RU2533997C1 - Water inflow zones cementing method - Google Patents

Abstract

FIELD: oil and gas industry.SUBSTANCE: water inflow zones cementing method includes running in of the tubing string into the well, setting of the tubing string open end above the water inflow zone. Specific permeability is determined for the water inflow zone in two operating modes of the pumping unit. When specific permeability is more than 2 m/(h·MPa) flush liquid and waterproofing compound are injected in sequence until specific permeability reaches 0.5-2 m/(h·MPa). Then total volume of cement suspension is determined against specific permeability of the water inflow zone. Simultaneously cement suspension is made of suspension of oil-well Portland cement in quantity of 35% of the total cement suspension volume and suspension of microcement quantity of 65% of the total cement suspension volume. When specific permeability is 0.5-2 m/(h·MPa) flush liquid, suspension of microcement quantity and suspension of oil-well Portland cement are injected in sequence. Then the consumption rate and injection pressure is increased up to the limit value for the production casing, and at this rate with this pressure maintained flush fluid and the whole volume of the microcement suspension is flushed. Then the consumption rate and injection pressure is decreased up to the permitted minimum value at which the well continues receipt, and oil-well Portland cement suspension is flushed to the water inflow zone until zero permeability is obtained. The flushing is stopped; the process is set to exposure, then remains of cement Portland cement suspension are washed with counterpressure flow equal to final pressure of flushing of the oil-well Portland cement suspension to the water inflow zone.EFFECT: increased efficiency of water inflow zones cementing in wells, increased coverage of the water inflow zones by cementing.2 tbl, 3 ex

Description

The proposal relates to the oil industry, in particular to the field of cementing water inflow zones in wells.

A known method of cementing a well, including the preparation, injection and sale of cement slurry (suspension) into a well (Vadetsky Yu.V. Drilling of oil and gas wells. Issue 4, revised and additional - M .: Nedra. - 1978. - S.387).

A significant drawback of standard cement slurry suspensions is that they cannot be used when eliminating behind-the-casing flows, shutting off formations, sealing production cores and waterproofing works, since a coarse slurry of cement slurry cannot be pumped into micro-gaps, microcracks and low-permeability sections.

Closest to the technical nature of the proposed solution is a method of cementing zones of water influx of wells, including lowering into the well columns of tubing (tubing), installing the open end of the tubing above the zone of water inflow, determining specific injectivity, preparing, pumping cement slurry, starting from the fraction with smaller particle size, displacement of the cement slurry, washing of the remains of the cement slurry for the time required to set the cement slurry at a pressure of 0.3-0.5 MPa lower f course prodavke under pressure and allowing for latency hardening cement slurry (Patent RU №2297515, IPC E21B 33/13, publ. 20.04.07, at Bul. №11).

The disadvantage of this method is its low efficiency due to the low penetrating ability of the cement slurry, prepared from standard Portland cement and divided into fractions, in low-permeability areas. The main disadvantage of standard Portland cement grouting is that most of the slurry (fraction with the smallest particles in a volume of 50 to 75% of the total) is limited by the size of the sieve with a number of 0.8, which prevents the cement slurry, divided into fractions, to penetrate micro-gaps, microcracks and low permeability areas. When selling cement slurry under normal flow and pressure conditions, the main part of the fine fraction will move mainly in high-permeability sections, and the next fraction will settle at the entrance to the pores of the low- and medium-permeability section, which will lead to insufficient coverage of water inflow areas with low and medium permeability . Then, the residues of the cement slurry are washed at a pressure of 0.3-0.5 MPa below the final pressure during delivery. At the same time, a significant part of the cement slurry previously absorbed by the water inflow zone is often washed out, which negatively affects the success of cementing wells and the need for repeated work to seal the production string with low-viscosity cured true solutions (synthetic resins or other materials) and, as a result, leads to additional material costs. When the specific injectivity of the water inflow zone is more than 2 m ³ / (h · MPa), in order to achieve the effectiveness of the work, it is necessary to pump a large volume of cement slurry.

The technical objectives of the proposal are to increase the efficiency of cementing water inflow zones in wells by redistributing the direction of movement of cement slurry, increasing the coverage of cementing water inflow zones while saving cement slurry, and also eliminating repeated cementing of water inflow zones.

Technical problems are solved by the proposed method of cementing the zones of water inflow of wells, including the descent of the tubing string into the well, installing the open end of the tubing above the inflow zone, determining the specific injectivity, preparing, injecting and selling cement slurry, flushing out the cement slurry and leaving it on hardening time of cement slurry.

New is that they determine the specific injectivity of the water inflow zone in two modes of operation of the pump unit, with a specific injectivity of more than 2 m ³ / (h · MPa), a buffer liquid and a water-insulating composition are pumped sequentially until a specific injectivity of 0.5-2 m ³ / ( h · MPa), then, depending on the specific injectivity of the water inflow zone, the total volume of cement slurry is determined, at the same time a cement slurry is prepared, consisting of a suspension of Portland cement grouting in an amount of 35% of the total volume of cement slurry and and a suspension of micro-cement in an amount of 65% of the total volume of the cement slurry is pumped sequentially buffer liquid cement slurry of micro-cement, Portland cement slurry from plugging when the specific water inflow zone injectivity of 0.5-2 m ³ / (h · MPa), and then increase the flow rate and injection pressure to the maximum permissible pressure on the production casing and at this rate, without reducing the pressure, squeeze the buffer fluid and the entire volume of the cement slurry from microcement, then reduce the flow rate injection pressure to the minimum possible at which the well continues to receive, and the cement slurry is pushed from the Portland cement cement to the water inflow zone to obtain zero injectivity, the cessation is stopped and technological aging is carried out, then the remaining cement slurry from the Portland cement cement is flushed with a backpressure equal to the final cushion pressure cement slurry from Portland cement grouting into the zone of water inflow.

The essence of the proposed method is as follows. The interval of the zone of water inflow is determined. A cement bridge is installed below the water inflow zone. The tubing string (tubing) is lowered into the well and the open end of the tubing is installed above the water inflow zone. The specific injectivity of the water inflow zone is determined in two operating modes of the pumping unit by pumping through the tubing of the process fluid with a density corresponding to the density of the well killing fluid.

With a specific injectivity of more than 2 m ³ / (h · MPa), determined at the maximum flow rate of the pump unit, in order to increase the strength characteristics of the stone and save cement slurry, high-permeability zones are clogged and the specific injectivity of the water inflow zone is reduced. A buffer liquid and a water-proofing composition are sequentially pumped up to a specific injection rate in the range of 0.5-2 m ³ / (h · MPa), which is detected when the specific injection rate is re-determined. For example, when watering a well with mineralized water with a density of 1150-1190 kg / m ³ , the water-insulating composition is injected according to the scheme "buffer liquid - low-modulus liquid glass - buffer liquid"; when watering a well with mineralized water with a density of 1100-1150 kg / m ³ , injection is carried out according to the scheme "Buffer liquid - an aqueous solution of calcium chloride - buffer liquid - low-modulus liquid glass - buffer liquid", etc. If necessary, the density of water glass can be adjusted by adding fresh water. Thanks to this, the scope of technology is expanding. The volume of the waterproofing composition is selected depending on the specific injectivity determined at the maximum flow rate of the pump unit, from table 1.

Table 1 Specific throttle response, m ³ / (h · MPa), within The volume of the waterproofing composition, m ³ 2.1-3              4-6 more than 3              7-8

Then, depending on the specific injectivity of the water inflow zone, determined at the maximum flow rate of the pump unit, the total volume of cement slurry is determined from table 2.

table 2 Specific throttle response, m ³ / (h · MPa), within The volume of cement slurry, m ³ 0.5-1 1.0-3.0 1-2 3.0-5.0

To implement the method, apply:

- Portland cement grouting grade PTC I-G-CC-I (GOST 1581-96) with a water-cement ratio of 0.44;

- fresh water with a density of 1000 kg / m ³ for the preparation of cement suspensions and as a buffer fluid;

- STM "Soldstone" microcement (TU 5732-001-91222887-2012) with a content of 95% particles no larger than 6 microns and a specific surface area of 900 m ² / kg at a water-cement ratio of 1 and modifying additives to it made by CHEVRON PHILLIPS CHEMICAL COMPANY LP , USA (there are certificates of conformity, certificates for the use of a chemical product in technological processes of oil production and transportation):

- anti-slip agent DIACEL ASA-100;

- water loss reducer DIACEL FL;

- plasticizer DIACEL RPM;

- defoamer DIACEL ATF;

- waterproofing compositions:

1) low-modulus liquid glass (sodium silicate), produced according to GOST 13078-81 "Sodium liquid glass." In the interaction of low-modulus liquid glass with mineralized water with a density of 1150-1190 kg / m ³ , a stable bulk gel precipitate is instantly formed, which clogs highly permeable zones, reduces the injectivity of the water inflow zone and has high mechanical strength;

2) an aqueous solution of calcium chloride with a density of 1300-1380 kg / m ³ (calcium chloride GOST 450-77). The interaction of an aqueous solution of sodium silicate and calcium chloride instantly forms a stable bulk precipitate of silicic acid gel and calcium silicate, which clogs highly permeable zones, reduces the pick-up of the zone of water inflow and has high mechanical strength.

At the same time, a cement slurry is prepared, consisting of a suspension of Portland cement grouting in the amount of 35% of the total volume of the cement slurry and a suspension of microcement in the amount of 65% of the total volume of the cement slurry.

A suspension of Portland cement grout is prepared as follows. Fresh water is supplied from the tanker by a pump of a cementing unit to a cement mixing unit with Portland cement grouting to prepare a suspension of Portland cement grouting with a water-cement ratio of 0.44 and a density in the range of 1890-1910 kg / m ³ . From the cement-mixing unit, a suspension of Portland cement grouting enters the chunk. Next, a suspension of Portland cement grouting cementing unit is served in a mixing-homogenizing installation for mixing until the density is equalized. At the same time, a suspension is prepared from microcement in a container. To prepare a suspension of microcement, the discharge line of the cementing unit is tied with a container and fresh water is pumped at a temperature of 20-23 ° C. Further, the operation of the cementing unit creates a circulation of fresh water in the tank. In a stream of water with constant circulation, the DIACEL ASA-100 anti-precipitating agent is uniformly added in small portions. After its dissolution, DIACEL FL water loss reducer is added uniformly in small portions, after its dissolution, DIACEL RPM plasticizer and DIACEL ATF antifoam are added in small portions and circulated until complete dissolution. Then, in the circulating water (with previously dissolved reagents), with constant stirring by the operation of the cementing unit, micro-cement STM “Soldstone” is gradually fed in small portions. After supplying the entire volume of dry microcement to the tank, the solution is circulated until its density is equalized. The density of the solution at a water-cement ratio of 1 is in the range of 1580-1670 kg / m ³ . Further, at a specific injection rate of 0.5-2 m ³ / (h · MPa) with an open annular valve, a buffer liquid, a cement slurry from microcement and a cement slurry from Portland cement grouting are sequentially pumped. Bring to the zone of water inflow technological fluid. Close the annular valve. Before selling cement slurry from microcement into the water inflow zone, its flow rate and pressure are increased from 0 to the maximum allowable pressure on the production casing, and at this flow rate, without reducing pressure, buffer fluid and the entire volume of cement slurry from microcement are forced to flow. Due to this, the coverage of the isolated water inflow zone is increased, which allows the cement slurry from microcement to penetrate into micro-gaps, microcracks and low-permeability sections, the sizes of which do not exceed 6-10 microns, where the usual cement slurry from Portland cement grouting does not penetrate, since the main small fraction of Portland cement grouting has sizes 10-50 microns and makes up 90% of the volume. At the same time, a cement suspension of microcement is fully consumed as intended. Then, the flow rate and pressure are reduced to the minimum possible at which the well continues to take, and the cement slurry is pushed from the Portland cement to the water inflow zone, while the injectivity of the water inflow zone decreases, the pressure rises and in the absence of injectivity (zero injectivity) the pressure rises sharply to the maximum permissible production casing. The sale is stopped and technological exposure is carried out for 5 minutes to determine the effectiveness of blockage of the water inflow zone. Due to this, the sale of cement slurry from Portland cement grouting allows the cement slurry to penetrate into other zones not cemented by the slurry from microcement, which reduces the injectivity to zero (absence). Thus, the mouth of the pores and cracks is fixed. If the pressure has not decreased, the interval of the water inflow zone is tight. In the event of a decrease in pressure, the squeeze is carried out in cycles, not exceeding the permissible pressure on the production casing. The residues of the cement slurry from grouting Portland cement are washed with a backpressure equal to the final pressure of the cement slurry being pushed from the Portland cement grouting to the water inflow zone, which helps to prevent the extrusion of cement suspensions from the water inflow zone (cement slurry from microcement, cement slurry from Portland cement swab). Due to this, there is no need to perform repeated work on the pressurization of the production string with low-viscosity reagents (synthetic resins or other materials). The well is closed and left for a while waiting for the hardening of the cement slurry (WSC) for 24 hours. After the expiration of the waiting time for the hardening of the cement slurry by retreating the tubing, the presence and location of the cement bridge are determined. Then, a cement bridge is drilled and the production string is pressed with excess pressure, and for production wells, an additional reduction in the level of swabbing is performed.

Examples of specific performance.

Example 1. In the interval 1770-1790 m was detected zone of water inflow. A cement bridge was installed at a depth of 1800 m. The tubing was lowered into the production string and the open end of the tubing was installed at a depth of 1750 m. The maximum allowable pressure on the production string is 10.0 MPa. The specific injectivity of the water inflow zone was determined:

- at a maximum flow rate of 4.2 l / s, the throttle response is 360 m ³ / day at a pressure of 10.0 MPa. Specific throttle response - 1.5 m ³ / h · MPa;

- at a minimum flow rate of 1.2 l / s, the throttle response is 100 m ³ / day at a pressure of 5.0 MPa. The specific throttle response is 0.8 m ³ / h · MPa.

The volume of cement slurry 4 m ^{3 was} selected according to table 2. A cement slurry was prepared consisting of Portland cement cement in an amount of 35% (1.4 m ³ ) of the total volume of cement slurry and a suspension of microcement in an amount of 65% (2.6 m ³ ) of the total volume of cement slurry. Then, with an open annular valve, 0.1 m ^{3 of} buffer fluid from fresh water, 2.6 m ^{3 of} cement slurry from microcement and 1.4 m ^{3 of} cement slurry from Portland cement grouting were pumped sequentially. Brought to the zone of water inflow with process fluid in a volume of 1.0 m ³ . They closed the annular valve. Before selling cement slurry from microcement to the water inflow zone, the flow rate was increased from 0 to 4.2 l / s and pressure from 0 to 10.0 MPa. With this flow rate, without reducing the pressure, we pumped a pumping unit of a buffer fluid from fresh water and 2.6 m ^{3 of} cement slurry from microcement. Then, the flow rate was reduced from 4.2 to 1.2 l / s and pressure from 10 to 5.0 MPa. At this flow rate, without decreasing the pressure, 0.7 m ^{3 of} cement slurry from Portland cement cement was pressed through, while the pressure gradually increased to 7.0 MPa and rose sharply to 10.0 MPa. The sale was stopped, technological exposure was carried out for 5 minutes - hermetically. Then, the pressure was reduced to 7.0 MPa (equal to the final pressure of the cement slurry being pumped from Portland cement grouting to the water inflow zone) and flushing was carried out with back pressure of the cement slurry from Portland cement grouting. Then the well was closed and left to wait for the hardening of the cement slurry (WSP) - for 24 hours. After the expiration of the time, the WSC through the access to the tubing determined the presence and location of the cement bridge. It was located at a depth of 1750 m. A cement bridge was drilled. When tested for tightness under a pressure of 10.0 MPa and a decrease in the level of swabbing, the production casing showed complete tightness.

Example 2. Perform, as example 1. The specific injectivity of the zone of water inflow at a maximum operating mode of the pump unit 3 m ³ / (h · MPa), the well is flooded with mineralized water with a density of 1150-1190 kg / m ³ . A sequentially pumped buffer liquid from fresh water, a waterproofing composition based on liquid glass in a volume of 6 m ³ to achieve a specific injection rate of 2 m ³ / (h · MPa). To carry out the work, low-modulus liquid glass manufactured according to GOST 13078-81 “Sodium liquid glass” was used. The specific injectivity of the water inflow zone was determined:

- at a maximum flow rate of 4.5 l / s, the throttle response is 390 m ³ / day at a pressure of 8.0 MPa. Specific throttle response - 2 m ³ / h · MPa;

- at a minimum flow rate of 1.2 l / s, the throttle response is 100 m ³ / day at a pressure of 4.0 MPa. The specific throttle response is 1 m ³ / h · MPa. The total volume of the cement slurry is 5 m ³ , a cement slurry was prepared consisting of Portland cement cement in the amount of 35% (1.75 m ³ ) of the total volume of the cement slurry and microcement slurry in the amount of 65% (3.25 m ³ ) of the total volume of cement slurry. The cement slurry was pumped, pushed and cut as in example 1.

Example 3. Perform, as example 1. The specific injectivity of the zone of water inflow of 3.5 m ³ / (h · MPa), the well is flooded with mineralized water with a density of 1100-1150 kg / m ³ . They made an injection of a waterproofing composition according to the scheme “buffer - an aqueous solution of calcium chloride — buffer — low-modulus liquid glass — buffer” until a specific injection rate of 0.5 m ³ / (h · MPa) was achieved. For work, low-modulus liquid glass manufactured according to GOST 13078-81 “Sodium liquid glass” was used, and an aqueous solution of calcium chloride with a density of 1.30-1.38 g / cm (calcium chloride GOST 450-77) was used as curing liquid. The specific injectivity of the water inflow zone was determined:

- at a maximum flow rate of 1.6 l / s, the throttle response is 140 m ³ / day at a pressure of 11.5 MPa. Specific throttle response - 0.5 m ³ / h · MPa;

- at a minimum flow rate of 0.7 l / s, the throttle response is 60 m ³ / day at a pressure of 7.0 MPa. The specific throttle response is 0.35 m ³ / h · MPa. The volume of cement slurry was 1 m ³ . A cement slurry was prepared consisting of Portland cement cement in the amount of 35% (0.35 m ³ ) of the total volume of the cement slurry and a suspension of microcement in the amount of 65% (0.65 m ³ ) of the total volume of the cement slurry. The cement slurry was pumped, pushed and cut as in example 1.

The proposed method allows to increase the efficiency of cementing water inflow zones in wells by redistributing the direction of movement of cement slurry, increasing the coverage of cementing water inflow zones while saving cement slurry, and also eliminating repeated work on cementing water inflow zones.

Claims (1)

A method of cementing water inflow zones of wells, including lowering the tubing string into the well, installing the open end of the tubing above the water inflow zone, determining the specific injectivity, preparing, injecting and selling cement slurry, flushing the cement slurry residues and leaving the cement slurry to wait suspension, characterized in that the water inflow determining the specific pickup area on the two modes of operation of the pump unit, at a weight pickup of more than 2 m ³ / (h · Pa) is injected sequentially buffer liquid waterproofing composition to achieve specific pickup 0.5-2 m ³ / (h · MPa), then depending on the specific water inflow zone injectivity determine the total amount of cement slurry, while preparing a cement slurry consisting of a suspension of Portland cement grouting in the amount of 35% of the total volume of the cement slurry and suspension from microcement in the amount of 65% of the total volume of the cement slurry, with a specific injectivity of the zone of water inflow of 0.5-2 m ³ / (h · MPa) is pumped after buffer fluid, cement slurry from microcement, cement slurry from Portland cement grouting, then increase the flow rate and injection pressure to the maximum permissible pressure on the production string and at this flow rate, without reducing the pressure, squeeze the buffer fluid and the entire volume of the cement slurry from microcement, then reduce the flow rate and injection pressure to the minimum possible, at which the well continues to receive, and push the cement slurry from Portland cement cement into the water inflow zone until zero injectivity is obtained, the discharging is stopped and technological exposure is carried out, then the residues of the cement slurry from Portland cement grouting are washed with a backpressure equal to the final pressure of the cement slurry from Portland cement grouting to the water inflow zone.