RU2203388C1 - Nonshrinking lightened oil-well cement - Google Patents

Abstract

FIELD: oil and gas industry, well cementing under intricate geological conditions. SUBSTANCE: nonshrinking lightened oil-well cement contains clinker, gypsum, bergmeal, sintered dust of cement production and salt NaCl with following proportion of components, mas.%: clinker, 55.0; gypsum, 5.0; bergmeal, 30.0; sintered dust, 9.5-9.8; salt NaCl, 0.2-05. EFFECT: increased strength and provision for nonshrinkage for qualitative cementing of casing strings in oil and gas wells. 2 tbl

Description

 The invention relates to deep drilling, in particular to compositions intended for cementing oil and gas wells.

At great depths, minerals with abnormally low reservoir pressures are found, the overlapping of which requires the use of lightweight grouting mixtures that provide uniform strength to the cement stone in the annular space in the temperature range of 20-120 ^o C. Currently, this problem is solved by using two types of cements, PCT-Schob -50 and PTsT-Schob-100 in two portions, which greatly complicates the cementing processes. In addition, these cements are shrinkable.

Known lightweight cement obtained on the basis of Portland cement and tripoli with a ratio of 60:40 [1, 2]. These cements form a stone with sufficient strength only at temperatures above 40 ^o C, and at temperatures below 40 ^o C, that is, in the upper interval of the rise of cement due to the low strength and shrinkage of the stone (0.3-0.4 MPa) not ensured sufficient tightness of the buried space.

Also known is lightweight cement cement [3] based on clinker, tripoli and gypsum, obtained by co-grinding them in a ball mill with a ratio of components,%:
Clinker - 55
Tripoli - 40
Gypsum - 5
This cement also at temperatures below 40 ^o C forms a stone with low strength in the range of 0.3-0.5 MPa.

The purpose of the invention is to improve the quality of lightweight cement by increasing strength, obtaining shrinkage stone and the formation of cement stone with uniform strength in the entire interval of lifting cement in the temperature range of 20-120 ^o C.

 The goal is achieved due to the fact that the non-shrinking lightweight cement, including clinker, gypsum, tripoli, additionally contains cement baking dust and NaCl salt in the following ratio, wt.%: Clinker 55, gypsum 5, tripoli 30, baking dust 9, 5-9.8, NaCl salt 0.2-0.5.

In the present invention was used:
- tripoli, having in its composition, wt.%: SiO ₂ 70-79; Al ₂ O ₃ 5-7.5; Fe ₂ O ₃ 2-4; CaO 45-48; MgO 0.8-2; SO ₃ 0.1-2; RFP 6-10%; activity according to GOST CaO - 270-320;
- baking dust Novotroitsk cement plant, having in its composition, wt.%: CaO 45-48; MgO 1-2; SiO ₂ 14-15; Al ₂ O ₃ 2.9-3.5; PPP 20-25; Na ₂ O + K ₂ O 6-8;
- gypsum two-water natural;
- crystalline salt of NaCl;
- clinker, consisting of,%: 3CaOSiO ₂ 58-64; β2CaO SiO ₂ 11-15; 3CaO Al ₂ O ₃ 5-8; 4CaO-Al ₂ O ₃ -Fe ₂ O ₃ 13-15.

Tripoli is an active hydraulic additive of sedimentary origin - loose rock, consisting of microscopic rounded grains and containing silica, mainly in an amorphous state. Specific gravity 2300 kg / m ³ , specific surface 20,000 g / cm ³ . The volumetric weight of tripoli in the dry state is 850 kg / m ³ . When stirring with water, yolk milk or dough is formed.

Cement baking dust is a fine powder containing free CaO, alkalis Na ₂ O and K ₂ O and clinker minerals and gypsum. The specific surface dust within 8000-10000 g / cm ²
In the table. 1 shows specific examples of non-shrink lightweight cement slurry.

 The composition is prepared as follows: clinker, gypsum, tripoli, baking dust and NaCl salt are crushed together in a ball mill in the required proportions. The resulting cement is packaged in bagging, or big-bag, or in cement trucks (dunkars).

A cement slurry is prepared at the rig using conventional technology. In the table. 2 shows the technological parameters of non-shrink lightweight cement slurry. Table 2 shows that the developed cement in the temperature range of 20-100 ^o With a bending strength in the range of 1.6-4.7 MPa, which significantly exceeds the tensile strength of the bent lightweight cement in accordance with GOST 1581-96.

 Non-shrinking lightweight cement provides good quality cementing of deep wells and the height of the rise of the solution to the design height in the presence of absorption zones and formations with abnormally low pressures. A solution of this cement is sedimentally stable (water separation of 0.2-0.25 ml), which prevents the formation of water zones and channels for the flow of reservoir fluids in the annulus. Reliably tight contacts are formed between the rock and cement, as well as between cement and the column. This is ensured by the shrinkage of the cement stone.

 Non-shrink lightweight cement grouting consists mainly of cheap additives (tripoli, baking dust, NaCl salt). The thickening and setting times necessary for pumping cement slurry to the required depth are easily regulated by known retarders or we accelerate setting times.

 The Novotroitsk cement plant organized the industrial production of non-shrink lightweight cement. Using the first batch of this cement, more than 5 wells were cemented at the Western Siberia Lukoil and Orenburgneft TNK fields. Cementing results are good. The cement slurry is raised to the full length of the production string.

Sources of information
1. Daniushevsky V.S., Tolstykh I.F., Melshtein V.M. Reference guide for cementing materials. - M .: Nedra, 1973, p. 247.

 2. Lutsenko NA, Obraztsov OI, Grouting mortars of low density. - M .: Nedra, 1972, p. 141.

 3. Trusov SB, Lightweight and lightweight cement cements. - M.: VNIIOENG, 1990, p. 62.

Claims (1)

Non-shrinking lightweight grouting cement, including clinker, gypsum, tripoli, characterized in that it additionally contains cement baking dust and NaCl salt in the following ratio of components, wt. %:
Clinker - 55
Gypsum - 5
Tripoli - 30
Baking dust - 9.5-9.8
Salt NaCl - 0.2-0.5

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