RU2531965C1 - Method of well abandonment - Google Patents

Abstract

FIELD: oil-and-gas industry.SUBSTANCE: invention relates to abandonment of evaluation and survey wells at thick oil deposits. Proposed method comprises lowering of string into well with casing string to operate to beds, placing of cement plug in well from mouth to bottom. At abandonment, part of casing string is cut from lower bed bottom to upper bed roof. Then, core sampler is lower in interval of cut section to sample to core located in said cut. Core is analysed to prepare clay with composition complying with that of rock is said cut. Then, small-diameter string plugged from below is lowered from wellhead to bottom. Thereafter, first cement plug is set from bottom to well interval 5 m abode lower bed bottom. Clay bridge is arranged in the well from top end of first cement plug to interval 5 m above upper bed rood. Thereafter, second cement plug is arranged from clay plug upper end to wellhead. First and second cement plugs are fitted using the heat-resistant cement with addition of fibres in amount of 0.2 wt % of dry cement. Small-diameter string is filled antifreeze fluid and FO is lowered down to bottom. Temperature variations are intermittently recorded in borehole after abandonment.EFFECT: higher efficiency and reliability.4 dwg

Description

The invention relates to the oil and gas industries, in particular to the elimination of appraisal and exploratory wells in super-viscous oil fields.

A known method of liquidation of wells (RD 39-2-1182-84. Instructions for the equipment of the mouths and dumps of reference, parametric, prospecting, exploration, structural and geochemical and special wells during their liquidation and conservation. - M., 1985), including installation over a productive layer of a cement bridge and placement under and above it packs of drilling mud treated with a corrosion inhibitor and a neutralizer of aggressive media.

The disadvantages of this method are:

- firstly, a long technological process of well liquidation (installation of a cement bridge, injection of packs of drilling fluid under and above the cement bridge) and, as a result, large material and financial costs for well liquidation;

- secondly, the low efficiency of the well liquidation process, since the implementation of this method does not allow to eliminate or prevent fluid flows between the layers in the annulus of the well;

- thirdly, the insufficient strength of the cement bridge for the conditions of a super-viscous oil field developed by steam gravity treatment, since the cement bridge was installed using ordinary (non-heat-resistant) cement.

Also known is a method of liquidation of a well with a source of annular pressure (patent RU No. 2168607, IPC ЕВВ 33/13, published on June 10, 2001, Bull. No. 16), including the implementation of the first cement bridge in the well above the productive horizon and below the interval of highly plastic rocks communicating the annulus of the well with its annulus within the interval of highly plastic rocks followed by the installation of a second cement bridge over the first and ensuring the flow of highly plastic rocks into the annulus of the well by reducing hydrostatic pressure in the well at the level of the interval of highly plastic rocks, at the same time choose a layer of highly plastic rocks located above the source of intercolumn pressure and the closest to it, the upper boundary of the first cement bridge is set at the level of the bottom of the layer of highly plastic rocks, the annulus of the well is communicated with the column space in the interval, making up part of the reservoir thickness of highly plastic rocks directly above its sole by removing part of the casing string, the second cement bridge pour from the "head" of the first cement bridge with a height equal to the interval between the annulus of the borehole and its casing space, and extending beyond the casing contour, after which annulus of the borehole is communicated on the remaining part of the thickness of the highly plastic rock formation with the annulus of the borehole by removing part of the casing columns, and then provide the flow of highly plastic rocks into the column space of the well.

The disadvantages of this method are:

- firstly, the long technological process of well liquidation (removal of several sections of the casing string, the installation of several cement bridges above each other) and, as a result, the large material and financial costs of well liquidation;

- secondly, the lack of reliability of the implementation of the method associated with the uncontrolled possible flow of fluid between the strata after the well has been liquidated, therefore, often the inter-interval (interstratal) fluid flows obtained due to the low cementation of the rocks in the annulus continue even after the well is liquidated;

- thirdly, the insufficient strength of the cement bridge for the conditions of a super-viscous oil field developed by steam gravity treatment, since it was installed using ordinary (non-heat-resistant) cement.

The closest in technical essence is a method of liquidation of a well with many intervals of leakage of the production string (patent RU No. 2436932, IPC ЕВВ 33/13, published on December 20, 2011, Bull. No. 35), in which the well with a casing and layers is jammed dismantle the fountain fittings to the pipe head body, mount blowout preventer (POP) on the pipe head body, lift pipe is removed from the well, flush pipes are lowered into the well, bind them to the pump unit, pump through full-time cement slurry pipes in a volume sufficient to fill the wellbore, with simultaneous lifting of flushing pipes along the wellbore to the wellhead and their removal from the well, with the installation of a cement bridge from the bottom to the wellhead, after completion of the waiting period for cement hardening (GC) in the wellbore the wells dismantle the air defense, mount a stand and a bench on the body of the pipe head.

The disadvantages of this method are:

- firstly, the low efficiency of the well liquidation process when filling the entire wellbore with cement mortar, while the inter-interval (inter-layer) flows in the annulus of the well continue;

- secondly, the lack of reliability of the implementation of the method associated with the uncontrolled flow of fluid between the layers during well liquidation, therefore, often the inter-interval (inter-layer) flows obtained due to poorly cemented rocks in the annulus continue even after the well is liquidated and it is impossible to detect them even after the well is liquidated ;

- thirdly, the insufficient strength of the cement bridge for the conditions of a super-viscous oil field developed by steam gravity treatment, since it is installed from ordinary (non-heat-resistant) cement.

The technical objectives of the proposal are to increase the efficiency of the well liquidation process by isolating the inter-reservoir flow in the annulus of the well and to increase the reliability of the liquidation of the well due to the ability to control the inter-reservoir fluid flows after the well liquidation and increase the strength of the cement bridge.

The tasks are solved by the method of well liquidation, including the descent of the pipe string into the well with the casing, operating two layers, the installation of a cement bridge in the well from the bottom to the mouth.

What is new is that during well abandonment, a part of the casing is cut from the bottom of the lower formation to the roof of the upper formation, between which annular fluid flows take place, then a core sampler is lowered into the interval of the cut section of the casing and the core sampled in the section of the cut section of the casing is selected wells, the core sampler is removed from the well and an analysis of the selected core is carried out, according to its results, clay is prepared whose composition corresponds to the composition of the rock located in after the cut-out section of the casing string of the well, then from the mouth to the bottom, a string of pipes of a small diameter muffled from below is lowered, then the tubing string is lowered into the well before the bottom and under pressure the first cement bridge is installed from the bottom to the interval of the well 5 m higher the bottom of the lower layer, remove the tubing string from the well, then in the well from the upper end of the first cement bridge to the interval 5 m below the top layer of the upper layer, install a clay bridge, why the tubing string is lowered into the well to the upper end of the clay bridge and a second cement bridge is installed to the wellhead under pressure, the tubing string is removed from the well, and the first and second cement bridges are installed using heat-resistant cement with the addition of fiber in an amount of 0.2% by weight of dry cement, after which they fill the pipe string of small diameter with non-freezing fluid, then lower the pipe into the pipe string of small diameter to the bottom wholesale curl cable with which are periodically fixed temperature changes in the wellbore after elimination.

When liquidating appraisal and exploratory wells at the Ashalchinskoye field of super-viscous oil of the Republic of Tatarstan, the development of which is carried out by steam gravity with the formation of a steam chamber, the main condition for effective well liquidation is to exclude the possibility of heat transfer from the Sheshminsky horizon to the absorbing fresh water layer of the Kazan horizon, therefore filling the entire trunk even the highest quality cement does not exclude annular flows that arise due to weak cement sawmills Hovhan the wellbore interval.

Figure 1, 2, 3, 4 schematically and sequentially shows the process of implementing the method of liquidation of the well.

The method of well liquidation is implemented as follows.

An appraisal well 1 (see Fig. 1), drilled at the Ashalchinskoye field of the super-viscous oil of the Republic of Tatarstan in the 70s of the last century and having fulfilled its intended purpose, is a source of annular flow of steam (condensate) 2 (heat loss) from reservoir 3 ( lower layer) of the Sheshminsky horizon, having pressure Р ₁ , into the absorbing layer 4 (upper layer) of fresh waters of the Kazan horizon, having pressure Р ₂ , with P ₁ > Р ₂ .

Due to the presence of behind-the-casing fluid flows, heat losses occur in the steam chamber, which reduces the efficiency of the development of an ultra-viscous oil field by steam gravity, therefore, appraisal well 1 is subject to physical liquidation. For example, according to data provided by the geological service of an oil and gas company, the depth of the appraisal well 1 is 105 m, the height l _{1 of the} lower formation 3 is 3 m; height l _{2 of the} upper layer 4 - 4 m.

To eliminate the well 1 (see Fig. 2), a part 5 of length H of the casing 6 is cut from the sole 7 of the lower formation 3 to the roof 8 of the upper formation 4, between which annular fluid flows 2 occur.

To do this, on a pipe string (not shown in FIGS. 1, 2, 3, 4), any known cutting device (not shown in FIGS. 1, 2, 3, 4) is lowered into the casing string 6 (see FIG. 2) of the well 1 ), for example, they use a universal cutting device manufactured at OAO Karpatneftemash (Kalush, Ivano-Frankivsk Oblast, Russia).

For example, the distance L from the sole 7 of the lower layer 3 to the roof 8 of the upper layer 4 is 12 m.

Part 5 is cut out (see FIG. 2) of the casing 6 in the borehole 1 with a height H = L + l ₁ + l ₂ ,

where H is the height of the cut section of the casing, m;

L is the distance from the sole 7 of the lower layer 3 to the roof 8 of the upper layer 4, m, for example 12 m;

l ₁ - the height of the lower layer 3, m;

l ₂ - the height of the upper layer 4, m

Substitute numerical values in the formula: N = 12 m + 3 m + 4 m = 19 m.

Next, remove the pipe string with a cutting device from the well 1.

Then, in the interval of the cutout section 5 of the casing string 6 of the well 1, a core sampler is lowered (not shown in FIGS. 1, 2, 3, and 4) and a core sample is taken that is in the section of the cutout section 5 of the casing string 6 of the well 1.

For example, a drilling lateral core sampler (RSCT ™) is lowered into the interval of the cutout section 5 of the casing 6 of well 1, which allows core sampling in one run without breaking the core structure for a wide range of petrophysical tests and analyzes, without microcracks.

A core sampler is removed from the well 1 with core samples and an analysis of the selected core samples is carried out, the mineral or chemical composition (content of components) is determined. For example, a core sample has the following mineral composition,% (by weight):

- mixed layer mineral - 48

- kaolinite - 19

- quartz - 17

- feldspar - 9

- hydromica - 7.

According to these data, in the workshop, for example, OOO NPO BentoTehnologii (Almetyevsk, Republic of Tatarstan, Russia) or ZAO Keramzit (Serpukhov, Russia), clay with a similar mineral composition is prepared (based on the obtained composition of the selected core , the composition of which corresponds to the composition of the breed).

Then, into the well 1 (see FIG. 2), from the wellhead 9 to the bottom 10, a pipe string 12 of small diameter, muffled from below by a plug 11 (FIG. 3) is lowered. For example, as a column of pipes 12 of small diameter, a column of sleeveless flexible pipes with a diameter of 38 mm or tubing pipes with a diameter of 48 mm is used. A pipe string 12 of small diameter is selected so that optical fiber cable 13 passes through its inner diameter (see FIG. 4).

Next, in the well 1 (see figure 3) from the mouth 9 to the bottom 10 lower the tubing string (tubing) (figure 1, 2, 3, 4 is not shown). Under pressure, cement mortar is pumped through the tubing string and the first cement bridge 14 is installed (see FIG. 3) from the bottom 10 to the interval of the well 1 5 m above the bottom of the lower formation 3. The tubing string is removed from the well 1 and maintained until the cement hardens.

Then, in the well 1, from the prepared clay, a clay bridge 15 is installed from the upper end of the first cement bridge 14 to an interval 5 m below the roof of the upper formation 4.

To install the clay bridge 15, clay is poured from the wellhead 9 of the well 1, followed by its compaction in the well 1 by running the tubing string.

The amount of clay poured into the borehole 1 is selected depending on the inner diameter of the casing string 6 (see FIG. 3) of the borehole 1, the height of the cut section 5 of the casing string 6 of the borehole 1, etc., which is determined by the geological service of the oil and gas company by experience.

Due to the selection of the clay composition similar to the composition of the rock in the section of the cut section 5 of the casing 6 of the well 1, adhesion occurs between them, i.e. adhesion of the surfaces of two adjoining heterogeneous solids (clay and rock), which is associated with intermolecular attraction, ensuring the integrity of substances in the contact points of their surfaces.

After the clay solidifies, the clay bridge 15 is obtained in the form of a dense clay layer of sufficient thickness, which eliminates the annular flow of steam (condensate) 2 between the lower 3 and upper 4 layers in the well 1.

The tubing string is lowered into the well to the upper end of the clay bridge 15 (see FIG. 3) and cement mortar is pumped through the tubing string under pressure and a second cement bridge 16 is installed to the wellhead 9 of well 1, after which the tubing string is removed from well 1.

The installation of the first 14 and second 16 cement bridges is carried out (see figure 3) using heat-resistant cement with the addition of basalt fiber in an amount of 0.2% by weight of dry cement.

The use of heat-resistant cement allows you to maintain the strength of the cement stone in conditions of cyclically changing temperatures (in steam cyclic wells), i.e. in fields developed by steam gravity, compared with conventional cement used in the prototype.

The addition of fiber to heat-resistant cement allows you to get a strong, plastic, non-shrink, impermeable and corrosion-resistant structure of cement stone, resistant to high temperatures.

As heat-resistant cement using well-known heat-resistant cement, for example CT Activ II KM-160, produced according to GOST 1581-96.

Fiber is produced at CJSC Mineral 7 according to TU B B.2.7-26.8-32673353-001: 2007. The amount of heat-resistant cement is selected depending on the depth of the borehole, the inner diameter of the casing string, etc., which are determined by the geological service of the oil and gas producing enterprise empirically.

Then, from the wellhead 9 (see FIG. 3), the wells 1 are filled with a pipe string 12 of small diameter with non-freezing fluid, for example diesel fuel.

The upper end of the pipe string 12 of small diameter is sealed at the wellhead 9 of the well 1 with a blind plug 17.

To do this, at the mouth 9 of well 1, unscrew the plug 17 (see Fig. 3), the upper end of the fiber optic cable 13 (see Fig. 4) is attached to the transport drum of the cable-container installation (CCU) 18 (Fig. 4 is shown conventionally) .

Next, a fiber optic cable (thermal sensors) 13 is lowered into the string of pipes 12 of small diameter to the bottom 10 of the well 1 (see FIG. 4). Fiber-optic cable 13 is manufactured at Spets-M LLC (Perm, Olkhovskaya St., 2). The diameter of the descent fiber optic cable 13 is selected with the condition of passing through the string of pipes 12 of small diameter.

Next, using the fiber-optic cable 13, the temperature distribution is recorded along the wellbore 1 from the bottom 10 to the wellhead 9 and data is transmitted from the transport drum KKU 18 wirelessly to the operator’s cabin KKU (control panel) on equipment equipped with an encoding and decoding system, and also specialized software used to obtain, display, monitor and record in real time the temperature distribution over the borehole 1. The equipment records the distribution the barrel temperature of the well 1 (First world experience geophysical surveys in producing wells using coiled tubing with the fiber optic cable / Nov B. [et al.] // Time CT -. 2011. - №37).

At the end of fixing the temperature distribution along the wellbore 1, the fiber optic cable 13 at the wellhead 9 of the well 1 is disconnected from the transport drum KKU 18. The fiber optic cable 13 is removed (see FIGS. 3 and 4) from the pipe string 12 of small diameter. The upper end of the pipe string 12 of small diameter is sealed at the wellhead 9 of the well 1 with plug 17.

Filling the pipe string 12 with small diameter non-freezing liquid allows you to lower into the pipe string 12 small diameter and remove from it the fiber optic cable 13 (see figure 4) regardless of the ambient temperature.

In the same way, as described above, for example, the temperature distribution in the wellbore is recorded quarterly after its elimination using KKU 18 at the wellhead 1 and using fiber optic cable 13. To do this, perform the above operations, starting from unscrewing the plug 17 from the pipe string 12 small diameter and ending with the sealing of the upper end of the pipe string 12 small diameter tube 17.

The immutability of the temperature regime in the wellbore 1 indicates the absence of steam flows (condensate) between the layers and reliable isolation of the source (layer) of inter-reservoir flows.

The proposed method of well liquidation allows to increase the efficiency of well liquidation due to isolation of the inter-reservoir flow in the annulus of the well by cutting the casing and installing a clay bridge, as well as to increase the reliability of liquidation of the well due to the possibility of controlling inter-layer fluid flows after liquidation of the well and increasing the strength of the cement bridge.

Claims (1)

A method of eliminating a well, including lowering a string of pipes into a well with a casing operating two layers, installing a cement bridge in the well from the bottom to the wellhead, characterized in that when the well is eliminated, a part of the casing is cut from the bottom of the lower formation to the roof of the upper formation, between with which the annular fluid flows take place, then in the interval of the cut out section of the casing string of the well, the core sampler is lowered and the core located in the section of the cut out section of the casing string is selected holes of the well, they take the core sampler from the well and analyze the selected core, according to its results, clay is prepared, the composition of which corresponds to the composition of the rock located in the section of the cut section of the casing string of the well, then a pipe string of small diameter, muffled from below, is lowered into the well from the mouth to the bottom, then a string of tubing is lowered into the well before the bottom and, under pressure, the first cement bridge is installed from the bottom to the interval of the well 5 m above the bottom of the lower layer, well, tubing from the well, then in the well from the upper end of the first cement bridge to an interval 5 m below the roof of the upper layer, a clay bridge is installed, after which the tubing string is lowered into the well to the upper end of the clay bridge and installation is performed under pressure the second cement bridge to the wellhead, the tubing string is removed from the well, and the first and second cement bridges are installed using heat-resistant cement with the addition of fiber windows in an amount of 0.2% by weight of dry cement, and then filled with a column of small diameter pipes with antifreeze description column of small diameter pipes are lowered to bottom fiber optic cable, by which are periodically fixed temperature changes in the wellbore after elimination.

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