Plugging compositions and their use

Abstract

The application provides a plugging composition and application thereof, and the plugging composition comprises, in volume parts, 50-150 parts of water, 50-200 parts of gel, and 350-700 parts of cement slurry, wherein the gel is an aqueous solution of water glass, and the cement slurry is a G-grade cement slurry. 3 The plugging composition of the application can be used in a lost circulation well with a leakage speed greater than 15 m 3 / h and a lost circulation, has a good plugging effect, is superior to the plugging effect of a conventional cement slurry system, avoids causing a large delay in construction period and loss of materials, has a good technical and economic effect, and has a good popularization and application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a plugging composition and its application, which is used for treating fracture leakage in the drilling process. BACKGROUND

[0002] Drilling encounters more complex formations in the drilling process. When drilling in pressure-depleted formations, broken or weakly cemented formations, fracture-developed formations and multiple layer systems, the well leakage problem is very prominent. The occurrence of well leakage will bring inconvenience and loss to drilling engineering (such as drilling time, loss of drilling fluid, plugging material), and once it is not handled in time, it will seriously damage the oil and gas layer, reduce the oil and gas well productivity, and even lead to the absolute production of oil and gas wells, and may also induce a series of downhole complex conditions such as sticking, blowout and well collapse, and even wellbore abandonment. In high-pressure high-sulfur gas fields, it will endanger personal safety and pollute the environment, causing significant economic losses and serious social impact.

[0003] Therefore, it is very important to manage well leakage in drilling. In recent years, the technology and process of plugging materials and plugging cement slurry systems have been continuously updated.

[0004] Gel is a chemical material that is applied to foundation grouting the earliest. In some foundation engineering, gel is mixed into cement as a quick-setting agent to achieve good results of accelerating the gelation of slurry and controlling the diffusion range. Because of its good quick-setting effect, it has been gradually applied to foundation seepage prevention and mine plugging construction, and has also achieved good results. Compared with high-molecular grouting plugging materials, gel has the advantages of low price, wide source and non-toxicity.

[0005] Based on the advantages of gel over traditional plugging materials, gel and cement slurry system are proportioned. After adding gel to the cement slurry, the gel will react with calcium hydroxide generated in the cement slurry to quickly generate a gel-hydrocalcite composite with certain strength, accelerate the coagulation of the cement slurry, shorten the gelation time, and achieve the effect of rapid setting and plugging. SUMMARY

[0006] The purpose of the present application is to provide a plugging composition and its application in view of the defects in the prior art. The plugging composition of the present application can achieve rapid plugging in the cementing process and improve the success rate of one-time plugging.

[0007] The first aspect of the present application provides a plugging composition.

[0008] As a specific embodiment, the plugging composition comprises: water 50-150 parts, gel 50-200 parts, and cement slurry 350-700 parts by volume fraction, wherein,

[0009] The gel is an aqueous solution of water glass, and the cement slurry is G-grade cement slurry.

[0010] In the present application, the G-grade cement slurry is generally a cement slurry for cementing oil and gas wells under certain well temperature conditions, which is prepared by finely grinding mixed materials such as silicate cement clinker composed of minerals and gypsum.

[0011] In the present application, during the plugging process, the water glass in the gel and the calcium hydroxide in the cement slurry react to generate calcium silicate hydrate, and the calcium silicate mineral in the cement further separates calcium hydroxide and continues to react until the reaction is completed. By adjusting the proportion of components in the plugging agent, the gelation time can be adjusted to meet the plugging requirements.

[0012] Preferably, the gel is prepared by mixing water glass and water in a volume ratio of 2-4:8-6, for example, 3:7, and / or the cement slurry is medium G cement or high G cement, preferably medium G cement, and / or the water is preferably field water.

[0013] Preferably, the thickening time of the plugging composition is 50 min-150 min / 40 Bc; and / or the volume ratio of the gel to the cement slurry is 1:9-2:8.

[0014] The second aspect of the present application provides a use of the plugging composition according to the first aspect as a plugging agent in a cementing process.

[0015] Preferably, the use comprises the following steps:

[0016] The gel, the water and the cement slurry are sequentially injected into the oil well.

[0017] By using the principle of density difference, the cement slurry has a fast downward speed and travels faster than field water and gel in the pipe, and gradually mixes with water and gel during the replacement process, and finally mixes and rapidly reacts and thickens at the lost circulation location, thereby achieving plugging.

[0018] Preferably, the use comprises the following steps:

[0019] The spacer fluid, the gel, the water and the cement slurry are sequentially injected into the oil well, wherein the spacer fluid is preferably a composition containing non-ionic surfactants, anionic surfactants and inorganic salt additives.

[0020] The spacer fluid functions to isolate the mud, improve the displacement efficiency, reduce the mixing of the composition with the mud, and improve the success rate of plugging.

[0021] Preferably, the spacer fluid comprises a rinse fluid of 5-10 wt.% nonylphenol polyoxyethylene (15) (TX-15), 5-10 wt.% coconut oil fatty acid diethanolamide (6501), 5-10 wt.% sodium dodecyl benzene sulfonate (SDBS), 0-1 wt.% sodium tripolyphosphate (STPP), 0-1 wt.% preservative kathon, 70-85 wt.% deionized water. For example, the spacer fluid comprises a rinse fluid of 6.4 wt.% nonylphenol polyoxyethylene (15) (TX-15), 6.4 wt.% coconut oil fatty acid diethanolamide (6501), 6.4 wt.% sodium dodecyl benzene sulfonate (SDBS), 0.64 wt.% sodium tripolyphosphate (STPP), 0.16 wt.% preservative kathon, 80 wt.% deionized water. In the present application, the rinse fluid of deionized water can be BH-Q812 rinse fluid.

[0022] Preferably, the application comprises the following steps:

[0023] The preflush, the spacer fluid, the gel, the water, the cement slurry and the postflush are injected into the oil well in sequence, wherein the spacer fluid is preferably a composition containing a combination of nonionic surfactants, anionic surfactants and inorganic salt additives; and / or preferably, the components of the preflush, the spacer fluid and the postflush are the same.

[0024] In the present application, the dosages of the preflush, the gel, the field water, the cement slurry and the postflush are combined with the plugging requirements on site. In some embodiments, the volume ratio of the preflush, the gel, the field water, the cement slurry and the postflush can be (1-2):1:(1-2):(2-5):(1-2).

[0025] Compared with the prior art, the present application has the following beneficial technical effects:

[0026] The plugging composition of the present application can be used in a lost circulation well with a leakage rate greater than 15 m 3 / h, and the plugging effect is better than that of a conventional cement slurry system, avoiding causing large delay in construction period and loss of materials, having good technical and economic effects, and having good prospects for popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of a pipe string into a well according to an embodiment of the present application.

[0028] BRIEF DESCRIPTION OF REFERENCE NUMERALS

[0029] 1, drilling tool; 2, conversion joint; 3, glass steel pipe; 4, cement slurry; 5, spacer fluid; 6, gel. DETAILED DESCRIPTION

[0030] In Example 1 and Example 2, two different G-grade cements were used to prepare the plugging agent, and the thickening time of the plugging agent was tested. The thickening time refers to the time required for the cement slurry to reach a consistency of 100 BC under specific temperature conditions. The experimental results are shown in Table 1 and Table 2, respectively.

[0031] Example 1

[0032] Table 1

[0033]

[0034]

[0035] The cement slurry in Table 1 is a medium G cement slurry with a density of 1.90 g / cm 3 . The gel in Table 1 is prepared by mixing water glass and water in a volume ratio of 3:7. In Example 1, the thickening temperature is 75°C.

[0036] Example 2

[0037] Table 2

[0038] Gel Water Cement paste (G) Experimental conditions Thickening time 60 mL 120 mL 420 mL 75 °C * 20.7 MPa 60 min = 100 Bc 80 mL 100 mL 420 mL 75 °C * 20.7 MPa 83 min = 100 Bc 100 mL 80 mL 420 mL 75 °C * 20.7 MPa 65 min = 100 Bc 120 mL 60 mL 420 mL 75 °C * 20.7 MPa No fluidity 200 mL 200 mL 200 mL 75 °C * 20.7 MPa No fluidity

[0039] The cement slurry in Table 2 is a high G cement slurry with a density of 1.90 g / cm 3 . The gel in Table 2 is prepared by mixing water glass and water in a volume ratio of 3:7. In Example 2, the thickening temperature is 75°C.

[0040] From the experimental results in Table 1 and Table 2, it can be seen that the time range required for the medium G cement slurry in Example 1 to reach a consistency of 100 BC is greater than that of the high G cement slurry in Example 2.

[0041] Example 3

[0042] The medium G cement slurry was selected for the orthogonal experiment of the gel-cement slurry plugging system. Under the premise of safe construction, the ratio of the gel-cement slurry plugging system was determined. In this system, by adjusting the amount of water in the system, the contact time of the gel and the cement slurry was adjusted. In Example 3, only the volume ratio of gel to cement slurry was used as a variable to test the thickening time of the plugging system under the experimental conditions of 75°C*20.7MPa.

[0043]

[0044]

[0045] From the above table, it can be seen that under the experimental conditions of 75°C*20.7MPa, when the volume ratio of gel to cement slurry is below 1:4, the plugging system has a certain thickening time.

[0046] Example 4

[0047] In this example, the lost circulation zone and the amount of cement slurry are determined, the cement slurry system is adjusted, and a large sample experiment is performed. Referring to Figure 1 , the specific experimental process is described below.

[0048] Compared with traditional steel pipes, the glass steel pipe 3 has the following characteristics: used in the lower part of the pipe string, can meet the needs of cementing and other operations; the price is relatively low; if the cement plug is welded to the pipe string, it can be broken or twisted, ensuring the safety of the drilling tool 1 and the subsequent working conditions of the well, therefore, the lost circulation experiment selects the glass steel pipe 3 as the material of the lower pipe string.

[0049] In order to prevent the downhole steel drilling tool from causing a serious cement welding drilling tool accident, commonly known as the "flag pole" accident, which affects subsequent work, the lower drilling tool is replaced with a glass steel pipe connected to the upper drilling tool, and the construction is completed quickly. If the lost circulation cement slurry has been thickened, the pipe material cannot be pulled out, then the upper drilling tool is rotated to twist the glass steel pipe and leave it in the well to achieve the effect of plugging and leaving the plug. The glass steel pipe has much lower tensile and torsional strength than the traditional steel drilling tool, and has little effect on the next step of drilling the plug.

[0050] The characteristics of the glass steel pipe material: 10Mpa internal pressure resistance, 40t tensile (at the coupling), poor torsional performance, the torsional strength of the glass steel pipe is 0.14KN.m, which is much smaller than that of the steel rod (the torsional strength of the steel rod (D grade) is 6.73KN.m).

[0051] The downhole pipe string structure is determined as a glass steel pipe (the length of the glass steel pipe string is determined according to the lost circulation layer and the amount of cement slurry) + a steel drilling tool.

[0052] The lost circulation zone and the amount of cement slurry (where the upper plug surface does not exceed the topmost end of the glass steel pipe conversion joint 2) are determined, the cement slurry system is adjusted, and a large sample experiment is performed.

[0053] The tensile, internal pressure and torsional strength of the drilling tool and the glass steel pipe are calculated, and the downhole pipe string structure is arranged according to the calculation results.

[0054] Lower the drilling tool into position, open the pump to top off the circulation and cool down, observe the annulus return and pump pressure conditions, and determine the injection and displacement capacity;

[0055] The slurry injection and cementing pipeline is pressure tested at 24.5MPa, and does not leak.

[0056] Check the flowmeter displacement;

[0057] Inject preflush;

[0058] Inject gel;

[0059] Inject field water;

[0060] Injecting cement slurry (density 1.90g / cm 3 );

[0061] Injecting post fluid;

[0062] Replaced by slurry to the equilibrium liquid level, and the drilling is conducted;

[0063] If the cement slurry has been thickened, the drilling tool cannot be pulled out, the glass fiber reinforced plastic pipe 3 is twisted and broken (the glass fiber reinforced plastic pipe is poor in torsional resistance and is easy to be twisted and broken) to pull out the drilling tool 1, and the drilling is rapidly conducted to a safe position, a large amount of circulation is conducted for two rounds, and the drilling tool is rotated and moved up and down, and the drilling is conducted to be coagulated.

[0064] The post fluid has the same chemical composition as the pre fluid, and includes 6.4% nonylphenol polyoxyethylene ether (15) (TX-15) + 6.4% coconut oil fatty acid diethanolamide (6501) + 6.4% sodium dodecyl benzene sulfonate (SDBS) + 0.64% sodium tripolyphosphate (STPP) + 0.16% preservative kathon + 80% deionized water, and is used as flushing fluid BH-Q812 to isolate the cement slurry from the mud and prevent the cement slurry from being contaminated by the mud and thickened and coagulated in advance.

[0065] The compositions of the gel and the cement slurry in the embodiment 4 are the same as those in the embodiment 1. The pre fluid, the gel, the field water, the cement slurry and the post fluid are used in a volume ratio of 1:1:1:(2-5):1 according to the plugging requirement of the field.

[0066] The large sample experiment result proves that the leakage rate of the plugging system is greater than 16m 3 / h, and the plugging system is suitable for the lost circulation, the invalid plugging of the drilling fluid, and the invalid plugging of the conventional cement slurry system and the large delay of the work period and the material loss of the leakage well.

[0067] The present application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application, and the changed content still belongs to the protection scope of the present application.

Claims

1. Use of a lost circulation composition as a lost circulation material in a cementing process, characterized in that, The lost circulation composition comprises: 50-150 parts by volume of water, 50-200 parts of gel, 350-700 parts of cement slurry, wherein, The gel is an aqueous solution of water glass, and the cement slurry is G-grade cement slurry; The application comprises the following steps: sequentially injecting spacer fluid, the gel, the water and the cement slurry into the oil well; The spacer fluid comprises 5-10 wt.% of nonylphenol polyoxyethylene ether (15) (TX-15), 5-10 wt.% of coconut oil fatty acid diethanolamide 6501, 5-10 wt.% of sodium dodecyl benzene sulfonate (SDBS), 0-1 wt.% of sodium tripolyphosphate (STPP), 0-1 wt.% of preservative Kathon, and 70-85 wt.% of BH-Q812 flushing fluid.

2. Use according to claim 1, characterized in that, The gel is prepared by mixing water glass and water in a volume ratio of 2-4:8-6, and / or the cement slurry is medium G cement, and / or the water is field water.

3. Use according to claim 2, characterized in that, The gel is prepared by mixing water glass and water in a volume ratio of 3:

7.

4. Use according to any one of claims 1 to 3, characterized in that, The thickening time of the lost circulation composition is 50 min-150 min / 40 Bc, and / or the volume ratio of the gel to the cement slurry is 1:9-2:

8.

5. The use according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The preflush, the spacer fluid, the gel, the water, the cement slurry and the postflush are sequentially injected into the oil well, and / or the components of the preflush, the spacer fluid and the postflush are the same.

6. Use according to any one of claims 1 to 3, characterized in that, The spacer fluid comprises 6.4 wt.% of nonylphenol polyoxyethylene ether (15) (TX-15), 6.4 wt.% of coconut oil fatty acid diethanolamide 6501, 6.4 wt.% of sodium dodecyl benzene sulfonate (SDBS), 0.64 wt.% of sodium tripolyphosphate (STPP), 0.16 wt.% of preservative Kathon, and 80 wt.% of BH-Q812 flushing fluid.

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