RU2489468C1 - Method for preparation of grouting mortar for insulation and prevention of earthfalls in cavernous part of shaft of wells, and mainly gently sloping and horizontal ones - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: in preparation method of grouting mortar for insulation and prevention of earthfalls in cavernous part of the shaft of wells, and mainly gently sloping and horizontal ones, by mixing Portland cement, clay powder, water and additives, which differs by the fact that as additives there used are silicates of alkali metals and derivatives of higher fatty acids, which are obtained at processing of wood or oil resins and tar oils. First, water solution of silicates of alkali metals is prepared by introducing the latter to water. Then, derivatives of higher fatty acids, which are obtained at processing of wood or oil resins and tar oils, are introduced to the above water solution. Mixture is mixed during at least 40 minutes. Then, while stirring, clay powder is added and mixed during 10-20 minutes, and then Portland cement is added, and the mixture is stirred during not less than 30 minutes. Clay powder providing the yield of clay mud with viscosity of 20 mPa*s of not less than 16 m³/t is used as clay powder at the following component ratio, wt %: silicates of alkali metals 10-20, Portland cement 20-70, the above derivatives of higher fatty acids 2-5, the above clay powder 10-25, and water 100.

EFFECT: excluding sedimentation phenomena, diffusion and sagging of an insulating or fixing bridge, including at construction of wells with big deviation of the well shaft from vertical plane; providing complete filling of an inclined shaft of the well, possibility of forming the structure and hardening of the mortar immediately in the zone of earthfalls; providing hydrophobisation and inhibition of the formation rocks.

2 cl, 3 tbl, 3 dwg

Description

The invention relates to the field of well construction, in particular to compositions for isolating and preventing collapse in the unstable cavernous part of the wellbore, and can find application in the construction and overhaul of wells, mainly with a large deviation of the wellbore from the vertical.

One of the technical problems in the construction of wells, which requires significant resources for its solution, is to ensure the deformation stability of the walls of the well during drilling during the passage of unstable clay deposits. The problem of ensuring the stability of the wellbore is even more relevant in the construction of wells with a large deviation of the wellbore from the vertical. To reduce the likelihood of collapse in the cavernous part of the wellbore, various technical means and technological compositions are used.

According to traditional technology, cement bridges with the use of grouting compositions based on Portland cement are provided for fixing unstable clay rocks and isolating the cavernous part of the wellbore. As practice shows, the use of traditional grouting compositions prepared by the traditional method with high structural characteristics and high specific gravity for fixing crumbling (clay) terrigenous rocks during construction of wells with a large deviation from the vertical does not give positive results, and in some cases exacerbates the complications that have begun. So, due to the fact that the strength of the cement stone exceeds the strength of the rock, in many cases there is a loss of the wellbore when drilling an installed cement bridge, which leads to an increase in time and material costs for the elimination of complications.

Grouting compositions are known whose preparation methods are based on the preparation of a mixing liquid from water and technological additives that regulate water loss and setting time, and subsequent mixing of Portland cement on it (Patents of the Russian Federation No. 2356930, 2305695, 2302444). However, these compositions, prepared in a known manner, are characterized by low insulating properties in relation to the cavernous part of the wellbore. In addition, they have a high density, significantly higher than the density of the drilling fluid, as a result of which the cement bridge sags with the formation of a channel in the vaulted part of the cavity, which makes the insulation of poor quality. These compositions have a coagulating effect on the drilling fluid, which leads to a sharp thickening of the latter and the difficulty of removing it from the cavernous part. In addition, when cement slurry enters the drilling fluid, a significant change in the properties of the drilling fluid occurs: an increase in the filtration and structural-rheological parameters, which leads to the need for a complete or partial replacement of the drilling fluid and increases the time and cost of insulation work.

Known methods for fixing (hardening) rocks of the near-stem zone with specially prepared fixing compositions based on precipitated reagents (mainly based on silicates or aluminum salts), which are pumped into the well after opening part of the interval or the entire interval of unstable rocks (Auth. Certificate of the USSR No. 1752750; US Patent No. 4120369; Bochko E.A., Nikishin V.A. Hardening of unstable rocks during well drilling. - M.: Nedra, 1979).

However, these known methods are not sufficiently effective and technological, because used specially prepared fixing compositions are characterized by incompatibility with the drilling fluid, high coagulating effect, low insulating properties in relation to the cavernous part of the wellbore.

A well-known grouting composition for isolating the cavernous part of the wellbore during drilling (Aut. Certificate of the USSR No. 1724855), which is prepared in the following way: to the MF-AR melamine-formaldehyde resin with a content of the main substance of 18-22 wt.% - 100, add sulfate with stirring aluminum, previously dissolved in water and, if necessary, an additional weighting agent is introduced, which is a mixture of clay powder and barite in a ratio of 1: 1-2. The specified composition, prepared in a known manner, is characterized by high resistance to erosion of the drilling fluid, a wide gelation interval, has high insulating properties in relation to the cavernous part due to almost zero water separation, low permeability and the absence of shrinkage of the resulting gel. Moreover, it is compatible with drilling fluid.

The disadvantages of the grouting composition based on melamine-formaldehyde resin and aluminum sulfate prepared in a known manner are:

- low density composition (1080-1100 kg / m ³ ), which necessitates the regulation of the density of the resulting composition due to the weighting agent, which is used as a mixture of barite and clay powder. With the additional introduction of the weighting agent, the effectiveness of insulation works decreases due to a sharp increase in the structural and rheological properties of the composition immediately after preparation and a decrease in the strength of the composition, an increase in the tendency to erosion by drilling fluid;

- high viscosity after preparation, which complicates their injection into the insulated part of the wellbore and does not provide complete displacement of the drilling fluid from the cavity;

- insufficiently high adhesive properties;

- insufficient inhibitory properties in relation to unstable rocks;

- low manufacturability, because said MF-AR resin in marketable form is a liquid freezing at temperatures below 4 ° C, which limits its use in the winter and requires additional equipment for insulation work. In addition, the shelf life of the resin MF-AR does not exceed 1 month, after which it is irreversibly polymerized and cannot be used to prepare the composition;

- increased technological risk in the performance of work associated with the fact that the time of loss of fluidity and gelation (hardening) depends only on the concentration of the components, and after the hardener is introduced into the resin, it is no longer possible to slow down the process.

The closest technical solution to the proposed one is a method of preparing a grouting composition for isolation and fixing by adding Portland cement and a setting accelerator to the clay slurry - calcium chloride, with the following ratio of components: grouting portland cement - 45.5-48.6%, clay powder - 8.5 -19%, calcium chloride - 1.7-1.9% and water - up to 100% [BCDanyushevsky, PMAliyev, I.F. Tolstykh. Reference guide for cementing materials. - M .: Nedra, 1987. - C.117, 119-121]. Clay minerals serve as the continuous structural phase in this composition, Portland cement clinker particles play the role of a filler, and hydration products are located in the interparticle space of the clay suspension. Clay particles settling in thin pores and cracks swell over time and clog them. As a result of thixotropic thickening of the clay-cement solution in the pore channels and rock cracks, structured suspension plugs are formed that are able to fix and isolate the cavernous part of the wellbore.

The specified composition, prepared in a known manner, has a relatively low density (1.56-1.73 g / cm ³ ) compared to the traditional composition based on Portland cement, which eliminates the "subsidence" of the composition and good sedimentation stability. However, the composition prepared by the specified method is characterized by high viscosity after preparation, which makes it difficult to pump it into the insulated part of the wellbore, insufficient resistance to erosion under the influence of the drilling fluid. In addition, this composition does not provide hydrophobization and the inhibitory effect of the formation rocks by the filtrate of the composition.

The technical result achieved by the present invention is to obtain a grouting composition that excludes sedimentation phenomena, spreading and subsidence of the insulating / fixing bridge, including during well construction with a large deviation of the wellbore from the vertical, ensuring the completeness of filling of the inclined wellbore, as well as the possibility of forming structure and hardening of the composition directly in the area of rock formation, providing hydrophobization and inhibition of rock formation filter that composition.

An additional technical result is the elimination of the harmful effects of the cement composition prepared by the proposed method on the technological parameters of the drilling fluid.

The specified technical result is achieved by the proposed method for the preparation of grouting composition for isolation and prevention of collapse in the cavernous part of the wellbore, mainly flat and horizontal, by mixing Portland cement, clay powder, water and additives, characterized in that alkali metal silicates and higher derivatives are used as additives fatty acids obtained in the processing of wood or petroleum resins and tars, while first preparing an aqueous solution of alkali silicates allov by introducing the latter into water, then derivatives of higher fatty acids obtained by processing wood or petroleum resins and tars are introduced into the specified aqueous solution, the mixture is stirred for at least 40 minutes, then clay powder is added sequentially with stirring, mixed for 10-20 min, and Portland cement, the mixture was agitated for at least 30 min, the clay powder is used as gel powder, providing an output slurry viscosity of 20 mPa.s at least 16 m ³ / g, with the following ratio of the components in, parts by weight:

alkali metal silicates 10-20 Portland cement 20-70 derivatives of higher fatty acids, obtained by processing wood or oil tar and tar 2-5 specified clay powder 10-25 water one hundred

When preparing the composition, an additional setting time accelerator is used - calcium chloride, or sodium chloride, or potassium chloride, which is introduced before the clay powder.

The specified technical result is achieved due to the following.

Due to a certain order of input of the composition components and their quantitative ratio, the composition is obtained with low rheological and high insulating properties, excluding sedimentation phenomena, spreading and subsidence of the insulating / fixing bridge and providing hydrophobization and inhibition of formation rocks by the composition filtrate.

A highly colloidal clay powder, which provides a clay solution with a viscosity of 20 mPa * s of at least 16 m ³ / t, is used as a structure-forming base of the composition. Due to a certain order of introducing components into the composition, namely, first alkali metal silicates, then additives - derivatives of higher fatty acids, and then clay powder, due to the slowdown of hydration processes of clay powder, it becomes possible to increase the concentration of said clay powder to 25 wt.h. while maintaining acceptable rheological composition indicators. The introduction into the composition of these additives in the claimed quantitative ratio will not completely inhibit the hydration (swelling) process in the composition of the clay powder, which makes it possible to control a set of high structure-forming and expanding properties of the composition after its injection into the cavernous part of the wellbore. The presence in the composition of Portland cement provides hardening of the composition in the immediate isolation zone with the formation of stone.

The presence of silicates in the solution ensures the colmatization and hardening of the walls of the cavernous part of the wellbore due to the formation of a gel-forming structure from polymer silicate complexes in the near-wall layer, which inhibit capillary moisture transfer and increase the stability of clay rocks.

Derivatives of higher fatty acids obtained from the processing of wood or petroleum resins and tars are used as a plasticizing and simultaneously hydrophobizing additive in the proposed method. Slowing down the speed and degree of swelling in the composition of the clay powder, this additive acts as a plasticizer of the composition and helps to obtain a composition with optimal rheological properties that ensure good pumpability of the composition on the surface in the pipes, and, at the same time, displacement of the drilling fluid and sludge from the caverns in inclined directions trunk and their full filling. In addition, the additive controls the hydration of unstable clay rocks both physically and (much more importantly) chemically. This is due to the unique mechanism of action of the additive. The water-soluble part of the additive is formed by large, polymer anions. These particles contribute to a decrease in the filtration rate of the composition and give the filtrate enhanced structural and rheological properties, limiting the radius of penetration of the filtrate into the wall zone of the wellbore. Attaching to the electropositive sites of clay long polymer anions cause their chemical neutralization and thereby inhibits the clay's natural tendency to absorb water. Thus, collapse, swelling and delamination of shales are prevented. The controlled and selective water-insoluble part of the additive helps a better particle size distribution, which helps to improve the clay cake on the wall of the wellbore and clogging microcracks.

The inventive method is illustrated by drawings, where Fig. 1 shows a graph of the dynamics of changes in the consistency (E _to , Sun) of the composition obtained by the proposed method, and the composition of the prototype; Fig. 2 is a graph of the dynamics of changes in static shear stress in statics over time of the composition obtained by the proposed method, and the composition of the prototype; Fig. 3 is a graph of the dynamics of changes in compressive strength in statics over time of the composition obtained by the proposed method, and the composition of the prototype.

The proposed method was tested in laboratory and field conditions. The following substances were used to prepare the composition:

- clay palygorskite PPB, providing a clay solution with a viscosity of 20 MPa · s not less than 16 m ³ / t, according to TU 39-0147-105-93;

- Portland cement PCT II-50 or PCT 1-G-CC-1 according to GOST 1581-96;

- sodium metasilicate, R-SIL according to TU 2145-006-40912231-2003;

- liquid potash glass, SKZH according to TU 2145-003-52257004-2003;

- derivatives of higher fatty acids obtained from the processing of wood or petroleum resins and tar, for example:

SAF according to TU 2471-037-40-912231-2006;

Soltex, a product of Drilling Specialties Company (USA), a division of Phillips Petroleum, is a sulfonated oil bitumen with the following characteristics: ash content of 36.3%; nitrogen content 0.3%; sulfur 10.9%; sulfonates - presence; solubility in water 80%; www.slidefinder.net/D//308123;

Baratrol, a patented reagent company Halliburton Baroid (USA); fine hydrocarbon powder, dispersed in water and oil, thermostable up to 400 degrees Fahrenheit, reduces high-temperature filtration and clogging microcracks in clays, www.Halliburton.com/Baroid;

- calcium chloride, sodium chloride, potassium chloride;

- technical water.

An example implementation of the proposed method.

200 g of P-SIL was dissolved in 1000 ml of industrial water, 50 g of SAF was added with stirring, the mixture was stirred for at least 40 minutes and 200 g of palygorskite clay powder was added gradually, providing a clay solution with a viscosity of 20 mPa * s of at least 16 m ³ / t, was stirred for 15 minutes, after which 500 g of cement was added. The mixture was stirred for at least 30 minutes. As a result, we obtained a composition for isolating and preventing collapse with the following ratio of components, parts by weight: specified clay powder - 20; cement - 50; R-STR - 20; SAF - 5; water - 100.

In the same way, the proposed method was carried out for the preparation of compositions for isolation and to prevent collapse with a different component content of the resulting composition.

When implementing the proposed method, an accelerator of setting time can be additionally used in an amount of up to 5 wt.%, Which is introduced with stirring into the mixture before clay powder.

In the process of laboratory research, the following properties of the compositions prepared by the proposed and known prototype methods were established:

- density, g / cm ³ ;

- thickening time, h-min;

- rate of filtration at 7 atm for 30 minutes, cm ³ ;

- water separation,%;

- setting start time, h-min;

- setting end time, h-min;

- compressive strength, MPa;

- erosion,% / day;

- adhesion with the breed, MPa;

- inhibitory ability, kg / m ³ .

The degree of isolation and fastening of unstable rocks with a grouting composition prepared by the proposed and known methods was assessed by the following indicators: erosion of the composition stone in fresh water, inhibitory ability of the composition filtrate.

Assessment of the inhibitory ability was carried out by determining the concentration of colloidal particles in the clay suspension under the influence of the filtrate of the compositions. The concentration of colloidal particles (C _{count on bentonite} , kg / m ³ ) is a value characterizing the content of particles less than 2 microns in size in a suspension of bentonite. This value determines the active component of the solid phase of the clay suspension and is a direct indicator of the degree of hydration and dispersion in a solution of bentonite particles. The concentration of colloidal particles was determined in a 12.5% suspension of Krasnodar bentonite (yield 7 m ³ / t) in industrial water, filtrates of the proposed and known compositions.

The compressive strength of the cement stone of grouting compositions was determined by fracturing the cement stone in a hand hydraulic press (CARVER, USA), the dynamics of changes in the compressive strength and static shear stress of the compositions under static conditions were determined using a Chandler Engineering static shear stress analyzer.

The thickening time and the dynamics of changes in the consistency of the compositions were determined on a ZM 1002 consistometer.

Adhesion with the rock was evaluated by the force of ejection of the compositions of oxide ceramic disks on a manual hydraulic press (CARVER, USA).

Data on the component content of the investigated compounds for isolation and fixing, prepared by the proposed and other methods are shown in table 1.

Data on the properties of these compounds obtained in the course of research are shown in table 2.

The data shown in table 2 show that the proposed method of preparing the composition for insulation and prevention of collapse allows:

- to obtain a composition with a density close to the density of the used drilling fluids (1.27-1.50 g / cm ³ ), which will eliminate the sedimentation phenomena and spreading of the insulating bridge in the directional and horizontal wellbore;

- to provide a time for the loss of fluidity of the composition within the technologically necessary time for the injection of the composition into an isolated interval (40-85 min);

- to eliminate the erosion of the stone composition with washing liquid during further drilling (erosion - 0.2-0.35% / day).

Other methods of preparing the proposed composition (experiments 9 and 10) do not allow to obtain a composition with the desired properties. Also, low properties are obtained with the exclusion of one of the components in the implementation of the proposed method (experiments 7 and 8).

Composition for isolation, prepared by a known method (experiment 11) does not provide the properties necessary for isolation and preventing collapse in the cavernous part of the trunk of directional and horizontal wells.

According to table 2, the grouting composition obtained by the proposed method, in comparison with the composition obtained in a known manner, is characterized by lower strength and greater adhesion to the rock. This will allow avoiding the drilling of a new wellbore in soft rocks of cavern formation zones (mudstone strength is 0.5-2.0 MPa) and at the same time ensure the stability of these zones for the entire period of well construction.

It is known that due to hydration during the initial opening and subsequent exposure to the filtrate of the composition, clay rocks can become softened after the installation of fixing compositions. The high inhibitory and hydrophobizing ability of the filtrate of the proposed composition (With a _{count of} 64-75 kg / m ³ ) helps to solve the problem of falling out the walls of the fixing composition during further drilling.

The dynamics of thickening of the compositions prepared by the proposed and known methods in motion was determined on an atmospheric consistometer (Fig. 1). The dynamics of structure formation in statics was determined by contact and non-contact methods (Figs. 2 and 3). The following regularity was established: both compositions during liquefaction are first liquefied, then their consistency practically does not change for a certain time, and in the end there is a rather sharp thickening (Fig. 1). Moreover, in motion, the fluidity of the composition prepared by the proposed method is much higher than that of the known one, and when the movement stops, the proposed composition instantly gains structural and rheological properties up to a non-flowing state, which confirms its special thixotropic properties (Fig. 2). This proves that the composition of the proposed method will provide for almost complete filling of the caverns and the wellbore during injection.

The advantage of the composition according to the proposed method in comparison with the known one is also that the new composition, having gained strength of 0.59-1.10 MPa, practically does not harden in the future (Fig. 3). That is, in the event of a change in the drilling time, cutting from the main trunk is also excluded.

Data on the impact of the proposed and known composition on the technological parameters of the properties of non-clay and low clay drilling fluids are shown in table 3.

The data shown in table 3 show that the entry into the drilling fluids of the composition according to the known method leads to coagulation and destabilization of the fluids, their separation and sedimentation. At the same time, the entry into the drilling fluids of the composition according to the proposed method does not have a destabilizing effect. The filtration rate remains normal, the stability of the solutions is quite high, structural and rheological indicators remain virtually unchanged.

The proposed method was also implemented in the field. Below is an example of its implementation at the well of the Chashkinskoye oil field in the Vereisk horizon for fixing unstable clay deposits after they are opened on mineralized water with a density of 1.13 g / cm ³ . 3 m ^{3 of} industrial water was poured into the averaging tank 1УСО-20, 450 kg of alkali metal silicates (R-SIL) were added with stirring, 30 minutes were stirred, then 150 kg of derivatives of higher fatty acids (SAF) were introduced, 40 minutes were mixed, then 450 were added kg of clay powder, stirred for 20 minutes, 1500 kg of PCT-50 cement were introduced. 40 minutes after stirring, a composition with a density of 1.38 g / cm ^{3 was} obtained. The composition was pumped into the well through the open end by the ANTs-320 unit with a flow rate of 6 l / sec, the buffer fluid was industrial water, the selling fluid was mineralized water with a density of 1.13 g / cm ³ used in drilling. They left the well at a pressure of 30 atm for 1 hour, then after the OZZ, the composition was drilled for 12 hours and continued further drilling. The time from the installation of the composition for insulation and the prevention of collapse to the attachment of the shank was 33 days. No landslide during subsequent drilling was observed.

The use of the composition to isolate and prevent collapse in the cavernous part of the wellbore obtained by the proposed method provides the following advantages compared with compositions prepared by known methods:

- provides an increase in the degree of isolation and fastening of unstable rocks due to the low erosion of the stone composition, high adhesion to the rock and high inhibitory properties of the filtrate composition;

- eliminates sedimentation phenomena and spreading of the insulating bridge due to the lack of sedimentation, low density composition;

- ensures the completeness of the filling of the barrel and the formation of the structure in the area of collapse due to the special thixotropic properties of the composition, short formation of plastic strength in static conditions;

- provides hydrophobization and inhibition of clay rocks and, as a consequence, prevention of their collapse due to the high inhibitory properties of the filtrate composition;

- provides a reduction in time for insulating work due to the quick set strength of the composition in static conditions and eliminates the need to restore the technological parameters of the drilling fluid after installing the composition;

- reduces the likelihood of drilling a new trunk due to the fact that the strength of the cement stone of the proposed composition practically does not exceed the strength of the insulated rocks.

Claims (2)

1. A method of preparing a grouting composition to isolate and prevent collapse in the cavernous part of the wellbore, mainly gentle and horizontal, by mixing Portland cement, clay powder, water and additives, characterized in that alkali metal silicates and derivatives of higher fatty acids are used as additives in the processing of wood or petroleum resins and tars, in this case, first prepare an aqueous solution of alkali metal silicates by introducing the latter into water, then enter into the specified derivatives of higher fatty acids obtained from the processing of wood or petroleum resins and tars, the mixture is stirred for at least 40 minutes, then clay powder is added sequentially with stirring, stirred for 10-20 minutes and Portland cement, the mixture is stirred for at least 30 minutes moreover, clay powder is used as clay powder, providing a clay solution yield of 20 mPa · s viscosity of at least 16 m ³ / t, in the following ratio of components, parts by weight:
alkali metal silicates 10-20 Portland cement 20-70 derivatives of higher fatty acids, obtained by processing wood or oil tar and tar 2-5 specified clay powder 10-25 water one hundred 2. The method according to claim 1, characterized in that in the preparation of the composition, an accelerator of setting time is additionally used - calcium chloride, or sodium chloride, or potassium chloride, which is introduced before the clay powder in an amount of up to 5 wt.%.

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