³ against 11540 m ³ (Table 1). Under such conditions, the process was carried out for three months. At the same time, the water cut of the produced oil amounted to 70.3% i.e. decreased by 17.3% relative to the water cut of oil produced by known technology.

All information on oil, liquid and water cut production under the above development conditions are given in Table 2. From consideration of the table materials follows:
during sequential work on cyclic impact, and then alignment of the injectivity profiles of injection wells, i.e. without their targeted integration, the effect in the form of additional oil production amounted to 3922 tons, incl. due to cyclic impact of 1173 tons and due to regulation of injectivity of wells, 2749 tons;
when carrying out work according to the recommended method, i.e. with their purposeful integration and implementation in a single technological cycle, the effect in the form of additional production amounted to 4823 tons, including due to work on the regulation of injectivity of injection wells of 2749 tons and due to the cyclic impact of 2074 tons

 Additional production by the recommended technology was 901 tons or 34.8% higher than oil production by the known technology. In this excess, a synergistic effect manifested due to the new quality.

Claims (1)

 A method for developing an oil reservoir, including oil extraction through production wells and water injection in a cyclic mode through injection wells, characterized in that at a late stage of development washed and oil-containing intervals of the section are identified, their capacitive and filtration properties are estimated, and the nature of the distribution of current oil reserves by construction is determined maps of current oil-saturated thicknesses and / or coefficient of current oil saturation, identify areas with different concentrations of current oil reserves, map out the reservoir Sites and areas for influencing the localized reserves in them carry out work to equalize the filtration properties of the reservoirs in the wells, and the cyclic injection of water is carried out with an increase in the volume of injection through the injection wells of the rows in which the increased oil saturation zone has shifted, providing oil movement to production wells and preventing it from moving to waterlogged areas.

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