WO2022214898A1

WO2022214898A1 - Synthetic fluid-loss reducer

Info

Publication number: WO2022214898A1
Application number: PCT/IB2022/052624
Authority: WO
Inventors: Semen Vladimirovich PESTEREV
Original assignee: «Oil Energy», Limited Liability Company
Priority date: 2021-04-07
Filing date: 2022-03-22
Publication date: 2022-10-13
Also published as: RU2763586C1

Abstract

The invention relates to synthetic fluid-loss reducers and may be used in the oil and gas industry in well construction as an additive to cement slurries. A synthetic fluid-loss reducer for cemented well construction characterized in that it comprises a 2-acrylamido-2-methylpropylsulfonic acid (AMPS) copolymer with a mass fraction of 5-90%, N,N-dimethylacrylamide (NNDMA) with a mass fraction of 5-80% and unsaturated carboxylic acid with a mass fraction of 5-80%. 2 independent and 12 dependent claims, 1 table.

Description

Synthetic fluid-loss reducer

Field of the Invention

The invention relates to synthetic fluid-loss reducers and may be used in oil and gas industry in well construction as an additive to cement slurries.

Background of the Invention

One of the main steps in well construction is well cementing. This step consists of inserting the casing column followed by cementing anulus, which makes it possible to avoid well collapse, preserve the reservoir properties of productive formations and form a leak proof and durable insulating well support complex that reliably separates fluid-containing formations.

Fluid loss in cement blend during solidification process leads to loss in strength of cement stone, formation of cracks, porosity, contamination of productive formations and respective decrease in well flow rate.

To eliminate this drawback, the use of synthetic fluid-loss reducers based on polymers comprising AMPS (2-Acrylamido-2-methylpropanesulfonic acid) is known. Fluid-loss reducers of that kind are widely used in the art and are produced by known synthetic methods in temperature-controlled reactors.

Known is a method for producing a synthetic fluid-loss reducer based on a sealing composition comprising an aqueous fluid, diutan composition, at least one gel system, and a leak-preventing material in the form of a crosslinkable water- soluble copolymer, for example, AMPS/N-N-dimethylacrylamide/acrylamide terpolymer. The synthetic fluid-loss reducer is introduced into the bore well and a plug is formed to seal the subterranean formation (patent RU No. 2564708C2, IPC C09K 8/42, E21B 33/138, 10.10.2015). The closest analogue (prototype) is a method for producing a synthetic fluid-loss reducer, comprising, as main components, a copolymer resin functionalized with sulfonic acid, which comprises a residue of 2-acrylamido-2- methylpropylsulfonic acid (AMPS) and N,N-dimethylacrylamide (NNDMA). The copolymer comprises from about 60 to 99 wt.% AMPS monomer units and from about 1 to 40 wt.% NNDMA monomer units. Total resin content in the fluid- loss reducer is approximately from 10 to 40 wt.%, and the viscosity ranges from 10 cPs to 15000 cPs at 20°C (application for invention RU 2007110164, 1PC C09K 8/487, 03.02.2006).

The known technology for producing a synthetic fluid-loss reducer makes it possible to achieve fluid loss of about 100 ml when loading no more than 0.6% of fluid-loss reducer and with oxygen content of no more than 0.6%. In the context of accelerated pace of well construction, leading to reduced time of waiting for cement solidification, increased horizontal lengths and increased hydraulic fracturing pressure, there is a need to increase the fluid-loss characteristics of cement blends.

The object of the present invention is to develop a synthetic fluid-loss reducer that improves the quality of well cementing, and a method for producing same.

The technical result to which the present invention is directed is to create a synthetic fluid-loss reducer to improve the fluid-loss characteristics of cement blends, in particular, to improve the quality of well cementing, reduce the risk of cracking and cross-flows, reduce the filter cake and increase well flow rate.

Disclosure of the invention

Said technical result is achieved by the fact that the synthetic fluid-loss reducer for bore wells comprises a 2-acrylamido-2-methylpropylsulfonic acid (AMPS) copolymer with a mass fraction of 5-90%, N,N-dimethylacrylamide (NNDMA) with a mass fraction of 5-80% and unsaturated carboxylic acid with a mass fraction of 5-80%.

An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-70%, NNDMA with a mass fraction of 5-20% and an unsaturated carboxylic acid with a mass fraction of 5-10%.

An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-60%, NNDMA with a mass fraction of 5-20% and an unsaturated carboxylic acid with a mass fraction of 5-20%.

An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-40%, NNDMA with a mass fraction of 5-20% and an unsaturated carboxylic acid with a mass fraction of 5-40%. An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-30%, NNDMA with a mass fraction of 5-30% and an unsaturated carboxylic acid with a mass fraction of 5-40%.

An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-10%, NNDMA with a mass fraction of 5-10% and an unsaturated carboxylic acid with a mass fraction of 5-80%.

An embodiment of the invention is possible, according to which the fluid- loss reducer comprises an AMPS copolymer with a mass fraction of 5-10%, NNDMA with a mass fraction of 5-80% and an unsaturated carboxylic acid with a mass fraction of 5-10%.

An embodiment of the invention is possible, according to which the unsaturated carboxylic acid is selected from acrylic, methacrylic, maleic or itaconic acids. An embodiment of the invention is possible, according to which 3-allyloxy- 2 -hydroxy- 1-propanesulfonic acid (AHPS) may be used instead of 2-acrylamido- 2-methylpropylsulfonic acid (AMPS).

An embodiment of the invention is possible, according to which acryloylmorpholine (ACMO) may be used instead of 3-allyloxy-2-hydroxy-l- propanesulfonic acid (AMPS).

An embodiment of the invention is possible, according to which a monomer selected from acrylamide, N-vinylacetamide, N-vinylcaprolactam, 4- hydroxybutyl ether, N-vinylpyrrolidone, dimethylaminoethyl methacrylate, vinyl imidazoline, N-isopropylacrylamide, N-methylolacrylamide, N- (meth)acryloylmorpholine may be used instead of NNDMA.

Another object of the subject technical solution is a method for synthesizing a fluid-loss reducer, comprising: supplying water to a reaction vessel using a pump and heating it to 60-70°C, introducing AMPS, NNDMA and unsaturated carboxylic acid into the mixing vessel, heating while stirring to 60-70°C via a coiled pipe using a heat transfer medium, pumping the resulting solution from the mixing vessel into the reaction vessel using a pump, introducing potassium persulfate while stirring and maintaining a temperature of 60-70°C for 120 minutes, offloading the reaction mass using a screw pump into an intermediate storage vessel, feeding the reaction mass into roller dryers, cutting off a thin film of the dried product with a knife, grinding dry powdery material to produce a dry synthetic fluid-loss reducer.

An embodiment of the method is possible, according to which calcium hydroxide is introduced into the reaction mixture to ensure the pH value is 6-10.

An embodiment of the method is possible, according to which the reaction mixture is purged with nitrogen at atmospheric pressure to remove atmospheric oxygen from the vessel until the oxygen content is not more than 0.6%.

Detailed description of the invention The subject synthetic fluid-loss reducer comprises a 2-acrylamido-2-m ethyl propyl sulfonic acid (AMPS) copolymer with a mass fraction of 5-90%, N,N- dimethylacrylamide (NNDMA) with a mass fraction of 5-80% and unsaturated carboxylic acid with a mass fraction of 5-80%.

2-Acrylamido-2-methylpropanesulfonic acid is a white powder and is a reactive hydrophilic acrylic sulfonic acid monomer with a non-volatile matter mass fraction of not less than 99.0%, water mass fraction of not more than 0.30% and iron mass fraction of not more than 0.001%.

N,N-dimethylacrylamide is a colorless liquid with a characteristic odor and base component content of at least 99.0%, boiling point of 80°C and density of 0.962 g/cm³. N,N-dimethylacrylamide is soluble in water and serves as the base component for producing a wide variety of polymers.

In other aspects, the fluid-loss reducer comprises an AMPS copolymer with a mass fraction of 5-70%, NNDMA with a mass fraction of 5-20% and unsaturated carboxylic acid with a mass fraction of 5-10%; AMPS copolymer with a mass fraction of 5-60%, NNDMA with a mass fraction of 5-20% and unsaturated carboxylic acid with a mass fraction of 5-20%; AMPS copolymer with a mass fraction of 5-40%, NNDMA with a mass fraction of 5-20% and unsaturated carboxylic acid with a mass fraction of 5-40; AMPS copolymer with a mass fraction of 5-30%, NNDMA with a mass fraction of 5-30% and unsaturated carboxylic acid with a mass fraction of 5-40%; AMPS copolymer with a mass fraction of 5-10%, NNDMA with a mass fraction of 5-10% and unsaturated carboxylic acid with a mass fraction of 5-80%; AMPS copolymer with a mass fraction of 5-10%, NNDMA with a mass fraction of 5-80% and unsaturated carboxylic acid with a mass fraction of 5-10%.

In one embodiment, the fluid-loss reducer comprises unsaturated carboxylic acid selected from acrylic, methacrylic, maleic, or itaconic acids.

In one embodiment, 3-allyloxy-2-hydroxy-l-propanesulfonic acid (AHPS) or acryloylmorpholine (ACMO) may be used instead of AMPS. In one embodiment, a monomer selected from acrylamide, N- vinylacetamide, N-vinylcaprolactam, 4-hydroxybutyl ether, N-vinylpyrrolidone, dimethylaminoethyl methacrylate, vinyl imidazoline, N-isopropylacrylamide, N- methylolacrylamide, N-(meth)acryloylmorpholine may be used instead of NNDMA.

The first step comprises batch process of synthesis of fluid-loss reducer by polymerizing initial monomers in aqueous medium. The first step ends with offloading of liquid reaction mass into an intermediate storage vessel intended for semi-finished product. The second step comprises continuous process of drying the liquid reaction mass on roller dryers, from which the dry powdery material is fed by a screw conveyor into portable plastic tanks. The third step comprises grinding and packing of the dry product.

All steps of the method are performed using standard equipment, in particular using reaction and mixing vessels with electric heating and cooling coil (for example, TI 10.01.EZ or IKA LR 1000 Control), chemical centrifugal pumps, screw pumps, spray heads, ventilation flanges, drum-type roller dryer with exhaust hood, etc.

To synthesize the synthetic fluid-loss reducer, water is drawn into the reaction vessel from a vessel using a pump. Contents of the vessel are heated while stirring to 60°C via jacket coiled pipe using heat transfer medium. Simultaneously, the initial raw material is added to the mixing vessel. pH is adjusted to the desired level by means of high grade calcium hydroxide, which is added through the hatch while stirring.

Within 10 minutes thereafter, the solutions of AMPS, NNDMA and unsaturated carboxylic acid are added through the hatch or funnel using a pump. Contents of the vessel are heated while stirring to 60-70°C via the jacket coiled pipe using heat transfer medium. After NNDMA is added, the resulting solution is pumped for 10 minutes while stirring by means of a pump into the reaction vessel. The mixing vessel is then washed with water by means of a spray head. After washing, water is pumped into the reaction vessel. If necessary, the reaction mass is heated to 60-70°C.

The vessel is purged with nitrogen from a nitrogen ramp at atmospheric pressure to remove atmospheric oxygen from the vessel. Air is removed through a vent flange connected through a back pressure valve or a water seal with a vent. All other valves on the vessel lid are closed. After purging with nitrogen, to start the reaction, potassium persulfate as the initiator is added while stirring through a funnel on the vessel lid. The reaction is continued while stirring, purging with nitrogen and maintaining a temperature of 60-70°C for 120 minutes. Radical polymerization is carried out by heating the reaction mixture with an external heat transfer medium to the required level.

After the reaction, the reaction mass is offloaded using a screw pump for 15 minutes into the intermediate storage vessel intended for semi-finished product. The reaction vessel is rinsed twice with water via the spray head. Two reactors operate alternately switching every 2-4 hours. While the first empty reactor is being loaded with water, the heated reaction mass is being offloaded from the second reactor. Heat exchange takes place in the heat exchanger.

The drying process is carried out around the clock and continuously. The liquid semi-finished product is fed from the vessel into the roller dryers equipped with level sensors, using screw pumps. The pumps maintain the liquid level in the tray under the dryer drum where the product adheres to the dryer drum. The drum of the roller dryer rotates continuously at a speed set by means of a frequency converter installed in the control cabinets of the dryers. The heat transfer medium is continuously pumped through the dryers at a constant speed and constant temperature, ensuring that the desired surface temperature is maintained. The thin film product dries on the outer surface of the drum in three-quarters of a revolution, following which it is cut off with a knife pressed against the front of the drum. The cut product is dumped into a screw conveyor that transports the dry product to the opening for offloading same. The dry product is offloaded into portable tanks. Heating of the heat transfer medium is provided by a thermal oil heater that uses natural gas as fuel. Each roller dryer is equipped with an exhaust hood connected to a blower fan for removal of water vapor.

The essence of the subject invention is illustrated by way of a table that shows fluid-loss properties of the resulting synthetic fluid-loss reducer under conditions of varying pH, viscosity and oxygen content in the system. To assess the degree of influence of synthesis conditions of the synthetic fluid-loss reducer, the fluid-loss value was measured according to the ISO 10426-2 (API 10B-2) method on cement blend samples at a temperature of 57 °C. The samples of the cement mixture comprised of Portland cement - 100%, water - 44% and synthetic fluid loss reducer - 0.6% were prepared according to the ISO 10426-2 method.

The invention is further illustrated by illustrative examples 1 to 6 of a specific embodiment of the subject fluid-loss reducer.

Example 1.

Water is fed to the reaction vessel using a pump and heated to 60°C. Calcium hydroxide, AMPS with a mass fraction of 70%, NNDMA with a mass fraction of 20% and acrylic acid with a mass fraction of 10% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 60°C, the solution is then pumped from the mixing vessel into the reaction vessel ft is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining a temperature of 60 °C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

Example 2.

Water is fed to the reaction vessel using a pump and heated to 65°C. Calcium hydroxide, AHPS with a mass fraction of 60%, NNDMA with a mass fraction of 20% and methacrylic acid with a mass fraction of 20% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 65°C, the solution is then pumped from the mixing vessel into the reaction vessel. It is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining the temperature of 65 °C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

Example 3.

Water is fed to the reaction vessel using a pump and heated to 70°C. Calcium hydroxide, AMPS with a mass fraction of 40%, N-vinylcaprolactam with a mass fraction of 20% and maleic acid with a mass fraction of 40% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 70°C, the solution is then pumped from the mixing vessel into the reaction vessel. It is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining the temperature of 70°C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

Example 4.

Water is fed to the reaction vessel using a pump and heated to 70°C. Calcium hydroxide, ACMO with a mass fraction of 30%, N-vinylpyrrolidone with a mass fraction of 30% and itaconic acid with a mass fraction of 40% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 70°C, the solution is then pumped from the mixing vessel into the reaction vessel. It is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining the temperature of 70°C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

Example 5.

Water is fed to the reaction vessel using a pump and heated to 60°C. Calcium hydroxide, AHPS with a mass fraction of 10%, N-isopropylacrylamide with a mass fraction of 10% and maleic acid with a mass fraction of 80% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 60°C, the solution is then pumped from the mixing vessel into the reaction vessel. It is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining a temperature of 60 °C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

Example 6.

Water is fed to the reaction vessel using a pump and heated to 65°C. Calcium hydroxide, AMPS with a mass fraction of 10%, N-methylolacrylamide with a mass fraction of 80% and methacrylic acid with a mass fraction of 10% are introduced into the mixing vessel, the resulting mixture is heated while stirring to 65°C, the solution is then pumped from the mixing vessel into the reaction vessel. It is purged with nitrogen at atmospheric pressure, and potassium persulfate is introduced while stirring and maintaining the temperature of 65 °C for 120 minutes. The resulting reaction mass is offloaded from the reaction vessel into a storage vessel, the reaction mass from the storage vessel is then dried using roller dryers, cut with a knife and crushed to a dry powdery material to produce the synthetic fluid-loss reducer.

To determine the optimal parameters for the synthesis of the synthetic fluid- loss reducer with minimum fluid-loss value of the cement mixture, a number of tests were carried out under conditions of varying pH of the system, oxygen content and viscosity:

1. Synthetic fluid-loss reducer produced by standard technology (solution pH = 7, synthesis temperature 60-70°C) Flo. 2. Synthetic fluid-loss reducer produced with high acidity (solution pH >

10, synthesis temperature 67-77°C) Fli.

3. Synthetic fluid-loss reducer produced with low acidity (solution pH = 6, synthesis temperature 67-77°C) Fh.

4. Synthetic fluid-loss reducer produced with reduced viscosity achieved by changing the ratios of the component composition (solution pH = 7, viscosity

= 2000 cP, synthesis temperature 67-77°C) Fh.

5. Synthetic fluid-loss reducer produced with increased oxygen content (solution pH = 7, viscosity = 3000 cP, synthesis temperature 67-77°C, oxygen content before reaction 0.6%) FU. 6. Synthetic fluid-loss reducer produced with controlled synthesis parameters (solution pH = 8, viscosity > 4000 cP, synthesis temperature 67-77°C) Fh

7. Class G Portland cement. Results of the experimental test of the method are shown in Table 1.

Table 1 - Test results for samples of synthetic fluid-loss reducer

* Monomers entered into inverse reaction ** Oxygen content 0.6%, monomers did not react

The results of the experiments showed that when the pH acidity index is more than 10, the monomers enter into a side reaction, which leads to deviation from the desired parameters. When the pH acidity index is equal to 6 or less, as well as when the viscosity drops below 3000 cP, the resulting product does not have the desired fluid-loss value. When synthesizing the fluid-loss reducer while maintaining pH=8 and the synthesis temperature of 70°C, the viscosity of the semi-finished product of 4000 cP is achieved and the fluid-loss value of cement blend containing 0.6% of the subject fluid-loss reducer is 42 ml. The fluid-loss value of cement blend containing a reference fluid-loss reducer class G Portland cement is 1157 ml.

By providing the synthesis process of the fluid-loss reducer at a temperature of 60-70°C, pH of 6-10 in the reactor and oxygen content of not more than 0.6%, it is possible to achieve low (less than 50 ml) fluid-loss values.

Thus, the claimed synthetic fluid-loss reducer shows a better fluid-loss value as compared to the prototype, and the provision of these characteristics is a necessary condition for achieving the claimed technical result.

Claims

1. A synthetic fluid-loss reducer for use as a cement blend additive for cemented well construction characterized in that it comprises a copolymer of: 2- acrylamido-2-methylpropylsulfonic acid (AMPS) with a mass fraction of 5-90%, N-dimethylacrylamide with a mass fraction of 5-80% and methacrylic acid with a mass fraction of 5-80%.

2. The fluid-loss reducer as claimed in claim 1, characterized in that it comprises a copolymer of: AMPS with a mass fraction of 10%, N- dimethylacrylamide with a mass fraction of 80% and methacrylic acid with a mass fraction of 10%.

3. A method for synthesizing the fluid-loss reducer as claimed in claims 1 to 2, comprising: supplying water to a reaction vessel using a pump and heating it to 60-70°C, introducing AMPS, N-dimethylacrylamide and methacrylic acid into the mixing vessel, heating while stirring to 60-70°C via a jacket coiled pipe using a heat transfer medium, pumping the resulting solution from the mixing vessel into the reaction vessel using a pump, purging the reaction mixture with nitrogen at atmospheric pressure to remove atmospheric oxygen from the vessel until the oxygen content is not more than 0.6%. introducing potassium persulfate while stirring and maintaining a temperature of 60-70°C for 120 minutes, offloading the reaction mass using a screw pump into an intermediate storage vessel, feeding the reaction mass into roller dryers, cutting off a thin film of the dried product with a knife, grinding dry powdery material to produce a dry synthetic fluid-loss reducer, wherein the solution pH is maintained within pH 6- 10 by adding calcium hydroxide.

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