Well Cementing Method for Improving Well Cementing Quality by Controlling Hydration Heat of Cement Slurry

Abstract

A well cementing method is described for improving cementing quality by controlling the hydration heat of cement slurry. By controlling the degree and/or rate of hydration heat release from cement slurry, the method improves the hydration heat release during formation of cement with curing of cement slurry, improves the binding quality between the cement and the interfaces, and in turn improves the cementing quality at the open hole section and/or the overlap section. The cementing method improves cementing quality of oil and gas wells and reduces the risk of annular pressure.

Claims

1. A well cementing method for improving cementing quality by controlling the hydration heat of cement slurry, wherein by controlling the degree and/or rate of hydration heat release from cement slurry, the method improves the hydration heat release during formation of cement with curing of cement slurry, improves the binding quality between the cement and the interfaces, and in turn improves the cementing quality at the open hole section and/or the overlap section; wherein the cementing quality at the open hole section is improved by increasing the degree and/or rate of hydration heat release from cement slurry; and the cementing quality at the overlap section is improved by lowering the degree and/or rate of hydration heat release from cement slurry.

2. The well cementing method according to claim 1, wherein increasing the degree of hydration heat release from cement slurry is achieved by adding a material generating a high hydration heat to cement slurry.

3. The well cementing method according the claim 2, wherein the material generating a high hydration heat includes an accelerating early strength agent.

4. The well cementing method according to claim 1, wherein increasing the rate of hydration heat release from cement slurry is achieved by either or both of adding an accelerating early strength agent, and shortening the additional safety time for thickening of cement slurry.

5. The well cementing method according to claim 4, wherein the accelerating early strength agent includes one of, or a combination of two or more of: sodium chloride, sodium carbonate, sodium formate, sodium nitrite, calcium chloride, calcium formate, calcium sulfate, calcium metasilicate, sodium aluminate, metakaolin, magnesium trisilicate, magnesium oxide, strontium sulfate, strontium carbonate, strontium nitrate, lithium carbonate, gypsum, hemihydrate gypsum, dihydrate gypsum, magnesium oxide, calcium oxide, activated slag, and ultra-fine cement.

6. The well cementing method according to claim 1, wherein lowering the degree of hydration heat release from cement slurry is achieved by adding an inert material to cement slurry, reducing the addition amount of a material generating a high hydration heat, and/or prolonging the additional safety time for thickening of cement slurry.

7. The well cementing method according to claim 6, wherein the inert material includes one of, or a combination of two or more of: iron ore powder, barite, hollow glass beads, and quartz sand.

8. The well cementing method according to claim 1, wherein lowering the rate of hydration heat release from cement slurry is achieved by adding a retarder and/or prolonging the additional safety time for thickening of cement slurry.

9. The well cementing method according to claim 8, wherein the retarder includes one of, or a combination of two or more of: an organic phosphonate-based retarder, an AMPS-based retarder, a phosphate-based retarder, glucose, and sodium borate.

10. The well cementing method according claim 1, wherein the cement component in the cement slurry is one of or a combination of two or more of: class A oil well cement, class B oil well cement, class C oil well cement, class D oil well cement, class E oil well cement, class F oil well cement, class G oil well cement, class H oil well cement, and class J oil well cement.

11. The well cementing method according to claim 10, wherein the cement slurry further contains one of or a combination of two or more of: a toughening agent, a fluid loss additive, a dispersant, a defoaming agent, a fleeing-proof agent, silica, and water.

12. The well cementing method according to claim 1, further comprising controlling the strength and/or elastic modulus of the cement formed from the cement slurry.

13. The well cementing method according to claim 1, wherein for well cementing of a well of a pure overlap section, hydration heat is controlled by lowering the degree and/or rate of hydration heat release from cement slurry; wherein the cement slurry is cement slurry with high strength and low elastic modulus, the additional safety time is 60-300 minutes for thickening of the lead slurry and 30-200 minutes for thickening of the tail slurry.

14. The well cementing method according to claim 1, wherein the well cementing is performed on a long-overlap-section well having a length of overlap section greater than 150 m; wherein for well cementing with single setting cement slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the cement slurry; wherein the cement slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; for well cementing with separable setting cement slurry, for the lead slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the slurry, wherein the lead slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; and for the tail slurry, controlling of hydration heat is achieved by increasing the degree and/or rate of hydration heat release from the slurry, wherein the tail slurry is cement slurry with high strength, and its additional safety time for thickening is 30-60 minutes; for well cementing with multi-setting cement slurry, for the lead slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the slurry, wherein the lead slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; for intermediate slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the slurry, wherein the intermediate slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-200 minutes; and for the tail slurry, controlling of hydration heat is achieved by increasing the degree and/or rate of hydration heat release from the slurry, wherein the tail slurry is cement slurry with high strength, and its additional safety time for thickening is 30-60 minutes.

15. The well cementing method according to claim 14, wherein for well cementing with separable setting cement slurry or multi-setting cement slurry, the tail slurry enters the overlap section by 100 m or more.

16. The well cementing method according to claim 15, wherein for well cementing with separable setting cement slurry or multi-setting cement slurry, the tail slurry enters the overlap section by 100 m to 300 m.

17. The well cementing method according to claim 1, wherein the well cementing is performed on a short-overlap-section well having a length of the overlap section not greater than 150 m; wherein for well cementing with single setting cement slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the cement slurry; wherein the cement slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; for well cementing with separable setting cement slurry, for the lead slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the slurry, wherein the lead slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; and for the tail slurry, controlling of hydration heat is achieved by increasing the degree and/or rate of hydration heat release from the slurry, wherein the tail slurry is cement slurry with high strength, and its additional safety time for thickening is 30-60 minutes; for well cementing with multi-setting cement slurry, for the lead slurry, controlling of hydration heat is achieved by lowering the degree and/or rate of hydration heat release from the slurry, wherein the lead slurry is cement slurry with high strength and low elastic modulus, and its additional safety time for thickening is 60-300 minutes; for intermediate slurry, controlling of hydration heat is achieved by increasing the degree and/or rate of hydration heat release from the slurry, wherein the intermediate slurry is cement slurry with high strength, and its additional safety time for thickening is 60-200 minutes; and for the tail slurry, controlling of hydration heat is achieved by increasing the degree and/or rate of hydration heat release from the slurry, wherein the tail slurry is cement slurry with high strength, and its additional safety time for thickening is 30-60 minutes.

18. The well cementing method according to claim 13, wherein the high strength occurs when the strength of the cement formed from the cement slurry is not lower than the compression strength of pure cement under the same conditions.

19. The well cementing method according to claim 18, wherein the high strength occurs when the 7-day strength is greater than 28 MPa.

20. The well cementing method according to claim 13, wherein the low elastic modulus occurs when the elastic modulus of the cement formed from the cement slurry is smaller than that of pure cement under the same conditions; wherein the low elastic modulus occurs when the elastic modulus is less than 10 GPa.

Description

BRIEF DESCRIPTION OF FIGURES

[0029] FIG. 1 shows the hydration heat release curves of the cement slurries in Example 1.

[0030] FIG. 2 shows the hydration heat release curves of the cement slurries in Example 2.

DETAILED DESCRIPTION

[0031] The technical solutions of the invention will be described in detail below in order to allow a clearer understanding of the technical features, purposes and beneficial effects of the present invention, but the following description should not be construed as limiting the implementable scope of the present invention.

Definitions

[0032] Well cementing: an operation of inserting casing(s) into a well and injecting cement into the annular space between the well bore and the casing(s).

[0033] Formation interface: the interface between the cement formed from cement slurry and the formation(s).

[0034] Casing interface: the interface between cement formed from cement slurry and the casing(s).

[0035] Hydration heat: the heat released when a substance is hydrated with water. The hydration heat of cement is also called hardening heat, which involves a series of actions such as hydration, hydrolysis and crystallization. The hydration heat can be measured directly in a calorimeter, or calculated indirectly from heat of fusion.

[0036] Degree of hydration heat release: represented by the peak temperature in the hydration heat release curve of cement slurry; the higher the temperature, the higher the degree of hydration heat release is, while the lower the temperature, the lower the degree of hydration heat release is.

[0037] Rate of hydration heat release: represented by the time interval from the peak temperature to the final temperature that no longer changes in the hydration heat release curve of cement slurry; the longer the time interval, the lower the rate of hydration heat release is, while the shorter the time interval, the higher the rate of hydration heat release is. The rate of hydration heat release may also be expressed as the slope of the curve after the point of peak temperature; the smaller the slope, the lower the rate of hydration heat release is, while the greater the slope, the higher the rate of hydration heat release is.

[0038] Initial setting: the initial setting of cement is a phenomenon that plastic cement slurry formed by mixing dry powder of Portland cement with a proper amount of water gradually thickens at normal temperature until it begins to lose plasticity.

[0039] Finial setting: a state that the cement slurry formed by mixing cement and water completely loses plasticity and completely hardens.

[0040] Lead slurry: the cement slurry first injected into the well during construction.

[0041] Tail slurry: the cement slurry finally injected into the well during construction.

[0042] Intermediate slurry: the cement slurry injected into the well between the lead slurry and the tail slurry during construction.

[0043] Open hole section: a section of a well having only one well pipe, outside which there is the formation(s). At this section, cement slurry hardens to form cement outside the well pipe after it is injected. During the hardening, the cement slurry is in contact with the formation(s) and forms an interface therewith, namely the formation interface.

[0044] Overlap section: a section of a well having casings consisting of two well pipes. At this section, the cement slurry enters the annular space between the two well pipes and hardens to form cement. During the hardening, the cement slurry is in contact with the two well pipes and form two interfaces, namely two casing interfaces.

[0045] Long-overlap-section well: a well having a length of the overlap section greater than 150 m.

[0046] Short-overlap-section well: a well having a length of the overlap section not greater than 150 m, excluding wells without an overlap section.

Example 1

[0047] The Example provides a well cementing method for a well with a pure overlap section. Since it is impossible to use different cement slurries for cementing of the same well, this Example used different cement slurries for cementing of two similar wells and compared the cementing quality. Well Moxi 009-4-X2 and Well Gaoshi 001-X7 both use 177.8 mm tie-back casings, that is, they are of a pure overlap section. Conventional cement slurry was used for Well Moxi 009-4-X2, and the cement slurry with controlled hydration heat was used for Well Gaoshi 001-X7. Specifically, the degree and rate of hydration heat release from the cement slurry were reduced by reducing the amount of an accelerating early strength agent used in the cement slurry to reduce the peak value of hydration heat release from the cement slurry, and simultaneously increasing the added amount of a retarder so as to extend the additional safety time for thickening of the cement slurry, so that the peak value and the rate of hydration heat release from the cement slurry were reduced.

[0048] The basic information is shown in Table 1, and the hydration heat release curves of the cement slurries are shown in FIG. 1.

TABLE-US-00001 TABLE 1 Cementing Casings Lead slurry Tail slurry quality Well Moxi High hydration heat; High hydration heat; Poor 009-4-X2, Fast development of early Fast development of early 177.8 mm strength; strength; tie-back Additional safety time for Additional safety time for casings thickening of the tail slurry: 95 thickening of the tail slurry: 34 minutes; minutes; Lead slurry formulation: Jiahua Tail slurry formulation: Jiahua Class G well cement + 4.2% Class G well cement + 3% accelerating early strength agent accelerating early strength agent (calcium sulfate:sodium (calcium sulfate:sodium sulfate:calcium formate = 2:2:1) + sulfate:calcium formate = 2:2:1) + 4% rubber toughening material + 2% 4% rubber toughening material + 2% AMPS-based fluid loss additive + AMPS-based fluid loss additive + 1% organic phosphonate-based 0.3% organic phosphonate- retarder + 0.5% aldehyde ketone based retarder + 0.4% aldehyde polymer dispersant + 0.2% ketone polymer dispersant + dimethyl silicone oil defoamer + 0.2% dimethyl silicone oil 46% tap water; defoamer + 45% tap water; Density: 1.92 g/cm.sup.3 Density: 1.92 g/cm.sup.3 Well Gaoshi Moderate-to-low hydration heat; Moderate-to-low hydration heat; Excellent 001-X7, Fairly fast development of early Fairly fast development of early 177.8 mm strength; strength; tieback Additional safety time for Additional safety time for casings thickening of the lead slurry: 149 thickening of the tail slurry: 116 minutes; minutes; Lead slurry formulation: Jiahua Tail slurry formulation: Jiahua Class G well cement + 1% Class G well cement + 4% accelerating early strength agent rubber toughening material + 2% (calcium sulfate:sodium AMPS-based fluid loss additive + sulfate:calcium formate = 2:2:1) + 0.8% organic phosphonate- 4% rubber toughening material + 2% based retarder + 0.4% aldehyde AMPS-based fluid loss additive + ketone polymer dispersant + 1.5% organic phosphonate- 0.2% dimethyl silicone oil based retarder + 0.5% aldehyde defoamer + 44% tap water; ketone polymer dispersant + Density: 1.92 g/cm.sup.3 0.2% dimethyl silicone oil defoamer + 45.5% tap water; Density: 1.92 g/cm.sup.3

[0049] FIG. 1 shows the hydration heat release curves of the two tail slurries in this Example. Through comparison of the peak value of heat release and the rate of heat release shown in FIG. 1, it can be seen that, as compared to the conventional cement slurry used for Well Moxi 009-4-X2, the cement slurry with controlled hydration heat used for Well Gaoshi 001-X7 not only contained a significantly lower amount of accelerating early strength agent (a material generating high hydration heat), which reduced the peak value of hydration heat release from the cement slurry; but also had more retarder, which prolonged the thickening time of the cement slurry to meet the requirement for a prolonged additional safety time for thickening of cement slurry, and reduced the peak value and rate of hydration heat release from the cement slurry. By such means, excellent cementing quality was obtained for Well Gaoshi 001-X7, while the cementing quality of Well Moxi 009-4-X2 using conventional cement slurry was poor.

[0050] The cementing quality was evaluated in accordance with the petroleum and natural gas industry standard of the People's Republic of China Cementing Quality Evaluation Method SY/T 6592-2016.

Example 2

[0051] This Example provided a well cementing method for a short-overlap-section well, by which cementing was performed on Well Moxi 008-X23 (177.8 mm tail casing), i.e. on the short overlap section, while tail slurry was not allowed to enter the overlap section.

[0052] The cement slurries used for Well Moxi 008-X23 were cement slurries with controlled hydration heat, which was specifically controlled as follows:

[0053] Lead slurry: as compared to the tail slurry, the lead slurry used a lower amount of accelerating early strength agent to reduce the peak value of hydration heat release from the cement slurry; and a higher amount of retarder to prolong the thickening time, meeting the required additional safety time for thickening of cement slurry; so that the peak value and the rate of hydration heat release from the cement slurry were reduced;

[0054] Tail slurry: as compared to the lead slurry, the tail slurry used a higher amount of accelerating early strength agent to increase the peak value of hydration heat release from the cement slurry; and a lower amount of retarder to shorten the thickening time, meeting the required additional safety time for thickening of cement slurry; so that the peak value and the rate of hydration heat release from the cement slurry were increased.

[0055] The basic information is shown in Table 2, and the hydration heat release curves of the cement slurries are shown in FIG. 2.

TABLE-US-00002 TABLE 2 Cementing Casing Lead slurry Tail slurry quality Well Moci Moderate-to-low hydration High hydration heat; Excellent 008-X23; heat; Fast development of early 177.8 mm Fairly fast development of strength; tail casing early strength; Additional safety time for Additional safety time for thickening of the tail slurry: 32 thickening of the lead slurry: minutes; 117 minutes; Lead slurry formulation: Jiahua Lead slurry formulation: Class G well cement + 6% Jiahua Class G well cement + accelerating early strength agent 1% accelerating early strength (calcium sulfate:sodium agent (calcium sulfate:sodium sulfate:magnesium oxide = 2:2:1) + sulfate:magnesium 30% quartz sand + 4% rubber oxide = 2:2:1) + 20% quartz toughening material + 2.8% sand + 4% rubber toughening AMPS-based fluid loss additive + material + 2.8% AMPS-based 1.3% AMPS-based retarder + fluid loss additive + 1.3% 1.2% Palygorskite suspending AMPS-based retarder + 1.2% agent + 90% iron ore powder + Palygorskite suspending agent + 0.9% aldehyde ketone polymer 90% iron ore powder + 0.9% dispersant + 0.2% dimethyl aldehyde ketone polymer silicone oil defoamer + 72.8% dispersant + 0.2% dimethyl tap water; silicone oil defoamer + 67.5% Density: 2.26 g/cm.sup.3 tap water; Density: 2.26 g/cm.sup.3

[0056] FIG. 2 showed the hydration heat release curves of the lead slurry and the tail slurry in this Example. It can be seen from FIG. 2 that different control means lead to different hydration heat releases between the lead slurry and the tail slurry. Therefore, excellent cementing quality was obtained for Well Moxi 008-X23.

[0057] The cementing quality was evaluated in accordance with the petroleum and natural gas industry standard of the People's Republic of China Cementing Quality Evaluation Method SY/T 6592-2016.

[0058] The experimental results of the above Examples indicate that the method according to the present invention can actually realize to a certain extent a solid improvement in the binding quality between the cement and the two interfaces at the open hole section and the overlap section, reduce the risk of poor cementing quality of the open hole section and the overlap section, and improve the cementing quality.