CN117535040A - Leakage prevention and plugging agent and its preparation method and application - Google Patents

Abstract

The invention discloses a leakage prevention and plugging agent and its preparation method and application. The leakage prevention and plugging agent includes the following mass percentage components: 5-13% multi-morphology alloy, 3% MDF, 0%-3% PF-EZCARB, 0.5%-1% brucite fiber, and the balance is Well mud. The leakage prevention and plugging agent may also include 3% SQD-98. For crack widths with different openings, the present invention optimizes the acid-soluble leakage plugging formula with a sealing pressure-bearing capacity of more than 10 MPa and an acid-soluble rate of more than 70%, and has broad application prospects.

Description

Leakage prevention and plugging agent and its preparation method and application

Technical field

The invention relates to the technical field of oil and gas plugging materials, and in particular to a deblockable and high-pressure anti-leakage and plugging agent suitable for fractured reservoirs and its preparation method and application.

Background technique

Lost circulation refers to the phenomenon that various working fluids are lost into the formation through leakage channels during the drilling process. Once lost circulation occurs, the resulting increase in drilling cycles, loss of drilling fluid, and consumption of plugging materials will lead to a large waste of manpower and material resources. About 20-25% of oil and gas wells around the world experience lost circulation every year. The problem of lost wells causes The economic loss is as high as 2 billion US dollars; for oil and gas production layer leakage, if the drilling fluid leaks into the formation, it may cause permanent damage to the production layer, reduce the oil and gas production in the later stage of exploitation, and more seriously, it may lead to the scrapping of the oil and gas well. With the continuous deepening of oil and gas resource exploration and development around the world, the number of marginal wells, deep wells, and special formation wells is increasing day by day. As the injection and production of oil and gas layers and the impact of acidification fracturing are becoming more and more serious, some formations are under pressure. The capacity is greatly reduced; in addition, in order to reduce the cost of exploration and development, many oilfield companies directly construct long open-hole wells in multi-pressure layers. The above situation makes the problem of well leakage more prominent. In addition, in order to ensure the safety, speed and efficiency of the drilling process, the bottom hole pressure must be kept higher than the formation pressure during drilling. This pressure difference will lead to the loss of drilling fluid when drilling into permeable or fractured formations.

Well leakage is mainly divided into porosity loss, fracture loss and cave loss according to the loss channel. Among them, crack leakage has the most frequent leakage and the most far-reaching impact. During the drilling process, natural fractures or artificially induced fractures are encountered. Once controlled improperly, leakage may occur, and they are often of the loss-return type. The existence of formation fractures is difficult to predict, so fracture leakage is difficult to prevent. And after the leakage occurs, since there are no relevant detection instruments to accurately analyze the location, opening and depth of the crack, on-site leakage plugging operations still rely on experience to judge and deal with the crack based on relevant data such as the location of the leakage, the rate of leakage, etc. This makes it difficult to prevent on-site well leakage, and it is difficult to successfully plug the leakage many times. Even if the leakage is successfully plugged, leakage will still occur repeatedly in the later period. Oilfield companies and scientific research units have not yet fully grasped the leakage mechanism and plugging mechanism of fracture leakage, which makes on-site plugging even more blind.

The most widely used plugging method at present is bridge plugging, and the reasonable selection of plugging materials is particularly important. Bridging lost circulation materials, also known as inert lost circulation materials, are chemically inert materials added to drilling fluids for drilling lost circulation. Bridging lost circulation agents are cheap and widely available. They are mostly inert materials. Apart from their own characteristics, they do not react with other components in the drilling fluid. In the particle size range below the millimeter level, they have little impact on the performance of the drilling fluid. In foreign countries, bridging lost circulation materials have been used earlier and are widely used. In the United States, 90% of drilling loss problems are solved with bridging lost circulation materials. In my country, as early as the 1960s, bridging leakage plugging materials such as rice husk, vermiculite, and walnut shells were used to plug leakage in drilling wells with severe leakage, and achieved certain results. With the progress of resource exploration and development, researchers have also studied the bridging and plugging technology. At the same time, many products with reasonable gradation and different specifications have been developed and gradually promoted and applied. After entering the new century, with the improvement of the national chemical industry, chemical plugging agents and other types of lost circulation materials have developed rapidly, but the use of bridging lost circulation materials is still the most important method to deal with drilling loss problems.

Bridging leakage plugging materials can be divided into three major categories according to their shapes: granular leakage plugging materials, fibrous leakage plugging materials and filled powder. Common leak-stopping materials are shown in Table 1.

Table 1 Common plugging materials

Bridging materials include single inert bridging plugging materials and multiple inert leak plugging materials, as well as composite bridging plugging materials composed of different particle sizes and proportions. Since a single leakage plugging material is limited by particle size and various functions, composite bridging leakage plugging materials have become the protagonist in on-site applications. Bridging leakage plugging materials are easy to use, safe and reliable, have a wide range of applications and have a high success rate. They are the main choice on site. Leak-proof and plugging materials.

Bridging and plugging mainly uses large particles to bridge narrow cracks, and uses particles at all levels to fill them. Through continuous leakage to filtration, a dense plugging layer is formed. In the bridge plugging formula, Wang Shuqi (Wang Shuqi, Tang Jiping, Zhang Bin et al. High-density drilling fluid plugging technology in the Tarim piedmont structural zone [J]. Drilling Fluids and Completion Fluids, 2006(01):76-77+91 .) proposed that the content of large-particle bridging plugging materials should be kept at about 10% to 20%, the content of fibrous plugging materials should be kept between 5% and 15%, and the total content of plugging materials should be kept at 20% to 35%. Xue Yuzhi (Xue Yuzhi, Liu Zhendong, Tang Daixu, et al. Research on the formula and regularity of leakage plugging in fractured formations [J]. Drilling and Completion Fluids, 2009, 26(06): 28-30+93-94.) pointed out that for fractures To effectively plug the formation, in addition to the skeleton material, the leakage plugging formula must be matched with flaky, granular, flocculent filling materials and fibrous materials, and the particle size matching is reasonable, so that rapid plugging can be achieved, and the leakage plugging device has the characteristics Higher pressure-bearing capacity, Wei Hongchao (Wei Hongchao, Tang Zhijin, Zhang Ling. Experiment on optimization of lost circulation agent formula for fractured reservoirs [J]. Drilling and Completion Fluids, 2010, 27(03): 38-40+97. ) conducted a comparative analysis of different bridging materials and proved that the selection of different bridging and plugging material types is of great significance for successful plugging; Li Jiaxue (Li Jiaxue, Huang Jinjun, Luo Pingya, et al. Mechanism and estimation of rigid particle plugging while drilling in fractured formations Model [J]. Acta Petroleum Sinica, 2011, 32(03):509-513.) A particle size and concentration estimation model was established for rigid particles blocked while drilling.

Through the above analysis, the problems and defects existing in the existing technology are:

(1) The existing leakage plugging materials have poor acid solubility and pressure-bearing properties, and can withstand low temperatures.

(2) The aging quality retention rate of existing leak plugging materials is low.

Contents of the invention

In order to solve the above technical problems, the present invention provides a leakage prevention and plugging agent and its preparation method and application.

In the first aspect, the present invention provides a first leakage prevention and plugging agent, which is achieved by adopting the following technical solutions.

A leakage prevention and plugging agent, including the following mass percentage components: 5-13% multi-morphology alloy, 3% MDF, 0%-3% PF-EZCARB, 0.5%-1% brucite fiber, the balance For well slurry.

Specifically, for long wedge-shaped cracks with an opening of 1×0.5mm, the anti-leakage and plugging agent includes the following mass percentage components: 18-30 mesh 5% alloy, 3% MDF, 3% PF-EZCARB, 0.5% brucite fiber and the rest is well slurry.

Specifically, for long wedge-shaped cracks with an opening of 2×1mm, the leakage prevention and plugging agent includes the following mass percentage components: 12-18 mesh 3% alloy, 18-30 mesh 3% alloy, 3% MDF, 3% PF- EZCARB, 0.6% brucite fiber, and the remainder is well slurry.

In the second aspect, the present invention provides a second leakage prevention and plugging agent, which is achieved by adopting the following technical solution.

A leakage prevention and plugging agent, including the following mass percentage components: 5-13% multi-morphology alloy, 3% MDF, 0%-3% PF-EZCARB, 0.5%-1% brucite fiber, 3% SQD-98, the balance is well mud.

Specifically, for long wedge-shaped cracks with an opening of 3×2mm, the leakage prevention and plugging agent includes the following mass percentage components: 10-12 mesh 4% alloy, 12-18 mesh 4% alloy, 18-30 mesh 3% alloy, 3% MDF, 3% PF-EZCARB, 3% SQD-98, 0.8% brucite fiber, and the rest is well slurry.

Specifically, for long wedge-shaped cracks with an opening of 4×3mm, the leakage prevention and plugging agent includes the following mass percentage components: 8-12 mesh 5% alloy, 12-18 mesh 4% alloy, 18-30 mesh 4% alloy, 3% MDF, 3% PF-EZCARB, 3% SQD-98, 1% brucite fiber, and the rest is well slurry.

In a third aspect, the present invention provides a method for preparing a leak prevention and plugging agent, which is achieved by adopting the following technical solutions.

A method for preparing the above-mentioned leak prevention and plugging agent, including the following steps:

S101: Well mud configuration;

S102: Add medium-fine particle alloy with a particle size of 1/4-1/3 of the average crack width into the mixed liquid prepared in step S101, and add 0.5%-1% brucite fiber. Add the particle size after it is evenly dispersed. Medium-coarse grained alloy with average crack width 1/3-1/2;

S103: Finally add the remaining ingredients, stir for 2-3h, and let stand for 12-15h to obtain a leak-proof and plugging agent.

Further, take a certain mass of water, add 0.15% NaOH to simulate the drilling fluid environment, add 0.6% SDTV as a tackifier, 1.5% PF-DFC-200 as an anti-high temperature fluid loss agent, and continue to add 0.5% Na ₂ SO ₃ . Stir for 2h and let stand for 24-36h.

In the fourth aspect, the present invention provides three uses of the leakage prevention and plugging agent, which are achieved by adopting the following technical solutions.

A kind of above-mentioned leakage prevention and plugging agent is used in the preparation of drilling working fluid bridging plugging agent, cementing working fluid bridging plugging agent or testing or workover working fluid bridging plugging agent in oil and natural gas development. application.

This application has the following beneficial effects.

(1) Through the analysis of the morphology of leakage plugging materials, acid-soluble properties, pressure-bearing properties and other basic performance evaluations, the present invention selects alloys as bridging particles. The GYD alloy particles have sharp edges and corners, which is beneficial to retention in cracks and the acid-soluble rate reaches 76.25%, can withstand temperatures up to 180°C, and has strong sealing and pressure-bearing capabilities;

(2) The present invention prefers brucite fiber as the fiber material captured by the netting. Its acid solubility rate reaches 59.5%, good dispersion performance, and its mass retention rate reaches 81.5% after aging for 48 hours at high temperature of 180°C. Under strong alkali conditions at high temperature of 180°C The quality retention rate after aging for 48 hours reached 75.2%;

(3) For crack widths with different openings, the present invention optimizes the acid-soluble leakage plugging formula with a sealing pressure-bearing capacity of more than 10 MPa and an acid-soluble rate of more than 70%.

Description of drawings

Figure 1 is a graph showing the mass retention rate of the leak-proofing fibers after hot rolling at 180°C for different times for three types of fibers of the present invention;

Figure 2 is a graph showing the quality retention rate of three types of leak-proofing fibers of the present invention in an alkaline system;

Figure 3 is a graph showing changes in the acid solubility rate and pressure-bearing capacity of the 1×0.5mm formula of the present invention as a function of reaction time;

Figure 4 is a graph showing changes in the acid solubility rate and pressure-bearing capacity of the 2×1mm formula of the present invention as a function of reaction time;

Figure 5 is a graph showing changes in the acid solubility rate and pressure-bearing capacity of the 3×2mm formula of the present invention as a function of reaction time;

Figure 6 is a graph showing changes in the acid solubility rate and pressure-bearing capacity of the 4×3mm formula of the present invention as a function of reaction time.

Detailed ways

The present invention will be further described below in conjunction with the drawings and examples.

1. Selection of leak-stopping materials

1.1 Bridging materials

Rigid particles play the role of a skeleton in the sealing layer structure and have the characteristics of high hardness and resistance to deformation. In actual operations, quartz, walnut shells, or broken rock cuttings are often used as rigid particles. However, their acid solubility is not good and they cannot effectively remove the blockage after sealing. Therefore, walnut shells, GYD alloys, and limestone are used as Bridging particles.

1.1.1 Morphology analysis

It can be seen from the morphology of walnut shells, GYD, and limestone that GYD alloy has sharper edges and corners than walnut shells and limestone. Materials with sharp edges and corners are easier to catch and bridge in cracks. The sharper the edges and corners of the particles, the more irregular the shape. The more conducive to the retention of leakage plugging materials in cracks.

1.1.2 Evaluation of temperature resistance performance

A certain mass of walnut shells, GYD alloy, and limestone were placed in an oven at 180°C for a 24-hour aging experiment. Through comparison before and after aging, it can be found that the color of the walnut shells becomes darker and black after aging, indicating that the walnut shells have undergone aging. Certain properties change, while GYD alloy and limestone have almost no changes before and after aging, indicating that GYD alloy and limestone can withstand 180°C.

1.1.3 Evaluation of acid solubility

The sample to be tested was baked at 105°C to a constant weight of 2g, dissolved in 100 mL of 15% dilute hydrochloric acid, and reacted in a constant temperature water bath at 80°C for 2 hours. After the reaction, filter with quantitative slow filter paper and wash with distilled water until there is no chloride ion. Dry the filter paper and insoluble matter at 90°C for 2 hours, cool in a desiccator for 30 minutes and then weigh. Calculate the acid solubility rate. Calculation formula: S＝ [m-(m ₂ -m ₁ )]/m×100%. In the formula, S is the acid solubility rate, %; m ₁ is the mass of filter paper; m ₂ is the mass of filter paper and insoluble matter; m is the mass of the sample. The experimental data and results are shown in Table 2.

Table 2 Acid solubility test of granular materials

Among the three bridging materials, limestone is almost completely acid-soluble, walnut shell is almost completely insoluble, and the acid-soluble rate of GYD alloy particles reaches 76.25%.

1.1.4 Evaluation of pressure bearing capacity

Base pulp: tap water

+0.15%NaOH+0.15%Na ₂ CO ₃ +0.6%SDTV+1.5%PF-DFC-200+0.5%Na ₂ SO ₃

Experimental slurry 1: 400mL well slurry + 3% walnut shell (80-120 mesh) + 5% calcium carbonate powder

Experimental slurry 2: 400mL well slurry + 3% GYD (80-120 mesh) + 5% calcium carbonate powder

Experimental slurry 3: 400mL well slurry + 3% limestone (80-120 mesh) + 5% calcium carbonate powder

Using the HTHP leakage plugging test, 5% PF-EZCARB used on site was added to walnut shells, GYD, and limestone to seal 400 μm micro-cracks. The test results are shown in Table 3.

Table 3 Evaluation of pressure-bearing performance of bridging particles

According to the experimental results, the pressure-bearing performance of GYD alloy is 5MPa, which is greater than the 4.5MPa of walnut shell and the 3Mpa of limestone, indicating that the pressure-bearing performance of GYD alloy is better.

1.2 Fiber materials

Fiber is a common leak-stopping material. After the fiber material is added to the drilling and completion fluid, it is evenly dispersed and enters the leakage channel as the drilling and completion fluid enters the leakage channel. When the fiber length is greater than the width of the crack, it is easy to form a bridge and capture other passing fibers, thereby pulling each other to form a network. Frame structure to enhance the overall structural stability of the sealing layer. Different fibers play different roles in the blocking process: hard fibers with high stiffness can achieve bridging, while soft fibers with low stiffness can make the grid structure denser by pulling each other. However, due to the overall stiffness of the fiber material itself, Not strong, it is prone to failure when the pressure difference reaches a certain value, and cannot meet the actual engineering needs when the pressure difference is large. See Table 4.

Table 4 Fiber Material Survey

serial number name Quantity/g form Sampling location 1 Sepiolite Fiber No. 1 380 powdered fiber Lingshou County Dianjin Mineral Products Processing Factory 2 Sepiolite Fiber No. 2 290 powdered fiber Lingshou County Dianjin Mineral Products Processing Factory 3 Aluminum silicate fiber 100 flocculent fiber Lingshou County Dianjin Mineral Products Processing Factory 4 mineral fiber 245 granular fiber Lingshou County Dianjin Mineral Products Processing Factory 5 wood fiber 60 flocculent fiber Lingshou County Dianjin Mineral Products Processing Factory 6 Brucite fiber 700 mixed fiber Lingshou County Dianjin Mineral Products Processing Factory

1.2.1 Morphology analysis

It can be seen from six fiber materials with different shapes: sepiolite fiber No. 1, sepiolite fiber No. 2, aluminum silicate fiber, mineral fiber, wood fiber and brucite fiber. Among them, sepiolite fiber is a natural Mineral fiber and aluminum silicate fiber are a mixture of flocculent plugging materials and fibers; mineral fiber is a fiber obtained from mineral rocks with a fibrous structure, and its main components are various oxides; wood fiber is a natural renewable wood after Organic flocculent fiber material obtained by chemical treatment and mechanical processing; brucite fiber is a rare fibrous hydroxide stone at home and abroad. It has the characteristics of white color, easy splitting, and high velvet yield.

1.2.2 Evaluation of acid solubility

Taking the acid solubility of fiber as an indicator, the acid solubility of fiber was experimentally evaluated. According to the site conditions, prepare a hydrochloric acid solution with a mass fraction of 15% and place it in a beaker. Take 1.2g (W ₁ ) of sepiolite fiber No. 1 and sepiolite fiber No. 2 respectively, soak them in the hydrochloric acid solution, and stir for 10 minutes. , make it fully contact with the hydrochloric acid solution, heat it in a 90°C water bath for 2 hours, sieve, wash and dry it, measure the mass of the remaining fiber (W ₂ ), and the acid solubility rate S = [(W ₁ -W ₂ )/W ₁ ]×100%.

According to the experimental results, the acid solubility rates of sepiolite fiber No. 1, sepiolite fiber No. 2, and brucite fiber are 60.75%, 67.92%, and 59.5% respectively. Therefore, sepiolite fiber No. 1, sepiolite fiber No. 2 and brucite fiber were initially selected as the leakage plugging materials. See Table 5.

Table 5 Acid solubility test of granular materials

1.2.3 Test on the impact of drilling fluid performance. Add sepiolite fiber No. 1, sepiolite fiber No. 2 and brucite fiber to the on-site drilling fluid respectively. After fully stirring with a low-speed mixer, test their basic properties, and then After being placed in aging tanks for aging for 16 hours, the hot rolling temperature was 180°C. The experimental results are shown in Table 6.

Table 6 Basic performance test of experimental pulp before and after adding fiber materials

After adding the three types of fibers, the apparent viscosity, plastic viscosity, and dynamic shear force of the experimental pulp increased to a certain extent, and the filter loss decreased, but they were not much different from the basic properties of the original pulp.

1.2.4 Evaluation of temperature resistance performance

Using the mass retention rate of the lost-circulation fiber hot-rolled at a certain temperature as an indicator, the temperature resistance performance of the lost-circulation fiber in the drilling fluid system was experimentally evaluated. Take a certain mass of three kinds of leak-proof fibers and add them to 400mL of experimental slurry. The experimental slurry formula is 0.6% SDTV + 1.5% PF-DFC-200. After heating at 180°C for 16h, 32h, and 48h respectively, wash and dry. The quality and breaking strength of three types of leak-proofing fibers after hot rolling were measured. The mass retention rate of the plugging fiber is calculated according to the following formula.

In the formula, α is the mass retention rate, %; M ₁ is the mass of the fiber plugging before hot rolling, g; M ₂ is the mass of the fiber plugging after hot rolling, g.

The mass retention rates of the three types of fibers are shown in Figure 1, which shows the mass retention rates of the leak-stopping fibers after hot rolling at 180°C for different times. The analysis shows that after hot rolling at 180°C for 16h, 32h, and 48h respectively, the mass retention rate of brucite fiber increased and decreased slightly with time, all remaining above 80%; the mass retention rate of sepiolite fiber No. 2 increased with time. The mass retention rate of sepiolite fiber No. 1 decreases with time, and the mass retention rate of sepiolite fiber No. 1 is lower than 80% after hot rolling at 180°C for 32 hours.

1.2.5 Evaluation of alkali resistance performance

The pH value of various commonly used drilling fluid systems is between 8 and 11, which means maintaining a weak alkaline environment. Therefore, the lost circulation fiber is required to have good alkali resistance, so that the lost circulation fiber can be used in drilling fluids with a pH value of 12. The quality retention rate and fracture strength retention rate of the system after hot rolling at 140°C are used as indicators to experimentally evaluate the alkali resistance of the leak-stopping fiber. Take a certain mass of 5 types of leak-stopping fibers and add them to 400mL of experimental slurry respectively. The experimental slurry formula is 0.6% SDTV + 1.5% PF-DFC-200 + 0.2% NaOH (add NaOH to adjust the pH value of the experimental slurry to 12). 180 After hot rolling for 16h, 32h, and 48h respectively at ℃, they were washed and dried. The quality and breaking strength of the five types of leak-proofing fibers after hot rolling were measured. The mass retention rate was calculated according to the following formula.

In the formula, α is the mass retention rate, %; M ₁ is the mass of the fiber plugging before hot rolling, g; M ₂ is the mass of the fiber plugging after hot rolling, g. The mass retention rates of the three types of plugging fibers can be seen from Figure 2. After hot rolling at 180°C for 16h, 32h, and 48h respectively, the mass retention rate of the brucite fiber decreased slightly as time increased, and remained above 75%; 180 The mass retention rates of the other two types of leak-proofing fibers after hot rolling at ℃ for 48 hours were both lower than 70%. Comparative experiments show that brucite fiber has excellent alkali resistance. (Through the acid melting rate evaluation, it was found that sepiolite No. 1 and No. 2 and brucite fibers have good acid solubility properties, so only the experimental results of these three fibers are shown)

1.3 Filling powders Three filling powders are selected in this application, namely MDF, SMGF-1 and PF-EZCARB. 1.3.1 Acid solubility (dilute hydrochloric acid with a concentration of 15%)

The test results of the acid solubility rate of filling materials are shown in Table 7. The acid solubility rate of MDF is 80.45%, the acid solubility rate of SMGF-1 is 64.7%, and the acid solubility rate of PF-EZCARB is the highest, almost completely acid solubility.

Table 7 Filling material acid solubility test results

1.3.2 Rheology and fluid loss performance evaluation

The experimental pulps are as follows:

Base slurry: tap water + 0.15% NaOH + 0.15% Na ₂ CO ₃ + 0.6% SDTV + 1.5% PF-DFC-200 + 0.5% Na ₂ SO ₃

Experimental slurry 1: Well slurry 400mL+10% PF-EZCARB

Experimental slurry 2: well slurry 400mL+10% SMGF-1

Experimental slurry 3: well slurry 400mL+10% MDF

The basic performance evaluation results are shown in Table 8. Before and after adding the plugging material while drilling, the apparent viscosity, plastic viscosity, dynamic shear force, and initial and final shear of the base slurry almost all increased. Comprehensive comparison shows that the performance of MDF's acid-soluble system is close to that of simulated well mud, and its temperature resistance is better.

Table 8 Changes in rheological and fluid loss properties of the drilling fluid system before and after the addition of lost circulation materials

Note: The ingredients of base slurry, experimental slurry 1, experimental slurry 2, and experimental slurry 3 in the table are the same as those in 1.3.3. 1.3.3 Blocking performance evaluation

The experimental pulps are as follows:

Base slurry: tap water + 0.15% NaOH + 0.15% Na ₂ CO ₃ + 0.6% SDTV + 1.5% PF-DFC-200 + 0.5% Na ₂ SO ₃

Experimental slurry 1: Well slurry 400mL+10% PF-EZCARB

Experimental slurry 2: well slurry 400mL+10% SMGF-1

Experimental slurry 3: well slurry 400mL+10% MDF

Using the HTHP leakage plugging experiment, three groups of experimental slurries, PF-EZCARB, SMGF-1, and MDF, were designed to plug 400 μm micro-cracks. The test results are shown in Table 9.

Table 9 Evaluation results of crack leak plugging performance for 400 μm crack width

The lost circulation plugging agents SMGF-1 and PF-EZCARB while drilling have a certain sealing effect on 400 μm fractures, and the pressure-bearing lost circulation agent MDF has a better pressure-bearing effect, reaching 10MPa.

2. Optimization and evaluation of leakage plugging system

2.1 Long crack plugging simulation experiment

(1) Opening 1×0.5mm wedge-shaped long crack

Well mud: tap water + 0.6% SDTV + 1.5% PF-DFC-200 + 0.5% Na ₂ SO ₃ , see Table 10.

Table 10 Experimental formula for sealing wedge-shaped long cracks with composite leakage plugging materials (1×0.5mm crack)

serial number Alloy (18-30 mesh) PF-EZCARB MDF Brucite fiber 1-1# 10% 1-2# 8% 3% 1-3# 8% 3% 0.5% 1-4# 5% 3% 3% 0.5%

Table 11 Experimental results of composite leakage plugging materials for plugging long wedge-shaped cracks (1×0.5mm crack)

serial number Pressure bearing capacity/MPa Loss/mL Crack sealing area/mm 1-1# 5 66 365-385 1-2# 5.5 50 330-350 1-3# 7 34 270-300 1-4# 10 0 100-240

The analysis shows that when 18-30 mesh alloy particles are used alone, the internal structure of the sealing layer is relatively loose, the pressure bearing capacity is as low as 5MPa, the leakage amount is as large as 66mL, and the crack sealing area is the crack outlet; adding ultrafine carbonic acid After adding calcium and brucite fibers, the sealing layer structure becomes denser, the pressure-bearing capacity of the sealing layer increases to 7MPa, the crack leakage decreases to 34mL, and the crack sealing area moves forward; finally, after the pressure-bearing leakage plugging agent MDF is added, the sealing layer The pressure-bearing capacity of the plugging layer reaches 10MPa. Therefore, formula 1-4# is selected as the formula for the wedge-shaped long crack system with an opening of 1×0.5mm. The specific formula is: well mud + 5% alloy (18-30 mesh) + 3% MDF + 3% PF-EZCARB + 0.5% Brucite fiber.

(2) Wedge-shaped long crack with an opening of 2×1mm

Well mud: tap water+0.6%SDTV+1.5%PF-DFC-200

Table 12 Experimental formula for sealing wedge-shaped long cracks with composite leakage plugging materials (2×1mm cracks)

Table 13 Experimental results of composite leakage plugging materials plugging long wedge-shaped cracks (2×1mm crack)

serial number Pressure bearing capacity/MPa Loss/mL Crack sealing area/mm 2-1# 5.5 230 600-750 2-2# 6.5 206 590-748 2-3# 7 195 575-732 2-4# - - - 2-5# 10 114 270-500/540-720

Brucite fibers can capture alloy particles through three-dimensional network reinforcement and bending, extrusion and restraint, forming agglomerates of leakage-blocking fibers and particles, increasing the migration resistance of bridging leakage-blocking particles, making them easier to stay in cracks and sealing them. The density of the plugging layer is significantly increased; at the same time, the plugging fiber can increase the compressive strength and shear strength of the plugging layer, preventing the plugging layer from experiencing extrusion, crushing, instability and shear slip instability under the action of external loads. However, if the concentration of brucite fiber is too high, it can easily cause door sealing, such as 2-4#. After finally adding pressure-bearing leakage plugging agent MDF, the pressure-bearing capacity of the plugging layer reaches 10MPa. Therefore, the 2-5# formula was selected as the high-temperature fiber plugging system formula for wedge-shaped long cracks with an opening of 2×1mm. The specific formula is: well mud + 3% alloy (12-18 mesh) + 3% alloy (18-30 mesh)+3% MDF+3% PF-EZCARB+0.6% brucite fiber.

(3) Wedge-shaped long crack with an opening of 3×2mm

Combined with the experimental formula results of composite leakage plugging materials for plugging wedge-shaped long cracks with an opening of 2×1mm, and through reasonable compounding of alloy particles, MDF pressure-bearing leakage plugging agent, PF-EZCARB and brucite fiber, a project with an opening of 3×2mm was carried out. Experimental study on formula optimization of wedge-shaped long crack plugging system. Table 13 and Table 14 show the experimental formula and results of alloy particles, pressure-bearing leakage plugging agent and brucite fiber plugging long wedge-shaped cracks with an opening of 3×2mm.

Well mud: tap water + 0.6% SDTV + 1.5% PF-DFC-200.

Table 14 Experimental formula for sealing wedge-shaped long cracks with composite leakage plugging materials (3×2mm cracks)

Table 15 Experimental results of composite leakage plugging materials plugging long wedge-shaped cracks (3×2mm crack)

serial number Pressure bearing capacity/MPa Loss/mL Crack sealing area/mm 3-1# 4 360 540-610 3-2# 5 350 523-602 3-3# 5 345 500-576 3-4# 7.5 280 466-526 3-5# 8 265 425-502 3-6# - - - 3-7# 10 138 348-428 3-8# 11 90 210-370

The analysis shows that when the experimental formulas for sealing of alloy particles with different mesh sizes are used, the pressure-bearing capacity of the sealing layer generally does not exceed 5MPa, and the crack leakage is large; as the concentration of brucite fiber and pressure-bearing leakage plugging agent increases, the sealing The density of the layer is significantly enhanced, the pressure-bearing capacity of the sealing layer is significantly increased, the leakage of the fracture is reduced to 90mL, and the fracture sealing area moves forward. Add 1% brucite plugging fiber. If its concentration is too high, it will overlap and form a network outside the crack opening, forming a "sealed door" with poor plugging effect.

The optimal amount of brucite plugging fiber is 1%, which can interact with alloy particles and pressure-bearing plugging agents to form a dense pressure-bearing plugging layer. Therefore, the 3-8# formula is selected as the formula of the anti-high temperature fiber plugging system for wedge-shaped long cracks with an opening of 3×2mm, which can withstand a pressure of 11Mpa. The specific formula is: well mud + 4% alloy (10-12 mesh) + 4% alloy (12-18 mesh)+3% alloy (18-30 mesh)+3% MDF+3% SQD-98+3% PF-EZCARB+0.8% brucite fiber.

(4) Wedge-shaped long crack with an opening of 4×3mm

Table 16 and Table 17 show the experimental formula and results of alloy particles, MDF pressure-bearing leakage plugging agent, SQD-98 and brucite fiber for plugging long wedge-shaped cracks with an opening of 4×3mm. The analysis shows that when alloy particles of different mesh sizes are used alone, the sealing layer structure is loose, the pressure-bearing capacity is as low as 5.5MPa, the crack leakage is large, and the crack sealing area is the crack exit end; after adding brucite fiber , the internal structure of the sealing layer has been further optimized, the pressure-bearing capacity of the sealing layer has been improved, the crack leakage has been significantly reduced, the crack sealing area has moved forward, and 1.2% brucite fiber has been added. If its concentration is too high, it will overlap outside the crack opening. It forms a network and forms a "closed door". The optimal addition amount of brucite fiber is 1%. After adding pressure-bearing leakage plugging agents MDF and SQD-98, they can fill the pores between alloy particles, increase the pressure-bearing capacity of the plugging layer to 11MPa, reduce the crack leakage to 104mL, and move the crack plugging area forward.

Therefore, the 4-8# formula was selected as the formula of the anti-high temperature fiber plugging system for wedge-shaped long cracks with an opening of 4×3mm. The specific formula is: well mud + 5% alloy (8-12 mesh) + 4% alloy (12-18 mesh) )+4% alloy (18-30 mesh)+3% MDF+3% SQD-98+3% PF-EZCARB+1% brucite fiber.

Table 16 Experimental formula for sealing wedge-shaped long cracks with composite leakage plugging materials (4×3mm cracks)

Table 17 Experimental results of composite leakage plugging materials for plugging wedge-shaped long cracks (4×3mm cracks)

serial number Pressure bearing capacity/MPa Loss/mL Crack sealing area/mm 4-1# 4 380 980-995 4-2# 5.5 334 975-990 4-3# 5.5 330 974-986 4-4# 6.5 270 850-890 4-5# 7 255 840-890 4-6# - - - 4-7# 9 135 790-835 4-8# 11 104 770-900

2.2 Acid dissolution plugging experiment

(1) Opening 1×0.5mm long wedge-shaped crack

According to the optimized formula "well slurry + 5% alloy (18-30 mesh) + 3% MDF + 3% PF-EZCARB + 0.5% brucite fiber", the pressure-bearing performance experiment after acid dissolution and acid dissolution was carried out. Put 5g alloy (18-30 mesh), 3gMDF, 3gPF-EZCARB and 0.5g brucite fiber into each of the 6 beakers, add 50mL15% dilute hydrochloric acid, and react for 2h, 4h, 6h, 8h, 16h, and 24h respectively. Finally, the acid solubility rate was tested, and the remaining samples were filtered, dried, and then added to 100 mL of base slurry to conduct a pressure-bearing performance test with a slit width of 1 mm. It can be seen from Figure 3 and Table 18 that the acid solubility rate of the formula can reach 71.5% after 8 hours of acid dissolution, and the pressure-bearing capacity is gradually lost.

Table 18 Changes in acid solubility rate and pressure bearing capacity of leak plugging formula over time

reaction time/h Acid solubility rate/% Pressure bearing capacity/MPa 2 31.8% 7 4 50.9% 4.5 6 62.6% 1.5 8 71.5% 0.5 16 78.5% twenty four 81.3%

(2) Wedge-shaped long crack with an opening of 2×1mm

Carry out acid dissolution and mixing according to the optimized formula "well slurry + 3% alloy (12-18 mesh) + 3% alloy (18-30 mesh) + 3% MDF + 3% PF-EZCARB + 0.6% brucite fiber" For the pressure-bearing performance test after acid dissolution, put 3g alloy (12-18 mesh), 3g alloy (18-30 mesh), 3gMDF, 3gPF-EZCARB and 0.6g brucite fiber into each of the six beakers. 50mL of 15% dilute hydrochloric acid was reacted for 2h, 4h, 6h, 8h, 16h, and 24h respectively to test its acid solubility. The remaining sample was filtered and dried and then added to 100mL of base slurry to carry out pressure-bearing with a gap width of 2mm. Performance Testing. It can be seen from Figure 4 and Table 19 that the acid solubility rate of the formula can reach 70.3% after acid dissolution for 8 hours, and the pressure-bearing capacity is gradually lost.

Table 19 Changes in acid solubility rate and pressure-bearing capacity of leak plugging formula over time

reaction time/h Acid solubility rate/% Pressure bearing capacity/MPa 2 30.6 6 4 49.5 3 6 62.8 1 8 70.3 0.5 16 75.6 0 twenty four 78.6 0

(3) Wedge-shaped long crack with an opening of 3×2mm

According to the optimized formula "well mud + 4% alloy (10-12 mesh) + 4% alloy (12-18 mesh) + 3% alloy (18-30 mesh) + 3% SQD-98 + 3% MDF + 3 %PF-EZCARB + 0.8% Brucite Fiber" was used to conduct acid-soluble and acid-soluble pressure-bearing performance experiments. Put 4g of alloy (10-12 mesh) and 4g of alloy (12-18 mesh) into 6 beakers respectively. ), 3g alloy (18-30 mesh), 3gMDF, 3gPF-EZCARB, 3gSQD-98 and 0.8g brucite fiber, add 50mL15% dilute hydrochloric acid, react for 2h, 4h, 6h, 8h, 16h and 24h respectively and then test Its acid solubility rate was determined, and the remaining sample was filtered, dried, and then added to 100 mL of base slurry to conduct a pressure-bearing performance test with a slit width of 3 mm. It can be seen from Figure 5 and Table 20 that the acid solubility rate of the formula can reach 69.4% after being acid-dissolved for 16 hours, and the pressure-bearing capacity is lost.

Table 20 Changes in acid solubility rate and pressure-bearing capacity of leak plugging formula over time

reaction time/h Acid solubility rate/% Pressure bearing capacity/MPa 2 28.9 5.5 4 41.2 2.5 6 51.3 3 8 64.6 1 16 69.4 0 twenty four 74.2 0

(4) Wedge-shaped long crack with an opening of 4×3mm

According to the optimized formula "well mud + 5% alloy (8-12 mesh) + 4% alloy (12-18 mesh) + 4% alloy (18-30 mesh) + 3% MDF + 3% SQD-98 + 3 %PF-EZCARB + 1% Brucite Fiber" was used to conduct acid-soluble and acid-soluble pressure-bearing performance experiments. Put 5g of alloy (8-12 mesh) and 4g of alloy (12-18 mesh) into 6 beakers respectively. ), 4g alloy (18-30 mesh), 3gMDF, 3gPF-EZCARB, 3gSQD-98 and 1g brucite fiber, add 50mL15% dilute hydrochloric acid, react for 2h, 4h, 6h, 8h, 16h, 24h respectively and then test it The acid solubility rate was determined, and the remaining sample was filtered, dried, and then added to 100 mL of base slurry to conduct a pressure-bearing performance test with a slit width of 4 mm. It can be seen from Figure 6 and Table 21 that the acid solubility rate of the formula can reach 61.1% after acid dissolution for 8 hours, and the pressure-bearing capacity is lost.

Table 21 Changes of acid solubility rate and pressure bearing capacity of leak plugging formula over time

reaction time/h Acid solubility rate/% Pressure bearing capacity/MPa 2 29.8 4 4 42.5 1.5 6 51.1 0.5 8 61.1 0 16 70.3 0 twenty four 76.4 0

The above experiments show that for millimeter-scale cracks, using a certain type of leakage plugging material alone will have poor plugging effect and fail to form a dense pressure-bearing plugging layer. It is necessary to rationally mix different types of leakage plugging materials to give full play to their synergy. Effect. Therefore, different types of high-temperature resistant leak-proofing materials were selected. Among them, alloy particles serve as bridging particles, which can bridge cracks and form the skeleton structure of the sealing layer; SQD-98 is an elastic deformation material with a large compression recovery rate; MDF and PF-EZCARB are filled with bridging particles. pores between, reducing crack leakage; brucite fibers can form a network structure in the sealing layer through three-dimensional network reinforcement and bending and extrusion binding, improving the compressive strength and shear strength of the sealing layer. It avoids the extrusion, crushing and shear slip instability of the sealing layer under the action of external loads, and improves the pressure-bearing capacity of the sealing layer.

The invention provides a method for preparing a deblockable and high-pressure anti-leakage and plugging agent for fractured reservoirs, which includes the following steps:

S101, well mud configuration: first take a certain quality of tap water, add 0.15% NaOH to simulate the drilling fluid environment, determine the salinity of the water, promote the dispersion of other reagents, add 0.6% SDTV as a tackifier, 1.5% PF-DFC- 200 is used as an anti-high temperature fluid loss agent. Continue to add 0.5% Na ₂ SO ₃ to improve the anti-aging performance of the drilling fluid. Use a slurry mixer to stir for 2 hours and let it stand for 24 hours;

S102, the leak plugging material, first adds GYD alloy mainly composed of medium and fine particles, with a particle size of 1/4-1/3 of the average crack width, supplemented by 0.5%-1% brucite fiber, brucite Stone fiber has the ability to spread the net and capture, which can improve the suspension of the leakage plugging material and make the leakage plugging material better dispersed. After it is evenly dispersed, add mainly medium and coarse particles with a particle size of 1/3-1/3 of the average width of the crack. 1/2 GYD alloy;

S103, finally add 3% MDF or 3% MDF and 3% PF-EZCARB or 3% MDF and SQD-98 to improve the overall pressure-bearing capacity of the leakage plugging slurry. Use a slurry mixer to stir for 2 hours and let it stand for 12 hours to obtain the result. A deblockable and high-pressure leak-proof and plugging agent for fractured reservoirs.

The reservoir space of the buried hill is dominated by fractures, and occasionally dissolution pores can be seen along the fractures, causing the strata near the buried hill to be broken and fracture networks to develop. The top surfaces of the Archaean in this area are geological interfaces that have been weathered and denuded for a long time. The flowers that make up these strata Gangneiss is a rock that is relatively easy to weather and fracture, and there are various fractures during the weathering period.

The shape and size of cracks are related to rock type, physical properties, strength, cementing surface type, shear strength, etc. The size gradation and concentration selection of leakage plugging materials must be comprehensively considered.

The bridge plugging efficiency enhancement technology adopts a two-stage process. The specific ideas are as follows: The bridge plugging slurry in the first stage is mainly medium and fine particles, and GYD alloy with a particle size of 1/4-1/3 of the average crack width is selected, 0.5%- 1% brucite fiber is pumped using a special device for plugging. After entering the depth of the leakage layer, the plugging material accumulates into a plug. As time goes by, the fiber binds the bridge blockage into a whole to avoid recurrence of leakage in the future; 2nd For section bridge plugging slurry, increase the amount of medium and coarse particles, and use MDF and PF-EZCARB at the same time to improve the overall pressure-bearing capacity of the leakage plugging slurry. During construction, coarse particles are added from the tank surface after the pump is turned on to achieve graded leakage plugging. Mud pump for pumping.

Application examples

Well BZ19-6-X is a deep exploration well in the BZ19-6 block. The target layer is the Archaean buried hill. During this period, frequent leakage occurred at 4898m, 4952m, 4960m and 4972.5m. It was judged that the upper fault was leaking again or drilling into a new micro-cracked formation. During the period when the leakage plugging slurry was ready for replacement, the land was notified to increase the concentration of the leakage plugging slurry to 35 %: 10 cubic meters of well mud + 15% PF-SZDL + 15% SEAL + 5% EZCARB, all of which are ineffective, we decided to use the indoor preferred formula "well mud + 5% alloy (8-12 mesh) + 4% alloy (12-18 mesh) + 4% alloy (18-30 mesh) + 3% MDF + 3% SQD-98 + 3% PF-EZCARB + 1% brucite fiber" small displacement pump into the leak-proofing slurry 8m ³ and replace it in place, The displacement displacement is increased to a maximum of 1100L/min. The drilling tool is lowered to the bottom of the well before the lost circulation slurry comes out of the drill bit. During this period, the lost circulation slurry exits the drill bit, the leakage rate decreases, and the liquid level in the circulation tank gradually stabilizes. Keep still and observe the liquid level at the wellhead to make sure there is no overflow or leakage.

The examples of this specific implementation mode are all preferred embodiments of the present invention, and do not limit the scope of protection of the present invention. Therefore, all equivalent changes made based on the structure, shape, and principle of the present invention should be covered by within the protection scope of the present invention.

Claims (9)

1. A leak-proof and plugging agent, characterized in that: it includes the following mass percentage components: 5-13% multi-morphology alloy, 3% MDF, 0%-3% PF-EZCARB, 0.5%-1% water Magnesite fiber, the balance is well slurry. 2. A leakage prevention and plugging agent according to claim 1, characterized in that: for a long wedge-shaped crack with an opening of 1×0.5mm, the leakage prevention and plugging agent includes the following mass percentage components: 18-30 mesh 5 % alloy, 3% MDF, 3% PF-EZCARB, 0.5% brucite fiber, and the rest is well slurry. 3. A leakage prevention and plugging agent according to claim 1, characterized in that: for a long wedge-shaped crack with an opening of 2×1mm, the leakage prevention and plugging agent includes the following mass percentage components: 12-18 mesh 3% Alloy, 18-30 mesh 3% alloy, 3% MDF, 3% PF-EZCARB, 0.6% brucite fiber, and the rest is well slurry. 4. An anti-leakage and plugging agent, characterized by: including the following mass percentage components: 5-13% multi-morphology alloy, 3% MDF, 0%-3% PF-EZCARB, 0.5%-1% water Magnesia fiber, 3% SQD-98, the balance is well slurry. 5. A leak prevention and plugging agent according to claim 4, characterized in that: for long wedge-shaped cracks with an opening of 3×2mm, the leak prevention and plugging agent includes the following mass percentage components: 10-12 mesh 4% Alloy, 12-18 mesh 4% alloy, 18-30 mesh 3% alloy, 3% MDF, 3% SQD-98, 3% PF-EZCARB, 0.8% brucite fiber, and the rest is well slurry. 6. A leakage prevention and plugging agent according to claim 4, characterized in that: for long wedge-shaped cracks with an opening of 4×3mm, the leakage prevention and plugging agent includes the following mass percentage components: 8-12 mesh 5% Alloy, 12-18 mesh 4% alloy, 18-30 mesh 4% alloy, 3% MDF, 3% PF-EZCARB, 3% SQD-98, 1% brucite fiber, and the rest is well mud. 7. A method for preparing the leakage prevention and plugging agent according to any one of claims 1 to 6, characterized in that it includes the following steps: S101: Well mud configuration; S102: Add medium-fine particle alloy with a particle size of 1/4-1/3 of the average crack width into the mixed liquid prepared in step S101, and add 0.5%-1% brucite fiber. Add the particle size after it is evenly dispersed. Medium-coarse grained alloy with average crack width 1/3-1/2; S103: Finally add the remaining ingredients, stir for 2-3h, and let stand for 12-15h to obtain a leak-proof and plugging agent. 8. The preparation method of a leakage prevention and plugging agent according to claim 7, characterized in that: in step S101, the configuration method of well mud configuration is as follows: take a certain mass of water, add 0.15% NaOH to simulate the drilling fluid environment. , add 0.6% SDTV as a tackifier, 1.5% PF-DFC-200 as a high temperature anti-filtration agent, continue to add 0.5% Na ₂ SO ₃ , stir for 2h, and let stand for 24-36h. 9. A leakage prevention and plugging agent according to any one of claims 1 to 6 used in the preparation of drilling working fluid bridging plugging agent, cementing working fluid bridging plugging agent or testing or well workover in oil and natural gas development Application of working fluid as bridging sealing agent.