CN106479460B - Permeable cement slurry for steam huff-puff to steam flooding oil layer transformation - Google Patents
Permeable cement slurry for steam huff-puff to steam flooding oil layer transformation Download PDFInfo
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- CN106479460B CN106479460B CN201610898885.0A CN201610898885A CN106479460B CN 106479460 B CN106479460 B CN 106479460B CN 201610898885 A CN201610898885 A CN 201610898885A CN 106479460 B CN106479460 B CN 106479460B
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- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
- C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
- C09K8/467—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement containing additives for specific purposes
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
- C04B28/06—Aluminous cements
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/50—Mortars, concrete or artificial stone characterised by specific physical values for the mechanical strength
Abstract
The invention discloses permeable cement slurry for steam huff-puff to steam flooding oil layer reconstruction, belongs to a cement slurry formula for oil and gas field well cementation, and mainly solves the problem of oil layer damage reconstruction caused by multiple rounds of high-temperature steam huff-puff before thermal recovery of thickened oil to steam flooding. The permeable cement slurry for steam huff-puff to steam flooding oil layer transformation consists of fine cement, aluminate cement, a high-temperature strength inhibitor, a permeation enhancer, a dispersant, a fluid loss reducer and a retarder, wherein the mass percentages are respectively as follows: 47.10% of fine cement, 20.20% of aluminate cement, 26.94% of high-temperature strength stabilizer, 3.50-4.50% of penetration enhancer, 0.80-1.40% of dispersant, 1.00-1.50% of fluid loss reducer and the balance of retarder. The high-temperature strength stabilizer is silica sand passing through 300 meshes, a penetration enhancer MAPT-1, a dispersing agent SXY, a fluid loss agent SWJ-4 and a retarder HP-2. The invention has good reservoir easy injection property and oil layer plugging effect, the solidified isolation layer has higher strength, cementing sand fixation property and temperature and salt resistance, a porous and communicated oil-gas transportation channel is formed under the seepage action of high-temperature crude oil, the oil phase has high selective permeability, the normal production of the transformed oil layer is favorably maintained, and the invention can be used for solving the problems of steam channeling, water outlet, sand production and the like in the transformation of high-temperature steam huff-puff-to-steam-drive oil layer and improving the overall well cementation quality of an oil-gas field.
Description
Technical Field
The invention relates to cement slurry for well cementation of oil and gas fields, in particular to high-temperature-resistant and permeability-resistant cement slurry with a repairing and reforming function on damaged oil layers subjected to excessive high-temperature steam huff-puff operations.
Background
Thermal oil recovery is an effective means for increasing the yield of thick oil at present, and the thick oil recovery in China mainly comprises three commercial thermal oil recovery technologies of steam huff and puff, steam flooding and in-situ oil combustion at present. The steam huff and puff technology is the main method for commercial exploitation of thick oil at present because of the advantages of simple construction, quick effect, direct implementation in a production well and the like. However, according to information fed back on site, after too many rounds of steam huff and puff, the rock skeleton and the oil and gas production layer of the steam wave zone are damaged in different degrees, steam is easy to generate channeling and heat loss is large, so that the single-well yield is always decreased rapidly, the economic benefit is poor, and meanwhile, the later-stage production of the oil well faces the troublesome problems of water outlet, sand outlet, steam channeling and the like. Practice proves that steam flooding can effectively take over steam huff and puff to recover thick oil, however, before the steam flooding is changed, the oil-gas layer which is damaged by high temperature must be repaired and reformed, namely the problems of steam channeling, water outlet, sand outlet and the like of a permeable layer are solved, and the normal and stable production of the oil-gas field in the later period of the steam flooding is ensured.
At present, aiming at the problems of steam channeling, water outlet, sand outlet and the like after high-temperature steam huffing and puff in China, a high-molecular plugging agent is mainly used for processing, and people who suffer from high-temperature steam channeling mutual influence in a certain block in the scene, such as Xuming dynasty, develop a thermosetting resin KLD-01 by themselves, can effectively plug a steam channeling channel of a huffing and puff well, can obviously improve the use efficiency of steam, has low economic cost and has potential application prospect. Liu Chengjie et al prepared a high temperature resistant (250-300 ℃) gel type plugging agent PST, which can simultaneously meet the requirements of water plugging of production wells and profile control of steam injection wells. The composite gel water plugging system FHG-1 suitable for early water plugging and high temperature resistance of the thermal recovery horizontal well is developed by aging, and has good temperature resistance and the function of plugging large pores and high permeability layers.
And the reports on the packer reconstruction of the oil-gas layer by using high-temperature-resistant permeable cement slurry are less. After the high-temperature-resistant permeable cement paste seals the damaged oil layer, the problems of gas channeling, water outlet, sand outlet and the like can be effectively solved due to the self-generated cementing effect of the cured cement paste, and meanwhile, the permeability of the sealing layer is improved by utilizing soluble components in the permeable cement paste so as to ensure that the cement paste has sufficient seepage and flow guiding effects and ensure the normal production of the oil well after the later-stage steam flooding.
Disclosure of Invention
The invention aims to provide high-temperature-resistant and permeability-increasing cement slurry with a repairing and reforming function on an oil layer damaged by multiple rounds of high-temperature steam huff and puff operations.
The technical scheme adopted by the invention is as follows:
the permeable cement slurry for steam huff-puff to steam flooding oil layer transformation is characterized by comprising fine cement, aluminate cement, a high-temperature strength inhibitor, a permeation enhancer, a dispersant, a fluid loss reducer and a retarder, wherein the mass percentages are respectively as follows: 47.10% of fine cement, 20.20% of aluminate cement, 25.75% of high-temperature strength stabilizer, 3.50-4.50% of penetration enhancer, 0.80-1.40% of dispersant, 1.00-1.50% of fluid loss reducer and the balance of retarder.
The high-temperature strength stabilizer is silica sand which passes through 300 meshes.
The penetration enhancer is MAPT-1.
The dispersant is SXY.
The fluid loss agent is SWJ-4.
The retarder is HP-2.
The weight percentage of the penetration enhancer MAPT-1 is 4.00%.
The mass percent of the dispersing agent SXY is 1.20%.
The mass percent of the fluid loss agent SWJ-4 is 1.25%.
The mass percent of the retarder HP-2 is 0.50%.
In consideration of the low porosity of the modified oil layer and the easy pumping, injecting and squeezing performance of cement paste, a large amount of experimental researches are carried out on ordinary portland cement and micro portland cement, and the matching performance of the particle size of micro cement particles and the pore size of the oil layer is good, so that the oil layer is easy to squeeze and seal, and therefore the micro cement is selected as a basic gel material of a permeable cement paste system; because the mining mode for repairing and reconstructing the stratum is high-temperature steam huff and puff and steam drive at the later stage, the set cement has enough strength under the high-temperature steam scouring (280-350 ℃), a compound system of aluminate cement and micro cement with good temperature resistance is selected as a basic gel material of the oil layer reconstruction high-temperature-resistant permeable cement slurry system, and the addition amounts are respectively 47.10% and 20.20% determined by a large number of experiments. Through the research on the temperature resistance of cement paste hydration products and silica sands with different particle sizes, the hydration products with low calcium-silica ratio and the silica sands with finer particle sizes are found to have positive effects on inhibiting the strength decay of the cement stone in a high-temperature environment, so that through a large amount of research on the adding amount and the particle sizes of the silica sands, the 300-mesh (28 mu m) silica sand with the adding amount of 25.75 percent is determined to be used as a high-temperature strength stabilizer of a cement paste system. The modified asphalt MAPT-1 is selected as a permeability enhancer of the permeable set cement, the flow guiding and permeability performance of the set cement in a high-temperature environment can be well improved when the addition amount is 3.50-4.50%, the SXY is selected as dispersion, the fluidity of a cement paste system can be well improved when the addition amount is 0.80-1.40%, the field pumping of the cement paste is easy, the SWJ-4 is selected as a fluid loss reducer, the filtration loss of the cement paste can be controlled within 100ml when the addition amount is 1.00-1.50%, the HP is selected as a high-temperature retarder, the addition amount is changed, and the thickening time of the cement paste system can be adjusted within 60-180 min.
Through analyzing the geological condition of the modified oil layer and researching the decay mechanism of the cement paste under the high-temperature environment, the basic gel material of a cement paste system is determined on the basis, and through reasonable material selection of a high-temperature strength stabilizer and a permeability-increasing agent and addition optimization of other additives, the oil layer modified permeable cement paste with high permeability and proper strength under the high-temperature condition is developed, so that the aim of comprehensively treating the water-yielding, sand-yielding and steam-channeling strata is fulfilled. The invention can obviously improve the transformation problems of oil layer water outlet, sand outlet, steam channeling and the like before the thick oil thermal recovery is converted into steam flooding, and improve the comprehensive recovery utilization rate of thick oil resources.
Detailed Description
In order to clearly understand the technical features and advantages of the present invention, the following detailed description is given of the technical solution of the present invention.
Example 1:
weighing 210g of fine cement, 90g of aluminate cement, 120g of high-temperature strength stabilizer, 3.6g of dispersing agent SXY, 4.5g of fluid loss agent SZ1-2 and 15.9g of permeation enhancer MAPT-1, uniformly mixing, weighing 226.8g of tap water, adding the uniformly mixed dry powder into a corrugated tank, stirring at a high speed for 45s, stirring at a low speed for 15s, and then performing 80 ℃ normal-pressure thickening for 20min to prepare the cement paste permeability for steam huff-puff-steam flooding oil layer transformation.
Example 2:
the formula of the cement paste is as follows:
210g of fine cement, 90g of aluminate cement, 120g of high-temperature strength stabilizer, 3.6g of SXY, 14.5gSZ1-2, 15.9g of MAPT-1, the water-solid ratio is 0.54, and the high-temperature strength stabilizer is silica sand with the average particle size of 48 mu m (300 meshes).
Preparing cement paste according to the formula, carrying out injection molding, carrying out water bath curing at the temperature of 60 ℃, 280 ℃ and 320 ℃ for 72h, and measuring the compressive strength and the oil phase permeability of the cement paste reaching the curing age. The test method of the compression strength of the set cement is shown in Table 1 according to GB/T19139-.
TABLE 1 set of Cement test results
As can be seen from the data in the table above, after the set cement is cured at high temperature (280 ℃ and 320 ℃), the compressive strength is maintained at about 9.6MPa, and the set cement has good high-temperature recession resistance; the permeability of the permeable set cement is 315.1 multiplied by 10 under the condition of low temperature (60 ℃), and the permeability is-3μm2At high temperatures (280 ℃ C., 320 ℃ C.)The permeability is increased to 561.2X 10-3μm2、669.6×10-3μm2And the permeable set cement meets the requirements of sealing and insulating the damaged stratum, reinforcing the well wall and increasing the permeability and flow conductivity of the reconstructed oil layer under the steam drive.
Example 3:
the formula of the cement paste is as follows:
210g of fine cement, 90g of aluminate cement, 120g of high-temperature strength stabilizer, 3.6g of SXY, 14.5gSZ1-2, 15.9g of MAPT-1, the water-solid ratio is 0.54, and the high-temperature strength stabilizer is silica sand with the average particle size of 48 mu m (300 meshes).
The cement slurry is prepared according to the formula, a permeable cement slurry system is injected into the rock core at the flow rate of 1mL/min, then the rock core injected with the cement slurry is taken out, is placed in a 80 ℃ constant temperature water bath system for maintenance for 1 day, is transferred into a 280 ℃ high-temperature high-pressure autoclave for maintenance for 2 days, is taken out and is placed in a rock core holder for carrying out a blocking effect experiment of the set cement, and the test result is shown in table 2.
Table 2 single core permeable set cement plugging data
As can be seen from the table above, after the permeable cement treatment, the permeability of the artificial core is reduced by about 90%, the plugging effect on the core is obvious, and the problems of steam channeling, water outflow and the like which damage an oil layer can be effectively prevented.
In conclusion, the invention is not limited to the above examples, and by reasonably selecting materials of the high-temperature strength stabilizer and the permeability-increasing agent and optimizing the addition of other additives, the oil layer modification permeable set cement with high permeability and proper strength under a high-temperature condition is developed, so that the modification problems of oil layer water outlet, sand outlet, steam channeling and the like before the thermal recovery of the heavy oil is converted into steam flooding can be obviously improved, and the recovery utilization rate of the heavy oil is greatly improved.
Claims (1)
1. The permeable cement slurry for steam huff-puff to steam flooding oil layer transformation is characterized by comprising fine cement, aluminate cement, a high-temperature strength stabilizer, a permeation enhancer, a dispersing agent SXY and a fluid loss reducer SZ1-2, wherein the formula of the cement slurry is as follows: 210g of fine cement, 90g of aluminate cement, 120g of high-temperature strength stabilizer, 3.6g of dispersing agent SXY, 14.5g of fluid loss agent SZ1-2 and 15.9g of permeation enhancer, wherein the water-solid ratio is 0.54, and the high-temperature strength stabilizer is silica sand with the average grain diameter of 48 mu m and the granularity of 300 meshes.
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1344775A (en) * | 2001-10-30 | 2002-04-17 | 中国石油大港油田油气勘探开发技术研究中心工艺所 | Sand preventing material for oil well |
| CN1810916A (en) * | 2006-03-01 | 2006-08-02 | 西南石油学院 | Cement permeation promoter for oil and gas well |
| CN102093861A (en) * | 2009-12-14 | 2011-06-15 | 武侯区巅峰机电科技研发中心 | High temperature-resistant steam huff and puff cement grout |
| CN102994058B (en) * | 2012-12-14 | 2014-02-26 | 西南石油大学 | High-temperature-resistant non-silicate cement paste system for cementing thermal production well of thickened oil |
| WO2016057045A1 (en) * | 2014-10-10 | 2016-04-14 | Halliburton Energy Services, Inc. | Extended-life calcium aluminate cementing methods |
| CN105670582A (en) * | 2016-03-09 | 2016-06-15 | 中石化石油工程技术服务有限公司 | Preparation method of high-temperature-resistant great-temperature-difference cement paste for oilfield well cementing |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NO165673C (en) * | 1987-11-16 | 1991-03-20 | Elkem As | HYDRAULIC CEMENT SUSPENSION. |
| CN1315971C (en) * | 2004-02-26 | 2007-05-16 | 同济大学 | High performance cement-base sealing up leading stoppage material |
| CN101157537A (en) * | 2007-08-02 | 2008-04-09 | 铁道科学研究院铁道建筑研究所 | Rapid-hardening self-leveling mortar material |
| CN101244922B (en) * | 2008-03-25 | 2011-02-09 | 万宇 | Impact resistant high-efficiency wear-resistant material |
| US8596356B2 (en) * | 2010-10-28 | 2013-12-03 | Baker Hughes Incorporated | Method of producing synthesis gas by the underground gasification of coal from a coal seam |
| CN102533234B (en) * | 2011-11-30 | 2014-01-01 | 中国神华能源股份有限公司 | Cement composition and application thereof |
| US9796622B2 (en) * | 2013-09-09 | 2017-10-24 | Saudi Arabian Oil Company | Development of high temperature low density cement |
| CN104944873A (en) * | 2015-06-30 | 2015-09-30 | 青岛精石通精密机械制造有限公司 | Energy-saving and environment-friendly grouting material |
| CN105018056B (en) * | 2015-08-13 | 2018-07-31 | 四川凯尔油气田技术服务有限公司 | Cementing cement system for combustion in situ |
| CN105295876B (en) * | 2015-10-12 | 2019-01-08 | 嘉华特种水泥股份有限公司 | A kind of microdilatancy oil-well cement |
| CN105694832B (en) * | 2016-03-09 | 2018-07-17 | 中石化石油工程技术服务有限公司 | The cement slurry of the big temperature difference of reinforcing oil well high temperature resistant |
-
2016
- 2016-10-17 CN CN201610898885.0A patent/CN106479460B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1344775A (en) * | 2001-10-30 | 2002-04-17 | 中国石油大港油田油气勘探开发技术研究中心工艺所 | Sand preventing material for oil well |
| CN1810916A (en) * | 2006-03-01 | 2006-08-02 | 西南石油学院 | Cement permeation promoter for oil and gas well |
| CN102093861A (en) * | 2009-12-14 | 2011-06-15 | 武侯区巅峰机电科技研发中心 | High temperature-resistant steam huff and puff cement grout |
| CN102994058B (en) * | 2012-12-14 | 2014-02-26 | 西南石油大学 | High-temperature-resistant non-silicate cement paste system for cementing thermal production well of thickened oil |
| WO2016057045A1 (en) * | 2014-10-10 | 2016-04-14 | Halliburton Energy Services, Inc. | Extended-life calcium aluminate cementing methods |
| CN105670582A (en) * | 2016-03-09 | 2016-06-15 | 中石化石油工程技术服务有限公司 | Preparation method of high-temperature-resistant great-temperature-difference cement paste for oilfield well cementing |
Non-Patent Citations (3)
| Title |
|---|
| 可渗透性微细水泥体系防砂技术研究;陈二丁;《中国博士学位论文数据库工程科技I辑》;20030228;5-119 * |
| 稠油热采高温防砂技术研究;耿娜娜;《中国优秀硕士学位论文全文数据库工程科技I辑》;20080331;5-60 * |
| 辽河油田水平井化学堵水技术研究与应用;陈小凯;《中国优秀硕士学位论文全文数据库工程科技I辑》;20160430;2-16 * |
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