RU2359988C1 - Oil-well composition for steam-injection wells - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to drilling and operation of oil and gas wells, in which there are applied thermal methods of increasing of reservoir recovery. Oil-well composition for steam-injection wells contains wt h.: Portland cement 50-80, high-silica sand 10-45, amorphous silicon dioxide up to 10, water up to "в/ц" 0.35-0.52. Oil-well composition in the capacity of regulator of processing characteristics additionally contains accelerant of setting-time - calcium chloride or sodium chloride up to 5 wt h. and/or oxy-ethyl-cellulose up to 0.5 wt h., and/or plasticiser - lignosulfonates or Melflux, or Cemplast MF of grade b.

EFFECT: absence of dehydration in grouting mortar, reduction of filtration, increasing of pumpability and setting time of cement stone in conditions of normal temperatures, increasing of adhesive behaviors of formed grouting stone and in providing of stability of it at conditions of sharp temperature fall from 22°C up to 180°C at simultaneous keeping of high durability at cyclic thermal influence during long period.

5 cl, 2 tbl, 1 ex

Description

The invention relates to the drilling and operation of oil and gas wells, which apply thermal methods to enhance oil recovery.

A well-known grouting composition for steam injection wells, containing in wt.%: Clinker 25-40; gypsum 3-6; silica sand 35 -38; main slag 20-22 and additive "IR-1" 2-9 (RF Patent No. 2220275, CL ЕВВ 33/138, publ. 2003). The specified known composition provides long-term strength of the cement stone, which is exposed to up to 10 cycles of hydrothermal heating with an amplitude from low positive temperatures to 360 ° C.

However, the specified known composition is characterized by insufficient adhesion to the metal of the casing string, which does not allow for its high-quality fastening in severe thermal conditions.

Grouting material is also known, containing in wt.%: Portland cement clinker 76-80; gypsum 4-5; ground nickel slag 15-20 (RF Patent No. 2111340, class ЕВВ 33/138, publ. 1998). This material provides thermal stability of the resulting stone for a long time. But its adhesive properties are also insufficient.

From a number of grouting compositions intended for use in steam injection wells, grouting material is also known, containing in wt.%: Slag sand cement 30–70 and Portland cement 30–70. At the same time, slag sand cement contains 50-60% of slag and 40-50% of quartz sand (Aut. Certificate of the USSR No. 981585, class E21B 33/138, publ. 1982). The specified known composition is characterized by the same disadvantages as the above analogues.

The closest to the proposed technical solution for the totality of the characteristics is a cementing material intended for use in wells exposed to thermal methods of exposure, and containing in wt.%: Cementing Portland cement 55-77; silica sand 20-35; synthetic lime-alumina slag 3-10 (Aut. certificate of the USSR No. 1654540, class ЕВВ 33/138, publ. 1991). A cement stone formed from a known material is heat-resistant upon cyclic heating to 400 ° C.

The disadvantages of this known cementing material is the following:

- large water separation of cement slurry, which leads to its separation;

- high filtration in conditions of moderate and elevated temperatures is comparable with the filtration rate of pure cement, which is 600 cm ³ at ΔP = 0.7 MPa, which can lead to premature thickening of grouting mortar;

- short setting time at normal temperatures, which does not provide a safe mode of pumping cement slurry into the well;

- insufficient adhesion to metal and rock;

- insufficient stone durability in the conditions of sharp temperature difference.

The technical result achieved by the invention consists in the absence of water separation in the grout, reducing filtration, increasing the thickening and setting time of the cement stone at normal temperatures, increasing the adhesive properties of the resulting grouting stone and ensuring its stability under the condition of a sharp temperature difference from 22 ° C up to 180 ° C while maintaining high strength with cyclic thermal effects for a long time.

The specified technical result is provided by the proposed grouting composition for steam injection wells containing Portland cement, silica sand, a silicon reagent and water, while according to the invention it contains amorphous silicon dioxide as a silicon reagent, in the following ratio, wt.h:

Portland cement 50-80 Quartz sand 10-45 Amorphous silicon dioxide to 10 Water up to v / c 0.35-0.52

The grouting composition additionally contains regulators of technological properties.

The grouting composition as a regulator of technological properties contains an accelerator of setting time up to 5 parts by weight, and / or hydroxyethyl cellulose up to 0.5 parts by weight, and / or a plasticizer up to 0.7 parts by weight, and / or a reagent Police DF up to 0.3 parts by weight

The grouting composition as an accelerator of setting time contains calcium chloride or sodium chloride.

The grouting composition as a plasticizer contains lignosulfonates or Melflux, or Zemplast MF brand b.

The grouting composition as a defoamer contains a modified silicone polymer.

The specified technical result is achieved due to the following.

Silicon is introduced into the proposed grouting composition in a different chemical activity form: in the form of silica sand and in the form of amorphous silicon dioxide. The mechanism of interaction of siliceous additives with Portland cement constituents consists in their binding of free calcium oxide as the main component and the formation of compounds more stable at elevated temperatures. Moreover, the stability of these compounds is maintained even with a temperature difference.

Quartz sand at normal temperatures will be an inert filler. With increasing temperature in the well during the period of steam injection to 180 ° C, silicates present in quartz sand contribute to the formation of low-basic calcium hydrosilicates. The presence in the claimed grouting material of an active silica additive - amorphous silica promotes the formation of low-basic hydrosilicates at the early stage of hardening, which are characterized by a low-fiber structure and contain colloidal crystals, which determines the formation of fine-porous, low-permeable stone with increased mechanical strength and temperature stability during hardening. The following additives can be suppliers of amorphous silicon dioxide: fly ash, aluminosilicate microspheres, fly ash of silica or silica fume, or silica, obtained artificially in the form of a white amorphous easily moving powder as a result of calcination of silicic acid. An important component in this case is the grain size of the additive - amorphous silicon dioxide. The greater the dispersion of this additive, the higher its activity when interacting with the minerals of cement clinker, i.e., for example, a dusty material is more active.

It was established experimentally that only with the stated ratio of the components in the proposed grouting composition the specified technical result is provided. So, with a decrease in the amount of Portland cement below 50 parts by weight sufficient strength of the cement stone is not ensured under normal temperatures (during the hardening and formation of the cement stone), and with an increase in its amount more than 80 parts by weight as the temperature rises during the period of steam injection into the well, the strength characteristics of the cement stone begin to decrease rapidly, i.e., the process of its destruction begins.

The decrease in the content of quartz sand less than 10 wt.h. leads to an insufficient increase in the heat resistance of cement stone, and an increase in its amount above 45 parts by weight leads to a decrease in the strength characteristics of cement stone during its formation at normal temperatures.

The use of amorphous silicon above 10 parts by weight causes increased water consumption of the grouting composition, which in turn leads to a decrease in the strength and permeability of cement stone, especially at temperature extremes.

A change in the water content beyond the proposed limits results in a composition with either short setting time, not allowing it to be pumped into the well, or, conversely, with a high setting time, which in well conditions will lead to erosion of the composition.

The inventive composition can also be used with technological additives that regulate technological properties, based on specific well conditions.

Thus, only the totality of the proposed components in the claimed quantitative ratio allows to obtain a grouting composition with the indicated properties.

The proposed grouting composition was tested in laboratory conditions. For its preparation, the following components were used:

- Portland cement grade PTsT-100 or PTsT G-CC-1 according to GOST 1581-96;

- quartz sand - GOST 8736-85, according to which SiO ₂ should be at least 90%, clay not more than 5%, mica not more than 5%, suitable for use is sand sifted through a sieve with 0.15 mm s cells the residue on the sieve is not more than 30%;

- amorphous silicon dioxide, for example silica fume, which is a by-product of the production of silicon or silicon alloys by the reduction of quartz in an electric furnace. The particles are spherical in shape, typically about 100 nm in diameter, and consist mostly of glass. The specific surface is 15-25 m ² , the true density is about 2000 kg / m ³ , the bulk density of the freshly filtered powder is 200 kg / m ³ . As a mineral additive for concrete, silica fume is distinguished by the smallest particle size and high pozzolanic activity. The addition of silica fume to cement is limited, due to its high water demand. Amorphous silicon oxide OSCH TU 6-09-4901-80, amorphous silicon dioxide H TU 6-09-5016-90, silicon dioxide OSCH TU 6-09-3379-73;

- calcium chloride or sodium chloride;

- hydroxyethyl cellulose (OEC) brand Hydrocem B, C, H;

- lignosulfonate, Melflux or Zemplast MF brand b;

- technical water.

Example. To prepare the proposed grouting composition, 70 g of Portland cement were taken, mixed with 25 g of quartz sand and 5 g of amorphous silicon dioxide. Got a composition with the following ratio of components, parts by weight: portland cement - 70; quartz sand - 25; amorphous silicon dioxide - 5. Next, the regulators of technological properties were added: 1.4 g of calcium chloride; 0.2 g of Hydrocem C, 0.2 g of Tsemplast MF brand b and 0.14 g of Polycem DF. The resulting mixture was shut with water at a water / cement ratio of 0.52.

Compositions with different component contents were prepared in a similar manner.

During laboratory tests, the following properties of the proposed grouting composition were determined:

- water separation;

- water loss of the grouting composition at ΔР = 0.7 MPa in 30 min;

- the setting time of cement stone;

- the strength of the cement stone in compression, MPa;

- the strength of the cement stone in bending, MPa

- force pushing samples, MPa;

- permeability of cement stone, MD.

Determination of the bending and compression strength of cement samples and water separation was carried out in accordance with GOST 26798.2-96. In addition, the compressive strength was determined by a non-destructive testing method using an ultrasonic cement strength analyzer. Determination of water loss, setting time, the forces of the ejection of the samples, the permeability of the cement stone were made by known methods.

Data on the content of components in the investigated grouting compositions (known and proposed) are shown in table 1.

Data on the properties of grouting compositions and on the properties of the resulting grouting stone are given in table 2.

The results are shown in tables 1 and 2, show the following advantages of the proposed cement composition over the known:

- lack of water separation;

- low filtration of grouting compositions;

- the setting time allows for trouble-free injection of cement into the well.

- high adhesive properties (20-78% higher than that of the known).

Thus, the use of the proposed grouting composition in steam injection wells will ensure high-quality fastening of casing strings, eliminating the thickening and setting of cement during the injection of cement into the well. The absence of water separation and low filtration will ensure the stability of the formed cement stone and will reduce the loss of the aqueous phase from the cement mortar during its contact with the permeable sections of the wellbore, which contributes to the formation of high-quality cement stone throughout the wellbore, including in the interval of permeable formations.

In addition, given that steam injection wells are not high-temperature, the formation of cement stone occurs at normal temperatures, and cracking of the cement stone due to a sharp temperature difference is excluded during commissioning after steam injection (oil temperature can be from 30 to 40 ° C, while the temperature of heating the cement stone with steam is up to 180 ° C), which means that high-quality fastening and cementing of the well are guaranteed.

At the same time, experiencing constant cyclic temperature loads, the cement stone formed from the proposed composition ensures high-quality isolation of the annulus and allows to reduce the number of repairs and the overhaul period during the operation of steam injection wells.

Claims (5)

1. The grouting composition for steam injection wells containing Portland cement, silica sand, a silicon reagent and water, characterized in that as a silicon reagent it contains amorphous silicon dioxide in the following ratio of components, parts by weight:
Portland cement 50-80 Quartz sand 10-45 Amorphous silicon dioxide To 10 Water Up to v / c 0.35-0.52 2. The grouting composition according to claim 1, characterized in that it further comprises regulators of technological properties. 3. The grouting composition according to claim 1 or 2, characterized in that as a regulator of technological properties it contains an accelerator of setting time of up to 5 parts by weight, and / or hydroxyethyl cellulose up to 0.5 parts by weight, and / or plasticizer up to 0.7 parts by weight and / or reagent by the Police DF to 0.3 parts by weight 4. The grouting composition according to claim 3, characterized in that it contains calcium chloride or sodium chloride as an accelerator of the setting time. 5. The grouting composition according to claim 3, characterized in that as a plasticizer it contains lignosulfonates, or Melflux, or Zemplast MF brand b.