RU2354818C2 - Method for development of high-viscosity oil deposit in slightly cemented beds - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: invention is related to methods for development of oil deposits in slightly cemented beds with the help of thermal action. Pressure and production wells are drilled. Coolant is pumped in pressure wells, and oil is extracted from production wells equipped with operational, pump-compressor pipes and equipment for liquid lifting from well. Operational column of production wells is installed below oil bed top. Shaft under operational column is left open to well bottom. Hydraulically isolated cavity is created through production well below oil bed. Protective jacket is installed under operational column to the depth of equipment lowering for liquid lifting. Equipment for liquid lifting is installed higher than the level of oil and water contact. Hydraulically isolated cavity is used for collection and storage of oil bed disintegration products.

EFFECT: increase of oil production due to reduction of number of operations on removal of sand plugs, creation of favourable conditions for operation of underground equipment with simultaneous increase of well debit.

3 cl, 4 dwg, 1 ex

Description

The invention relates to methods for developing oil fields in weakly cemented formations using heat exposure.

A known method of developing oil deposits in poorly cemented formations, in which to combat sand formation during oil production, the bottom of the producing well is blocked with filters or the rocks are fixed with plastics, resins, etc. (book edited by prof. I. Muraviev, “Development and operation of oil and gas fields”, Nedra Publishing House, Moscow, 1965, pp. 158-159).

However, during the production of high-viscosity oil, when the oil is heated to a temperature at which it gains fluidity in the pore space, high-viscosity oil loses its ability to cement unstable rock, which leads to a large amount of sand entering the well with the oil, clogging filters. When fixing the bottomhole of a producing well with plastics, resins, etc. the high temperatures necessary for heating high-viscosity oil break down binders, as a result of which sand plugs are formed in production wells that stop the flow of oil.

Also known is a method of developing an oil deposit in weakly cemented formations, in which, to combat sand development during oil production, the deep well pump of the producing well is equipped with a gas sand separator with a sand trap (AS USSR No. 1760099 dated 08/10/1989, Е21В 43/38).

The disadvantage of the method when using it in the production of highly viscous oil in weakly cemented formations, carried out by means of heat exposure, when sand is actively developing, is the rapid clogging of the sand trap with the products of the destruction of the productive formation, which complicates the operation of the deep pump and necessitates the raising of the sand trap to the surface for cleaning. As a rule, due to the limited size of the sand trap, its clogging occurs more often than the overhaul period of the pump. As a result, oil production in the reservoir is reduced.

There is also a known method for developing a reservoir of high-viscosity oil in weakly cemented formations, adopted by the authors as a prototype, which includes drilling injection and production wells, pumping coolant into injection wells and selecting oil from production wells equipped with production, tubing and equipment for lifting liquid from the well ( RF patent No. 2232263 dated 05/27/2002, ЕВВ 43/24). According to the method, the bottom hole of the vertical wellbore is positioned below the bottom of the oil formation with the formation of an airtight cement cup, a sidetrack is drilled from the vertical wellbore, which is planted with an uncemented slit-like shank, the coolant being pumped into the sidetrack, and oil is taken from the vertical wellbore using a rod pump, installed at the bottom, it was assumed that sand was prevented from entering the sump of the vertical trunk and favorable working conditions for the rod were created th pump.

However, as already mentioned, when high-viscosity oil is heated to a fluidity state, oil loses its ability to cement unstable rock, which leads to a large amount of sand entering the well with oil, therefore, in this method, sand will accumulate in an airtight cement glass and sand will form plugs and, as a result, there is a need for repair work to remove the sand plug at least at least the overhaul period of the sucker rod pump, that is, the production idle time kvazhiny increases.

The objective of the present invention is to increase oil production by reducing the number of operations to remove sand plugs, creating favorable conditions for the operation of underground equipment while increasing the flow rate of the well.

The task is achieved by the fact that for the development of deposits of highly viscous oil in weakly cemented formations, injection and production wells are drilled, coolant is injected into injection wells and oil is extracted from production wells equipped with production, tubing and equipment for lifting liquid from the well.

Salient features of the claimed invention are:

- set the production casing of production wells below the roof of the oil reservoir;

- leave the trunk open under the production string until the bottom of the well;

- create a hydraulically isolated cavity through the production well below the oil reservoir;

- have equipment for lifting fluid from the well above the level of oil-water contact;

- use a hydraulically isolated cavity to collect and store products of the destruction of the oil reservoir;

- install a protective casing under the production casing to the depth of descent of the equipment for lifting liquid;

- the selection of the products of the destruction of the oil reservoir from a hydraulically isolated cavity is carried out cyclically.

The specified set of essential features ensures an increase in oil production by reducing the number of operations to remove sand plugs, creating favorable conditions for the operation of underground equipment while increasing the flow rate of the well, namely: creating a hydraulically isolated cavity below the oil reservoir will allow the collection and storage of oil formation destruction products a long time, for several years, and, as a result, will significantly reduce the idle time I mine well during repair work, installation of a production string below the roof of the oil reservoir will prevent direct breakthroughs of the coolant from the injection wells into the production along the most permeable near-bed part of the reservoir without performing useful work on heating and moving oil through the reservoir, while there is an open bore under the reservoir the column will allow unhindered showers into the isolated cavity to the products of the destruction of the oil reservoir, and the protection of downhole equipment from blockages, in the case of active destruction of the oil reservoir, is carried out using a special protective cementless casing. Thus, a significant reduction in the idle time of the producing well due to a reduction in the number of repair work to remove sand plugs, an increase in the diameter of the well as a result of the destruction of the oil reservoir, which reduces the filtration resistance in the bottomhole zone of the well and increases the flow rate of the well, creates favorable conditions for the operation of underground equipment beyond by preventing the ingress of oil destruction products at its intake and protection of equipment from accidental collapses with a casing provide the creation of conditions for a significant increase in oil production during the implementation of the proposed method.

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 fully implement the method.

In Fig.1 shows a diagram of a producing well in the context.

Figure 2 shows a diagram of a producing well in the context of the original hydraulically isolated cavity.

Figure 3 shows a diagram of a producing well in section with an additional enlarged hydraulically isolated cavity at the bottom of the well.

Figure 4 shows a diagram of a producing well in section with a hydraulically isolated cavity and with equipment for lifting fluid from the well.

The method is as follows. The area of the deposit area is drilled by injection (not shown) and production wells. Each production well 1 (Fig. 1) is drilled from the surface of the earth below the roof of the oil reservoir 2 by 1-3 m. Then, production casing 3 is lowered into the well and cemented. Then, the wells are drilled to the design depth at which the bottom is located below the oil reservoir 2, while the well is left open until the bottom of the well.

In the interval of the production well from the bottom of the oil reservoir 2 to the bottom of the well form a hydraulically isolated cavity. At the first stage of the formation of a hydraulically isolated cavity, blasting, for example a shooting charge, is carried out from the bottom of the oil reservoir 2 to the bottom of the well, forming a cavity 4 of a given size while strengthening and waterproofing the walls of the cavity as a result of the explosion. Torpedoes, for example TShB, are used as a perforated charge. Then, in the near-well part of the well, a more powerful charge, for example, a boiler charge, is placed in the created cavity, and a larger hydraulically isolated cavity 5 is created. An explosive, for example TNT or RDX, is used as a boiler charge. When blasting boom and boiler charges, oil cement mixture with setting accelerator is used as a stemming device. This allows simultaneously with the compaction and fusion of the walls of the cavity 5 as a result of the explosion to create a solid insulating coating on its surface, which prevents the walls from shedding and water entering the cavity.

Blasting operations are carried out according to a specially compiled project for which the calculation of the charge, the design of torpedoes and boiler charges, measures to protect the casing from damage, work safety conditions, etc.

Then, under the production casing 3, a protective casing 6 is installed to the depth of descent of the equipment for lifting liquid. As a protective casing, continuous casing pipes, perforated casing pipes, filter arrangements, etc. may be used, while the diameter of the protective casing is smaller than the diameter of the production string.

In the production wells 1 on the tubing 7, the downhole pumping equipment 8 is lowered to raise the fluid, and rod, electric centrifugal, screw and other pumps can be used.

To reduce the viscosity of oil through injection wells (not shown), the oil formation 2 is heated. Oil under the action of the driving forces that occur when the coolant is injected into the formation 2 enters the producing well 1. When the bottom-hole zone of the well 1 is heated under the influence of the coolant and rock pressure forces there is an intensive destruction of the reservoir and the removal of sand into the cavity 5. At the same time, the radius of well 1 increases. It is known that the amount of fluid inflow into the well according to the Dupuis equation depends on the number of params trench formation, borehole and formation fluid, including the borehole radius. The ratio of flow rates of wells with different radii (all other things being equal) is determined by the dependence:

where Q _p and Q is the oil flow rate of the well with extended and initial radii;

R _to - the radius of the well supply circuit;

r _cf and r _c are the extended and initial radii of the well.

Therefore, as the bottom-hole part of the producing well is destroyed and sand is crushed into the cavity 5, the radius of the well increases in the interval of the reservoir and, as a result, its production rate increases. At the same time, the sand brought out by oil to the intake of the downhole pumping equipment 8 is prevented by the deposition of sand into the cavity 5 under its own weight, which provides favorable conditions for the operation of the downhole pumping equipment, and there is no need for regular shutdowns of production wells 1 for underground repairs associated with the removal of sand plugs, which increases the coefficient of exploitation of wells and, as a result, there is a significant increase in oil production.

An example of a specific implementation. The claimed method can be implemented on the Yaregskoye field of high viscosity oil. The productive layer lies at a depth of 200 m and contains oil with a viscosity of up to 15 thousand Pa · s. The collector is composed mainly of medium- and fine-grained quartz weakly cemented sandstone. When heated, the sandstone is prone to destruction, which leads to intensive removal of sand into production wells. When implementing the method, production wells 1 are drilled from the earth’s surface (Fig. 1) with a bit ⌀ 215 mm to a depth below the oil formation roof by 1 m. The well is cased with a production casing ⌀ 168 mm and cemented to the mouth. Further drilling is carried out with a bit ⌀ 140 mm to a depth of 30 m below the bottom of the oil reservoir.

In the interval of the well 1 from the bottom of the formation to the bottom blasting is carried out to form a hydraulically isolated cavity (figure 2). At the first stage of the formation of a hydraulically isolated cavity, blasting is carried out, for example, of a perforated charge from the bottom of the oil reservoir 2 to the bottom of the well, forming a cavity 4 with a diameter of 0.7 m while strengthening and waterproofing the walls of the cavity as a result of the explosion. Torpedoes, for example TShB, are used as a perforated charge. Then, a more powerful charge, for example, a boiler charge with TNT, is placed in the bottom hole of the well in the created cavity, and a larger hydraulically isolated cavity 5 of a larger diameter with a diameter of 1.8 m is created at a height of 5 m from the bottom of the well.

Thus, the volume of the cavity 5 will be approximately 15 m ³ . A cavity of this volume, given the coefficient of loosening (K _p = 0.8), can accommodate the volume of the reservoir of the initial density, equal to 12 m ³ .

Next, under the production casing 3 install a protective casing 5 to the depth of descent of equipment for lifting liquid. Then, production wells are equipped with downhole pumping equipment, for example, rod pumps, НВ1Б-44-30-15 complete with rocking machines SK-3-1515 or a screw installation UVNP-15/800. The receiving node of the pumps is located in the lower part of the oil reservoir.

The oil reservoir is heated through injection wells (not shown), and the heated oil is pumped to the surface through production wells 1. As the formation 2 warms up, the reservoir breaks down in the bottomhole zone of the well 1. Sand crumbles into the cavity 4. As the reservoir collapses, the borehole diameter increases, which reduces filtration resistance in the bottomhole zone. With a decrease in filtration resistances, an increase in well production is ensured. So, with the destruction of 12 m ^{3 of} sandstone and shedding it into the underlying cavity 4, the diameter of the well 1 in the interval of the oil reservoir 2 will increase on average from 0.14 m to 0.76 m. According to the mathematical dependence (1), the well’s production will increase by 1 , 5 times, based on the condition that the well supply circuit (R _k ) is 25 meters.

When the cavity 5 is filled with sand, the well is stopped, the downhole pumping equipment 8 from the well 1 is lifted and underground repair is performed to remove sand from the cavity 5. From the experience of operating vertical production wells during the development of the Yaregskoye field, it is known that the rate of destruction of the bottomhole zone during heating is approximately 1.8-2.0 m ³ per year. In order to remove the formed sand plugs in the sump of each well and above it, underground repairs are carried out with a regularity of approximately two times a year. The formation of a hydraulically isolated cavity with a volume of about 15 m ³ will reduce the frequency of underground repairs to remove sand plugs by about 6 times.

Thus, a significant reduction in the idle time of the producing well due to a reduction in the number of repair work to remove sand plugs, an increase in the flow rate of the well due to an increase in its diameter as a result of the destruction of the oil reservoir, the creation of favorable conditions for the operation of underground equipment by preventing products from the destruction of the oil reservoir its reception and protection of equipment from accidental collapses with a special casing ensure the creation of conditions for a significant increase in oil production in the development of deposits of heavy oil in weak strata by the proposed method.

Claims (3)

1. A method of developing a reservoir of high-viscosity oil in weakly cemented formations, including drilling injection and producing wells, pumping coolant into injection wells and selecting oil from production wells equipped with production, tubing and equipment for lifting liquid from the well, characterized in that production the casing of production wells is installed below the roof of the oil reservoir, and the trunk under the production casing is left open until the bottom of the well, created through d a hydraulically isolated cavity below the oil reservoir, a protective casing is installed under the production casing to the depth of descent of the equipment for lifting the liquid, while the equipment for lifting the liquid is located above the level of the oil-water contact, and the hydraulically isolated cavity is used to collect and store the products of the destruction of the oil reservoir. 2. The method according to claim 1, characterized in that the hydraulically isolated cavity is created by densification, fusion of its walls and the creation of a solid insulating coating on its surface by first blasting a blast charge in the interval from the bottom of the oil reservoir to the bottom of the well, and then the boiler charge in created cavity shooting charge with the use of stemming from a cement mixture with a setting accelerator. 3. The method according to claim 1, characterized in that the selection of the products of the destruction of the oil reservoir from a hydraulically isolated cavity is carried out cyclically.

Images