Compressible high-resilience well wall pressure-bearing plugging material and preparation process thereof

Abstract

The invention relates to the technical field of well drilling treatment materials, in particular to a compressible high-resilience well wall pressure-bearing plugging material and a preparation process thereof. The compressible high-resilience well wall pressure-bearing plugging material is prepared from the following components in parts by weight: 500 to 1000 parts of graphitized petroleum coke, 70 to 100 parts of nano silicon dioxide and 3 to 5 parts of sodium tripolyphosphate. The preparation process comprises the following steps: selecting the powder needle-like petroleum coke according to the ratio, graphitizing at high temperature, adding the powder needle-like petroleum coke into the nano silicon dioxide and sodium tripolyphosphate suspension, uniformly stirring, standing, collecting, and drying. The preparation process of the material has the advantages of higher operation convenience, low cost, fewer required raw materials, simplicity and high efficiency, and better popularization value.

Description

Technical Field

[0001] The invention relates to the technical field of drilling processing materials, and in particular to a compressible high-resilient well wall pressure-bearing plugging material and a preparation process thereof. Background Art

[0002] Well leakage is a common underground complex situation in the process of drilling and well repairing, which will bring many hazards to the construction work. To prevent the occurrence of well leakage or to eliminate the leakage that has occurred, the most commonly used technical means is to plug the leakage channel by using different plugging materials. Among them, granular materials are the most mature type of materials used in plugging operations. They block the "throat" of the leakage channel during the plugging process and play a "bridging" role, so they are also called "bridging agents."

[0003] Granular plugging materials mainly include plant shells, calcium carbonate and rubber particles, and common application materials include walnut shells, rubber particles, coke particles, crushed plastic particles, shell powder, limestone and asphalt, etc. Plant shell plugging materials have the characteristic of swelling when exposed to water, calcium carbonate and other particles have extremely high compressive strength and are widely used, and rubber particles have the characteristic of softening and deformation. In order to improve the strength and density of the plugging layer, these granular materials are usually used in combination.

[0004] Although these granular materials have played a certain role in actual operations, they also have their own shortcomings. Walnut shells will absorb water and expand to a certain extent, and the matching degree of the leakage channel is poor; the plugging effect of rubber particles and asphalt will be affected by the softening point, and the plugging layer formed by plastic particles and some gel materials has weak pressure bearing capacity; shell powder, limestone, etc., have very strong rigidity and good pressure bearing capacity, but because they are non-deformable and non-compressible, the selection and requirements of their particle size distribution in actual application are high, and a large number of evaluation experiments are required. Summary of the invention

[0005] The present invention proposes a compressible high-resilient well wall pressure-bearing plugging material and a preparation process thereof, aiming to provide a solution to the above technical problems.

[0006] To achieve the above object, the technical solution of one aspect of the present invention is:

[0007] A compressible high-resilience well wall pressure-bearing plugging material comprises the following components by weight: 500-1000 parts of graphitized petroleum coke, 70-100 parts of nano silicon dioxide and 3-5 parts of sodium tripolyphosphate.

[0008] In some preferred embodiments, the particle size of the graphitized petroleum coke is less than 500 μm.

[0009] In some preferred embodiments, the nano-silica particle size is 20nm-50nm.

[0010] One aspect of the technical solution of the present invention is: A preparation process of a compressible and highly elastic wellbore pressure-bearing plugging material, comprising the following steps:

[0011] 1) Select powdered needle coke with a particle size less than 500μm according to the ratio, after high-temperature graphitization, pass through a standard sieve with 80 meshes, and take the undersize part for drying and cooling;

[0012] 2) Prepare a 7%-10% nano-silica suspension with a viscosity (25°C) not higher than 50mPa·s;

[0013] 3) Add 0.5% of sodium tripolyphosphate to the nano-silica suspension prepared in step 2), and stir evenly;

[0014] 4) Slowly add the graphitized needle coke in step 1) to the nano-silica and sodium tripolyphosphate mixture prepared in step 2) according to the ratio (1:0.5-1), stir evenly and then let it stand;

[0015] 5) Dry the product after standing in step 4) to make a dry powder final product.

[0016] In some preferred embodiments, step 1) is specifically to select needle coke, crush, grind and screen it into powder with a particle size less than 500μm, put it into a high-temperature graphitization furnace, stand for 1-2 hours under the condition of 2500°C - 3000°C, cool at room temperature, pass through a standard sieve with 80 meshes, take the undersize part and put it into an oven, dry it at 105°C for 2h, and collect it.

[0017] In some preferred embodiments, the stirring in step 3) is low-speed stirring, and the stirring time is not less than 30min.

[0018] In some preferred embodiments, step 4) is specifically to weigh the graphitized needle coke according to the ratio, slowly add it to the nano-silica and sodium tripolyphosphate mixture while stirring, select a stirring speed of 6000rpm, after adding, continue to stir for more than 10min and then let it stand for more than 2h.

[0019] In some preferred embodiments, the drying in step 5) is to put the product after standing in step 4) into an oven and dry it at 80°C for more than 6h to make a dry powder final product.

[0020] The beneficial effects achieved by the present invention are:

[0021] The high-rebound wellbore pressure-bearing plugging material can effectively cope with the changes in bottom-hole pressure during the drilling process, ensure formation integrity and enhance wellbore stability. When drilling through the leaky formation section, the material can quickly enter the formation cracks and form a plugging layer. When the bottom-hole pressure changes, the compression and rebound characteristics of the material ensure that the plugging layer always maintains a fixed position in the formation leakage channel, achieving the purpose of continuous and effective plugging. In addition, the preparation process of this material has high operational simplicity and low cost, requires few raw materials, and the method is simple and efficient, with good promotion value. Description of the Drawings

[0022] Figure 1 is a schematic diagram of the application scenario of the compressible high-rebound wellbore pressure-bearing plugging material of the present invention;

[0023] Figure 2 is a schematic diagram of the pressure-bearing of the test sample of the present invention;

[0024] Figure 3 is a schematic diagram of the rebound recovery of the test sample of the present invention.

[0025] In the figure: 1. Compressible high-rebound wellbore pressure-bearing plugging material; 2. Crack. Detailed Embodiments

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] For all raw materials of the present invention, there is no special limitation on their sources, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0028] For all raw materials of the present invention, there is no special limitation on their purity. The present invention preferably uses analytical pure or prepared

[0029] For all raw materials and process procedures of the present invention, their trademarks or abbreviations are all conventional trademarks or abbreviations in the art. Each trademark or abbreviation is clear and definite in the field of its relevant uses. Those skilled in the art can purchase or prepare them by conventional methods according to the trademark, abbreviation and corresponding uses, or implement them using the corresponding equipment.

[0030] Example 1:

[0031] 1) Select needle-shaped petroleum coke, crush, grind and screen it into powder less than 500 μm, and then put it into a high-temperature graphitization furnace and let it stand for 1-2 hours at 2500°C - 3000°C.

[0032] 2) Take out the needle coke that has been at high temperature, cool it at room temperature to obtain product A;

[0033] 3) Take product A, pass it through a standard sieve with 80 meshes, take the part passing through the sieve and put it into an oven, dry it at 105 °C for 2 h, take it out and cool it in a drying dish for later use as product B.

[0034] 4) Select silica powder with a particle size of 20 nm - 50 nm, prepare a 7% suspension with a viscosity (25 °C) not higher than 50 mPa·s;

[0035] 5) Add 0.3% sodium tripolyphosphate to the nano-silica suspension and stir it at low speed for 30 min as product C.

[0036] 6) Measure 1 L of product C, then weigh 500 g of product B, and slowly add it to product C while stirring, with the stirring speed selected as 6000 rpm.

[0037] 7) After adding, continue to stir for 10 min and let it stand for more than 2 h to obtain product D.

[0038] 8) Put product D into an oven and dry it at 80 °C for more than 6 h, and remake it into dry powder to obtain the final product, a compressible and highly elastic wellbore pressure-bearing plugging material E.

[0039] Example 2

[0040] 1) Select needle coke, crush, grind and sieve it into powder less than 500 μm, then put it into a high-temperature graphitization furnace and let it stand for 1 - 2 hours under the condition of 2500 °C - 3000 °C.

[0041] 2) Take out the needle coke that has been at high temperature, cool it at room temperature to obtain product A;

[0042] 3) Take product A, pass it through a standard sieve with 80 meshes, take the part passing through the sieve and put it into an oven, dry it at 105 °C for 2 h, take it out and cool it in a drying dish for later use as product B.

[0043] 4) Select silica powder with a particle size of 20 nm - 50 nm, prepare an 8% suspension with a viscosity (25 °C) not higher than 50 mPa·s.

[0044] 5) Add 0.5% sodium tripolyphosphate to the nano-silica suspension and stir it at low speed for 30 min as product C.

[0045] 6) Measure 1 L of product C, then weigh 500 g of product B, and slowly add it to product C while stirring, with the stirring speed selected as 6000 rpm.

[0046] 7) After the addition is complete, continue stirring for 10 min and let it stand for more than 2 h to obtain Product D.

[0047] 8) Put Product D into an oven and dry it at 80 °C for more than 6 h, and remanufacture it into dry powder to obtain the final product, the compressible and highly elastic wellbore pressure-bearing plugging material E.

[0048] Example 3

[0049] 1) Select needle-shaped petroleum coke, crush, grind and screen it into powders smaller than 500 μm, and then put it into a high-temperature graphitization furnace and let it stand for 1-2 hours under the condition of 2500 °C - 3000 °C.

[0050] 2) Take out the needle-shaped petroleum coke that has been heated at high temperature and cool it at room temperature to obtain Product A;

[0051] 3) Take Product A, pass it through a standard sieve with 80 meshes, take the part under the sieve and put it into an oven, dry it at 105 °C for 2 h, take it out and cool it in a drying dish for later use as Product B.

[0052] 4) Select silicon dioxide powder with a particle size of 20 nm - 50 nm, prepare a 10% suspension with a viscosity (25 °C) not higher than 50 mPa·s;

[0053] 5) Add 0.3% of sodium tripolyphosphate to the nano-silicon dioxide suspension and stir it at low speed for 30 min as Product C.

[0054] 6) Measure 1 L of Product C, and then weigh 1000 g of Product B, and slowly add it to Product C while stirring, and select a stirring speed of 6000 rpm.

[0055] 7) After the addition is complete, continue stirring for 10 min and let it stand for more than 2 h to obtain Product D.

[0056] 8) Put Product D into an oven and dry it at 80 °C for more than 6 h, and remanufacture it into dry powder to obtain the final product, the compressible and highly elastic wellbore pressure-bearing plugging material E.

[0057] Please refer to Figure 1, in the drilling operation, due to reasons such as changes in mud pump strokes, pauses during tripping, changes in equivalent circulating density (ECD) in the wellbore, and different properties of the working fluid, the bottom hole pressure changes constantly. When drilling in a lost circulation interval, when the circulating pressure is greater than the pore pressure, the compressible and highly resilient wellbore pressure-bearing plugging material 1 can enter the fractures 2 in the formation and quickly form a plugging layer; when the circulating pressure decreases, due to the compressible characteristics of the material of the present invention, the entire plugging layer is compressed by the fracture closing force; when the circulating pressure increases, the resilient characteristics of the material of the present invention cause the compressed plugging layer to gradually return to its original shape. When the material is extruded, its volume is compressed and it can enter the microfractures for plugging; when the pressure decreases, the volume of the material gradually rebounds to its original size, so that the plugging layer always remains in its fixed position. During the entire process of bottom hole pressure change, due to the presence of the material of the present invention, the plugging layer always stays at the fixed position of the formation loss channel, maintaining the integrity of the formation, thus achieving the purpose of wellbore strengthening.

[0058] Compression and Rebound Performance Evaluation

[0059] Name of test equipment: Press, code: YLJ600, manufacturer: Qingdao Haitongda Special Instrument Co., Ltd.

[0060] Put the product B and the final product in Example 1 into an oven at a constant temperature of 105 ± 2 °C and dry for 2 h, take them out and put them in a desiccator to cool to room temperature, and then place them on the press for testing. The pressure test sample loading assembly includes a pressure rod, a pressure cylinder, a cushion block and a base. Put the cushion block into the pressure cylinder, and then place the pressure cylinder on the base. Weigh a certain mass of the dried sample and slowly pour it into the pressure cylinder.

[0061] Install the pressure rod at the upper end of the pressure cylinder, first compact it manually, and then place it on the press platform. Slowly apply pressure to 10000 psi, keep the pressure for 1 min, and compact the sample in the pressure cylinder. When the pressure-bearing ends, make a mark at the position corresponding to the pressure rod on the upper end face of the pressure cylinder, record the length from the upper end face of the pressure rod to the marked position of the pressure rod, and calculate the height H1 of the compressed sample (as Figure 2 shown).

[0062] Reduce the pressure to 0 psi, quickly lift the pressure rod, let it stand for 5 min, then put the pressure rod back into the core barrel, make a mark at the position corresponding to the pressure rod on the upper end face of the core barrel, and finally calculate the height H2 of the compressed sample (as Figure 3 described).

[0063] The rebound rate is calculated according to the following formula.

[0064]

[0065] In the formula:

[0066] K - Rebound rate, %;

[0067] 2.2.8 The experimental data are recorded in Table 1 as follows:

[0068] Table 1 Data Sheet of Pressure Test

[0069]

[0070]

[0071] From the experimental results, it can be seen that for products B with different masses under pressures of 10,000 Psi and 6,500 Psi, the rebound rate is basically between 30% and 50%. The final product, the elastic plugging agent E, obtained after coating with nano - silica solution, is evaluated under the same experimental conditions. Compared with product B, the rebound rate is basically increased to more than 100%.

[0072] This shows that compared with product B, the elastic plugging agent E has better strength and toughness. After being coated with nano - silica, its anti - fragmentation ability is greatly improved, and it still maintains extremely high rebound performance after high - pressure compression.

[0073] The above has described the present invention in detail. The purpose is to enable those skilled in this field to understand the content of the present invention and implement it, but it cannot be used to limit the protection scope of the present invention. Moreover, the present invention is not limited to the above - mentioned embodiments. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A compressible and highly resilient wellbore pressure-bearing plugging material, characterized in that, The components of the compressible high-resilient well wall pressure-bearing plugging material are 500-1000 parts by weight of graphitized petroleum coke, 70-100 parts by weight of nano silicon dioxide and 3-5 parts by weight of sodium tripolyphosphate.

2. The compressible and highly resilient wellbore pressure-bearing plugging material according to claim 1, wherein, The particle size of the graphitized petroleum coke is less than 500 μm.

3. The compressible and highly resilient wellbore pressure-bearing plugging material according to claim 1, wherein The nano silicon dioxide particle size is 20nm-50nm.

4. Preparation process of a compressible and highly elastic wellbore pressure-bearing plugging material, characterized in that, The following steps are involved: 1) Powdered needle-shaped petroleum coke with a size less than 500 μm is selected according to the proportion, graphitized at high temperature, passed through a standard sieve of 80 mesh, and the part under the sieve is taken for drying and cooling; 2) preparing a 7%-10% nano-silicon dioxide suspension with a viscosity (25°C) not higher than 50 mPa·s; 3) adding 0.5% sodium tripolyphosphate to the nano-silicon dioxide suspension obtained in step 2) and stirring evenly; 4) Slowly adding the nano-silicon dioxide and sodium tripolyphosphate mixture prepared in step 2) into the graphitized petroleum coke in step 1) in a ratio of (1:0.5-1), stirring evenly and then letting stand; 5) drying the product after standing in step 4) to obtain a dry powder final product.

5. The preparation process of a compressible and highly resilient wellbore pressure-bearing plugging material according to claim 4, characterized in that, The step 1) specifically comprises selecting needle-shaped petroleum coke, crushing, grinding and screening it into powder less than 500 μm, placing it in a high-temperature graphitization furnace, standing it at 2500° C.-3000° C. for 1-2 hours, cooling it at room temperature, passing it through a standard sieve of 80 meshes, taking the part under the sieve and placing it in an oven, drying it at 105° C. for 2 hours, and collecting it.

6. The preparation process of a compressible and highly resilient wellbore pressure-bearing plugging material according to claim 4, characterized in that, The stirring in step 3) is low speed stirring, and the stirring time is not less than 30 minutes.

7. The preparation process of a compressible and highly resilient wellbore pressure-bearing plugging material according to claim 4, characterized in that, The step 4) specifically comprises weighing graphitized petroleum coke according to the ratio, slowly adding the mixture of nano-silicon dioxide and sodium tripolyphosphate while stirring, the stirring speed is selected to be 6000 rpm, and after the addition is completed, stirring is continued for more than 10 minutes and then allowed to stand for more than 2 hours.

8. The preparation process of a compressible and highly resilient wellbore pressure-bearing plugging material according to claim 4, characterized in that, The drying in step 5) is to place the product after standing in step 4) in an oven and dry it at 80° C. for more than 6 hours to obtain a dry powder final product.

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