RU2149981C1 - Grouting mortar - Google Patents

Abstract

FIELD: oil and gas production. SUBSTANCE: mortar contains, wt parts: cement 100, hydroxyethylcellulose 0.3-0.6, melamine-containing product (melamine-formaldehyde resin or melamine resin-based mixture) 0.5-1.0, water 40-50, and additionally ethyl silicate condensate. EFFECT: increased quality of mortar under moderate temperature (up to 100 C) conditions thanks to increased heat resistance, increased mortar stability against formation water inrush over the coagulation structure formation period, and improved pumpability. 3 cl, 3 tbl

Description

 The invention relates to the construction of oil and gas wells, in particular to cement slurries intended for their fastening, and can be used in enterprises of the oil and gas industry.

 Known cement slurry containing in its composition the following ingredients, parts by weight: cement - 100; hydroxyethyl cellulose (OEC) - 0.3-0.4; dextrin - 0.1-0.2; water - 55-60. (see Auth. St. USSR N 1714089, class E 21 B 33/138, 1989).

 The disadvantages of the well-known grouting mortar are the low strength of the resulting stone and the lack of mobility of the grouting mortar at the time of injection.

Closest to the proposed technical solution for the technical essence is cement slurry, which includes, parts by weight: cement - 100; OEC - 0.25-0.5; oxinaftolinesulfonic acid-formaldehyde resin (C-3) - 0.1-0.75; CaCl ₂ - 3.0; water - 50. ("Complex reagents for the treatment of cement slurries" V.M. Medentsev, A.K. Kuksov, M.O. Ashrafyan, Yu.V. Grinko, journal "Oil industry", N 7, 1997, p. thirty).

The specified cement slurry is intended for use under temperature conditions from 60 to 100 ^o C.

However, the well-known cement slurry does not have sufficient thermal stability. When the temperature rises to 75 ^o C, the yield of the specified cement slurry increases two or more times. At this level of water loss during coagulation structure formation, the well-known cement slurry does not provide its resistance to breakthrough by formation fluids.

 In addition, the known solution has insufficient sedimentation stability, which leads to the formation of vertical channels in the body of the cement sheath.

The aim of the present invention is to improve the quality of the cement slurry at moderate temperatures (up to 100 ^o C) by reducing the filtration processes in the cement slurry - water loss and sedimentation, by imparting thermal stability to hydroxyethyl cellulose, by increasing the stability of the solution during its coagulation structure formation breakthrough formation fluids and by improving the pumpability of the cement slurry by reducing its structural viscosity.

This goal is achieved in that the well-known cement slurry containing cement, hydroxyethyl cellulose, an additive based on polymer resins and water, as an additive based on polymer resins it contains a melamine-containing product, and as hydroxyethyl cellulose - high viscosity grades of OEC, a viscosity of 2% solution which is not less than 6000 MPa • s, in the following ratio of ingredients, parts by weight:
Cement - 100
The specified hydroxyethyl cellulose is 0.3-0.5
Melamine-containing product - 0.5-1.0
water - 40-50
From the patent and scientific and technical literature we are not aware of cement slurries containing the combination of the above ingredients in the proposed quantitative ratio, which allows us to conclude that the claimed technical solution is new.

 The achievement of the goal of the invention is provided, apparently, due to the following.

 The proposed grouting composition due to the combination of a melamine-containing product in it and a highly viscous OEC allows reducing the water loss of the grouting mixture, giving it stability under conditions of not only normal, but also moderate temperatures. This is ensured, apparently, due to the formation of complex compounds with an optimal ratio of hydrophilic and lyophilic reaction groups, as a result of which they are able to bind a free dispersion medium.

It is known that the introduction into the grouting composition of highly viscous OEC strongly thickens the grouting solution, which makes it practically non-pumpable. Additives of low viscosity OEC, which do not thicken the solution, lead to unregulated setting times at low and moderate temperatures, and to reduce the water loss of the additive in grouting mortar, it is required approximately two times higher than high viscosity OEC. In addition, cement slurry with the addition of OEC does not have temperature resistance. At temperatures above 50 ^o C hydroxyethyl cellulose reduces water retention capacity, which leads to a decrease in sedimentation stability and increased water loss.

 The addition of a melamine-containing product to the cement mortar of the OEC allows increasing the thermostability of the mortar.

 And besides, it unexpectedly turned out that the structure of the solution formed during the coagulation structure formation period becomes more resistant to breakthrough by formation fluids, i.e. will be resistant to differential pressure between the layers. This is ensured, apparently, due to the high colmatizing ability of the resulting complex compound of the OEC with the melamine-containing product, and also due to the sufficiently high viscosity of the liquid in the capillaries.

 From the current level of technology, we do not know that the ingredients included in the proposed grouting mortar, provide the above properties, which allows us to conclude that the proposed technical solution meets the criterion of "inventive step".

 For the preparation of the inventive cement slurry in laboratory conditions, the following substances were used.

 1. Grouting Portland cement GOST 1581-91, for example, the PTsT D20-50 grade of the Gornozavodsky cement plant or the PTsT D0-100 of the Sukholozhsky cement plant.

 2. Oxyethyl cellulose (OEC) of high viscosity grades (type EHM, EHL).

 3. Melamine-containing product: melamine-formaldehyde resin of the MFAR brand (TU 6-05-1926-82), the MS-P100-C brand (TU 6-05-18-67-79), a mixture based on melamine resins of the ML-95 brand.

 The essence of the invention is illustrated by the following example.

 Example. To obtain the inventive grouting solution, 2 g of EHM grade ECI, 3.5 g of MFAR melamine-formaldehyde resin were added to 250 ml of technical water, and after stirring for 0.5 h, 500 g of cement was added to the mixture, mixed for 0.5 h and a grouting solution was obtained with the following ingredients, parts by weight: cement - 100; OEC - 0.4; melamine-containing product - 0.7, water - 50.

 Other inventive solutions with different ratios of ingredients were prepared in a similar manner.

 It was experimentally proved that the addition of a melamine-containing product to the OEC solution allows increasing the thermostability of the OEC (Table 1).

 In the table. Figure 1 shows the effect on the change in water loss of solutions prepared in fresh water and in a 40% solution of calcium chloride, which simulates the calcium environment of a cement mortar. A similar result was obtained when both components (hydroxyethyl cellulose and melamine formaldehyde resin) were added together in a cement mortar. In addition to the fact that the solution acquires thermal stability, the rheological properties of the cement slurry are significantly improved by the addition of melamine-formaldehyde resin. With a high spreading ability and low water yield, the composition retains its mobility for 3 or more hours, while the setting time does not exceed 10 hours.

In laboratory conditions, the following properties of the claimed and well-known according to the prototype of grouting mortars were investigated: the spreadability of grouting mortar (a cone shape and a measuring scale were used for measurement); filtration rate (water yield) (Ф ₃₀ , cm ³ at a pressure drop of 0.7 MPa was measured on an OFI Testiing Equipment filter press); thickening time of grouting mortar (measured on a KC-5 consistometer); setting time for grouting mortar (device with a Vick needle); bending strength (a device for testing the bending of samples of MII-100 beams); the stability of the cement test at the time of “freezing” by breakthrough with formation fluids (at a pressure drop of 0.1-0.7 MPa was measured on a Baroid filter press. For this, cement slurry was poured into the filter chamber and kept at rest until the period coagulation structure formation - before the formation of the “test.” Then a fluid simulating the formation fluid was poured from above, the chamber was hermetically closed and a pressure of 0.1 to 0.7 MPa was applied per 7 cm of cement mortar column. breakthrough of formation fluid at a certain pressure gradient determined from the filtered liquid volume and liquid volume, which was poured on top of cement slurry). The study of the indicated properties of cement slurries was carried out in accordance with the requirements of GOST 1581-96 and GOST 26798.1-91.

 Based on the spreadability and thickening time of grouting mortars, the mobility of the grouting mortar and the time required to ensure trouble-free delivery of grouting mortar into the well were judged.

The change in filtration at temperatures of 20 - 75 ^o C was used to judge the thermal stability of the mortar and the reduction of the fluid loss of grouting mortars at these temperatures.

 According to the setting time of the cement slurry, its compliance with the requirements of the standard (GOST 26798.1-91) was evaluated.

 The change in strength characteristics was determined by the ultimate tensile strength.

 The ability to withstand a certain pressure gradient (from 0.1 to 0.7 MPa) during the coagulation structure formation period, namely during the period of “hanging” of the cement slurry, determined the resistance of the cement slurry to breakthrough formation fluids.

 Data on the composition of the studied grouting solutions are given in table. 2.

 Data on the properties of the proposed and well-known prototype cement slurries are given in table. 3.

 From the tabular data it follows that the proposed grouting mortar at low and moderate temperatures has the following advantages compared to the known mortar: higher thermal stability, low filtration rates (water loss and sedimentation stability), providing resistance to breakthrough of formation fluids during coagulation formation, higher rheological indicators and consistency, which allows to guarantee trouble-free delivery of cement composition in the well.

 To regulate the setting time and increase the strength of cement stone in the proposed cement slurry, it is recommended to introduce ethyl silicate condensate. Data on the properties of this solution are also given in table. 3 (experiment 10).

 Using the proposed solution under field conditions will improve the quality of well cementing, eliminate flow of formation fluids and, as a result, reduce the water cut of well production.

 In addition, with high spreading ability and low water yield, the inventive cement slurry retains its mobility for 3 or more hours, while the setting time does not exceed 10 hours, which indicates its high adaptability.

 It was experimentally proved that the proposed solution is able to withstand a pressure gradient of 7.0 - 10.0 MPa / m, preventing breakthrough of formation fluids during the coagulation structure formation ("hang") of this grouting composition, which excludes the formation of fluid-conducting channels in the cement test during the formation cement stone in the annular space. The well-known grouting mortar according to the prototype withstands a pressure gradient of not more than 5 MPa / m, even in an already formed cement stone.

Claims (2)

1. A cement slurry containing cement, hydroxyethyl cellulose, an additive based on polymeric resins and water, characterized in that it contains a melamine-containing product as an additive based on polymeric resins, and high viscosity grades of hydroxyethyl cellulose with a viscosity of 2% solution of which are used as hydroxyethyl cellulose is at least 6000 MPa • s, with the following ratio of ingredients, parts by weight:
Cement - 100
The specified hydroxyethyl cellulose is 0.3-0.5
Melamine-containing product - 0.5-1.0
Water - 40-50
2. The grouting mortar according to claim 1, characterized in that as the melamine-containing product it contains, for example, a melamine-formaldehyde resin or a mixture based on melamine resins. 3. The grouting mortar according to claim 1, characterized in that, in order to regulate the setting time, it additionally contains an organosilicon product, for example ethyl silicate-condensate, in the following ratio of ingredients, parts by weight:
Cement - 100
The specified hydroxyethyl cellulose is 0.3-0.5
Melamine-containing product - 0.5-1.0
Organosilicon product - 0.4-0.6
Water - 40-50

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