RU2639341C1 - Method for development of nonuniform permeability reservoirs - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: method involves injecting aqueous suspension of pre-crosslinked polymer into the formation. For this purpose, a brand of pre-crosslinked polymer and processing technological parameters are selected taking into account individual geological and physical characteristics of the facility. Initial suspension of the pre-crosslinked polymer is prepared on the well by mixing at least two volumes of water and one volume of reagent, which is particles with initial size from 0.1 to 10 mm. After maturation for not more than 120 min the produced suspension is stirred in tank with water and pumped into injection well in working concentration of 0.1-0.5%. When pumping, the suspension of reagent particles is maintained in suspended state. At the same time, it prevents filtration of reagent particles into low- permeability portion of the reservoir due to initial sizes of reagent particles and their subsequent swelling. The range of permeability threshold below which the reagent is not filtered into the formation is permitted from 200 to 500 md depending on initial fraction and swelling value. Reagent concentration is controlled depending on reagent injection pressure.EFFECT: increased efficiency when developing non-uniform permeability reservoirs with water drive operation mode due to additional oil production, reduced or stabilized rate of water content growth.6 cl, 7 dwg, 1 tbl

Description

Technical field

The invention relates to the field of geology and field development.

State of the art

There is a method of developing a watered heterogeneous oil reservoir, including the injection into the reservoir of an aqueous suspension of dispersed particles (US Pat. RU No. 2043494, IPC ЕВВ 43/32, Е21В 33/138, publ. 09/10/1995). As dispersed particles, wood flour is used.

The disadvantage of this method is the low efficiency due to insufficient water-insulating ability due to its rapid erosion by pumped water, as well as a limited degree of penetration of the reagent into the reservoir, which does not allow to reduce the mobility of water in remote areas.

There is a known method of developing a heterogeneous oil reservoir, according to which a dispersion of gel particles in an aqueous polymer solution is pumped into the reservoir in the form of a first rim, and an aqueous polymer solution and a polyvalent metal salt are pumped in the form of a second rim (RF patent No. 2299319, IPC ЕВВ 43/22) .

The method is not effective enough due to the fact that it is proposed to use industrially produced water-absorbing acrylamide polymers that are not soluble in water as dispersed gel particles. The indicated class of polymers is characterized by a strong dependence of the degree of swelling on mineralization, and in waters with a salinity of more than 10 g / l these polymers practically do not swell and, accordingly, do not form gel particles.

A known method of regulating the development of oil fields by water flooding, including the injection into the formation of an aqueous polymer solution and a suspension of dispersed particles (US Pat. RU No. 2090746, IPC EV 43/22, publ. 09/20/1997). The polymer used is polyacrylamide or polyoxyethylene, or carboxymethyl cellulose. As dispersed particles, lime powder, quartz sand, diamite flour, a mixture of wood flour with clay powder, clay powder are used.

The disadvantage of this method is the low efficiency due to the low values of the residual resistance factor and the limited degree of penetration of the reagent into the formation, which does not allow to reduce the mobility of water in remote areas.

The use of water-soluble polymers to solve problems of reducing permeability heterogeneity has a number of significant drawbacks: low selectivity — the gelling agent falls into all intervals, including oil-saturated ones; the absence of an effect of increasing filtration resistance in highly permeable zones in reservoirs with high contrast in permeability and / or the presence of fracture zones.

The use of water-soluble polymers to solve problems of reducing permeability heterogeneity for cases with highly saline water is inefficient due to the deterioration of rheological properties, and is also limited by the upper limit of reservoir temperature, up to 90 ° C.

Closest to the claimed invention is a method of developing a heterogeneous oil reservoir, comprising sequentially injecting a gel disperse system (GDS) into the reservoir to isolate an existing system of technogenic cracks and highly conductive channels in the bottomhole zone and then injecting a crosslinked polymer system (ATP) to control the injectivity profile and filtration flows in heterogeneous pore and fractured-pore formations from the side of injection wells (application for invention No. 2008134827/03, IPC ЕВВ 43/22, publication 02.27.2010).

The disadvantage of this method is the low efficiency of isolation of different permeability fractured channels due to the low dispersion of gel particles obtained in the process of pumping a polymer composition on water of one mineralization.

As the analysis of the prior art by the generally accepted approach to the implementation of analogues shows, the use of a fixed volume of reagent for each well or “conditional” division per meter of power, which does not take into account the geological features of the formation, the actual data on the work of the well, the studies conducted on it. Large-scale features such as cracks and highly permeable zones adversely affect the uniformity of the displacement process. Through a system of fractures and highly permeable zones, water quickly reaches production wells and does not displace oil from low-permeability oil-saturated zones of the reservoir. For the effective development of reservoirs of heterogeneous permeability with a water-pressure regime, it is necessary to constantly control water flows and redirect them to oil-saturated zones. The known methods do not provide for control of the flow of injected water.

Disclosure of invention

The aim of the present invention is to provide an effective method for the development of heterogeneous permeability reservoirs with water pressure.

The technical result consists in increasing the efficiency of developing heterogeneous permeability reservoirs with a water mode, expressed in obtaining additional oil production, reducing and / or stabilizing the rate of water cut growth, increasing the current and final oil recovery coefficient (CIN), oil recovery rate, and increasing pressure at the stage injection of a suspension of pre-crosslinked PSP polymer (PPG) and its preservation after injection, reducing unproductive water injection in injection wells.

The essence of the proposed solution lies in the injection of a single-component composition, which forms swollen gel particles in the presence of water, without the occurrence of chemical reactions with a preliminary calculation of the processing technological parameters and technological efficiency. The method allows you to control water flows and redirect them to oil-saturated zones, not only in the near-well zone of the wells, but also in the interwell space.

The technical result is achieved due to the fact that at the first stage the PPP brand and processing parameters are selected taking into account the individual geological and physical characteristics of the object, after which an initial suspension of PPP (PPG) is prepared at the well by mixing at least two volumes of water and one volume of reagent, representing particles of a pre-crosslinked polymer with an initial particle size of from 0.1 to 10 mm; after ripening, the initial suspension is sent to a mixing tank, where it is mixed with water in concentrations of 0.1-0.5% and pumped into an injection well using pumping units such as ACN (CA) -320 and SIN-32, while the suspension of reagent particles during injection it is maintained in suspension, either with special pumping equipment that allows you to create the necessary turbulent flow in the entire volume of the used tank, or using paddle mixers to create a turbulent mode in the volume of used e capacities. Technological tanks included in the ACN (CA) -320 or SIN-32 set can also be used as containers.

All the signs of the above method are significant and are in a causal relationship with the technical result.

Brief Description of the Drawings

Figure 1. Layered models, which are a heterogeneous formation in the form of a series of hydrodynamically isolated layers, each of which is characterized by its thickness, porosity and permeability, which vary in spatial coordinates;

Figure 2. Lognormal distribution of permeability over the thickness of the reservoir.

Figure 3. Geological and hydrodynamic model (GDM) based on the GFC of the object after adaptation according to the actual history of development;

Figure 4. Technology design.

Figure 5. Comparative analysis of technologies: crosslinked polymer systems, gel disperse systems, PSP (PPG);

6. Injection profile before and after PPP injection;

7. Research results for different contrasts between the permeability of the layer K1 and K2;

The implementation of the invention

One of the important conditions for the implementation of the proposed method is a qualitative selection of technological parameters of the injected rim, affecting the parameters of the bottom-hole and remote zone of the reservoir as applied to each injection well at the site of impact.

To do this, for a section of the oil reservoir where it is supposed to be treated with reagent PSP (PPG), a complex of design works is carried out, including:

- analysis of the development of the object on the basis of static data (reservoir properties) and dynamic data (development parameters) in order to determine the hierarchy of wells, characterized by the presence and degree of communication in the reservoir, to determine the hierarchy of wells by the degree of heterogeneity;

- analysis of data from previous well surveys: geophysical studies of flowmetry and thermometry to analyze data on injection well profiles and production well flow profiles, hydrodynamic research data to analyze established relationships in the system of injection and production wells, to determine the response time of a production well to injection into the injection well, tracer studies of the interwell space with the aim of analyzing the filtration-reservoir capacities parameters of the reservoir, of the links in the system of injection and production wells;

- studies of PPP (PPG) with actual solvents in order to make decisions adequate to the conditions of the studied oil production facility. At the same time, adequate solutions are understood to mean solutions that provide the necessary level of technological parameters: the required characteristics of the PSP (PPG) (degree of dispersion, degree of swelling, the elastic modulus of the maximum swollen PSP), the required parameters of the working suspension (rim volume). Parameters can be adjusted during the injection based on the result of pressure;

- conducting a feasibility study to select the composition for optimal technological (additional oil production) and economic effect (PI profitability index, NPV discounted cash flow).

The proposed algorithm for the selection of technological parameters of treatments takes into account the individual characteristics of the processed object and is based on modeling a stratigraphic reservoir with heterogeneous permeability using initial information, including geological and physical characteristics (GPC) of the reservoir, data on the actual development of the object, data on geological and field studies.

The algorithm uses layered models, which are a heterogeneous formation in the form of a series of hydrodynamically isolated layers, each of which is characterized by its thickness, porosity and permeability, which vary in spatial coordinates - Figure 1. The reservoir is characterized by a lognormal distribution of permeability over the thickness of the reservoir - Figure 2. Liquids are considered incompressible, gravitational and capillary forces are not taken into account, piston displacement.

The calculation is carried out for each section of the oil reservoir, where it is supposed to be treated with reagent PSP (PPG), with the adaptation of the model according to the actual indicators of well development included in the section - Figure 3. and the subsequent forecast of technological efficiency - Figure 4.

In figure 3. The geological and hydrodynamic model (GDM) based on the GFC of the object after adaptation according to the actual development history is given. 1 - design oil recovery factor, 2 - design oil displacement coefficient, 3 - oil and gas production without adaptation, 4 - point for the last actual date, 5 - oil and gas after adaptation, 6 - actual points, 7 - point for the last actual date.

Based on the obtained data on the contrast of the permeability of the washed high-permeability zone and the oil-saturated low-permeability zone, crack opening, the boundary value of the permeability between the washed intervals and the oil-saturated intervals of oil displacement, a conclusion is drawn about the structure of the formation and the degree of its heterogeneity. In accordance with these data, select the brand and volume of the rim of the PSP (PPG).

Such a preliminary calculation allows to reduce the risks of inefficient treatments, to choose the right volumes of the composition in order to achieve the maximum technological and economic effect, to reduce unproductive reagent consumption.

PSP (PPG) polymer is a one-component reagent that forms a particle gel, in the presence of water, without chemical reactions. The absence of other components ensures the formation of the required structures when large volumes of reagent are injected into the formation.

Preparation of the initial suspension is carried out directly at the well by mixing the reagent with water in the ratio of at least 2 volumes of water and 1 volume of reagent PSP (PPG), depending on the specific conditions and tasks, the properties of the water and brand PSP (PPG) .

The initial particle size of the reagent is from 0.1 to 10 mm. Depending on the particle size, the following grades of PPP (PPG) are used (Table 1):

PSP brand Particle size PSP-1 0.1-1 mm PSP-3 1-3 mm PSP-5 3-5 mm PSP-10 5-10 mm

The selection of the PPG brand is determined based on the calculated indices of reservoir heterogeneity: the contrast of the permeability of the washed high-permeability zone and the oil-saturated low-permeability zone, crack opening, the boundary value of the permeability between the washed intervals and the oil-saturated intervals of oil displacement, as well as the values of the salinity of the injected and produced water. Moreover, the higher the heterogeneity of the formation and the salinity of the waters, the larger the particle size of the PSP (PPG) must be chosen.

When it enters the water, the particles begin to actively absorb water, increasing in size from 2 to 15 times. According to laboratory data, the degree of swelling at 120 ° C (times) after 1 hour with solvent mineralization, respectively, 10 g / l and 100 g / l: (4.4), (2.3); after 72 hours: (7.6), (5.6). Ripening time is from 30 to 120 minutes.

PSP (PPG) is characterized by a limited degree of influence of mineralization on the degree of swelling within 30% with a ten-fold increase in mineralization and the absence of thermal degradation within formation temperatures up to 120 ° C.

After maturation, the required amount of reagent, determined during design, is pumped into the well using the pumping unit ACN (CA) -320 and SIN-32 at a working concentration of 0.1-0.5%.

The suspension of reagent particles during injection is maintained in suspension by special pumping equipment that allows you to create the necessary turbulent flow in the entire volume of the tank used, exceeding the sedimentation rate of the particles, taking into account the fraction and degree of swelling, or using paddle mixers to create a turbulent mode in the volume of used capacities. Technological capacities included in the ACN (CA) -320 or SIN-32 set can also be used as containers.

The concentration of the reagent during injection depends on the resistance pressure during the passage of the reagent through the perforations and the function of pressure growth as cracks and / or highly permeable zones are filled. A gradual increase in pressure means an increase in resistance in the crack and / or highly permeable zone as it is filled with reagent and transitions of the flow to other zones with lower permeability. If the injection pressure approaches the maximum, the concentration decreases to a level that allows continuing the injection of the reagent, or a temporary transition to the injection of water is carried out in order to move the injected reagent deep into the reservoir, followed by returning to the injection at the minimum concentration and continuing the injection as described above until the planned injection the amount of reagent in full.

The reagent is able to selectively penetrate into cracks and a highly permeable matrix due to initially relatively large particle sizes, followed by their accumulation and compaction in the crack and / or highly permeable matrix. As the crack fills, the pressure gradient increases, which leads to a redistribution of the composition flows into the next highly permeable zone (less highly permeable relative to the previous one). Thus, high selectivity of processing is achieved.

According to laboratory data, the swollen particle is not filtered into the low-permeability part of the reservoir even at high pressure gradients, which eliminates damage to the oil-saturated part of the reservoir. The range of the threshold permeability below which the reagent is not filtered into the reservoir is from 200 to 500 mD, depending on the initial fraction and the amount of swelling.

For the preparation and injection of PPP (PPG), there is no need to use specialized equipment such as KUDR, which allows the implementation of the invention to use widely used special equipment - SIN-32, ACN (CA) -320.

A comparative analysis of the invention with currently applied technologies: crosslinked polymer systems, gel-dispersed systems is shown in FIG. 5. The advantage of the present invention is that the proposed method:

- not limited by the time of gelation, not limited by the time of swelling, because swollen gel particles are deformed under pressure, do not stick together and constantly maintain their mobility in the formation, which allows them to penetrate into remote zones of the formation, thereby increasing the efficiency of the technology;

- provides increased filtration resistances in high-permeability layers in the bottom-hole zone of wells and in inter-well space, while not damaging the low-permeable oil-saturated part of the reservoir, due to which high selectivity of treatment is achieved (Fig.6);

- provides increased filtering resistances in highly permeable zones for reservoirs with fracture zones and high permeability contrasts (Fig. 7), including for cases characterized by the presence of in-situ flows between layers with high and low permeability;

- not limited in effective use for cases with high salinity of formation and / or injected water, can be used in conditions of high formation temperatures up to 120 ° C;

- provides the ability to set the desired level of injectivity after reagent injection, by selecting technology parameters.

- provides a long effect time, since PSP (PPG) is guaranteed to retain its properties in reservoir conditions for more than 1 year.

Claims (6)

1. A method of developing reservoirs heterogeneous in permeability, including injecting a pre-crosslinked polymer — PSP into the formation of an aqueous suspension, characterized in that the PSP brand and processing parameters are selected taking into account the individual geological and physical characteristics of the object, after which the initial PSP suspension is prepared at the well by mixing at least two volumes of water and one volume of reagent, which is a particle with an initial size of from 0.1 to 10 mm, after maturing for no more than 120 minutes This suspension is mixed in a container with water and pumped into the injection well at a working concentration of 0.1-0.5%, while the suspension of reagent particles is kept in suspension during the injection, while at the same time filtering of the reagent particles into the low-permeability part of the reservoir is prevented due to the initial the size of the reagent particles and their subsequent swelling, while the range of the threshold permeability below which the reagent is not filtered into the reservoir, allow from 200 to 500 mD depending on the initial fraction and the degree of swelling, the concentration of the reagent is regulated depending on the injection pressure of the reagent. 2. The method according to p. 1, characterized in that the PSP is taken in the form of a single-component reagent with a wide fractional composition from 0.1 to 10 mm with a limited degree of swelling from 2 to 15, with a limited degree of influence of mineralization on the degree of swelling within 30% with a tenfold increase in mineralization and the absence of thermal degradation within formation temperatures up to 120 ° C; 3. The method according to p. 1, characterized in that the reagent is pumped into the well using a pump unit CA-320 or SIN-32. 4. The method according to p. 1, characterized in that the suspension of reagent particles during injection is maintained in suspension by pumping equipment that allows you to create the necessary turbulent flow in the entire volume of the used tank, or using paddle mixers to create a turbulent mode in the volume of the used tank. 5. The method according to p. 1, characterized in that the technological tanks included in the set of CA-320 or SIN-32 are used as containers for mixing the reagent with water. 6. The method according to p. 1, characterized in that the concentration of the reagent is regulated depending on the injection pressure of the reagent so that if the injection pressure approaches the maximum concentration, it is reduced to a level that allows continued injection of the reagent, or a temporary transition to the injection of water is carried out, followed by return to injection at minimum concentration.

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