RU2504650C1 - Method of development of flooded oil deposit - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: casing is sunk into well to perforate the bed. Oil and water saturation intervals and impermeable seam sizes are analysed. Casing part is cut out to expand the borehole in said interval. Fluid is injected in string for packer to define the bed specific capacity. Fluid circulation is defined by injecting fluid via casing string-borehole annulus. In case circulation exists, isolation composition is injected to produce isolation bridge inside casing string 20-30 m above perforation interval. In case circulation does not exist, isolation composition is discharged via casing string-borehole annulus to interval of perforation of oil-and water saturated bed zone to fill expanded bore expanded interval with isolation composition. After hardening of isolation composition, isolation composition is drilled to produce the shield opposite said saturated zone. Isolation quality is analysed. Bed perforation is repeated to resume its development.

EFFECT: lower labour input, accelerated process, higher isolation quality.

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Description

The invention relates to the field of development of oil fields, the layers of which are water and oil saturated zones, separated by impermeable natural layers, and is intended to isolate annular flows in the wells between the oil and water saturated zones of the formation.

A known method for the development of oil-water deposits (patent RU 2015312, IPC ЕВВ 43/22, published on 06/30/1994), including the injection of the insulating composition into the reservoir and the creation of an artificial screen, and before the injection of the insulating composition determine the minimum cross-sectional size of the natural lenticular layer in monolithic deposits and the thickness of the cut-off layer of the aquifer, and an artificial screen is created under the lenticular layer with a radius equal to twice the thickness of the cut-off layer of the aquifer and Pressure speed to 3.0-8.0 MPa.

The disadvantage of this method is the low strength of the created screens.

There is a method of developing waterlogged oil fields (patent RU 2065025, IPC ЕВВ 33/13, published on 08/10/1996 in Bull. 22), including drilling their production wells, at least part of which crosses natural impermeable layers in the reservoir, and the creation of screens based on insulating compositions that separate the water-saturated zones of the formation from oil-saturated, while the insulating composition is fed into the reservoir under the natural layer and above it with the possibility of setting the natural layer of screens bottom and top, while the thickness of the screen above the natural layer is taken from the condition of isolation of the natural layer from the reservoir, and the total thickness of the screens is taken from the condition of their resistance to the pressure drop that occurs during well operation.

The disadvantages of this method are:

- firstly, the total thickness of the screens is taken from the condition of their resistance to the pressure drop that occurs during well operation, and the volume of insulating material is determined from the ratio determined by calculation, while the pressure drop can vary with time, and the radius of the insulating screen may be insufficient for reliable isolation of the water-saturated zone from the oil-saturated zone of the formation with a sharp jump in pressure drop;

- secondly, in the best case scenario, the radius of the screen should correspond to twice the thickness of the cut-off water-saturated zone of the formation, and the thickness of the screen should provide its resistance to the maximum possible pressure drop that occurs during well operation, it should be borne in mind that one meter of the thickness of the natural layer withstands the pressure drop up to 1.5 MPa. This condition is not always maintained, which leads to premature flooding of the oil-saturated zone of the reservoir;

- thirdly, the low efficiency of the method, due to the fact that the presence of a screen opposite and lower than the natural layer during the development of an irrigated oil reservoir does not exclude the possibility of a breakthrough of water from the bottom up (behind-the-casing flows) into the oil-saturated zone of the reservoir due to their low strength, which reduces anhydrous well operation period;

- fourthly, the complex technology of preparing the insulating composition, which is prepared by mixing equal parts of an organosilicon emulsion, oil and water in a mixing unit and pumped into the perforated intervals of the formation with the sale of its cement, also the high costs of the components of the insulating composition.

The closest in technical essence and the achieved result is a method of developing flooded oil fields (patent RU 2420657, IPC ЕВВ 43/32, published in bulletin No. 16 dated 06/10/2011), including drilling their production wells intersecting impermeable natural layers in a productive formation, descent of casing strings with subsequent perforation of the productive formation, study of its oil and water saturation and intervals of their occurrence, sizes of impenetrable natural layer and creation of insulating screens composition, separating the water-saturated zone of the formation of oil-saturated zones. Based on the research results, the thickness of the oil-saturated zone of the formation is determined, when the thickness of the oil-saturated zone of the formation is more than 4 m, a part of the casing string is cut out in the interval above the lower perforations of the oil-saturated zone of the formation and until the bottom of the well, the wellbore is expanded in this interval, the extended interval of the wellbore is filled with an insulating composition, which is used as a cement mortar, and when the thickness of the oil-saturated zone of the formation is less than 4 m, temporary isolation of the intervals of perforation of the productive surface is performed with a colmatizing compound, cut out a part of the casing from the roof of an impenetrable natural layer to the bottom of the well, expand the wellbore in this interval, fill the extended interval of the well with the insulating composition and create a packer by introducing into the bottomhole zone of the oil saturated zone of the well, after waiting for the insulating composition to solidify, make a hole packer to the roof of the natural interlayer with leaving a screen opposite the oil-saturated zone, after which repeated perforation of adnoy column opposite net pay zone formation and development wells, with inflow of oil from the oil saturated formation zone below produce viable quantities without acid treatment pressure.

The disadvantages of this method are:

- firstly, when implementing this method, a significant part of the casing is cut out (from the roof of an impenetrable natural layer to the bottom), which leads to an increase in the complexity of the method. From the experience of practical application in SLE. No. 8607 NGDU "Aznakaevskneft" cutting 6 m of string with a diameter of 168 mm lasted 20 hours, so when deep bottom, for example 40 m, cutting the casing is delayed for 5-6 days, which leads to very large financial and material costs and to the inappropriateness of using this method;

- secondly, the low quality of annular cross-flow isolation in the well, which is associated with the possible watering of the well through the bottom during the subsequent development of the flooded field during the operation of the oil-saturated zone of the formation, since the isolation of the annular cross-flow is carried out without pressure, while its quality is not controlled in addition, cement as an insulating composition does not provide uniform penetration into the pores of an impermeable natural layer, which means that it is not possible to obtain a reliable monolithic a screen from an insulating composition separating the water-saturated zone from the oil-saturated zone of the formation in the range of an impermeable natural layer;

- thirdly, the low efficiency of development of waterlogged oil fields, since isolation of the annular flow according to this method leads to a complete rejection of the water-saturated zone of the reservoir and its withdrawal from further development of the water-logged oil field, and often in the process of developing a water-saturated oil field, it becomes necessary to use a water-saturated formation zones both for maintaining reservoir pressure and for intra or inter-well pumping of water.

The technical objectives of the invention are to increase the efficiency of the method of developing a watered oil field by eliminating annular flows, reducing the complexity and duration of its implementation, as well as increasing the efficiency of the method of developing a watered oil field due to the possibility of involving a water-saturated zone of the formation in the development of a watered oil field.

The problem is solved by a method of developing an irrigated oil field, including drilling it with production wells crossing a formation consisting of a water-saturated zone separated by an impermeable natural layer with an oil-saturated zone, lowering the casing followed by perforation of the formation, studying its oil saturation and the intervals of their occurrence, the size of impermeable interlayers and creating a screen from an insulating composition that separates the water-saturated zone of the reservoir tons of oil-saturated zone, cutting out a part of the casing string, expanding the borehole in this interval, filling the extended interval of the wellbore with an insulating composition, after waiting for the insulating composition to solidify, drilling an insulating composition with a screen on the opposite to the oil-saturated zone of the formation, perforation opposite the oil-saturated zone of the formation.

What is new is that when placing the water-saturated zone below the oil-saturated zone of the formation and the thickness of the impermeable natural layer from 4 to 8 m, a part of the casing string is cut out in the interval 1-1.5 m below the roof of the water-saturated zone of the formation and at least half of the impermeable natural layer from the roof water-saturated part of the reservoir, expand the borehole in this interval, lower the mechanical packer on the pipe string, make it land in the casing string above the cut-out part of the casing string, but below the perforation intervals the oil saturated zone of the formation, by injecting liquid through the pipe string under the packer, the specific injectivity of the formation is determined, with the specific injectivity of the formation below 0.5 m ³ / (h · MPa), an clay solution heated to a temperature of 40-50 ° C is injected and the specific throttle response to a value of 0.5 m ³ / (h · MPa) and higher, after which the presence of fluid circulation is determined by pumping fluid through the annular space with fluid exit through the intervals of perforation of the oil-saturated zone of the formation to the surface, then the pipe string is removed from the fur using an anic packer and lowering the pipe fill string with the drillable packer and planting it in the same interval as the mechanical packer, if there is circulation under pressure, the insulating composition is injected with its output through the annular space and the formation of an insulating bridge inside the casing for 20-30 m above the interval of perforation of the oil-saturated zone of the formation, in the absence of circulation, the insulating composition is removed along the annular space to the interval of perforation of the oil-saturated zone of the formation, as an isol of the lining composition, microcement is used, the pipe filling string is removed, after waiting for the hardening of the microcement, the insulating bridge is drilled to the packer to be drilled, then the quality of isolation of the casing flow is determined by pumping isotope-labeled fluids into the well; waterlogged oil field, in the presence of a casing crossflow, the isolation work of the casing crossflow is repeated, then the water-saturated zone of the formation is introduced into the development.

The proposed method is carried out when placing the water-saturated zone below the oil-saturated zone of the formation and with a thickness of the impermeable natural layer from 4 to 8 m, and the cutting interval is selected taking into account the maximum possible sump and the possibility of opening the roof of the aquifer, so cut out part of the casing in the interval of 1- 1.5 m above the roof of the water-saturated zone of the formation and at least half of the impenetrable natural layer above the roof of the water-saturated part of the formation.

It has been experimentally established that when the thickness of the impermeable natural layer 4 is less than 4 m, the application of the proposed method is ineffective, due to the fact that the strength of the screen of the insulating composition in the annular space 8 will not provide reliable isolation of the annular flow in the well between the water and oil-saturated zones of the formation, and the thickness of the impermeable natural layer 4 of more than 8 m, the application of the proposed method is ineffective due to the high cost, complexity and duration of its implementation.

Figure 1, 2, 3, 4, 5, 6, 7 schematically depicts the implementation of the method of developing a watered oil field

The method is implemented as follows.

A method for developing a watered oil field involves drilling it with production wells 1 (see FIG. 1) intersecting formation 2.

The formation 2 consists of a water-saturated zone 3, separated by an impermeable natural layer 4 and located above the oil-saturated zone 5. A casing 6 is lowered into the well 1 and fixed in it.

In the casing 6 of the well 1, the oil-saturated zone 5 of the formation 2 was perforated with the formation of perforations 7. During the operation of the well 1, the wastewater from the water-saturated zone 3 of the formation 2 along the annular space 8 of the casing 6 of the well 1 and the impermeable natural layer 4, represented by clays, breaks through the perforation holes 7 of the oil-saturated zone 5 of the formation 2 into the well 1, and the produced oil is flooded. This is due to the fact that the pressure in the water-saturated zone 3 of formation 2 is higher than in the oil-saturated zone 5 of formation 2. According to field studies, the nature of oil saturation and the intervals of their occurrence, the size of the impermeable natural layer 4 are determined. The porosity and residual oil saturation of formation 2 are determined.

When the thickness of the impermeable natural layer is from 4 m to 8 m, for example, 7 m, part 9 (see FIG. 2) of the casing 6 (see FIG. 1) is cut out in the range of 1-1.5 m below the roof of the water-saturated zone 3 layer 2 (for example, 1, 5 m) and at least half the thickness of the impermeable natural layer from the roof of the water-saturated zone 3 of layer 2, for example, with a thickness of the impermeable natural layer h = 7 m, cut out h = 7/2 = 3.5 m. Thus, the height of the cut-out part 9 of the casing 6 is: 3.5 + 1.5 = 5 m. Cutting is carried out by any known device, for example, with with the help of a universal cutting device (UVU), lowered into the well on a pipe string (not shown in FIGS. 1, 2, 3, 4, 5).

For example, the interval of occurrence of the oil-saturated zone 5 of formation 2 is 1720-1725 m, below in the interval 1725-1732 m there is an impenetrable natural layer 4, below which in the interval 1732-1739 m lies the water-saturated zone 3 of formation 2. Thus, part 9 is cut out ( see figure 2) in the range of 1728.5-1733.5 m casing 6 (see figure 1).

The wellbore 1 is expanded in the interval 1728.5-1733.5 m of the cut-out part 9 (see FIG. 2) of the casing 6 (see FIG. 1), for example, by lowering the hydraulic nozzle 10 (see FIG. 3) on the string pipes 11 and pumping a liquid, for example fresh water, through a pipe string 11 through a hydraulic nozzle 10. An extension 12 of the wellbore 1 (see Fig. 1) is made in the interval of the cut-out part 9 (see Fig. 2) of the casing 6 (see figure 1).

After removing the nozzle 10 (see FIG. 3) with the pipe string 11 into the well 1 on the pipe string 13 (see FIG. 4), the mechanical packer 14 is lowered (for example, the mechanical action packer of the PRO-YAMO grade manufactured by NPF PACKER ", Oktyabrsky, Republic of Bashkortostan, Russian Federation). The mechanical packer 14 is planted in the casing 6 above the cutout part 9 of the casing 6, but below the perforation intervals 7 of the oil-saturated zone 5 (see Fig. 1) of formation 2, i.e. in the range of 1725-1728.5 m.

The fluid injection through the pipe string 13 (see Fig. 4) under the packer 14 determines the specific injectivity of the formation 2. For example, the specific injectivity of the formation 2 was 0.3 m ³ / (h · MPa).

Since the specific injectivity of formation 2 turned out to be lower than 0.5 m ³ / (h · MPa), a clay-acid solution heated to a temperature of 40-50 ° C, represented by mixtures of hydrochloric and hydrofluoric acids, is injected into the formation, for example, a mixture of 10- 15% HCl + 3-5% NH ₄ F · HF with the addition of 1% to 2% acetic acid CH ₃ COOH. The specific throttle response is adjusted to the above value, i.e. up to 0.5 m ³ / (h · MPa) and higher, for example up to 0.7 m ³ / (h · MPa).

Apply:

- synthetic acetic or regenerated acid (CH ₃ COOH) according to GOST 19814-74;

- technical hydrochloric acid (HCl) according to GOST 857-95;

- acid ammonium fluoride (N ₄ F · HF), hydrofluoric acid GOST 9546-75.

A clay-acid solution, heated to a temperature of 40-50 ° C, captures sandy water-saturated rocks and intensifies the dissolution of clay formations in the rock, which allows to increase the specific injectivity of the formation.

Then, the presence of fluid circulation, for example, fresh water, is determined by pumping it from the wellhead through a pipe string 13 (Fig. 4) under the packer 14 and then through the annular space 8 with fluid outlet through the perforation intervals 7 of the oil-saturated zone 5 (Fig. 1) of the formation 2 along the annular space 15 (see figure 4) to the surface.

Next, remove the pipe string 13 with a mechanical packer 14 and lower the casting pipe string (not shown in FIGS. 1, 2, 3, 4, 5, 6, 7) with the drill-through packer 16 through passage (see FIG. 5) and land it in the same interval (1725-1728.5 m) as the mechanical packer 14. As a drill-through packer 16 used, for example, a TatNIPIneft design packer (see patent RU No. 2395669 “Drillable packer”, IPC E 21 V 33/12 publ. In bulletin No. 21 dated 07/27/2010 or patent RU No. 2374427 "Drill packer", IPC Е21В 33/12 publ. In bulletin No. 23 dated 11/27/2011).

In the presence of fluid circulation under pressure, not exceeding the maximum allowable pressure on the casing 6, for example up to 9 MPa, the insulating composition 17 is pumped through the pipe string 13 (see figure 4). Then, the pipe string 13 is pressed through using a squeezing liquid, for example, waste water, with a density of 1180 kg / m ³ with the output of the insulating composition through the annular space 8 (see Figs. 4 and 5) with the formation of an insulating bridge 18 (see Fig. 5) inside the casing 6 at 20-30 m above the perforation interval 7 (Fig. 1) of the oil-saturated zone 5 of the formation 2. The estimated amount of the insulating composition is determined by the geological service of the repair enterprise empirically.

In the absence of fluid circulation through the annular space 8 (see Fig. 6) and the fluid escapes into the water-saturated zone 3 of the formation 2, the insulating composition 17 is pumped along the pipe string 13. Then the pipe string 13 is forced through the pumping liquid, for example, waste water density of 1180 kg / m with the conclusion of the insulating composition in the annular space 8 (see Fig.7) to the perforation interval 7 (see Fig.1) of the oil-saturated zone 5 of formation 2.

As an insulating composition, microcement is used, for example, superthin ultracement produced by NPO Polytsell CJSC (Vladimir) according to TU 5739-019-56864391-2010. Fresh water with a density of 1000 kg / m ^{3 is} mixed with microcement in a mass ratio of 2: 3, respectively. The use of microcement ensures the penetration of a mixture of water and microcement into thin pores and cracks. A mixture of water and microcement has high mobility, and the strength of the hardened mixture is higher than the strength of cement stone obtained from a mixture of water with conventional cement used in well repair, which allows you to create a reliable and durable screen that prevents the influx of water. The estimated volume of the used insulating composition is determined by the technological service of the repair enterprise empirically.

Then remove the casting pipe string and leave the well 1 to wait for the hardening of microcement (OZM).

After waiting for the hardening of microcement, the insulating bridge 18 (see Fig. 5) is drilled to the drillable packer 16 (see Fig. 7). Drilling is carried out using a bit and a downhole screw motor lowered into the well 1 on a pipe string (not shown in FIGS. 1, 2, 3, 4, 5, 6, 7).

A study is made of the quality of isolation of the annular flow by injection of isotope-labeled fluid into the well 1 (see Fig. 7). For this, a pipe string 19 is lowered into the perforation interval 7 of the oil-saturated zone 5 of the formation 2.

Further, for example, according to the technology for determining annular flows by injection of isotope-labeled liquids (fresh water with a density of 1000 kg / m ³ containing radon) introduced by TNG-Group LLC in the wells of OAO Tatneft. This method is based on the introduction into the well of a certain volume of radon-labeled fluid and subsequent control of its distribution by gamma-ray logging (GC) along the wellbore, the results of which determine the presence or absence of a casing flow in the well. Or, for example, ferromagnetic fluid is used as isotope-labeled fluid, which is pumped under pressure into the well, after which the signal changes depending on time, based on the data obtained from the measuring sensors, conclusions are made about the presence of casing flows, their direction and size. To do this, lower the device described in patent RU No. 2255220, “Device for monitoring annular flows”, IPC Е21В 47/10, publ. in bull. No 18 of June 27, 2005

According to the results of the study, in the absence of a casing overflow, repeated perforation (not shown in Figs. 1, 2, 3, 4, 5, 6, 7) of the oil-saturated zone 5 (see Fig. 1) of the formation 2 and it is introduced into the development of the flooded oil Place of Birth.

If there is a casing overflow, the isolation of the casing overflow is repeated as described above.

Next, a water-saturated zone 3 (see Fig. 1) of formation 2 is introduced into the development of a water-saturated oil field. To do this, a packer 16 (see Fig. 5) and an insulating composition 17 are drilled to the bottom of the water-saturated zone 3 (see Fig. 1) of the formation 2, then re-perforate the water-saturated zone 3 of the formation 2 and put it into operation, for example, for downhole pumping of wastewater in order to maintain reservoir pressure.

Implementation of the proposed method will reduce the complexity, reduce the duration of the isolation annulus flow in the well, which in turn will reduce material and financial costs and create a reliable and durable screen from an insulating composition that separates the water-saturated zones of the reservoir from oil-saturated zones, which ensures the effective exclusion of the annular flow from the water saturated zone of the formation to the oil saturated zone.

In addition, the possibility of including in the development of an irrigated oil field a water-saturated zone of the formation allows to increase the efficiency of developing an irrigated oil field.

Claims (1)

A method of developing a water-flooded oil field, including drilling it with production wells intersecting a formation, consisting of a water-saturated zone separated by an impenetrable natural layer with an oil-saturated zone, lowering a casing string followed by perforation of the formation, studying its oil saturation and intervals of their occurrence, the size of an impermeable natural layer and a screen from an insulating composition separating the water-saturated zone of the formation from the oil-saturated zone is cut out e parts of the casing string, expansion of the borehole in this interval, filling of the extended interval of the borehole with an insulating composition, after waiting for the insulating composition to solidify, drilling an insulating composition with a screen opposite the oil-saturated zone of the formation, perforation opposite the oil-saturated zone of the formation, characterized in that when placing the water-saturated zone below the oil-saturated zone of the reservoir and the thickness of the impermeable natural layer from 4 to 8 m, a part of the casing string is cut in the range of 1-1.5 m the same as the roof of the water-saturated zone of the formation and at least half of the impermeable natural layer from the roof of the water-saturated part of the formation, expand the wellbore in this interval, run the mechanical packer on the pipe string, plant it in the casing string above the cut part of the casing string, but below the intervals of perforation of the oil-saturated zone formation, pumping fluid through the pipe string below the packer define specific pickup reservoir when the specific pickup reservoir below 0.5 m ³ / (h · MPa) to produce a preheated injection layer to a temperature of 40-50 ° C glinokislotnogo solution and adjusted to a specific acceleration value of 0.5 m ³ / (h · MPa) or higher, and then detect the presence of circulating the liquid by pumping the liquid from the annulus fluid outlet perforations at intervals oil saturated formation zone to the surface, then remove the pipe string with a mechanical packer and lower the pipe fill string with the drillable packer and land it in the same interval as the mechanical packer, if there is circulation under pressure, pump and gelling composition with its withdrawal through the annulus and the formation of an insulating bridge inside the casing string 20-30 m higher than the perforation interval of the oil-saturated zone of the formation, in the absence of circulation, the insulating composition is taken out of the casing space to the perforation interval of the oil-saturated zone of the formation, microcement is used as the insulating composition, the casting pipe string is removed, after waiting for the hardening of microcement, the insulating bridge is drilled to the drilled packer, then pumped Isotope-labeled fluids into the well determine the quality of annular cross-flow isolation, in the absence of a cross-over flow, re-perforate the oil-saturated zone of the formation and introduce it into the development of a water-saturated oil field, if there is a cross-flow, the work to isolate the annular cross-flow is repeated, and then the water-saturated zone of the formation is introduced into the development.

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