A cementing solid wall agent while drilling and its preparation method and application process

Abstract

The application discloses a drilling cementing wall stabilizing agent and a preparation method and application process thereof, and belongs to the technical field of oil field chemistry, and particularly relates to a preparation of the drilling cementing wall stabilizing agent. The preparation method of the drilling cementing wall stabilizing agent can be that thermoplastic resin, a curing agent and inorganic powder are uniformly mixed and stirred at normal temperature and normal pressure according to proportions. The wall stabilizing agent material has the advantages of simple production process, safety, low material cost and convenience for large-scale production and application. The product can not only plug pores and reduce filtration loss, but also cement sand and mudstone strata and improve stratum pressure-bearing capacity, so that the purpose of stabilizing a well wall is achieved. The application further provides an application process of the drilling cementing wall stabilizing agent, which comprises a suitable drilling fluid system and an adding amount and construction process under different stratum porosities and different working conditions.

Description

A drilling cementing wall-stabilizing agent, its preparation method and application process Technical Field

[0001] This invention relates to the fields of oilfield chemistry and drilling fluid technology, and in particular to a drilling cementing and wall-stabilizing agent and its preparation method and application process. Background Technology

[0002] During drilling through sandstone and mudstone formations, especially when encountering long open-hole formations with multiple pressure systems, wellbore instability is highly likely. For example, the Qianfoya Formation in the Puguang Gas Field's terrestrial structural belt is mainly composed of interbedded sandstone and mudstone with multiple pressure systems in the vertical direction. The collapse pressure of terrestrial formations is high, and the drilling fluid density designed according to formation pore pressure is insufficient to maintain wellbore stability. The drilling fluid safety density window is narrow or even negative, leading to frequent well leakage and collapse during drilling. Statistics show that in this block, five wells drilled by Sinopec Zhongyuan Petroleum Engineering Co., Ltd. in 2022, targeting the Qianfoya mudstone and shale, all experienced severe collapses in the horizontal sections. Two of these wells suffered stuck pipe due to collapses, making well leakage and collapse the most significant bottleneck restricting the development of this block. Currently, most wall-stabilizing agents improve the stability of near-wellbore formations by sealing micropores, reducing filtrate ingress into the formation, or inhibiting mudstone and shale hydration, but they are insufficient to solve the collapse problem in long open-hole, multi-pressure sandstone and mudstone formations. Therefore, it is necessary to adopt wall-stabilizing technology to improve the cementation capacity of sandstone and mudstone, thereby achieving the goal of stabilizing the formation and accelerating drilling.

[0003] Several wall-stabilizing agents have been developed within the industry. For example, Chinese patent document CN114075065A discloses a chemical wall-stabilizing agent for fractured formations, its preparation method, application, and pre-injection method. This chemical wall-stabilizing agent is composed of slag, bentonite, water glass, gypsum, ultrafine calcite, and water. Before exposing the fractured zone, the wall-stabilizing agent is displaced into the formation. After standing for 4 to 16 hours and solidifying, it is then used for sweeping and plugging drilling. This type of wall-stabilizing agent requires stopping drilling operations and is not considered drilling-while-drilling wall stabilization.

[0004] In drilling wall stabilization technology, Chinese patent document with application number 202010681904.0 provides a wall stabilizing agent for drilling fluid, its preparation method and application. The wall stabilizing agent is synthesized from raw materials such as acrylamide, dimethyl diallyl ammonium chloride, acrylic acid, and 2-acrylamido-2-methylpropanesulfonic acid in a certain proportion. When this material is added to water-based drilling fluid, it can enhance the cohesion and adhesion between rock particles, thereby improving the strength of the wellbore rock and stabilizing the wall to prevent collapse. Chinese patent application number 202210826056.7 discloses a wall-stabilizing agent, its preparation method, and its application. This wall-stabilizing agent is composed of dispersible latex powder, rubber, thermosetting resin, epoxy resin, chloroprene latex, and nano-silica in a specific ratio. The thermosetting resin undergoes a thermosetting reaction under the influence of formation temperature and drilling pressure differential, solidifying formation micro-fractures and micropores, thereby improving the strength of the wellbore rock. When used in conjunction with the dispersible latex powder, rubber, epoxy resin, chloroprene latex, and nano-silica, it can further strengthen the wellbore, improve its pressure-bearing capacity, and achieve an anti-collapse effect. In its preparation process, the thermosetting resin, epoxy resin, and chloroprene latex are mixed in a solvent at 100℃~150℃, and then mixed with the dispersible latex powder and nano-silica for 1~3 hours at a mixing temperature of 180℃~220℃.

[0005] The wall-stabilizing agents described above can be used during drilling, but their complex composition, cumbersome preparation methods, and high production costs make them unsuitable for widespread application. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a drilling cementing and wall-stabilizing agent, its preparation method, and application process. The wall-stabilizing agent can cement sandstone and mudstone, thereby improving the formation's bearing capacity and stabilizing the formation. It can effectively prevent the collapse of sandstone and mudstone formations, is easy to prepare, and can be applied while drilling, fundamentally solving the problem of wellbore instability and avoiding complex phenomena such as stuck drill and collapse caused by wellbore instability.

[0007] One object of the present invention is to provide a drilling cementing and wall-stabilizing agent, which is made from the following raw materials in parts by weight:

[0008] 35-65 parts thermoplastic resin, 5-15 parts curing agent and 25-65 parts inorganic powder; wherein the inorganic powder is calcium carbonate and silicon dioxide;

[0009] The thermoplastic resin is one or more of thermoplastic phenolic resin, thermoplastic urea-formaldehyde resin, thermoplastic epoxy resin, and thermoplastic melamine resin; the curing agent is one or two of hexamethylenetetramine, polyamide, and oxalic acid.

[0010] The wall-stabilizing agent material provided by this invention can not only seal pores and reduce filtration loss, but also cement sandstone and mudstone formations, improving the formation's pressure-bearing capacity, thereby stabilizing the wellbore. The product has a simple and safe manufacturing process, low material costs, and is suitable for large-scale production and application.

[0011] In an embodiment of the present invention, the particle size of the inorganic powder is 10-1000 nm.

[0012] In an embodiment of the present invention, the calcium carbonate is nano-micron grade calcium carbonate, and the silica has a particle size at the nanometer level.

[0013] In an embodiment of the present invention, the drilling cement wall consolidation agent is made from the following raw materials in parts by weight: 45-60 parts thermoplastic resin, 8-12 parts curing agent and 35-50 parts inorganic powder.

[0014] This invention provides a method for preparing a drilling cementing and wall-stabilizing agent, comprising:

[0015] Mix 35-65 parts by weight of thermoplastic resin, 5-15 parts by weight of curing agent and 25-65 parts by weight of inorganic powder to obtain a drilling cement wall consolidation agent.

[0016] The inorganic powder is calcium carbonate and silicon dioxide; the thermoplastic resin is one or more of thermoplastic phenolic resin, thermoplastic urea-formaldehyde resin, thermoplastic epoxy resin and thermoplastic melamine resin; the curing agent is one or two of hexamethylenetetramine, polyamide and oxalic acid.

[0017] In this embodiment of the invention, thermoplastic resin, curing agent, calcium carbonate, and silicon dioxide are mixed in proportion at room temperature and pressure, and the mixture is stirred evenly to obtain the wall-solidifying agent product.

[0018] In the raw materials for preparing the drilling cementitious wall-consolidating agent of the present invention, the thermoplastic resin comprises 35-65 parts by weight, preferably 45-60 parts. The thermoplastic resin of the present invention is one or more of thermoplastic phenolic resin, thermoplastic urea-formaldehyde resin, thermoplastic epoxy resin, and thermoplastic melamine resin, preferably thermoplastic phenolic resin and / or thermoplastic epoxy resin. The thermoplastic resins of the present invention are all in powder form at room temperature and pressure, with a predominantly linear molecular structure, exhibiting properties of softening upon heating and hardening upon cooling, and are curable. Particularly preferred are the thermoplastic phenolic resin with a degree of polymerization of 4-12 and the thermoplastic epoxy resin of type E42. The present invention does not impose any special restrictions on the source of the thermoplastic resin; commercially available products well known to those skilled in the art can be used.

[0019] In this invention, the curing agent is 5 to 15 parts by weight, preferably 8 to 12 parts. The curing agent is one or two of hexamethylenetetramine, polyamide, and oxalic acid, preferably hexamethylenetetramine and / or polyamide. For example, the polyamide is one of DJ2421H, DJ2323, DJ2428, and DJ2431 produced by Shandong Deyuan Epoxy Technology Co., Ltd. In this invention, the type and amount of curing agent determine the curing temperature and curing strength; the curing temperature of this invention is generally 80℃ to 150℃. This invention does not have special restrictions on the source of the curing agent; commercially available products well known to those skilled in the art can be used.

[0020] Furthermore, the inorganic powders used in preparing the drilling cementitious wall-consolidating agent according to the present invention are calcium carbonate and silicon dioxide; the particle size of the calcium carbonate and silicon dioxide can be adjusted according to the formation conditions, and the particle size is preferably 10-1000 nm. For example, nano-micron-sized calcium carbonate and nano-sized silicon dioxide can be used.

[0021] In the raw materials of the drilling cementitious wall-consolidating agent of this invention, the total mass fraction of calcium carbonate and silica is 25-65 parts, preferably 35-50 parts. In this invention, the calcium carbonate and silica can seal the pores of sandstone and mudstone, thereby reducing filtration loss, strengthening the wellbore, and lowering product costs. This invention does not impose any special restrictions on the proportion and source of the calcium carbonate and silica; commercially available products well known to those skilled in the art can be used. The mass ratio of nano-micron grade calcium carbonate to nano-silica can be 1-2:2.2.

[0022] In this invention, the drilling cementing and wall-stabilizing agent enters the pores or microfractures of shale and sandstone formations as the newly exposed formation is exposed or due to drilling pressure differential. Calcium carbonate and silica bridge at narrow pore or fracture points to form a sealing layer. The thermoplastic resin softens under formation temperature and then polymerizes with a curing agent to solidify, further filling, accumulating, and cementing the formation microfractures, micropores, and sealing layer. This improves the strength of the near-wellbore formation rock and creates a denser filter cake, effectively preventing drilling fluid and its filtrate from invading the formation. Through the synergistic effect of sealing and cementation, the wellbore is strengthened, its pressure-bearing capacity is improved, and it has a good anti-collapse effect.

[0023] Another objective of this invention is to provide an application process for a drilling cementing wall stabilizing agent, which uses the aforementioned drilling cementing wall stabilizing agent to perform drilling wall stabilization and drilling slug wall stabilization.

[0024] The application process of this invention consists of a drilling wall stabilization application process and a drilling slug wall stabilization application process; wherein, the drilling wall stabilization application process is achieved by the following technical measures: 50 to 100 meters before encountering easily unstable sandstone and mudstone formations, the drilling fluid properties are adjusted and a specified amount of the drilling cementing wall stabilizing agent is added according to the drilling fluid system and formation characteristics.

[0025] In embodiments of the present invention, the drilling fluid system is a brine drilling fluid system or an oil-based drilling fluid system, preferably a drilling fluid system containing 15 wt% to saturated sodium chloride (NaCl), a white oil-based drilling fluid system, or a diesel-based drilling fluid system; the density of the drilling fluid system is preferably 1.1 g / cm³. 3 ~1.8g / cm 3 .

[0026] In embodiments of the present invention, the amount of wall-stabilizing agent added during drilling, based on the drilling fluid system and formation characteristics, is 3% to 10% of the drilling fluid volume. For example, in a 100m... 3 Add 3% to the drilling fluid, which is equivalent to adding 3 tons of drilling cementitious wall-stabilizing agent (the same applies below). More preferably, it is 1.1 g / cm³. 3 ~1.3g / cm 3 The addition amount is 3% at the drilling fluid density; at 1.3 g / cm³ 3 ~1.6g / cm 3 Drilling fluid density is low and leakage velocity is <5m 3 The addition rate in the formation is 5% per hour, with a leakage velocity of 5 m / h. 3 / h~10m 3 The addition amount in the formation was 7% at 1.6 g / cm³. 3 ~1.8g / cm 3 Drilling fluid density is low, and permeability loss and leakage rate are <5m. 3 The addition rate in the formation is 7% per hour, with a leakage velocity of 5 m / h. 3 / h~10m 3 The addition rate in the formation is 10% per hour; when drilling into sections with high formation pressure coefficients but requiring improved formation pressure bearing capacity, or in easily collapsible sandstone or mudstone formations, the leakage rate is 10 m / s. 3 / h~15m 3 The addition amount in the formation is 10% per hour.

[0027] In embodiments of the present invention, the drilling fluid wall-stabilizing process is achieved through the following technical measures: When drilling fluid density needs to be increased in easily leaking or collapsible shale formations, 3%–5% of a drilling fluid wall-stabilizing agent is first added to the entire well. Then, the flow rate is increased to 1–1.5 times the normal rate to circulate and flush the wellbore, clean the wellbore, and check for leaks. After the drilling fluid circulation is uniform and there is no leakage, the flow rate is reduced to 0.6–0.8 times the normal rate to increase the density, controlling the density increase per cycle to not exceed 0.02 g / cm³. 3For every 0.06 g / cm 3 The process is repeated once a week, using the density-increasing pressure difference to gradually compact the mud cake, cement the formation, and stabilize the wellbore, allowing the formation to gradually adapt to changes in wellbore pressure; the above steps are repeated until the density reaches the design value.

[0028] When drilling encountered a formation where collapse and leakage coexisted (leakage velocity 10m / s), 3 / h~15m 3 / h), a certain volume of high-concentration slug wall-stabilizing slurry (hereinafter referred to as slug) is pumped in. When the slug emerges from the drill string water front, the flow rate is increased to 1 to 1.5 times the normal rate. After pumping and displacing, the drill string is pulled out to 100m to 150m above the slug. Depending on the downhole conditions, the flow rate is gradually increased to 1 to 1.5 times the normal rate and circulated for 2 weeks. The drill string is then run down to the bottom of the well in sections, and the flow rate is reduced (to ensure no leakage). Drilling is attempted using the high-concentration slug. If the downhole conditions are normal, normal flow rate is resumed after 1 to 2 days. If the conditions are still abnormal, the concentration of the slug wall-stabilizing slurry is increased, and the slug is injected repeatedly. After drilling through the unstable formation, the wellbore retention layer and loose mud cake are destroyed by short trips and high-flow-rate circulation. The slug is then pumped in again to improve formation stability.

[0029] In the above embodiment, the high-concentration drilling slurry formulation is: well slurry + 8% to 15% drilling cementing agent.

[0030] Furthermore, the pumping volume of the high-concentration wall-stabilizing slurry in the drilling section is the wellbore volume of the unstable formation plus 3m³. 3 ~5m 3 .

[0031] Compared with existing technologies, the beneficial effects of this invention include: the drilling cementing wall-stabilizing agent provided by this invention can seal the wellbore while drilling, eliminating the need for tripping in and out of the drill string. The construction process is simple, and it is applicable to both brine and oil-based drilling fluid systems, covering a wide range of drilling fluid systems. The drilling cementing wall-stabilizing agent provided by this invention can cement sandstone and mudstone formations, improving their pressure-bearing capacity. Through the synergistic sealing effect of calcium carbonate and silica, it reduces filtration loss, improves wellbore stability, and enhances the safety and efficiency of drilling operations. This wall-stabilizing agent uses abundant raw materials, has a simple and safe composition and preparation process, and is inexpensive, facilitating large-scale production and application. Attached Figure Description

[0032] Figure 1 is a comparison diagram of mud cakes #4 and #6 in an embodiment of the present invention;

[0033] Figure 2 is a graph showing the performance evaluation of the bonded wall consolidation in an embodiment of the present invention. Detailed Implementation

[0034] The technical content disclosed in this invention will be clearly and completely described below with reference to the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] This invention discloses a simple-to-operate, low-cost drilling cementing and wall-stabilizing agent, its preparation method, and application process. This technology can solve the wellbore instability problem in sandstone and mudstone long open-hole multi-pressure formations, cement sandstone and mudstone, improve the formation's pressure-bearing capacity, operate safely and efficiently, and has good economic benefits, making it suitable for widespread application.

[0036] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0037] In the following examples and comparative examples, the thermoplastic resins used are in powder form at room temperature and pressure. The degree of polymerization of the thermoplastic phenolic resin is 4–12, and the thermoplastic epoxy resin is type E42. The nano-micron-sized calcium carbonate particles have a diameter of 150–1000 nm, and the nano-silica particles have a diameter of 20–60 nm. The polyamide is type DJ2421H. There are no special restrictions on the source of the above raw materials; commercially available products well-known to those skilled in the art can be used.

[0038] Example 1

[0039] The wall-fixing agent is prepared by uniformly mixing 60 kg of thermoplastic phenolic resin, 10 kg of hexamethylenetetramine, 20 kg of nano-micron-sized calcium carbonate, and 10 kg of nano-silica.

[0040] Example 2

[0041] The wall-fixing agent is prepared by uniformly mixing 50 kg of thermoplastic epoxy resin, 8 kg of polyamide, 20 kg of nano-micron-sized calcium carbonate, and 22 kg of nano-silica.

[0042] Example 3

[0043] The wall-fixing agent is prepared by uniformly mixing 45 kg of thermoplastic phenolic resin, 10 kg of thermoplastic epoxy resin, 5 kg of polyamide, 10 kg of hexamethylenetetramine, 10 kg of nano-micron-sized calcium carbonate, and 20 kg of nano-silica.

[0044] Comparative Example 1

[0045] 50 kg of nano-micron grade calcium carbonate and 50 kg of nano-silica were uniformly mixed together to obtain inorganic powder.

[0046] Comparative Example 2

[0047] 80 kg of thermoplastic phenolic resin and 20 kg of hexamethylenetetramine were mixed evenly to obtain the resin material.

[0048] Comparative Example 3

[0049] 60 kg of thermoplastic phenolic resin, 20 kg of thermoplastic epoxy resin, 5 kg of polyamide, and 15 kg of hexamethylenetetramine were mixed evenly to obtain the resin material.

[0050] Performance Evaluation

[0051] The LV-CMC used was low-viscosity carboxymethyl cellulose sodium salt, purchased from Hengda Hydrocolloids Taizhou Co., Ltd.; SMP was sulfonyl methyl phenolic resin for drilling fluid, purchased from Henan Desheng Drilling Fluid Technology Co., Ltd.; SMC was sulfonated lignite, purchased from Shandong Zhengyang New Material Technology Co., Ltd.; NaOH was sodium hydroxide, purchased from Nanyang Boya Fine Chemical Co., Ltd.; the density of barite was 4.2 g / cm³. 3 The following materials were purchased from Henan Aotai Chemical Co., Ltd.: CaO (calcium oxide) was purchased from Puyang Zhongyuan Sanli Industrial Co., Ltd.; bentonite was purchased from Lingshou Yuchuan Mineral Products Co., Ltd.; CaCl2 (calcium chloride) was purchased from Puyang Jintai Chemical Co., Ltd.; and the integrated emulsifier and oil-based drilling fluid asphalt resin filtration reducer were provided by the Drilling Engineering Technology Research Institute of Zhongyuan Petroleum Engineering Co., Ltd.

[0052] (1) Evaluation of sealing performance

[0053] Evaluation methods: Saltwater drilling fluid was prepared and evaluated in accordance with "GBT 16783.1-2014 Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 1: Water-based Drilling Fluids"; oil-based drilling fluid was prepared and evaluated in accordance with "GBT 16783.2-2012 Field Testing of Drilling Fluids for Petroleum and Natural Gas Industry - Part 2: Oil-based Drilling Fluids".

[0054] According to the formulation shown in Table 1, the compatibility and plugging performance of the drilling cementing wall stabilizer in brine and oil-based drilling fluids of different densities were investigated. The results showed that after adding the drilling cementing wall stabilizer of this invention, the apparent viscosity AV, plastic viscosity PV, and dynamic shear force YP of the drilling fluid did not change significantly, indicating that the drilling cementing wall stabilizer has good compatibility with the drilling fluid and meets the requirements of drilling.

[0055] Compared to the comparative examples (numbers 1#, 2#, 4#, 5#, 7#, and 8#), the high-temperature and high-pressure fluid loss (HTHP) of different drilling fluid systems after adding drilling cementitious wall-stabilizing agents (numbers 3#, 6#, and 9#) was significantly different. 120℃The density of the mud cake is significantly reduced, resulting in a substantial improvement in its compactness (see Figure 1). This enhanced sealing performance helps reduce the amount of filtrate entering the formation, thus maintaining the stability of the shale. In Figure 1, the left side shows mud cake #4, and the right side shows mud cake #6, which exhibits even higher compactness.

[0056] Table 1. Effect of sealing agent dosage on drilling fluid properties

[0057]

[0058] Saltwater drilling fluid formulation: 4% bentonite + 0.3% LV-CMC + 4% SMP + 4% SMC + 0.3% NaOH + 15% NaCl + barite;

[0059] Oil-based drilling fluid formulation: 240mL 0 # Diesel fuel + 4% integrated emulsifier + 60g CaCl2 aqueous solution + 2% CaO + 1% oil-based drilling fluid, asphalt resin, filtration loss reducer + barite.

[0060] (2) Evaluation of the bonding and wall-consolidation capabilities of different types of leaky layers

[0061] Evaluation method: River sand of different particle sizes was used to simulate the leakage layer, with 60-90 mesh sand simulating permeable leakage, i.e., leakage velocity <5m / s. 3 / h; 40-60 mesh sand simulates small-scale leakage, i.e., leakage velocity of 5-10m / h. 3 / h; 20-40 mesh sand simulates medium-sized leakage, i.e., leakage velocity of 10-15m / h. 3 / h; at 1.5g / cm 3 5% of Example 1 and 5% of Comparative Example 1 were added to brine drilling fluid to obtain experimental sample slurries, and their cementing and wall-consolidation properties were investigated. On a Type 71 high-temperature and high-pressure filter press, a filter screen was first placed inside the filter press, followed by the addition of 100g of river sand of different particle sizes, leveling the surface as much as possible. Then, the experimental sample slurry was slowly and evenly added along the wall of the press. The press was cured at 100℃ / 4.2MPa for 30 minutes to investigate its ability to bind river sand of different particle sizes.

[0062] The results show that after adding Comparative Example 1, sand particles of different sizes remained loose and had no cementing effect. Adding the drilling cementing agent from Example 1 could bind loose sand of different particle sizes (20–90 mesh) into a cohesive whole, exhibiting a certain compressive strength, as shown in Figure 2. Figure 2 shows the cementing and wall-consolidation conditions for 60–90 mesh, 40–60 mesh, and 20–40 mesh particles, respectively.

[0063] (3) Comprehensive performance evaluation

[0064] Evaluation method: On a visual medium-pressure sand bed filtration analyzer, fill the drilling fluid cup with 40-60 mesh sand to the 350mL mark, slowly pour in 200mL of sample slurry as shown in Table 2, tighten the cup lid, connect the air source, slowly adjust the pressure to 0.7MPa, open the vent valve, maintain for 30min, measure the volume of filtrate in the graduated cylinder, or read and record the depth of filtrate penetration into the sand layer. After completing the first step of the experiment, remove the portion of filtrate that has penetrated the sand layer, seal it, and cure it in a 90℃ water bath for 24h and 72h. After cooling to room temperature, test the bonding and curing strength using a servo pressure testing machine.

[0065] The results in Table 2 indicate that serial numbers 5#, 6#, and 7#... # As a single inorganic physical sealing material, it has low pressure resistance, large leakage, and no bonding ability; No. 8 and No. 9 are single-component resin and curing agent, with weak sealing ability and limited improvement in bonding ability. Considering that their prices generally exceed 15,000 yuan / ton, the overall economic benefits are poor.

[0066] After adding the drilling cementing and wall-stabilizing agent of the present invention, the pressure bearing capacity of the sand bed and the ability to prevent filtrate intrusion are significantly improved due to the synergistic effect of multiple components. At the same time, after the filtrate intrudes into the sand layer, a cementing and solidification reaction occurs, and the reaction continues over time. This feature is conducive to gradually strengthening the well wall, improving the formation pressure bearing capacity, and creating favorable conditions for subsequent density increase, cementing, etc.

[0067] Table 2 Comparison and Evaluation of Plugging and Solidification Performance

[0068]

[0069] Saltwater drilling fluid formulation: 4% bentonite + 0.3% LV-CMC + 4% SMP + 4% SMC + 0.3% NaOH + 15% NaCl + barite.

[0070] The above experiments demonstrate that the drilling cementing and wall-stabilizing agent of the present invention has a synergistic effect of plugging and cementing, which is beneficial to stabilizing the wellbore and improving the formation's pressure-bearing capacity, thus solving the problem of wellbore instability in sandstone and mudstone formations. In particular, it can solve the problem of the difficulty in maintaining wellbore stability in long open-hole, multi-pressure formations where the drilling fluid density is designed according to the formation pore pressure.

[0071] Application Example 1

[0072] Well TSX is an exploratory well deployed by CNPC on the southeastern slope of the Sichuan Basin's central ancient uplift, targeting the Maokou Formation. The designed well depth is 4688m. The second section, a 311.2mm section, used a 1.5g / cm³ wellbore. 3 The composite salt drilling fluid was used to open the artesian well, which is mainly composed of sandstone and mudstone. This formation is characterized by low pressure, well-developed microfractures, and is prone to inducing leakage. The lower part needs to be densified to 1.6 g / cm³.3 Only by balancing the gypsum layer and the stabilized gas layer at Leikoupo can the contradiction of leakage and overflow become prominent.

[0073] To address this complex situation, a combination of drilling wall stabilization and drilling slugging wall stabilization was adopted. The specific implementation method is as follows: At 1450m (52m from the Ziliu well), 5% of the drilling cementitious wall stabilizing agent described in Example 1 was added once according to the well slurry volume to improve the formation's pressure-bearing capacity and widen the safe density window. No leakage occurred after drilling through the Ziliu well group. After using the drilling slugging wall stabilization process (well slurry + 10% drilling cementitious wall stabilizing agent) to consolidate the wellbore and improve the formation's pressure-bearing capacity, the density was gradually increased to 1.6 g / cm³ using the drilling slugging wall stabilization process. 3 The drilling fluid was maintained at this density until completion at a depth of 2921m, with no loss of fluid or overflow occurring downhole. In contrast, the adjacent TSX well, due to its narrow safety density window, experienced a loss of 1380.45m³ of drilling fluid due to loss of fluid and overflow. 3 It took 23.28 days to complete, and the application effect was significant.

[0074] Application Example 2

[0075] Well HYX-XHF is a horizontal shale gas well deployed by Sinopec in the Jiannan structure of the Shizhu syncline in the eastern Sichuan Basin's high-steep fold belt. It is a key appraisal well with a designed depth of 5520m. The target layer, Wujiaping, is black siliceous mudstone and shale with well-developed local fractures and a high degree of fragmentation. The well has a 215.9mm borehole diameter and uses a density of 1.45g / cm³. 3 The oil-based drilling fluid experienced leakage at a depth of 4100m, with a leakage rate of 10m / s. 3 / h, after multiple attempts at plugging the leak were unsatisfactory, the density was reduced to 1.40 g / cm³ to mitigate the leakage. 3 Adding 6% of the lost circulation fluid plugging agent while drilling resumed drilling. However, due to the narrow drilling fluid density window, it was impossible to maintain wellbore stability by increasing the density (adjacent well density 1.47 g / cm³). 3 To prevent rockfalls, rockfalls gradually increased in the 4200-4345m section during subsequent drilling, making normal construction impossible.

[0076] Therefore, a drilling slug wall consolidation process was adopted, incorporating 5% of the drilling cementing agent described in Example 3, and gradually increasing the density to 1.47 g / cm³ according to process requirements. 3 After one week of circulation, no downhole leakage was observed, and no new blockages appeared after circulation and cleaning of the wellbore. Subsequently, the well fluid was maintained at a 5% content of drilling cementitious filler, and this density was maintained until the completion depth of 5435m, without any well leakage or well collapse. Completion logging showed that the average wellbore enlargement rate was 15.26% in the 4200m–4354m section and 6.32% in the 4355m–5434m section, indicating good anti-collapse effect. Simultaneously, after adding the drilling cementitious filler, the oil-based drilling fluid loss decreased from 0.12m³ / min. 3 / m decreased to 0.075m 3 / m, significantly reducing filtration loss.

[0077] As can be seen from the above embodiments, the preparation method of the drilling cementing wall stabilizing agent provided by the present invention can be as follows: thermoplastic resin, curing agent, and inorganic powder are mixed evenly at room temperature and pressure in a certain proportion. The present invention also provides the application process of the drilling cementing wall stabilizing agent, including: suitable drilling fluid system and dosage and construction process under different formation porosity and different working conditions. The drilling cementing wall stabilizing agent has a simple and safe material composition and production process, low material cost, and is convenient for large-scale production and application; this product can not only seal pores and reduce filtration loss, but also cement sandstone and mudstone formations to improve the formation pressure bearing capacity, thereby achieving the purpose of stabilizing the wellbore and facilitating field application.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A drilling-while-drilling cementitious wall-stabilizing agent, characterized in that, It is made from the following raw materials in parts by weight: 35-65 parts thermoplastic resin, 5-15 parts curing agent and 25-65 parts inorganic powder; wherein the inorganic powder is calcium carbonate and silicon dioxide; wherein the calcium carbonate has a particle size of 150-1000 nm and the silicon dioxide has a particle size of 20-60 nm; wherein the thermoplastic resin is thermoplastic phenolic resin and the curing agent is hexamethylenetetramine; or, wherein the thermoplastic resin is thermoplastic epoxy resin and the curing agent is polyamide; or, wherein the thermoplastic resin is thermoplastic phenolic resin and thermoplastic epoxy resin and the curing agent is hexamethylenetetramine and polyamide.

2. The drilling cementing and wall-stabilizing agent according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 45-60 parts thermoplastic resin, 8-12 parts curing agent and 35-50 parts inorganic powder.

3. A method for preparing a drilling-while-drilling cementitious wall-consolidating agent, characterized in that, include: A drilling cementitious wall-consolidating agent is obtained by mixing 35-65 parts by weight of thermoplastic resin, 5-15 parts by weight of curing agent, and 25-65 parts by weight of inorganic powder; wherein the inorganic powder is calcium carbonate and silicon dioxide; wherein the calcium carbonate has a particle size of 150-1000 nm and the silicon dioxide has a particle size of 20-60 nm; wherein the thermoplastic resin is thermoplastic phenolic resin and the curing agent is hexamethylenetetramine; or, wherein the thermoplastic resin is thermoplastic epoxy resin and the curing agent is polyamide; or, wherein the thermoplastic resin is thermoplastic phenolic resin and thermoplastic epoxy resin, and the curing agent is hexamethylenetetramine and polyamide.

4. An application process for a drilling-while-drilling cementitious wall stabilizing agent, characterized in that, The drilling cementing and wall-stabilizing agent according to any one of claims 1-2 is used for drilling wall stabilization and drilling slug wall stabilization.

5. The application process according to claim 4, characterized in that, The drilling wall stabilization process includes: adjusting the drilling fluid properties and adding a specified amount of the drilling cementing agent according to the drilling fluid system and formation characteristics 50-100 meters before encountering easily unstable sandstone and mudstone formations.

6. The application process according to claim 5, characterized in that, The drilling fluid system is either a brine drilling fluid system or an oil-based drilling fluid system.

7. The application process according to claim 6, characterized in that, The drilling fluid is a drilling fluid system containing 15% to saturated NaCl, a white oil-based drilling fluid system, or a diesel-based drilling fluid system.

8. The application process according to claim 7, characterized in that, The density of the drilling fluid system is 1.1 g / cm³. 3 ~1.8g / cm 3 .

9. The application process according to claim 5, characterized in that, The amount of wall-stabilizing agent added during drilling, depending on the drilling fluid system and formation characteristics, is 3% to 10%.

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