RU2398095C1 - Method for string cementing in well using cement mortar with erosion properties - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: invention relates to the field of well building and will find application in oil or gas well casing, and also in repair works related to cementing. Method provides for serial pumping of washing spacer fluid and three portions of cement mortar, the third of which is for productive zone. At the same time the first portion pumped following spacer fluid is cement mortar with erosion properties prepared from at least 5 tons of oil-well portland cement mixed with abrasive material in the ratio of 100:8 in weight and with density of 1.64 g/cm³, where abrasive material is represented by quartz sand with average grain size of 0.28-1.0 mm. Method application provides for maximum removal of drilling fluid remains from walls of string and well, as well as for efficient damage of adhesion film and filtration crust of clayey solution.

EFFECT: increased intensity of string cement stone contact with environment, and accordingly, high-quality isolation of beds.

1 tbl

Description

The invention relates to the field of well construction and will find application in fastening an oil or gas well, as well as in repair work related to cementing.

A known method of securing a well (see AS SU No. 1686129, 5 EV 33/13, published in BI No. 39, 10/23/1991), including the preparation of the wellbore, casing, flushing the well with flushing fluid, injection buffer fluid and cement slurry and pushing them into the annulus. In this case, the preparation of the wellbore is carried out by treatment with a cement-water suspension with a water-solid ratio of 10-15 with the creation of cavitation wave processes in its stream.

The disadvantage of this method is that its implementation does not provide complete removal of the drilling fluid due to sedimentary delamination of the cement-water suspension, and the introduction of polymer additives in the suspension such as PAA, CMC, HIPAN is not possible, since there is no optimal dosage as well as price. In addition, the method requires additional tripping operations to treat the well wall by creating cavitation wave processes, which requires time and technical means.

A known method of preparing a well for cementing (see the description by AS SU No. 825864, 6 ЕВВ 33/138, 1981), in which an abrasive-washing liquid is used to improve the washing off of clay cake or the removal of drilling mud residues.

The essence of the method is as follows. A viscoelastic separator and an abrasive washing liquid are sequentially pumped into the well, and before the injection of the abrasive washing liquid, the clay cake baking powder is injected, and after the injection of the abrasive washing liquid, the pores of the borehole walls are matted.

As a viscoelastic separator, a 0.5% aqueous solution of polyacrylamide with a 2% aqueous solution of hexarezorcin resin and with 37% formalin is pumped.

As a disintegrant, a 1-5% aqueous solution of aluminum sulfate is pumped.

As an abrasive washing liquid, 100 parts by weight are pumped. self-crumbling slag production of ferrochrome with 96-104 parts by weight sand and from 126-132 parts by weight water. Colmatization is carried out 100 parts by weight cement with 15-20 parts by weight rubber crumbs and with 67-73 weight.h. water.

The disadvantage of this method is the use of a large number of multicomponent buffer fluids, the complexity of the technology for their preparation. In addition, the viscoelastic separation fluid used to displace the drilling fluid is not effective enough. This is explained by the low shear stresses created by polyacrylamide-containing BZ on the walls of the well due to the presence of a “sliding effect”, a decrease in viscosity and dynamic shear stress due to mechanical destruction of the VUR, as well as the impossibility of displacing heavier drilling fluids due to the unregulated density of the BZ by the known method.

Buffer fluid is also known (see patent No. 2268350, 6 ЕВВ 33/138, BI No. 2 of 01/20/2006), in which aluminosilicate microspheres with the use of buffering solution and removing clay peel are used to ensure the quality of cementing of the well abrasive property. It contains in its composition the following components, wt.%:

Cement 30-45 Sodium Tripolyphosphate 0.1-1.0 Sulfacillus 0.2-0.3 Neonol 0.05-0.1 Aluminosilicate Microspheres 5-10 Water 64.65-43.6

This composition of the buffer fluid partially eliminates the disadvantages of the buffer fluid used in the method as. SU No. 825864 noted above. However, it is also multicomponent and has the same drawbacks in terms of removing mud cake and mud residues. Due to the presence of a “sliding effect”, an abrasive material in the form of an aluminosilicate microsphere does not fully perform its function and the expected effect of removing a completely clay filter cake is not provided.

Known abrasive grouting mixture (see patent RU No. 22495989, IPC 721B 33/138, publ. In BI No. 4, 02/10/2005), which includes, wt.%: Portland cement 50-76; ground dust-like quartz of grade “B” 20-40 and caustic magnesite powder PMK-87 - the rest. Grouting mortar prepared from this grouting mixture - provides a decrease in the rate of filtration and shrinkage of grouting mortar.

However, the quartz dust included in the grouting mixture of grade “B” as an abrasive has low efficiency in terms of removing residual drilling fluid from the walls of the column and the walls of the well due to its use as a fine grinding to a dust state.

The well-known "Method of cementing a well" (see patent RU No. 2266390, 7 ЕВВ 33/14, published in BI No. 35 dated 12/20/2005), which provides for the displacement of drilling fluid and the removal of its residues from the walls of the well.

The method includes the sequential injection of a washing buffer solution in a volume of 6 m ³ prepared from a modified buffer detergent powder, a “thickened pack” of high viscosity cement slurry in a volume of 4 m ³ and cementing cement slurry and a portion of cement mortar for a productive zone with a volume of 10 m ³ .

The known method in its technical essence is closer to the proposed one and can be adopted as a prototype. Its disadvantage is that a thickened pack of cement mortar with sodium silicate in an amount of 1-1.5%, having a high viscosity (1.92 g / cm ³ ), does not have high efficiency in removing residual drilling fluid from the walls of the column and well because it does not contain abrasive material. In addition, the implementation of the method is non-technological, entails the preparation of several types of multicomponent solutions, which requires a lot of time, as well as the involvement of many technical means.

The technical task of the present invention is to increase the efficiency and quality of removal of drilling fluid from the walls of the columns and wells, simplifying the technology of cementing, as well as reducing material costs.

The problem is solved by the described method, including sequential pumping after washing buffer fluid of three portions of the cement mortar.

New is that as the first portion, injected after the buffer fluid, use a cement mortar with erosion properties, prepared from at least 5 tons of a mixture of Portland cement grouting with abrasive material in a ratio of 100: 8 by weight and with a density of 1.64 g / cm ³ , in the composition of which quartz sand with an average grain size of 0.28-1.0 mm is used as an abrasive material.

According to the authors, these distinguishing features of the proposal are significant, and the method itself is novel, because, as shown by patent research conducted for a period of 20 years on the patent fund of the TatNIPIneft Institute, objects of similar purpose and in the aggregate of essential features, as proposed, not found and not used in fishing practice.

The method is carried out in the following sequence.

Before starting the geological and technical service of the drilling enterprise, the section intervals to be hydro-blasted and other parameters of the well, such as the depth of the face, the depth of installation of the technical equipment for the equipment of the production string, the intervals of the cut with caverns, their diameter, and the zenith angle, are specified according to a set of final geophysical studies axis of the well, the magnitude of the pressure of the separated layers. Then they begin to prepare the wellbore for fastening, which provides for isolation of the mud absorption zones, strengthening of the walls of the well in the intervals of occurrence of rock prone to destruction, removing the filter cake from the permeable sections of the well, strengthening the adhesive film on the walls of the well and ensuring the passage of the column to the design depth without complications.

At the end of the above work, preparatory operations for cementing the column are carried out. For this, cementing equipment is placed on a horizontal platform, the injection and water supply lines are assembled, water is drawn into the measuring tanks CA-320M, the injection line is pressurized at a pressure 1.5 times higher than the expected working pressure when cementing the column. After lowering the casing string to a predetermined depth of the well, it is washed and then buffer fluid is pumped into it to separate the drilling fluid from the cement, wash the clay cake, oil and polymer film from the walls of the wellbore and the outer surface of the string.

Next, washing buffer liquid is pumped into the column in a volume of about 6-10 m ³ . Following it, the first portion of an abrasive-containing cement mortar (ACR) with a density of 1.64 g / cm ^{3 is} pumped through the averaging tank using a cementing aggregate CA-320M with a water-cement ratio of 0.43, prepared from 5 tons of cement cement with an abrasive material in a ratio of 100 : 8 by weight. As abrasive material, quartz sand with an average grain size of 0.28-1.0 mm produced by the domestic industry, for example, according to GOST 22551-77 or GOST 2138-91, is used. As bench and field studies have shown, the above mix ratio is optimal. So, when the content of abrasive material is more than 8, the strength characteristics of the cement stone formed from this composition are reduced, and when the content of abrasive is less than 8, the efficiency of removing residual drilling fluid from the surface of the column walls and well walls decreases. Then the second and third portions of the cement mortar are subsequently pumped. In this case, as a second portion, a traditional cement mortar with a density of 1.82 g / cm ^{3 is} pumped.

The preparation of an abrasive-containing cement mortar in the field was carried out by adding 800 kg of silica sand manually in a chunk with a cement mortar of the cementing unit ЦА-320М prepared from cement Portland cement in the amount of 10 tons.

With the serial use of abrasive-containing cement mortar, it is prepared centrally by mixing a mixture of cement cement with abrasive in a special installation based on the control of cement work with a water-cement ratio of 0.43. Without interrupting the injection process, after the first portion of the cement mortar using cementing units CA-320 M, the second portion of the standard cement mortar prepared by traditional technology is pumped in the required volume depending on the depth of the well with a density of 1.82 g / cm ³ . Following the second portion, a third portion of the cement slurry is pumped for the zone of the reservoir, which has a low filtration rate and minimal shrinkage. Corresponding to these criteria are grouting mixtures, known from the full description of the patents of the Russian Federation No. 2255989, ЕВВ 33/138, containing, wt.%:

Portland cement 50-76 Dust quartz powder grade B 20-40 Caustic magnesite powder PMK 87 rest

or grouting composition used in steam injection wells according to the patent of the Russian Federation No. 2220275, IPC 7E21 B33 / 138, containing the following ingredients in a ratio, wt.%:

Clinker 25-40 Gypsum 3-6 Quartz sand 35-38 Main slag 20-22 Additive IR-1 2-9

After pumping the third portion of the cement mortar of the calculated volume, it is pressed through with a corking screw until the latter is planted on the stop ring.

Abrasive cement mortar, when moving along a pipe string and annulus, in contact with the walls of the column and the wellbore, erodes and destroys the adhesive film and filter cake of the mud. As a result, the maximum removal of drilling mud residues in the annulus is ensured, which leads to high-quality separation of the strata and an increase in the contact strength of the annular cement stone with the environment.

After the completion of the cementing works, and consequently, the OZC geophysical studies, for example, according to the data of acoustic logging (ACC) and SRS, cementation quality is assessed.

An abrasive-containing cement mortar with erosion properties was analyzed in laboratory conditions of the TatNIPIneft Institute and Ecobur LLC at t = 20 ° C. The results of laboratory tests are summarized in table.

As can be seen from the indicators of the table, the characteristics of the abrasive-containing cement mortar exceed the performance of the base cement mortar.

The method was tested in the field conditions of OAO Tatneft. The test results are positive.

The technical and economic advantage of the invention is as follows. Using the method provides the maximum removal of residual drilling fluid from the walls of the column and well, as well as the effective destruction of the adhesive film and filter cake of the mud. As a result, the contact strength of the annular cement stone with the environment increases and, as a result, the qualitative separation of the layers due to the addition of accessible abrasive material to the cement mortar, which increases the erosion properties of the cement mortar - finely dispersed silica sand in comparison with the known abrasive materials such as cement-water suspension or aluminosilicate microspheres.

Claims (1)

A method of cementing a column in a well using a cement slurry with erosive properties, comprising sequentially pumping three portions of a cement slurry after a washing buffer liquid, characterized in that an erosive cement slurry prepared from non-erosive properties is used as the first portion being pumped after the buffer fluid less than 5 tons of a mixture of Portland cement grouting with abrasive material in a ratio of 100: 8 by weight and with a density of 1.64 g / cm ³ , the composition of which as an abrasive The material used is quartz sand with an average grain size of 0.28-1.0 mm.