RU2559983C1 - Method of high-viscosity massive oil pool development - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method of high-viscosity massive oil pool development includes identifying separate production zones with similar oil-filled thickness in the pool cut, drilling of the pool as per any known scheme of injectors and producers with as dense grid as possible. At that productive formations of the lower production zone are penetrated in all drilled wells, oil is extracted from the lower production zone in natural mode from all wells and formation pressure is monitored at all production zones. When formation pressure in the upper production zone comes close to saturation pressure, in the well grid injectors and producers are identified to form the first and second orbits in regard to injectors, then the lower zone is isolated in injectors and producers and productive formations of the upper production zone are penetrated. Working agent in the form of steam is injected through injectors to the upper production zone and oil is extracted from producers of the first orbit in the lower zone and from producers of the second orbit in the upper production zone. Temperature of extracted oil is monitored. When temperature of extracted oil comes close in the producer to maximum permitted value, for the purpose of operation of downhole pumping equipment the operating interval is isolated in the well and penetration is performed of productive formations not included into development before; an then at increase in current steam and oil ratio above the profitable value steam injection to injectors is stopped and working fluid in the form of cold water is injected into them until limit water cut of extracted oil is reached.

EFFECT: increased efficiency of oil pool efficiency development due to regulated oil extraction process in the pool cut considering changes in parameters of formations and oil in the pool.

2 tbl, 9 dwg

Description

The invention relates to the oil industry and may find application in the development of deposits of high-viscosity oil of massive type.

A known method of developing a massive reservoir of highly viscous oil, including the allocation of separate production facilities into the deposits, drilling wells, injecting steam alternating with air into upstream horizontal injection wells, taking oil through downstream horizontal production wells in each facility, while producing oil from the facilities carried out from top to bottom and reduce the temperature of the injected coolant from object to object by 30-60 ° C, and in the lower object maintain the temperature Ura coolant not lower than 100 ° C. The development of each downstream object is carried out after the development of a deposit zone in the upstream object (see RF patent No. 2334096 of 09.24.2007, IPC: Е21В 4/24).

However, the use of this method in the development of a massive reservoir with a hydrodynamic connection between production facilities due to the development of the reservoir from top to bottom leads to the advancement of bottom water, an increase in water cut, as well as to partial burial of oil in the pillars of the reservoir of the lower object due to the breakdown of bottom water and, as result, to reduce the effectiveness of reservoir development.

There is also a known method for developing a massive reservoir of highly viscous oil, adopted by the authors as a prototype, which includes separating individual production facilities into the deposits by section, drilling wells to the bottom of the lower production facility using one of the systems, pumping coolant into the wells and taking oil. According to the method, in each vertical well, as a rule, lateral horizontal shafts are drilled in the lower part of each production facility, changing their azimuthal direction relative to each other. Given the presence of a hydrodynamic connection between production facilities, sidetracking is carried out sequentially from the bottom up. When developing one sidetrack, a special thermally insulated string is lowered to the sidetrack in the vertical wellbore, and conventional tubing pipes are introduced into the sidetrack. Then steam is pumped into the sidetrack and the well is left for impregnation. Next, a thermally insulated column is removed, and a sucker rod pump is lowered into the well and put into operation until a minimum cost-effective oil production rate is achieved. The steam injection and oil extraction cycles are repeated until the maximum permissible flooding of the produced products is achieved, while all sidetracks are sequentially developed and transferred to the areal injection of the displacing agent, for example, water, steam, into injection wells and oil is taken through production wells (see RF patent No. 2213857 dated 09.24.2007, IPC: Е21В 4/24).

However, taking into account that the massive reservoir is a hydrodynamically coupled system, when oil is taken from the lower object, the pressure in all objects decreases along the reservoir section and when the pressure decreases below the saturation pressure, the gas released from the oil locks the oil into dead ends. At the same time, due to the loss of gas dissolved in oil, a multiple increase in oil viscosity occurs, which leads to a decrease in the potential oil recovery coefficient for the period of development of the reservoir, and, as a result, to a decrease in the efficiency of development of the reservoir.

The objective of the present invention is to increase the efficiency of the development of deposits by regulating the process of extracting oil through the section of the reservoir, taking into account changes in the parameters of the reservoirs and oil in the reservoir.

This object is achieved by the fact that in the inventive method of developing a massive reservoir of highly viscous oil, individual production facilities with the same oil-saturated thickness are separated by the reservoir, the reservoir is drilled according to any known arrangement of injection and production wells, the working agent is injected into injection wells and oil is taken from producing wells.

The salient features of the claimed method are:

- drilling a deposit is carried out with the maximum possible mesh density;

- open productive formations of the lower production facility in all drilled wells;

- carry out the selection of oil from the lower production facility in natural mode from all wells;

- carry out monitoring of reservoir pressure in all production facilities;

- when the formation pressure in the upper production facility approaches the saturation pressure in the well network, injection wells and production wells are distinguished that form the first and second orbits relative to the injection wells;

- in injection wells and production wells of the second orbit, the lower object is isolated, productive formations of the upper production object are opened;

- carry out the injection into the injection wells of the working agent in the form of steam in the upper object;

- carry out the selection of oil from the lower object of producing wells of the first orbit and from the upper object of producing wells of the second orbit;

- when approaching the temperature of the extracted oil in the producing well to the maximum allowable temperature for the operation of the deep pumping equipment in the well, the working interval is isolated and productive formations not previously covered by the development are opened and oil is selected from them;

- when the current oil-steam ratio rises above a cost-effective level, steam is stopped pumping into injection wells and the working agent is pumped into them in the form of cold water until the maximum water cut of the produced oil is reached.

The specified set of essential features provides an increase in the efficiency of reservoir development due to the regulation of the oil extraction process along the reservoir section, taking into account changes in the parameters of the reservoir and fluids in the reservoir during the development process. So at the first stage of development, oil is taken from the lower production facility from all drilled wells in a natural mode, while using the natural energy of the formation to the maximum, reservoir pressure is monitored in all production facilities and oil is sampled until the reservoir pressure approaches the pressure in the upper object saturation, preventing the release of dissolved gas from oil and increasing the viscosity of oil. Thus, the “effect of foamed oil” is maintained when it moves to the selection zone together with the gas dissolved in it in an “occluded state”, preventing the chaotic movement of oil and the dissolved gas released from it in the free phase when the gas begins to “overtake” the oil, not participating in its displacement. When the reservoir pressure in the upper production facility approaches the oil saturation pressure of the gas, the development mode of the reservoir is changed, while injection wells and production wells of the first and second orbits are distinguished from the wells in injection wells, the lower object is isolated in injection wells and production wells of the second orbit and the open productive formations of the upper production facility, and then injected into the injection wells of the working agent in the form of steam in the upper object and carry out the selection of oil from the lower object of the producing wells of the first orbit and from the upper object of the producing wells of the second orbit. When steam is injected into the upper zone of the reservoir, the resulting vapor chamber spreads over the reservoir area from the injection well to the opened productive formations of the producing wells of the first and second orbits, heating high-viscosity oil. Due to the continuously injected steam, the steam chamber is constantly expanding. At the same time, condensate formed as a result of steam cooling under the influence of gravitational forces penetrates into the lower zones and simultaneously with the steam provides oil displacement from these zones from top to bottom. Each zone also transfers its heat to the neighboring zone due to heat transfer. It should also be noted that, as a rule, the lower zones are characterized by deteriorated productivity compared to the upper ones; therefore, in the lower zone, lateral filtration is slower than in the upper ones, and the influence of gravitational forces, on the contrary, is greater. At the same time, monitoring the temperature of the produced product allows you to timely change the selection area of the produced product for individual wells and change the movement of the heat front, increasing the coverage of the reservoir by heat. Thus, the proposed method, providing regulation of the oil recovery process along the section of the reservoir, taking into account changes in the parameters of the reservoirs and fluids in the reservoir, improves the efficiency of developing a massive reservoir of highly viscous oil.

The claimed combination of essential features is not known to us from the prior art, therefore, the claimed invention is new. The claimed features of the invention are not obvious to the average person skilled in the art. In this regard, we believe that the claimed invention has an inventive level. The invention is industrially applicable, since the available equipment and technology developed by us, allow us to implement the method in full.

In FIG. 1 shows an area pattern for drilling a deposit; in FIG. 2 - in-line scheme for drilling a deposit; in FIG. 3 - option of opening productive formations in injection and producing wells at the first stage of development when two production facilities are allocated to deposits; in FIG. 4 - option of opening productive formations in injection and production wells at the second stage of development during the injection of a working agent in the form of steam when two production facilities are allocated to deposits; in FIG. Figure 5 shows the dependence of oil viscosity on pressure during the transition to the dissolved gas mode after the reservoir pressure drops below the saturation pressure for the reservoir conditions of the Perm – Carbon deposit of the Usinsk deposit; in FIG. 6 shows an unloading from a model constructed according to the areal pattern for drilling a deposit shown in FIG. 1, showing the distribution of the temperature front with various options for opening productive formations of producing wells according to options 1-3 and 5-10; in FIG. 7 - unloading from a model constructed according to the areal pattern of drilling a deposit shown in FIG. 1, in the form of streamlines characterizing the movement of filtration flows, showing the relationship between injection and production wells according to options 1-3 and 5-10; in FIG. 8 - unloading from a model constructed according to the areal pattern of drilling a deposit shown in FIG. 1, showing the propagation of a temperature front according to embodiment 4; in FIG. 9 - unloading from a model constructed according to the areal pattern of drilling a deposit shown in FIG. 1, in the form of streamlines characterizing the movement of the filtration flows, showing the relationship between the injection and production wells according to option 4.

The method is implemented as follows.

Production facilities are allocated in the context of the deposit, taking into account the same total effective oil-saturated thickness of the combined reservoirs. The drilling of the deposits is carried out with the maximum possible density of the grid according to any of the known patterns of the location of injection and producing wells, for example, according to the areal scheme (see Fig. 1) or in-line scheme (see Fig. 2). In all drilled wells, productive formations of the lower production facility are opened. The deep pumping equipment is lowered into the wells and the first stage of development is carried out - the selection of oil from the lower production facility in natural mode from all wells. They monitor reservoir pressure in all production facilities using control wells (not shown in the diagram). Preliminarily, in laboratory conditions, the dependence of oil viscosity on pressure is established during the transition to the dissolved gas mode after the reservoir pressure drops below the saturation pressure. So, by laboratory tests it was established that the pressure of oil saturation with gas for reservoir conditions of the Perm-Carbon deposits of the Usinsk deposit is 7350 kPa (see Fig. 5). When the reservoir pressure in the upper production facility approaches the saturation pressure, they move to the second stage of development. In the well network, injection wells 1 and production wells 2 are formed that form the first orbit relative to the injection wells and production wells 3 that form the second orbit relative to the injection wells (see Fig. 1). In the injection wells 1 and production wells 3 of the second orbit, the lower object is isolated, for example, using a packer, the productive formations of the upper production object are opened and the working agent is injected into the injection wells 1 in the form of steam into the upper object. Oil is sampled from the lower object of production wells 2 of the first orbit and from the upper object of production wells 3 of the second orbit using deep pumping equipment lowered into production wells. Monitor the temperature of the selected oil. When the temperature of the selected oil in any production well approaches the maximum allowable temperature for the operation of the deep-pumping equipment, they go to the third stage of development, that is, they isolate the working interval, for example, using a packer, open, for example, by perforation, productive formations not previously covered by development and carry out oil selection from them.

Variants of the method are possible when, in the context of a deposit, two or three operational objects are distinguished depending on its thickness. When two production facilities are identified at the third stage of development, when the temperature of the extracted oil in any producing well of the first orbit approaches the maximum allowable temperature for the operation of the deep pumping equipment in the well, the working interval of the lower object is isolated, for example, using a packer and the productive formations of the upper producing object are opened wells of the first orbit. When the temperature of the selected oil in any producing well of the second orbit of the upper object approaches the maximum permissible temperature for the operation of the deep pumping equipment, they again proceed to take oil from the lower object of the second orbit, that is, they remove the packer, which insulates the lower object of the second orbit, and lowers it the lower object is a deep-pumping equipment, since due to gravitational forces, the condensate formed displaces the oil from top to bottom. With repeated increases in the temperature of the extracted oil in any producing well of the first and second orbits, the well is transferred to the cyclic oil selection mode. With an increase in the current oil-gas ratio above a profitable level, they proceed to the fourth stage of development - they stop pumping steam into injection wells and pump the working agent in them in the form of cold water until the maximum water cut of produced oil is reached - 98%.

With an increase in the thickness of the deposit to 150 m, three operational facilities with the same oil-saturated thickness are distinguished in the section of the deposit (not shown in the diagrams). In this case, at the third stage of development, when the temperature of the extracted oil in any production well of the first orbit approaches the maximum allowable temperature for the operation of the deep pumping equipment, as well as when two objects are separated, the working interval of the lower object is isolated in the production well of the first orbit, for example using a packer and open productive formations of the upper object of the producing wells of the first orbit. With a further increase in the temperature of the extracted oil to the maximum permissible temperature for operation of the deep-pumping equipment in the producing wells of the first and second orbits, open, for example, by perforation, productive formations of the middle object that were not previously covered by the development. The option of re-commissioning the lower object in the production wells of the first and second orbits is possible. With repeated increases in the temperature of the extracted oil in any producing well of the first and second orbits, the well is transferred to the cyclic oil selection mode. With an increase in the current oil-gas ratio above a profitable level, they proceed to the fourth stage of development - they stop pumping steam into injection wells and pump the working agent in them in the form of cold water until the maximum water cut of produced oil is reached - 98%.

It is possible that in each production facility (regardless of their number) sidetracks or radial bends are drilled in each vertical well, while during the commissioning of each production facility, the working agent is injected and (or) oil is taken simultaneously through all sidetracks or radial bends.

The proposed method can be implemented on the Permian-Carboniferous deposits of the Usinsky field with an oil-saturated thickness of 100-150 m. The deposit is located at a depth of 1500 m with an oil viscosity of about 710 MPa · s. In the context of the deposit, from 2 to 3 production facilities with a thickness of each object of 50 m can be distinguished. When implementing the method, vertical injection and producing wells with a depth of 1,500 m are drilled to the bottom of the lower object, for example, positioning them along a five-point system along a 250 × grid 250 m. The cost-effective steam-oil ratio for the Perm-Carboniferous deposits of the Usinskoye field is 7-8 t / t.

The possibility of implementing the proposed method and its advantages over other methods is proved by the created geological and technological model. Thermohydrodynamic calculations for predicting technological indicators for the options were carried out using an applied simulator.

When updating the created geological and technological model, it was accepted that the oil is heavy, highly viscous. In connection with the application of thermal methods to increase oil recovery, the modeling of the corresponding production period was carried out using the thermal option of the simulator.

The updated model is represented by a sector of four 5-point development elements with dimensions along the x and y axis of 1900 × 1650 m with a total reservoir thickness of 160 m with an injection vertical well in the center of each element and vertical production wells around, the total number of active cells of the model was 114838 units , the boundary conditions were set taking into account the actual decrease in reservoir pressure at the level of the initial position of the VNK (-1310 m).

Initially, using the updated model, it was found that the distribution of the working agent in the form of steam through the section of the deposit occurs most optimally when it is pumped into the upper object of injection wells, regardless of the number of selected objects. Further studies were carried out for a period of 30 years of development when the formation pressure in the upper production facility approached the saturation pressure, that is, from the second stage of development. During the research, various options for the sequence of opening productive intervals in production wells of the first and second orbits were considered. In all cases, one development period of the deposit was considered - 30 years and the same cumulative injection of steam - 4371 thousand tons. The main research results are shown in table 2.

As can be seen from the table below, under the same scenario conditions in options 1-3 and 5-10, cumulative oil production, steam-oil ratio and oil recovery coefficient are comparable. The research results are also confirmed by the presented discharges from the hydrodynamic model in FIG. 6 and 7. As can be seen in FIG. 6, corresponding to research options 1-3 and 5-10, the temperature front propagation when steam is injected into the injection well and oil is taken from various objects of production wells of the first and second orbits is observed mainly along the injection wellbore. At the same time in FIG. 7, also corresponding to research options 1-3 and 5-10, it can be seen that the movement of the filtration flows through the formation is observed mainly in the upper object.

The best results were obtained according to option 4, corresponding to the claimed method, namely, the highest cumulative oil production was obtained - 1318 thousand tons, the maximum oil recovery coefficient - 8.5% and the minimum vapor-oil ratio - 3.3 t / t. The research results of the present method are also confirmed by the presented unloading from the hydrodynamic model in FIG. 8 and 9. As seen in FIG. 8, the temperature front when steam is injected into the injection well and oil is taken from the lower object of the first orbit and the upper object of the second orbit extends significantly further relative to the injection well bore. At the same time in FIG. 9, also corresponding to research option 4, it can be seen that the movement of filtration flows is observed throughout the section of the reservoir.

Thus, studies have confirmed the effectiveness of the proposed method and the ability to achieve the stated goal is to increase the efficiency of reservoir development by regulating the process of oil recovery through the reservoir section, taking into account changes in the parameters of the reservoirs and oil in the reservoir, namely changes in reservoir pressure, oil temperature, and also the oil and gas ratio .

Claims (1)

A method for developing a massive reservoir of highly viscous oil, including isolating, by the reservoir, individual production facilities with the same oil-saturated thickness, drilling the reservoir according to any of the known patterns of injection and production wells, pumping a working agent into injection wells and extracting oil from production wells, characterized in that drilling of the deposit is carried out with the maximum possible density of the mesh, open the productive layers of the lower production facility in all drilled with wells, they select oil from the lower production facility in natural mode from all wells, monitor reservoir pressure in all production facilities and, when the formation pressure in the upper production facility approaches the saturation pressure in the well network, injection wells and production wells are formed that form the first and second orbits relative to the injection wells, while in the injection wells and production wells of the second orbit the lower object and openings are isolated tons of productive formations of the upper production facility, inject the working agent into the injection wells in the form of steam into the upper facility and take oil from the lower production well of the first orbit and from the upper production well of the second orbit, monitor the temperature of the oil being sampled and, when the temperature is selected, oil in the production well to the maximum allowable temperature for the operation of the deep pumping equipment in the well isolate the working interval and vayut productive layers that were not previously covered by the design, and further by increasing the current attitude above paroneftyanogo profitable level stop steam injection into injection wells and produce therein download working agent in the form of cold water until the water cut marginal oil.

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