Low-cost biopolymer drilling fluid tackifying and shear strength improving agent and application thereof
By compounding xanthan gum, sodium carboxymethyl cellulose, sodium silicate, and rutile powder, a ternary synergistic structure was constructed, which solved the problem of insufficient viscosity and shear force of drilling fluid at high temperatures, achieving low-cost and efficient viscosity enhancement and shear force improvement, and improving the suspension and wellbore stability of drilling fluid.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-19
- Publication Date
- 2026-03-27
AI Technical Summary
Existing drilling fluid thickeners and shear enhancers, such as xanthan gum, are expensive, have poor stability at high temperatures, and are poorly controlled for filtration loss, which affects drilling efficiency and economy.
A compound of xanthan gum, sodium carboxymethyl cellulose, sodium silicate, and rutile powder is used to form a ternary synergistic structure. Through chemical cross-linking and physical reinforcement, the viscosity, shear stress, and filtration loss control of drilling fluid are improved.
It maintains excellent viscosity and shear strength at high temperatures, significantly reduces filtration loss, lowers costs, and improves the suspension performance and wellbore stability of drilling fluids.
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Abstract
Description
Technical Field
[0001] This invention pertains to oilfield chemical products, and in particular relates to a low-cost biopolymer drilling fluid thickener and cutting agent and its application. Background Technology
[0002] To accelerate the efficient exploitation of oil and gas resources, improving both quality and speed has become a key technical focus in the drilling process of major oilfields. One way to achieve this goal is to use low-solids or solids-free drilling fluids during drilling. These fluids do not cause blockage or damage to the bottom hole space and equipment, resulting in higher drilling efficiency. While low-solids and solids-free drilling fluids can achieve rapid drilling, they have drawbacks in terms of rock carrying capacity and wellbore stability. Therefore, when using them, corresponding measures must be taken to improve the viscosity shear stress and inhibition performance of the drilling fluid system, reduce its leakage, and thus ensure stable drilling. For this purpose, viscosity enhancers and shear stress improvers need to be added to the drilling fluid. Common examples include biopolymers, synthetic copolymers, and organic / inorganic nanomaterials. Among these, biopolymers have advantages such as being environmentally friendly, having excellent viscosity-enhancing effects, and good salt resistance, and have a wide range of applications. Starch, cellulose, and xanthan gum are currently the main biopolymers used in drilling fluids. Among them, xanthan gum, due to its good room temperature rheological properties and superior shear dilution and thickening / shear-lifting properties, has been used by many oilfields as a thickening / shear-lifting agent in brine low-solids drilling fluid systems in recent years, achieving goals such as rapid drilling, wellbore stability, and significantly improved oil recovery.
[0003] However, although drilling fluid systems using xanthan gum as a thickener have excellent rock-carrying and suspension properties, on the one hand, due to the high production cost of xanthan gum, with an average market price of around 20,000 yuan / ton and a common addition ratio of 0.6%-1.0%, the addition cost is between 120-200 yuan / ton of drilling fluid. This makes the drilling fluid addition cost too high, which is not conducive to the economics of drilling and also limits the application of such drilling fluids to a certain extent. On the other hand, xanthan gum and sodium carboxymethyl cellulose are known thickening technologies in this field. Xanthan gum provides a three-dimensional network skeleton, giving the fluid good pseudoplasticity; sodium carboxymethyl cellulose fills and densifies the network, assisting in thickening and controlling filtration loss. However, this pure polymer network has inherent defects: (1) the thermal motion of molecular chains intensifies at high temperatures, the hydrogen bonding effect weakens, resulting in a loose network structure and a sharp decrease in viscosity shear force; (2) the formed filter cake is not tough enough and is easily crushed under high pressure differential, and the filtration loss is unstable; (3) the ability to build static shear force for suspended drill cuttings, especially after high-temperature aging, still has room for improvement. Existing technologies have not effectively solved these problems.
[0004] Furthermore, the shortcomings of existing pure polymers or simple compounded thickeners in terms of high-temperature stability, shear stress retention, and filtration loss control paved the way for the necessity of proposing this invention.
[0005] Therefore, this invention provides a low-cost biopolymer drilling fluid viscosity enhancer and cutting agent that achieves viscosity enhancement and cutting efficiency while effectively reducing costs. Summary of the Invention
[0006] The present invention aims to overcome the shortcomings of the prior art and provide a low-cost biopolymer drilling fluid viscosity enhancer and shear strength agent and its application. This biopolymer drilling fluid viscosity enhancer and shear strength agent can effectively improve the viscosity and shear strength of drilling fluid, enabling low-solids or solid-free drilling fluids to have good suspension performance, while reducing the cost of existing biopolymer viscosity enhancers and shear strength agents.
[0007] The present invention provides a low-cost biopolymer drilling fluid thickener and shearing agent, which is made from the following components in weight percentage: xanthan gum 35% to 55%, sodium carboxymethyl cellulose 10% to 30%, sodium silicate 10% to 45%, and rutile powder 5% to 26%.
[0008] As a further modification of the present invention, the cutting agent is a white solid powder with a particle size of 3000-5000 mesh.
[0009] As a further improvement of the present invention, the cutting agent is applicable to drilling fluid systems with a temperature below 120°C.
[0010] The above-mentioned low-cost biopolymer drilling fluid thickener and shearing agent is applied to the drilling fluid formulation system. It is made by mixing the following components in weight percentage: shearing agent 0.5%~1.0%, slab mud 0.5~1.5%, sodium hydroxide 0.1~0.2%, PAC-LV 0.3~1%, emulsion macromolecule 0.3~1%, amine inhibitor 0.3~1%, KCl 3~8%, and the balance is water.
[0011] The biopolymer drilling fluid thickener and shear-lifting agent provided by this invention is a compound of xanthan gum, sodium carboxymethyl cellulose, sodium silicate, and rutile powder. Its thickening and shear-lifting properties stem from the unique and synergistic mechanism of action of each component, which is described in detail below: 1. Xanthan gum – Constructing the framework of a three-dimensional network structure: Xanthan gum, as a core thickener, has long-chain polysaccharide molecules that intertwine with each other in aqueous solution through hydrogen bonds and van der Waals forces, forming a rigid, ordered three-dimensional network structure. This structure efficiently binds and fixes a large amount of free water, transforming the system from a solution state to a stable gel structure, thereby providing the basic viscosity and dynamic plasticity ratio required by the drilling fluid. More importantly, the molecular structure of xanthan gum endows the fluid with excellent pseudoplasticity, meaning that under high shear (such as at the drill bit water inlet), the viscosity rapidly decreases to reduce pump pressure loss, while under low shear (such as in the annular quiescent region), it can quickly recover high viscosity, thus effectively suspending and carrying drill cuttings. 2. Sodium carboxymethyl cellulose – enhances network density and filtration loss control: Sodium carboxymethyl cellulose, as a linear polymer, has molecular chains that can permeate and interweave within the three-dimensional network constructed by xanthan gum. On one hand, the carboxymethyl anionic groups on its molecular chains form a hydration layer through hydration, increasing the hydrodynamic volume of the molecular chains and further enhancing the system viscosity through interchain entanglement. On the other hand, it complements and interweaves with the xanthan gum molecular chains, effectively densifying the entire polymer network. This not only improves structural viscosity but, more importantly, forms a dense and tough filter cake on the wellbore, significantly reducing filtration loss, protecting the reservoir, and maintaining wellbore stability. 3. Sodium silicate – Enhanced in-situ reaction and synergistic wall stabilization: The addition of xanthan gum is one of the key innovations of this invention. In the alkaline environment of drilling fluid, it can slowly hydrolyze to generate silica sol and silicate ions. These active silica species can react with polyvalent cations (such as Ca²⁺ and Mg²⁺) in the formation, or interact with hydroxyl groups on the polymer chain under specific conditions, acting as an "in-situ crosslinking agent." This slight crosslinking effect can further enhance and stabilize the composite network structure constructed by xanthan gum and sodium carboxymethyl cellulose, thereby improving the high-temperature stability and structural strength of the system. Simultaneously, xanthan gum itself has good inhibitory and plugging properties, and can synergistically work with the polymer to plug formation micro-fractures, inhibit clay hydration and swelling, and further enhance wellbore stability. 4. Rutile powder – physical filler and synergistic shear enhancement: Rutile powder (mainly composed of TiO2), as an inert rigid particle with moderate density and high hardness, plays multiple roles in the system. First, these fine rigid particles can be uniformly dispersed in the polymer three-dimensional network, producing a physical filling and reinforcing effect. They hinder the free movement of polymer chain segments, increasing fluid flow resistance, thus significantly improving viscosity and shear stress, especially low-shear-rate (LSYP), and significantly enhancing wellbore cleaning capability. Second, the presence of rutile powder particles optimizes the quality of the filter cake, making it thinner and more robust, complementing the plugging effect of sodium silicate. Furthermore, its chemical inertness ensures compatibility with other components in the drilling fluid system.
[0012] This invention incorporates sodium silicate and rutile powder into the compound of xanthan gum and sodium carboxymethyl cellulose. The functions of sodium silicate and rutile powder are as follows: 1. This formula includes sodium silicate, which acts as a "chemical crosslinking and stabilizing agent," far exceeding the effects of conventional pH adjusters or inhibitors. The active silicic acid species generated by its hydrolysis in the alkaline environment of drilling fluid can undergo in-situ, controllable weak crosslinking reactions with the hydroxyl groups on the molecular chains of xanthan gum and sodium carboxymethyl cellulose. (1) Synergistic viscosity enhancement and shear strength mechanism: This crosslinking forms additional "anchor points" in the polymer three-dimensional network, significantly enhancing the rigidity and thermal stability of the network structure. This enables the composite system to maintain excellent viscosity and shear strength at high temperatures, effectively overcoming the thermal degradation defects of the pure xanthan gum system; (2) Synergistic wall stabilization mechanism: The hydrolysis products can react with calcium and magnesium ions in the formation and combine with clay minerals to form a dense and tough "composite sealing layer" with the filter cake, which greatly improves the quality of the filter cake and achieves ultra-low control of filtration loss. This is an effect that cannot be achieved by a single polymer or a simple binary compound. 2. Rutile powder is added to this formula. Its function as a "physical reinforcing and structural modifier" is not simply to increase weight or fill, but rather as a functional physical reinforcing particle: (1) Synergistic shear enhancement and suspension mechanism: The micro- and nano-sized rigid particles of rutile powder are uniformly dispersed and embedded in the polymer-silicone composite network, serving as numerous physical cross-linking points, which greatly hinders the slippage of polymer chain segments. This significantly improves the dynamic plasticity ratio and shear force at low shear rates (LSYP) of the system, thereby achieving superior suspension and carrying capacity for drill cuttings and weighting materials, effectively preventing wellbore cleaning problems; (2) Synergistic improvement of filter cake mechanism: These hard, fine particles, together with polymers and silica gel, participate in the formation of filter cake, optimize the particle size distribution of filter cake, make it more dense, wear-resistant and with extremely low permeability, and further synergistically reduce the filtration loss under high temperature and high pressure.
[0013] Compared with existing technologies, the technical solution of this application presents the following advantages: Existing technologies (such as those containing only xanthan gum and sodium carboxymethyl cellulose) can be considered as a "flexible polymer network," which inherently suffers from insufficient structural strength and performance degradation under harsh operating conditions (high temperature, high pressure). The technical solution of this application, however, constructs a novel ternary synergistic structure of "polymer-chemical crosslinking-physical reinforcement" by introducing sodium silicate and rutile powder. Xanthan gum / sodium carboxymethyl cellulose constitute the "skeleton" of the network. Sodium silicate acts as the "ligament," strengthening the connection between the skeleton and the skeleton through in-situ chemical crosslinking. Rutile powder acts as the "muscle," further consolidating and supporting the entire structure through physical filling. This multi-component, multi-mechanism synergistic effect enables the thickener and shear enhancer provided by this invention to not only exhibit excellent performance at room temperature, but more importantly, to maintain extremely high viscosity, shear strength, and excellent filtration control even after high-temperature aging.
[0014] This invention provides a low-cost biopolymer drilling fluid viscosity enhancer and shearing agent. By introducing sodium silicate and rutile powder, it achieves a profound synergistic effect with traditional polymers (xanthan gum and sodium carboxymethyl cellulose), providing a high-efficiency viscosity enhancer and shearing agent solution with performance far exceeding existing technologies, especially suitable for high-temperature deep well drilling. It solves the technical bottlenecks of single or binary polymer systems in terms of high-temperature stability, shearing force retention, and wellbore sealing performance. At the same time, the viscosity enhancer of this invention can simultaneously achieve multiple uses such as viscosity enhancement and shearing, filtration loss reduction, and improved sealing ability, which is not available in conventional viscosity enhancers such as xanthan gum / sodium carboxymethyl cellulose. In addition, this invention provides a low-cost biopolymer drilling fluid viscosity enhancer and shearing agent with the following beneficial effects: (1) The biopolymer drilling fluid viscosity enhancer and shearing agent provided by this invention can be directly added to water-based drilling fluid in appropriate amounts according to drilling requirements. It has good solubility and is easy to apply; (2) The biopolymer drilling fluid viscosity enhancer and shearing agent provided by this invention has a simple composition and reduced addition cost. Detailed Implementation
[0015] Example 1
[0016] The present invention discloses a low-cost biopolymer drilling fluid thickener and shearing agent, which is made from the following components in weight percentage: xanthan gum 35%, sodium carboxymethyl cellulose 30%, sodium silicate 30%, and rutile powder 5%. The drilling fluid formulation system prepared using the above-mentioned cutting agent is as follows: cutting agent 0.5%, slab soil 1.5%, sodium hydroxide 0.1%, PAC-LV 0.3%, emulsion macromolecule 0.3%, amine inhibitor 0.3%, KCl 3%, and the balance is water.
[0017] Example 2
[0018] The present invention provides a low-cost biopolymer drilling fluid thickener and shearing enhancer, which is made from the following components in weight percentage: 50% xanthan gum, 10% sodium carboxymethyl cellulose, 15% sodium silicate, and 25% rutile powder. The drilling fluid formulation system prepared using the above-mentioned cutting agent is as follows: cutting agent 1.0%, slab soil 0.5%, sodium hydroxide 0.2%, PAC-LV 1%, emulsion macromolecule 1%, amine inhibitor 1%, KCl 8%, and the balance is water.
[0019] Example 3
[0020] This invention discloses a low-cost biopolymer drilling fluid thickener and shearing agent, which is composed of xanthan gum, sodium carboxymethyl cellulose, sodium silicate, and rutile powder, with the following respective contents: xanthan gum 45%, sodium carboxymethyl cellulose 25%, sodium silicate 20%, and rutile powder 10%. During preparation, the above four raw materials are stirred and mixed evenly in a mixer according to their respective proportions. The resulting agent is then directly added to the drilling fluid according to the required dosage.
[0021] After the above materials are thoroughly mixed, they are added to the drilling fluid at a rate of 0.7% (by mass). The drilling fluid formula is as follows: 1% slab mud, 0.15% sodium hydroxide, 0.5% PAC-LV (polyanionic cellulose), 0.5% emulsion macromolecule (drilling fluid emulsion polymer coating agent, produced and sold by Puyang Dongsheng Petroleum Drilling and Production Technology Co., Ltd.), 0.5% amine inhibitor (produced and sold by Tianjin Xiongguan Technology Development Co., Ltd.), 5% KCl, and the balance water. The drilling fluid formula system is thus obtained. After being stirred evenly, it is aged at 80℃ for 16 hours. Then, the rheological and filtration loss properties of the drilling fluid are measured at 50℃. See Table 1. Table 1. Comparison of the thickening and cutting efficiency of the drilling fluid thickener and xanthan gum of the present invention with their respective costs.
[0022] As shown in Table 1, under the same dosage, the biopolymer thickener and cuttings-enhancing agent prepared in this invention significantly increases the shear force compared to xanthan gum used in the field. Specifically, the dynamic shear force increases by approximately 1.8 times, while the initial and final shear forces increase by 1.4 times and 1.5 times, respectively. This demonstrates that the biopolymer thickener and cuttings-enhancing agent prepared in this invention has a stronger ability to suspend cuttings in both dynamic and static states. Compared to xanthan gum used in the field, the addition of the biopolymer thickener and cuttings-enhancing agent prepared in this invention increases the apparent viscosity and plastic viscosity of the drilling fluid to some extent, but this increase is relatively small compared to the increase in shear force. This indicates that the biopolymer thickener and cuttings-enhancing agent of this invention does not increase the shear force by increasing the viscosity of the drilling fluid, thus promoting the advantage of low viscosity and high shear force in the drilling fluid. This ensures the drilling fluid has a good ability to suspend cuttings while avoiding the problem of increased drilling friction caused by excessive drilling fluid viscosity.
[0023] As can also be seen from Table 1, under the same dosage, the cost of the biopolymer thickener and cutting agent prepared by this invention is reduced by 29.3% compared with xanthan gum used on site, thus achieving the goal of reducing drilling costs.
[0024] The drilling fluid formulation system prepared in Example 3 was mixed evenly and aged at different temperatures for 16 hours. Then, its viscosity shear force was measured at 50°C. The experimental results are shown in Table 2. Table 2. Changes in rheological properties of drilling fluids with the drilling fluid thickener and shearing agent of this invention after aging at different temperatures.
[0025] Table 2 shows that when the aging temperature is below 120℃, the viscosity and shear stress of the drilling fluid gradually decrease with increasing aging temperature, while the dynamic-plastic ratio remains relatively stable. However, when the temperature exceeds 120℃, the viscosity and shear stress of the drilling fluid decrease rapidly, the dynamic-plastic ratio drops to 0.2, and the apparent viscosity value is below 30 mPa·s, which fails to meet the requirements for effective suspension of cuttings in the drilling fluid. This indicates that under high-temperature conditions, the molecular structure of the cutting agent changes, the molecular chains break, and the stability deteriorates, resulting in a poorer cutting effect on the drilling fluid. Therefore, the effective operating temperature of the drilling fluid viscosity-enhancing and cutting agent of this invention should not exceed 120℃.
[0026] Different mass fractions of NaCl were added to the drilling fluid (1% slurry, 0.15% sodium hydroxide, 0.5% PAC-LV, 0.5% emulsion macromolecule, 0.5% amine inhibitor, 5% KCl, and the balance water). After stirring for 30 min to ensure complete dissolution, 0.7% of the biopolymer thickener and shearing agent prepared in Example 3 was added, and the mixture was stirred again for 30 min. The drilling fluid was then placed in an aging tank and aged at 80°C for 16 h. The viscosity, shear force, and filtration loss at different NaCl contents were measured. The results are shown in Table 3. Table 3. Effects of adding the drilling fluid thickener and shearing agent of this invention on the rheological properties of drilling fluids with different NaCl contents.
[0027] As shown in Table 3, the biopolymer thickening and shearing agent prepared in this invention exhibits a thickening and viscous effect with increasing NaCl content; even at high salt concentrations, the system still maintains high viscosity and shear force. This is because the biopolymer thickening and shearing agent prepared in this invention contains a relatively high amount of CO, which reacts with NaCl... + The formation of a network complex increases the frictional force between particles, and the cementation of the macromolecular complex molecular chains also increases the structural viscosity, ultimately leading to an increase in viscous shear force. Therefore, the biopolymer thickener and shear enhancer prepared in this invention still exhibits good salt resistance at a salt concentration of 12%.
Claims
1. A low-cost biopolymer drilling fluid thickener and shearing enhancer, characterized in that... It is made from the following components in weight percentage: xanthan gum 35%–55%, sodium carboxymethyl cellulose 10%–30%, sodium silicate 10%–45%, and rutile powder 5%–26%.
2. The low-cost biopolymer drilling fluid thickener and cutting agent as described in claim 1, characterized in that... The cutting agent is a white solid powder with a particle size of 3000-5000 mesh.
3. The low-cost biopolymer drilling fluid thickener and cutting agent as described in claim 1, characterized in that... This cutting agent is suitable for use in drilling fluid systems with temperatures below 120°C.
4. The application of the low-cost biopolymer drilling fluid thickener and shear-enhancing agent according to claim 1 in a drilling fluid formulation system, characterized in that: Cutting agent 0.5%–1.0%, slab clay slurry 0.5%–1.5%, sodium hydroxide 0.1%–0.2%, PAC-LV 0.3%–1%, emulsion macromolecules 0.3%–1%, amine inhibitors 0.3%–1%, KCl 3%–8%, balance is water.