RU2304697C1 - Well completion method - Google Patents

Abstract

FIELD: methods or devices for cementing, for plugging holes, crevices, or the like for well construction and workover.

SUBSTANCE: method involves primary exposing productive reservoir; preparing casing pipe for lowering in well; lowering casing pipe provided with shoe, check valve and baffle plate in well; performing direct casing pipe cementing through the shoe along with following cement mix, baffle plug and two portions of displacement liquid injection so that density of the first displacement liquid portion exceeds that of the second one to obtain summary hydrostatic pressure of above two portions in casing pipe greater than productive bed pressure; waiting for cement mix hardening; performing pressure testing of casing pipe; secondary exposing productive reservoir with perforation operation; providing productive reservoir inflow. Casing pipe preparation includes covering of inner and sections of outer casing pipe surfaces arranged within perforation interval with heat-insulation material so that heat insulation layer extends at least from shoe to the first displacement liquid portion level. Before cement mix injection buffer liquid is additionally injected in well. Lubrication hydrophobic liquid in injected in well between cement mix and buffer plug injection. Amount of lubricating hydrophobic liquid is equal to casing pipe volume defined by baffle plate and check valve and summed with reserve volume corresponding to casing pipe section length spaced 1-3 m below check valve. The casing pipe is covered with several heat insulation layers. Maximal total heat insulation layer thickness is selected with taking into consideration of free cylindrical former passage through the casing pipe and possibility of casing pipe fishing from outside with elevator. Minimal heat insulation layer thickness is 0.5 mm. Cement mix is injected in two portions. The second portion is supplied in amount equal to hole annuity volume around casing pipe and inner casing pipe volume defined by baffle plate and shoe additionally has swelling additive.

EFFECT: extended time of water-free well operation, decreased quantity of well workover for water shutoff, prevention of asphalt-tar-paraffin deposit generation in bottomhole reservoir zone, improved bottomhole reservoir zone treatment, extended range of suitable compositions, including corrosive compositions, to be used.

3 cl, 1 ex, 2 tbl, 2 dwg

Description

The invention relates to the completion of construction and overhaul of wells in complex fields, in particular to the processes of opening productive formations, fastening the wellbore, treatment of the bottom-hole zone of oil and gas wells and development, as well as methods for preventing cracking of cement stone in the annular space, methods of protection against corrosion of the borehole equipment and methods for preventing the occurrence of deposits of asphalt-resin-paraffin components.

A well-known method of well completion, including drilling a producing formation, overlapping a producing formation with a casing string and uncoupling by cementing, perforation against the producing formation and intensifying the flow of formation fluid [1].

The disadvantages of this method are the high likelihood of cracks in the hardened cement stone (ring) during perforation, which can lead to accelerated flooding of well products in the annulus with water above or below the formation. As well as a high degree of corrosion of the casing string during measures to intensify oil production by eliminating formation pollution by acid treatments of the bottom-hole zone of the reservoir (PZP). In addition, for the processing of PPP, it will be necessary to lower tubing pipes (tubing) into the column space, which will entail additional costs of time and money.

The closest is the method of completion, including the initial opening of the reservoir, preparation for lowering the casing, lowering the casing equipped with a shoe, non-return valve and a stop ring, direct cementing of the casing through the shoe with sequential injection of cement, separation plug and two servings of squeezing fluid provided that the density of the first portion of the supply liquid exceeds the density of the second portion of the supply liquid and the total hydrostat pressure in the casing of these two portions, exceeding the pressure in the reservoir, waiting for the cement to harden, crimping the casing, re-opening the reservoir with perforation and treating the bottom-hole zone of the reservoir, causing formation fluid to flow [2].

The disadvantage of this method is that it also does not provide measures to prevent cracking of cement stone in the annular space of the well during perforation and, as a result, annular flows of formation fluids occur. In particular, a rigid-elastic casing string is in direct contact with the cement ring and, upon elastic expansion, instantly transfers a breaking force to the cement stone.

The method does not provide for the suppression of pressure pulses in the explosion of charges of a perforator and propagating wave sound pulses in the vertical direction up the casing and in the radial direction to the cement ring and rock. In addition, cement hardening is subject to contraction during hardening, which reduces adhesion in the contact areas “casing - cement stone - rock”. As a result, there is another additional factor contributing to the occurrence of crossflows of formation fluids, and measures that reduce this negative factor, in the known method is also not provided.

In addition, in the prototype, however, as in the analogue, the check valve at the end of cementing remains filled with cement mortar. In this case, in practice, there are often cases of failure (usually a ball check valve) due to the high structural and rheological properties of the thickened cement mortar, the presence of large abrasive (and therefore high hardness) particles and crystals that have fallen into the sealing zone and other reasons . Therefore, resorting to the creation of excess pressure at the wellhead. Under these conditions, while waiting for the cement to harden (MLC), the casing stays inflated. After the OZC, the pressure in the column space is released and the casing, unlike the cement ring, is compressed. This in the future also leads to the occurrence of annular crossflows of formation fluids in the contact zone "casing - cement stone". Leaks in the above contact zone and cracking of cement stone at an early stage of hardening (which has not reached the potential strength) can also occur due to the operation of crimping the casing. As a result of many of the above processes, annular space sealing remains insufficiently reliable.

In this method, it is impossible to use even slightly concentrated acid solutions as the first portion of the squeezing liquid. Since the time between the end of cementing and perforation can be very long, in fact, during this period, the acid (even if inhibited by additives) is neutralized and intense casing corrosion occurs. Meanwhile, acid treatments are the most highly effective methods of intensifying oil production during the treatment of bottom-hole zones (BHP).

When an inflow is triggered, the moving oil from the bottom of the well to the wellhead cools significantly (loses its initial reservoir temperature), as a result of which asphalt-resin-paraffin deposits (AFS) are deposited on the walls. And this process in a known manner is uncontrollably fast.

The technical task of the claimed invention is to improve the quality of annular space insulation in the bottomhole formation zone, to reduce the consequences of negative processes that create conditions for the occurrence of annular crossflows and watering of well products, expanding the range of compositions used, including those which are corrosive to SCR, and preventing the formation of paraffin deposits in the well.

The solution of the technical problem is achieved by the fact that in the method of completion of the well, including the initial opening of the reservoir, preparation for lowering the casing, lowering the casing equipped with a shoe, non-return valve and a stop ring, direct cementing of the casing through the shoe with sequential injection of cement a solution, a separation plug and two servings of the squeezing liquid, provided that the density of the first portion of the squeezing liquid is higher than the density of the second portion and obtaining the sum hydrostatic pressure in the casing of the indicated two portions, exceeding the pressure in the reservoir, waiting for the cement to harden, crimping the casing, re-opening the reservoir with perforation and treating the bottom-hole zone of the reservoir, causing formation fluid to flow in preparation for the casing in the section opposite the reservoir at least from the shoe to the level of the first portion of the squeezing fluid in the casing, it is covered inside and outside the mat Isalat heat-insulating material, an additional buffer fluid is pumped in front of the cement mortar, and a portion of the hydrophobic lubricant in the volume equal to the casing string space from the stop ring to the non-return valve plus a spare volume below the non-return valve by 1 between the cement and the separation plug -3m.

In addition, the casing is covered with several layers of Isollat, the maximum total thickness of which is selected taking into account the passage of the cylindrical template inside the casing and the possibility of the elevator being taken up by the elevator from the outside, and the minimum is 0.5 mm.

In addition, the cement mortar is injected in two packs, and an expanding additive is introduced into the second pack, in the volume of the annular space of the well opposite the casing with the specified material from the outside and the inner space of the casing from the stop ring to the shoe.

Heat-insulating material "Isollat" is made in accordance with TU 2216-001-59277205-2002 and Amendment No. 1 to it of 2005. Material of polymer microspheres (microspheres) with water, polymer binder compositions and other additives (flame retardant - flame retardant additives, rust converters, inhibitors corrosion, white and coloring pigments, surfactants). Microscopic (from 10 to 500 microns in size with different bulk density in the range from 50 to 650 kg / m ³ ), filled with discharged air, these balls are suspended in a thick viscous (1400 - 3000 cP) liquid and therefore it is convenient to apply it on the surface any form. The consumption of material per layer is 0.25-0.50 kg / m ² (or about 1 liter per 2 m ² ), the thickness of one coating layer is 0.038 cm. After drying of the Izollat material, an elastic coating forms with good adhesion. The density of the Isollat liquid material, depending on the brand, varies in the range of 500-750 kg / m ³ , and the dried coating - 300-410 kg / m. The drying time of one layer is 24 hours with a polymerization period of 12 hours at room temperature. The boiling point of the material "Isollat" + 118 ° C. The temperature of the surface on which the Isollat material is applied should be from +7 to 120 ° C. The finished coating is operated at temperatures from -45 to + 150 ° C (short-term up to + 200 ° C). The Isollat material is transported in vehicles with a temperature not lower than + 4 ° С and not higher than + 45 ° С. Under the same conditions, it is stored in a sealed plastic or metal container. The Isollat material is low toxic and belongs to the 4th hazard group according to GOST 12.1.007. After drying, the Isollat material does not emit harmful chemicals.

Figure 1 shows a casing string coated with inside and outside a coating of material "Isollat"; figure 2 shows the moment of completion of cementing of the well.

The method is as follows.

They open the reservoir by drilling and go deeper below the sump. The face is washed and the drill string is raised. Replace the layout of the bottom of the drill string to a rigid one to carry out a series of works on preparing the wellbore for launching the production casing string. In particular, complicated narrowed areas with ledges and sharp bends of the wellbore are being worked out, thereby calibrating the wellbore, and also washing the well and the bottom hole zone of the formation, possibly using “controlled mud” methods. At the end of the flushing, a lubricant is added to the circulating drilling fluid. In the meantime, drilling equipment is being prepared for running the casing and the casing itself. The latter are brought to the rig and placed on racks in sections in the order of their descent. The casing string is subjected to inspection, inspection and control tests. In particular, they inspect, measure lengths and diameters, check threads, perform hydraulic tests, etc. In addition, a section for attaching a section of a wellbore opposite the reservoir, at least from a shoe to the level of the first portion of the squeezing fluid, is subsequently portions of perforation fluid in the casing string are coated inside and outside with Isollat insulation material in several layers. The casing is coated with the Isollat material with a brush, roller, or spray gun as usual. Each layer is dried during the day and only then the next layer is applied. This operation can be performed in the summer directly on the rig. But since the temperature of the surface on which the Isollat material should be applied must be positive and considerable time is required to cover several layers with drying of each layer, these types of work can be done in advance at the indoor pipe-metal base of the drilling enterprise or in a factory manufacturer. However, regardless of where the coating will be made with the Isollat material, the following condition must be observed (Fig. 1). The casing inside is coated with Isollat material for a total thickness, based on the condition of the subsequent passage of a cylindrical template into them.

For example, for casing with a nominal diameter D _HT = 114-219 mm, the difference between the inner nominal diameter of the pipe d _BT and the outer diameter of the cylindrical template d _{H. Ш.} is 3 mm. This means that the maximum thickness of the inner layer of the Isollat material for these pipes should not exceed 1.5 mm.

The total thickness of the Izollat coating on the outer surface of the casing, taking into account the outer diameter D _HT, should not be greater than the inner diameter of the elevator D _V.E. used when lowering the casing string. For lowering casing strings with a diameter of 146-219 mm, the inner diameter of the elevator used is 4 mm larger. This means that the maximum thickness of the outer layer of Izollat material for them should not exceed 2 mm, which is a condition for the possibility of guaranteed capture of the casing by the elevator from the outside and its closure.

At the same time, the dried coating on pipes made of Isollat material should subsequently perform many functions in the well: anticorrosive, damping, soundproof, increasing the adhesion of cement stone to the coated casing, and thermal insulation. Therefore, for the successful manifestation of these properties, it is advisable to create a coating thickness of both inside and outside, at least 0.5 mm.

After the preparation of the wellbore, the drill string is lifted and installed by the finger (during cluster drilling) or thrown onto bridges for transportation to another drilling rig.

Start the casing descent (figure 2). First, the bottom of the casing is lowered into the well, including a shoe 7, a filling pipe 2, a check valve 3, an intermediate pipe 4, a stop ring 5 and the first section 6 of the casing coated with Izollat material inside and out.

When casing pipes are fed to the rotor block in the order of descent, a rigid cylindrical template is introduced into the pipe from the coupling side. When lifting the pipe for extension, the template should pass through it and fall out. This is one of the conditions that the squeezing separation plug during cementing does not get stuck in the narrowed inner space of the casing covered with the Isollat material. Next, the subsequent sections 7 of the uncased casing string are lowered. During and after the casing is lowered, preventive flushing of the well is carried out. 8. The necessary volumes of technological solutions are prepared, then cementing the casing is carried out by the usual direct method with cement injected into the casing space and exiting into the annular space of the borehole through casing shoe 1. At the same time, a buffer fluid (not shown), cement mortar and a portion of a hydrophobic lubricating fluid are pumped sequentially, after which the separation plug is dropped and forced through with a two-portion composite process fluid. The cement slurry is pumped in the volume of the annular space of the well from the bottom 9 to the wellhead 10 and the cement nozzle 77 in the casing from the check valve 3 to the shoe 7. Moreover, the cement slurry can also be composite, consisting of the first ordinary pack 12 (in the volume of the annular space of the well from wellhead 10 to the level 13 of the first section 6 of the casing with the material "Izollat"), and the second pack of cement mortar 14 in volume from the level 13 of the first section 6 of the casing to the bottom 9 and the cement nozzle 77 in the casing, into which d pumping spreading additive. The expanding additive for the second pack of cement mortar 14 is introduced either into the mixing fluid for this pack or is added directly to the cement, and then they are dissolved together in water. The volume of hydrophobic lubricating fluid 75, which can be used as oil, motor, transmission or waste oil, etc., is taken from the conditions of filling the inner space of the casing in the section from the stop ring 5 to the check valve 3 plus an additional spare volume below the check valve 3 by 1-3 m, that is, the volume of the part of the filling pipe 2. The last additional spare volume below the check valve will automatically be an additional reserve volume of cement. The volume of the first portion 16 of the process (squeezing and perforating) fluid is taken from the condition of filling the casing opposite the reservoir and with a length of at least 320-350 m. This condition is justified by the fact that traditionally the volume of the perforating fluid filling the space in the casing to this height, for example, with a diameter of 146 mm, choose equal to 4 m ³ and a diameter of 168 mm, equal to 6 m ³ . As the first portion 16 of the selling liquid, for example, a polymer, or salt, or polymer salt, or hydrochloric acid solution, etc., treated with a surface-active additive (surfactant) is used. Moreover, the density of the first portion of the squeezing liquid should be somewhat (usually 30-50 kg / m ³ ) higher than the density of the second portion 17 of the squeezing liquid. As the second portion 17 of the squeezing liquid, an oil product, industrial water or an aqueous solution of polymers or saline solution, etc. are used. The volume of the second portion 17 of the squeezing liquid is equal to the internal volume of the casing string from the level 13 of the first portion 16 of the squeezing liquid, which should coincide with the height at the end of cementing 13 of the first casing string 6, up to the wellhead 10 plus the spare volume. In all cases, it is assumed that the hydrostatic pressure in the casing of two portions 16 and 17 of the squeeze (perforation) fluid in total should exceed the pore pressure in the reservoir by the amount stipulated by the “Unified technical rules for work in the construction of oil, gas and gas condensate fields. " For example, for wells deeper than 2500 m, the excess should be 4-7%.

During the sales process, a hydrophobic lubricating fluid 75 covers the inner surface of the casing with a thin layer and this facilitates the sliding of the rubber separation plug 18 down to the stop ring 5. This positive lubricating effect of the hydrophobic fluid 15 is especially important when passing the separation plug 18 inside the casing string 6, coated inside with Isollat material. In this case, the rubber elements easily slide on the coating of the material "Isollat", and do not peel it off the metal casing. In addition, the hydrophobic film on the casing created by the hydrophobic lubricating fluid 15 protects the metal casing from corrosion in the case of applying the aggressive first portion of the squeezing liquid 16. Considering that the dried coating of Izollat material on the casing exhibits predominantly hydrophobic properties, then the adsorption of hydrophobic liquid 75 on it will be better, and, as a result, the degree of protection against aggressive environment will be higher.

Immediately before receiving a “stop”, a hydrophobic lubricating fluid 75 washes the check valve 3 from the remnants of the second pack of cement mortar 14. Of course, when selling a certain part of the hydrophobic lubricating fluid 75 is consumed during adsorption on the inner surfaces of the column. Therefore, a certain supply is required (1-3 m below the check valve 3) of the hydrophobic lubricating fluid 15 in order to guarantee that the check valve 3 is washed from the cement slurry. After receiving a “stop”, the pressure inside the casing is relieved, and the check valve 3 is reliably triggered (that is, there is no reverse movement of the injected cement mortar 14 and 12 into the string due to the excess of their density over the density of the composite displacement fluid 16 and 17) .

At the end of the sale (upon receipt of the “stop”), the level 13 of the first portion of the squeezing liquid 16 should at least coincide with the upper mark of the Isollat coated first section 6 of the casing. Or better, if the height of the first section 6 of the coated casing is slightly higher (with a certain margin). This is important, since then the well is left on the OZZ. The Isollat material exhibits anticorrosion properties against all types of chemical aggression (acidic, alkaline, etc.), especially since together with the film of a lubricating hydrophobic fluid 15, the protective properties of the obtained two-layer insulation are enhanced. Since the sufficiently low initial water permeability of the coating material "Isollat" in the experiment, equal to 30 g / m ^2/24 hours, it declined to near zero when applied to it the used oil film. In fact, an aggressive chemical environment has been unable for a long time to penetrate through the two-layer insulation to the casing metal, therefore its corrosion is practically absent.

In the period of the OZC, pressure changes on the casing occur. At the initial stage, due to the excess of external pressure in the annular space over the internal in the casing space, the casing is in a compressed state. Moreover, it is quite natural that the coating on the casing of Izollat material both on the inner and outer surfaces is also in a somewhat compressed state due to the hydrostatic pressure of the liquid columns. In turn, the walls of the well 19 in the bottom-hole zone of the formation, on the contrary, expanded elastically (radially shifted). As the cement slurry hardens, pressure from the outside decreases, the casing begins to expand, and the walls of the well shift inward (contract). As a result, a certain pressing force of the hardened cement stone to the walls of the casing is retained. In the bottomhole formation zone, the resulting radial stresses are maximum in magnitude. The mechanism of their action is comparable to the stresses that arise when using an expanding cement mortar. Therefore, despite the phenomena of contraction and shrinkage of ordinary Portland cement stone, nevertheless, the contact pressure of the cement stone with the column remains, and the quality of cementing in the PPP is quite high.

In order to simulate the downhole conditions of cement mortar hardening, we conducted a series of experiments to determine the adhesion strength of a cement stone with a metal and with a metal coated with Izollat material. We took several tubes (bushings) with a diameter of 4 cm and a height of 3 cm, on the inner surface of which the Isollat material was manually applied with a brush. After the coating has dried for at least 24 hours, the lower end of the sleeve was installed in a sealing disk. A cement mortar (Portland cement with W / C = 0.5) was poured inside the sleeve. After 3 days of hardening of the cement stone, the disk was removed and the extrusion force was determined by extrusion.

Given the contact area of the cement stone with the coated sleeve, shear stress (in MPa) was determined, the value of which judged the adhesion quality. For comparison, the shear stress of a cement stone solidified for 3 days in an uncoated sleeve was taken as a base value. The shear stress in the contact of the cement stone with the metal of the sleeve was conventionally taken as unity. In other bushings, the inside was covered with several layers of Isollat material and each of them was dried before subsequent application. The experimental results are presented in table 1.

According to the data obtained, the Isollat material on the tubes in the presence of ordinary cement stone and without excess pressure (at atmospheric pressure) reduces adhesion in the contact zone. The shift usually occurs on the material "Isollat". However, the adhesion quality depends on the thickness of the coating layer of the Izollat material. The maximum shear stresses in the presence of coating on the sleeve were obtained with a total thickness of 1 mm.

Table 1 The effect of the Izollat material on the shear stress of a shrink cement in a metal sleeve No. The number of coating layers from the material "Isollat", pcs. Drying time of the next coating layer, days. The total thickness of the coating of the material "Isollat", mm Shear stress, shares units. from the initial value I II III IV V VI VII one - 0 1.00 2 I one 0.25 0.37 3 II one one 0.50 0.41 four III one one four 0.75 0.62 5 IV one one four one 1.00 0.65 6 V one one four 3 one 1.25 0.51 7 VII one one four 3 one 3 one 1.75 0.34

Next, we conducted comparative studies of bushings without coating and coated with Isollat material in four layers with a total optimal thickness of 1 mm, but in this case, SIGB expansion additive was added to Portland cement (TU 5744-001-00282369-93, TU 5744-002-00282369 -00) and shut the cement slurry at W / C = 0.5.

The calcareous mixture for mining and drilling operations - SIGB - is an analogue of NRS-1, is a powder obtained by grinding the calcined product of a mixture of carbonate rock, phosphogypsum and calcium chloride with additives.

SIGB indicators: content of active CaO + MgO - not less than 80%; CaSO ₄ content - 6-12%; loss on ignition - not more than 3%; fineness of grinding, the residue on the sieve with the side size of the cell in the light - 0.08 mm according to GOST 6613-66 - not more than 25%; blanking time - 100-250 min; water demand - not more than 30%; expanding pressure (for 24 hours at 20 ± 2 ° C) - at least 45 MPa.

The volumetric expansion of cement from Portland cement and the expanding additive SIGB was determined by a known method on a Zhigach-Yarov instrument. After three minutes of mixing, the cement mortar was poured into a glass with a tray on which filter paper was placed inside. The height of the solution in the beaker was approximately 10 mm.

After 10 minutes, a circle of filter paper and a piston with a rod were also placed on top of the cement mortar. They closed the glass with a lid and immersed it in a container with liquid on a tripod. The piston rod was connected to the indicator probe and measured. Based on the difference in indicator indicators, after a certain time, the volume expansion of cement stone was calculated.

A cement mortar with a given concentration of the expanding additive SIGB was also poured into bushings with a sealing disk from below. The basis of the comparison was the shear stress on the press of an ordinary cement mortar from the same Portland cement, but without the SIGB expanding additive. The research results are presented in table.2.

From the data of Table 2 it can be seen that with the expansion of the cement mortar, the adhesion of the cement stone both directly with the metal and with the coating of Isollat material on the metal increases. The volumetric expansion of cement stone in these experiments with a low (up to 1%) SIGB content models the above elastic deformations of the casing string and the borehole wall in the bottomhole formation zone. Therefore, the adhesion of cement stone even without an expanding additive in the PPP will be slightly higher if the Isollat material is present on the casing, or at least it will be the same as when the cement stone is in direct contact with the metal casing.

table 2 Effect of Izollat material on the shear stress of an expanding cement stone with a metal sleeve wall (T = 20 ° C, V / C = 0.525) No. The composition of the mixture,% Volumetric expansion after 2 days.,% Shear stress, shares units. from the initial value Permeability on the 6th day. hardening, micron ² The strength of the cement stone after 2 days., MPa PCT SIGB To bend Compression without cover coated with 1 mm of Isollat material in a free state limited in form in a free state in a closed state in a free state in a closed state one one hundred - 0 1.00 1.00 0.71 - 3.6 - 8.4 - 2 99 one 0.15 1.20 1.22 0.70 - 2.9 - 7.5 - 3 98 2 0.23 - - 1.17 0,095 2.1 2,8 6.7 8.8 four 97 3 1.27 1,58 2.78 1.34 0.143 1.7 3.0 5.9 9.5 5 95 5 5.24 1.79 4.11 2.10 0.147 1,2 2.9 3,5 8.4 6 92.5 7.5 7.02 - - 5.16 0,087 0.5 3.2 2,3 7.2 7 90 10 16.68 1.90 4.16 13.63 - - - 1.3 -

If an expanding cement slurry is pumped into the PZP, then the increasing contact pressure on the Izollat material will significantly increase the shear stress. So, for example, claim 5, at 5% SIGB and, accordingly, a volume expansion of cement stone of 5.24%, shear stress without coating increased only by 79%, and with Izollat material - by 311%. A further increase in the volume expansion of cement stone no longer leads to such a significant increase in shear stresses (Clause 7, with an expansion of 16.68%, the shear stress increased by 4.16, i.e. by another 5% compared to Clause 5).

During the hardening of the cement slurry, temperature changes also occur in the well, as a result of which the casing is either stretched or compressed. A sufficiently thick coating of Izollat material can relax and lengthen — compress directly inside the layer relative to its various sections. Relative displacements inside the Izollat material layer will smooth out some of the vertical displacements (micromotors) of the casing and not transfer them to the cement stone. This will prevent a periodic sharp breakdown of the latter from the rock wall.

After the OZC, the casing string is checked for leaks by injection of liquid into the column. Casing expands when pressure testing. Depending on the diameter, the pressure test for operational casing strings is 7.5-12.0 MPa. In this case, the pipe deformation along the perimeter (generatrix) does not exceed 0.05-0.10%. The coating on the tubes of Izollat material can be extended without disruption of continuity (tears and cracks) by up to 5%. If the amount of expansion of the cement in the PPP is up to 5-6%, then the Izollat material will also withstand (perceive) the radial compression deformation, since up to almost 17% of the volume expansion of the cement stone in laboratory experiments (Table 2, Clause 7) traction was still improving. That is, the forces on testing the casing for tightness due to the presence of a damping elastic coating of Izollat material are practically not transferred to the cement ring.

In addition, Table 2 provides information on the properties of cement stone, in particular permeability, bending strength and compressive strength, obtained from solutions with an expanding SIGB additive. However, some samples were stored in a humid environment in molds for 24 hours before being tested for permeability (at an excess pressure of 4 MPa) and then continued to harden in a humid environment in a free state for 5 days. And other samples were stored during the same time under conditions close to the borehole, i.e. under conditions of comprehensive compression (limited) in forms that prevent the free expansion of cement stone. When testing the strength of cement stone, also some samples were removed from the mold in a day and hardened in a moist environment in a free state, while others were hardened taking into account borehole conditions only in molds (in a closed state) and in a moist environment until the moment of testing.

According to the data obtained, the permeability of cement stone hardening under conditions of comprehensive compression is approximately 1-2 orders of magnitude less than that of hardening in a free state. Moreover, regardless of the amount of SIGB expanding additive, the permeability of the compressed stone remains approximately at the same level, while the permeability of an unlimited stone increases exponentially. In addition, the permeability of the compressed expanding cement stone is multiple and even almost an order of magnitude lower than conventional Portland cement stone.

As can be seen from table 2, the flexural and compressive strength of expanding cement stone, hardening in a free state with increasing concentration of expanding additives SIGB, decreases. The same indicators for expanding cement stone in the closed state are significantly (tens of percent and multiple) higher, and at higher concentrations of SIGB additives they meet the requirements of the norms.

The results of the studies suggest that cementing quality will be significantly improved with the use of an expanding additive SIGB not only by increasing the adhesion of cement stone with a sealing coating of Izollat material on the casing, but also by reducing the permeability of cement stone obtained in borehole conditions and increase strength. The latter property is of particular importance during crimping operations and subsequently during casing perforation, as its resistance to cracking and fracture increases. As a result, the tightness is increased not only in the contact zones, but also of the cement stone itself, as a result, the lining life of the well is increased, since the low-permeability and non-cracked cement stone is resistant to aggressive aqueous media (reservoir fluids and process fluids) and limits their access to the casing along with the Isollat material.

Then the well during canned drilling canned for a period (up to 1-3 months) of the liberation of the estuarine space from the drilling. During this period, the inner layer of the Isollat material, together with a film of a lubricating hydrophobic fluid on it, allows us to maintain the quality of the first (lower) portion of the squeezing (future perforation) fluid 16, since it is isolated from interaction with the casing string metal. When using acid solutions, they will not be neutralized. In turn, aggressive media will not corrode the coated casing.

Then proceed to the perforation of the casing and cement ring opposite the reservoir 19. The most commonly used cumulative perforation. The operation of cumulative perforators is accompanied by large (up to 200 MPa) explosive pressures. Moreover, only a small part of the energy of the explosion does a useful job - creating a hydraulic connection between the column space and the reservoir. The rest of the energy can degrade the quality of the opening of the reservoir due to the impulsive deformation of the casing string during the explosion of charges and subsequent repeated hydraulic shocks caused by the raising of the column of the borehole (perforation) fluid and its subsequent drop, up to the equalization of pressure in the column and annular spaces. In addition, along with pressure pulsations and temperature changes, vertical movements (elongation - compression) of the casing relative to the cement ring are possible. Moreover, the propagation of a sound wave during the explosion of charges and fluid pulsations (periodic movements from the column space into the reservoir) contribute to the formation of stable emulsions of filtrates of drilling and cement solutions, buffer and perforation fluids with formation fluids (oil, oil and water) that had previously entered the formation. sustainable microemulsions. These stable microemulsions significantly reduce the permeability of the bottomhole formation zone and worsen the conditions for oil to move through this area when the well inflow and operation are triggered.

The presence of the Isollat material simultaneously on the inner and outer surfaces of the casing allows creating conditions for a gentle perforation mode. In particular, a pulsed shock wave is primarily perceived by the inner coating, as a result of which a certain part of the microspheres collapse upon elastic deformation of the polymer skeleton. The amplitude of the first pressure pulse will decrease, and hence the subsequent ones. After pulsed deformation of the casing string, the layer will also shrink sharply. It will also collapse the majority of the microspheres (not all due to the presence of a polymer skeleton) and damp the polymer skeleton. Thus, the Izollat material will absorb most of the deformation from the outside and only part of the expansion deformation force will affect the cement stone. And as previously indicated, the cement stone formed in borehole conditions with an expanding additive has increased strength and is therefore quite capable of withstanding significantly reduced forces without cracking. In addition, the soundproofing properties of the Isollat material will reduce the propagation range of the shock wave up the casing, and in the radial direction will further reduce the likelihood of stable microemulsions from process filtrates and formation oil fluids due to vibration phenomena. Subsequent hydroblows will also be damped with the polymer frame and the remnants of the Isollat coating microspheres, so pressure equalization in pipes and annulus will be faster. However, due to the presence of the polymer skeleton of the Isollat material, collapse of all the microspheres will still not occur. The vertical movements of the casing string during pressure pulsations will be partially perceived by the outer layer and extinguished within the Isollat material itself. In general, the degree of hydrodynamic perfection of the opening of the reservoir due to the described mechanisms will already be higher.

In addition, the high anticorrosive properties of the Isollat material on the casing inside and out make it possible to use not only weakly acidic, but also medium acidic (with an increased concentration of acid) perforation liquids. Acidic solutions successfully dissolve the fused elements of the punch in the perforation channels, sediments of the mud screen and rock, however, the casing will not only be exposed to the corrosive environment from the inside, but also from the outside. With less permeability, the cement stone expanding under borehole conditions will also dissolve to a lesser extent with an acid solution. Since the latter will predominantly penetrate into the more highly permeable sections of the reservoir — the reservoir due to the natural absorption of the first squeeze — perforation fluid 16 during perforation and subsequently before the inflow is called.

After perforation, they begin to call the inflow. While the reservoir is being treated with perforation fluid, tubing pipes with downhole equipment for reservoir testing are being lowered. At the end of the tubing descent, the well fluid consisting of the first and second portions of the feed fluid is replaced with a fluid of lower density (for example, fresh water), then its level in the well is reduced by compression. As a result, the hydrostatic pressure in the wellbore will decrease below the pore reservoir and an inflow of formation fluid (oil) will be triggered. Minimum depression on the reservoir should provide the pressure drop necessary to overcome the forces of resistance to the movement of the fluid in the PPP. At this moment, the temperature of the borehole fluid, and consequently, of the downhole equipment (tubing, casing, etc.) is usually lower than in the reservoir. The maximum heat removal occurs when the oil that has entered the well from the reservoir comes into contact with the reservoir temperature of the oil. But since the casing is coated with Isollat insulation material, there will be no sharp cooling of the oil upon contact with this surface of the casing. So, in the PZP, the intensity of the deposition of paraffin will be significantly slowed down. Due to the lower heat dissipation of the coated casing, the tubing warms up faster. Ultimately, the likelihood of the occurrence of a paraffin in the PPP during an inflow call will be significantly reduced.

An example of the method

The depth of the well is 2801 m, the diameter of the bit is 0.2159 m, and the cavernous coefficient of the wellbore is 1.05. The depth of the conductor descent is 500 m, the diameter of the conductor is 0.245 m with a wall thickness of 0.01 m. The diameter of the casing is 0.146 m, the wall thickness of the lower section of the casing with the Izollat material is 0.010 m, the sections are higher on average - 0.008 m. Height from shoe to the non-return valve is 7 m, and from the non-return valve to the stop ring 3 m. The thickness of the productive formation is 15 m, the reservoir pressure is 27 MPa. The distance from the lower level of the reservoir to the “stop” ring is 5 m. We take the stock of hydrophobic lubricant below the check valve to a height of 2 m. The volume of the hydrophobic lubricant will be:

0.785 · (0.146-0.02) ² · 3 + 0.785 · (0.146-0.02) ² · 2 = 0.062 m ³ (or 62 l).

Take the volume of the first portion of the squeezing liquid 4 m ³ . As the latter, we choose a 15% hydrochloric acid solution with a density of 1070 kg / m ³ with a surfactant. The height of the first portion of the squeezing fluid, taking into account the thickness of the Izollat coating inside the casing, will be:

4 / 0.785 · (0.146-0.02) ² = 333 m.

Taking into account the distance from the bottom to the lower level of the reservoir 7 + 3 + 5 = 15 m, we roundly accept the length of the first section of the casing string coated with Izollat material inside for a total layer thickness of 1 mm and outside for a total layer thickness of 1.5 mm , slightly more than 333 + 15 = 348 m and equal to 350 m. The consumption of the Izollat material for coating the casing pipes inside:

3.14 · 0.126 · 350 · 0.001 = 0.14 m ³ .

Isollat material consumption for casing coating from the outside:

3.14 · 0.146 · 350 · 0.0015 = 0.24 m ³ .

Total consumption of Isollat material:

0.14 + 0.24 = 0.38 m ³ (or 380 l).

The composition of the Izollat material is selected from the condition for the maximum content of hollow microspheres (microspheres), for example, consisting of, vol.%:

- polyvinyl acetate latex (50%) - 12;

- surfactant (OP-7) - 2;

- water - 6;

- hollow microspheres (a mixture of glass, ceramic, polymer and ash microspheres) - 80.

The length of the remaining column to the mouth is 2450 m. The volume of the second portion of the squeezing liquid will be:

0.785 · (0.146-0.016) ² · 2450 = 32.5 m ³ .

The density of the second portion of a low concentration (2-4%) KCl saline solution in industrial water is 1040 kg / m ³ . The total pressure of two servings of squeezing liquids in the PPP will be:

1070 · 9.81 · 335 + 1040 · 9.81 · 2450 = 28.5 MPa.

The excess is 28.5 / 127.0 = 1,056, which meets the requirements.

The total volume of two servings of squeezing liquids:

4.0 + 32.5 = 36.5 m ³ .

As a buffer fluid used industrial water in a volume of 6 m ³ .

The volume of the first pack of cement mortar is:

0.785 · 0.225 ² · 500-0.785 · 0.146 ² · 500 + 0.785 · 0.2159 ² · 1.05 · 1950-0.785-0.146 ² · 1950 = 53.79 m ³ .

The density of the first pack of cement mortar with W / C = 0.525 is 1810 kg / m ³ , D _CP = 228 mm, the beginning of thickening 160 minutes (at 30 UEK). The volume of the second pack of cement mortar with W / C = 0.525 from Portland cement and an expanding additive of 5% SIGB (density 1815 kg / m ³ , D _CP = 257 mm, the beginning of thickening 100 min), is equal to:

0.785 · 1.05 · 0.2159 ² · 350-0.785 · 0.1475 ² · 350 + 0.785 · (0.146-0.02) ² · 7 = 7.55 m ³ .

The total volume of cement mortar is:

53.79 + 7.55 = 61.34 m ³ .

In the method, the first portion of the squeezing fluid is simultaneously a perforating fluid. Therefore, it can be pumped when cementing a well, as described above. In addition, all the protective properties of coatings made of Isollat material on the casing inside and outside can also occur if the perforation fluid is pumped through tubing run into the well immediately before perforation. The latter can also be produced in case of SCR with acid solutions in the process of well overhaul. In all cases, the total hydrostatic pressure of two portions of fluids usually exceeds reservoir pressure. The inflow of formation fluid is called up by partially replacing two portions of the feed fluid in the casing with compression.

The effectiveness of the proposed method consists in improving the quality of cementing and the secondary opening of the reservoir by perforation, which will subsequently affect the increase in oil production and the period of waterless operation of the well, reducing the degree of water cut in the production of the well, increasing the overhaul period of the well, increasing the durability of the capital structure - well.

Information sources

1. The technology of drilling deep wells. Textbook for high schools / Mavlyutov M.R., Alekseev L.A., Vdovin K.I. and others. Under the general. ed. prof. M.R. Mavlyutova. - M .: Nedra, 1982.287 s. (p. 245-250).

2. RF patent No. 2054525, Cl. ЕВВ 33/13, application No. 5046284/03 of 06/08/92 / N.A. Petrov, I.S. Khaerov, M.L. Vetland / Publ. 02/20/96. Bull.№5.

Claims (3)

1. The method of well completion, including the initial opening of the reservoir, preparation for lowering the casing, lowering the casing equipped with a shoe, non-return valve and a stop ring, direct cementing of the casing through the shoe with sequential injection of cement, separation plug and two portions squeezing fluid provided that the density of the first portion of squeezing fluid exceeds the density of the second portion of squeezing fluid and the total hydrostatic pressure in bottom of the specified two portions, exceeding the pressure in the reservoir, waiting for the cement to harden, crimping the casing, re-opening the reservoir with perforation and treating the bottom-hole zone of the reservoir, causing formation fluid to flow, characterized in that when preparing to run the casing in the area opposite the reservoir at least from the shoe to the level of the first portion of the squeezing fluid in the casing, it is coated inside and outside with a thermal insulation material With Isollat, an additional buffer fluid is pumped in front of the cement slurry, and between the cement slurry and the separation plug, a portion of the hydrophobic lubricant in a volume equal to the volume of the casing from the stop ring to the check valve plus a spare volume 1- below the check valve 3m. 2. The method according to claim 1, characterized in that the casing is covered with several layers of the specified material, the maximum total thickness of which is selected taking into account the passage of the cylindrical template inside the casing and the possibility of the elevator picking up the casing from the outside, and the minimum is 0.5 mm. 3. The method according to claim 1, characterized in that the cement mortar is injected in two packs, and in the second pack of cement mortar, in the volume of the annular space of the well opposite the casing with the specified material outside and the inner space of the casing from the stop ring to shoes, introduce an expanding additive.

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