High-temperature Oil Research Articles

Numerical study on drag reduction and heat collection efficiency of oil based on solar concentrating system

Traditional onshore crude oil storage and transportation consumes a lot of energy. In this paper, a concentrating type of high-temperature crude oil transportation pipeline heating system is proposed, which uses concentrators to collect and focus sunlight on the pipeline. The high-temperature oil flows through the heat exchanger at the end of the pipeline, where it exchanges heat with water to store and recover heat for utilization in the heat collector. The temperature rise is significant and the uniformity improves as oil extends through the pipeline under various multiples of solar radiation achieved with concentrators. The inlet rate of oil is a negative factor affecting the outlet temperature. Compared to non-concentrated light, the friction coefficient and viscosity of oil are reduced, resulting in a more effective drag reduction effect. To validate the accuracy of simulation results and compare them with theoretical calculations, ensuring that the margin of error is within 8.5%. The type of concentrators, laying distance of the concentrators below the pipeline, concentration ratio (CR), and the inlet rate can be adjusted based on climatic conditions and required oil temperature. This paper is of great significance for reducing energy consumption in long-distance oil transportation and realizing the energy transition.

Experimental investigation on heat transfer characteristics and thermal optimization methods of the storage-type downhole visual tool

The storage-type downhole visual tool is a crucial device for monitoring the technical condition of the downhole tubing string. However, prolonged exposure to the high-temperature downhole environment leads to an increase in the internal temperature of the tool, causing instability in the operation of electronic devices. To address this issue, a thermal optimization scheme for the tool’s internal cavity has been proposed, combining a distributed lens structure with vacuum phase-change composite materials. An environmental-tool heat transfer model has been established to study the temperature rise characteristics during the entry stage (ES) and the operation stage (OS). Comparative analysis shows that this optimization scheme can effectively reduce the internal cavity temperature by 32.5 °C, a decrease of 41.7 %, during the entry stage. During the operation stage, the heat absorption by the composite phase-change material results in a 6.3 °C drop in the internal cavity temperature and a 30.1 °C reduction in the circuit board temperature. The model was validated through the high-temperature oil bath experiment, with the calculation results showing errors below 8 % compared to experimental results. Implementing this thermal optimization scheme in case wells ensures the tool’s continuous and stable operation for 6 h, with the internal cavity temperature maintained below 100 °C and the circuit board temperature kept within 140 °C. This significantly enhances the safety and stability of downhole electronic devices and provides guidance for the selection of temperature control strategies for downhole tools in high-temperature environments.

Modified guanidine gel fracturing fluid system and performance optimization for ultra-deep and ultra-high temperature oil and gas reservoirs

The development of deep high-temperature oil and gas reservoirs gives rise to a rise in reservoir temperature along with the depth of the oil reservoir, thereby imposing higher requirements on the heat resistance of fracturing fluid. Guar gum fracturing fluid has difficulty tolerating temperatures exceeding 160 °C, thereby demanding the development of corresponding cross-linking agents, temperature stabilizers, and other additives to enhance the thermal stability of the fracturing system. Considering the distinctive characteristics of deep and ultra-deep reservoirs, such as extreme burial depth (exceeding 6000 m), ultra-high temperature (higher than 160 °C), and high fracturing pressure, an experimental modification of a guar gum fracturing fluid system was carried out, specifically tailored for ultra-high temperatures. The experiment identified and selected individual agents for ultra-high temperature fracturing fluids, including crosslinking agents, thermal stabilizers, flowback aids, and clay inhibitors. Through rigorous experimentation, these key agents for an ultra-high temperature fracturing fluid system have been successfully developed, including the optimal thickener GBA1-2, crosslinking agent BA1-1, anti-swelling agent FB-1, and gel breaker TS-1. The evaluation of diverse additive dosages has facilitated the development of an optimal guar fracturing fluid system, which exhibits outstanding high-temperature resistance while minimizing damage and friction. The outcomes of our experiments indicate that even after subjecting our ultra-high temperature fracturing fluid to 2 h of shearing at 170 s−1 at 180 °C, its viscosity remained above 200 mPa s—a distinct proof of its superior performance in withstanding high temperatures. This achievement represents a substantial progress in providing a suitable fracturing fluid system for the transformation and stimulation of ultra-deep and ultra-high temperature reservoirs, and also lays a solid foundation for further exploration and application in related fields in the future.

Appropriate characterization of reservoir properties and investigation of their effect on microbial enhanced oil recovery through simulated laboratory studies

Appropriate characterization of reservoir properties and investigation of the effect of these properties on microbial metabolism and oil recovery under simulated reservoir conditions can aid in development of a sustainable microbial enhanced oil recovery (MEOR) process. Our present study has unveiled the promising potential of the hyperthermophilic archaeon, identified as Thermococcus petroboostus sp. nov. 101C5, to positively influence the microenvironment within simulated oil reservoirs, by producing significant amounts of metabolites, such as biosurfactants, biopolymers, biomass, acids, solvents, gases. These MEOR desired metabolites were found to cause a series of desirable changes in the physicochemical properties of crude oil and reservoir rocks, thereby enhancing oil recovery. Furthermore, our study demonstrated that the microbial activity of 101C5 led to the mobilization of crude oil, consequently resulting in enhanced production rates and increased efficiency in simulated sand pack trials. 101C5 exhibited considerable potential as a versatile microorganism for MEOR applications across diverse reservoir conditions, mediating significant light as well as heavy oil recovery from Berea/carbonaceous nature of rock bearing intergranular/vugular/fracture porosity at extreme reservoir conditions characterized by high temperature (80–101 °C) and high pressure (700–1300 psi). Core flood study, which truly mimicked the reservoir conditions demonstrated 29.5% incremental oil recovery by 101C5 action from Berea sandstone at 900 psi and 96 °C, underscoring the potential of strain 101C5 for application in the depleted high temperature oil wells.

Effects of slag on mechanical and microstructural properties of iron-rich phosphoaluminate cement subjected to high temperature oil well environment

Iron-rich phosphoaluminate cement (shortened as PAC) exhibits excellent high temperature resistance characteristic, enabling it to withstand the ultrahigh temperatures required for the in situ combustion (ISC) of heavy oil. The addition of slag could influence its high temperature resistance by altering its hydration products. Hence the thickening time, physical properties, phase components and microstructure of PAC with slag that were subjected to different high temperature environment (315, 550 and 800 °C) were investigated deeply in this paper. The experimental analysis results revealed that PAC had better high temperature resistance than CAC with and without slag. The addition of slag improved effectively the high temperature resistance of PAC. The influencing mechanism of slag were as follows. C2ASH8 formed at 50 °C inhibited the conversion of C(A,P)H10 to C3AH6. C2AS3H, C3AS2H2 and C3(Fe,Al)S3 formed at 315 °C alleviated the rapid release of the compound water. The phase Ca5(PO4)3OH and C2AS was stable in the range of 550–800 °C. In addition, the capillary pore structure of PAC was optimized. Therefore, PAC with slag had the potential to be used for high temperature oil well cementing.

Design and fabrication of PPTA-braid-reinforced PFA/GE hollow fiber composite membranes

Due to the effects of the rapid development of modern society and fresh water resource pollution, water shortage has further accelerated, which is becoming a very urgent problem. Herein, the poly (p-phenylene terephthalamide)-(PPTA-) braid-reinforced (PBR) poly(tetrafluoroethylene-co-perfluoropropylvinylether)/graphene (PFA/GE) hollow fiber composite membranes (HFCMs) were prepared by dipping coating-thermal sintering coupling technique with a green process. GE is an emerging type of two-dimensional functional nanoparticle with a tunable passageway for oil molecules. The influences of the GE concentration in the casting solution on the structure and performance of the PBR−PFA/GE HFCMs were investigated. The results showed that the addition of GE produced a finger-like pore structure suitable for oil channels. Meanwhile, the roughness and contact angle of the composite membrane increased accordingly, and the water contact angle increased from 115° to 120°. The permeation fluxes of kerosene also increased obviously with the increase of GE contents, and the maximum flux of M-3 reached as high as 217.66 L·m−2·h−1. The application of the lubricating oil flux test under working conditions of 60–150 °C has demonstrated the high-temperature oil permeability resistance of the composite membrane. Even after long-term use, its separation efficiency for water-in-oil emulsions still remains above 99.5 %. In addition, the membrane separation-efficiency both up to 99.9 % for activated carbon and silica dioxide (SiO2) in kerosene. Overall, the PBR-PFA/GE HFCMs with excellent lipophilicity presented great potential for oily wastewater treatment at high temperatures.

Safety evaluation of offshore oil and gas well string based on corrosion rate prediction

The combined effects of corrosion, temperature, and pressure can cause safety issues such as shortened lifespan and failure of offshore high temperature and high pressure oil and gas well strings. This paper focuses on a certain sea area and conducts experiments on CO2 corrosion of different string materials under different temperature and partial pressure conditions. Combined with the two-phase flow wellbore temperature and pressure-coupling model, a corrosion rate prediction model based on Back Propagation Neural Network optimized by Genetic Algorithm (GA-BPNN) is established for predicting corrosion rate along the wellbore depth. At the same time, based on the API 5C3 standard, considering the degradation effect of thermally induced metal string strength and the influence of environmental pressure, a safety evaluation model of offshore oil and gas well string based on corrosion rate prediction was established, and analysis of the change law of residual strength of the string and prediction of remaining life under the influence of different factors were carried out.

Magnetic smart polymer gel with directional plugging for conformance control in oil reservoirs

Polymer gel technology has been proven to be one of the most effective methods for conformance control and enhanced oil recovery. However, to effectively gel highly permeable layers, precise placement of the gelant within the formation is required. Herein, to make the most use of polymer gel in conformance control, a novel magnetic smart polymer gel consisting of polyacrylamide and Fe3O4@polyethylenimine, is designed and prepared as a conformance fluid to achieve directional plugging in target reservoirs. To deeper understanding of the properties of Fe3O4@polyethylenimine and smart gel, as well as how they are formed and function, the microstructure of these materials was characterized through various techniques, including analysis of their crystal and chemical structures, micromorphology, and cross-linking mechanism, et al. The rheological tests suggest that the system has good viscosity and elasticity, and the gel strength can reach 105,463 mPa⋅s after aging 30 days at 120 °C. Furthermore, the controlled manipulation indicated that smart gel can move quickly and repeatedly to a designated location under a magnetic field. Additionally, the influence of the magnetic generator on the intelligent plugging performance of the smart gel system is also explored. It has been found that magnetic plugging can extend the effective lifespan of smart gel. Finally, the conformance control performance of the smart gel system is revealed by the parallel cores flow experiment. This work presents a novel smart gel system designed for directional plugging, to enhance conformance control in high-temperature oil reservoirs.

Dynamic simulation of double-cased perforation in deepwater high temperature and high-pressure oil and gas wells

In order to ensure the penetrability of double-cased perforation in offshore oil and gas fields and to maximize the capacity of perforation completion, This study establishes a dynamic model of double-cased perforation using ANSYS/LS-DYNA simulation technology. The combination of critical perforation parameters for double casing is obtained by studying the influencing factors of the jet-forming process, perforation depth, diameter, and stress changes of the inner and outer casing. The single-target perforation experiments under high-temperature and high-pressure (HTHP) conditions and ground full-scale ring target perforation tests are designed to verify the accuracy of numerical simulation results. The reduced factor is adopted as the quantitative measure of perforation depth and diameter for different types of perforation charge under different conditions. The results show that the perforation depth reduction increases with temperature and pressure, and the reduced factor is between 0.67 and 0.87 under HTHP conditions of 130 °C/44 MPa and 137 °C/60 MPa. Comparing the results of the numerical simulation and the full-scale test correction, the maximum error is less than 8.91%, and this numerical simulation has strong reliability. This research provides a basis for a reasonable range of double-cased perforation parameters and their optimal selection.

Draft genome sequence of Dietzia sp. strain CH92 isolated from oil reservoir.

We report the draft genome sequence of Dietzia sp. strain CH92, isolated from a high temperature oil well in Baolige oilfield, China. The estimated genome is 3.73 Mb, with 3,479 protein-coding sequences.

A robust viscoelastic surfactant tolerating 20% HCl up to 150 °C for oil well stimulation

Viscoelastic surfactants (VES) are often used as viscous diverters in acidizing stimulation to prolong the acid consumption time and maximize zonal coverage of the acid for improving well productivity. However, the ceiling temperature of commercial VES cannot exceed 120 °C in practical use because of the poor thermal stability and fragile molecular structure, hindering their implementation in high-temperature oil reservoirs, i.e., ≥150 °C. Here we synthesized a novel C22-tailed diamine, N-erucaminopropyl-N,N-dimethylamine (EDPA), and examined comparatively its rheological behavior, assemblies morphology and molecular stability in 20 wt% HCl with a commercial VES, erucyl dimethyl amidopropyl betaine (EDAB). The feasibility of EDPA for acidizing stimulation was assessed by acid etching of carbonate rock with its HCl solution at 150 °C. Rheological results showed that the 2.5 wt% EDPA–20 wt% HCl solution maintains stable viscosity of 90 mPa s at 150 °C for 60 min, while that of 2.0 wt% EDAB HCl solution is just 1 mPa s under identical conditions. 1H NMR spectra and cryo-TEM observations revealed that the chemical structure and self-assembled architectures of EDPA remained intact in such context, but the EDAB suffered from degradation due to the hydrolysis of the amide group, accounting for the poor heat-resistance and acid-tolerance. The reaction rate of 2.5 wt% EDPA HCl solution with carbonate rock was one order of magnitude lower than that of 20 wt% HCl solution at 150 °C, underpinning the potential of EDPA to be used in the high-temperature reservoirs acidizing. This work improved the thermal tolerance of VES in highly concentrated HCl solution, paving a feasible way for the acidization of high-temperature reservoir environments (∼150 °C).

Tribo-dynamics analysis of engine small-end bearing under real temperature boundary conditions by a wireless in-situ measuring technology

Tribo-dynamics analysis of engine small-end bearings can help to find potential schemes to avoid seizure failure that is common in today's engines under heavy loads and high temperatures. The challenge lies in determining real temperature boundary conditions due to the combined effects of frictional heat and environmental sources. This study develops a new in-situ temperature measuring and wireless transmission system, implemented in a full-scale engine under various conditions. Combining simulation and experiment provides a comprehensive understanding of the difficult-to-measure oil temperature and tribo-dynamics behavior. Results show the test bearing upper part reaches 165 °C due to piston heat transfer. Simulated high-temperature oil aggregation on the lower edges corresponds nicely to oil overheating carbonization at the same locations of the test bearing.

Effect of hydroxy group activity on the hydrogel formation temperature of β-cyclodextrins and its application in profile control

In order to increase the gelling temperature of β-CD-based hydrogels and expand the application range of β-CD-based hydrogels in oil reservoirs, glycidyl ethers with different chain lengths were prepared for modification of β-CDs, and then the modified β-CD was chemically crosslinked with epichlorohydrin (EPI) to prepare hydrogels. Thus, the gelling temperature of β-CD hydrogels was successfully increased from 65 to 125 °C. FTIR, 1H NMR, XRD and DSC were used to investigate the mechanism of the changing of gelling temperature. The results showed that the long chain alkyl changed the electron cloud density on the β-CD ring, increased the difficulty of hydroxyl group leaving, thus increased the gel forming temperature. Furthermore, the swelling behavior and the core plugging performance of the gel were evaluated. The results indicated that the maximum swelling rate of modified β-CD gel was 75 %. The core displacement experiment showed that the plugging rate was greater than 95 %, the unplugging rate was greater than 90 %, and the maximum breakthrough pressure of water flooding reached 7.43 MPa. These results indicated the practical value of β-CD hydrogels in high temperature (60–125 °C) oil fields.

Effect of crosslinking agent dosage on the morphology and properties of thermoplastic vulcanizates based on hydrogenated acrylonitrile butadiene rubber and thermoplastic polyester elastomer

This work aims to develop heat- and oil-resistant thermoplastic vulcanizates (TPVs) based on hydrogenated acrylonitrile butadiene rubber (HNBR) and thermoplastic polyester elastomer (TPEE) using dynamic vulcanization and following a masterbatch procedure. It focuses on the effect of the cross-linking agent dosage on the morphology and properties of HNBR/TPEE-TPVs. An increase in the peroxide dosage yields a higher cross-linking degree of the HNBR, a smaller size and a more uniform distribution of the HNBR domains, and a stronger rubber network. Consequently, the elasticity and high-temperature oil resistance of the TPV increases, but its flowability in the molten state, tensile properties, and heat resistance decrease. It turns out that a peroxide dosage of 1.5 phr is preferred for the preparation of HNBR/TPEE-TPV under the specified processing conditions to achieve a more comprehensive TPV performance.

Design and numerical study of active cooling system of measurement while drilling for high temperature based on supersonic

Measurement while drilling (MWD) plays an important role in controlling well trajectory, improving drilling efficiency and saving drilling cost. In recent years, a large number of high-temperature wells have appeared, which makes the traditional MWD instruments no longer applicable. So far, no active cooling method has been successfully applied to MWD instruments for high-temperature oil and gas wells. This paper presents a new active cooling method for air drilling by utilizing the throttling and cooling of drilling gas, and the cooling system is designed. An axisymmetric numerical model of internal fluid is established, and different drilling gas flow channel design methods are discussed. The research results indicate that the wall temperature of the cooling section is much higher than the center fluid temperature, but lower than the ambient temperature, and can be used for active cooling of downhole drilling instruments. Compared with other design methods, the supersonic nozzle designed using the Bezier method has better parallelism of the gas in cooling section. The diffusion capability of straight wall diffuser is better than that of curved wall diffuser, and it can withstand greater back pressure. For straight wall diffuser, increasing the throat length and reducing the contraction and expansion angle can improve the diffusion capacity, but they also lead to a longer diffuser.

The Properties of Modified Bagasse Fiber/Nano-TiO2 Composite Asphalt in a High-Temperature and High-Humidity Salt Environment.

The southern tropical coastal areas of China are high-temperature and high-humidity salt environments, which hinder the durability and service life of ordinary asphalt pavement. To enhance the durability of asphalt pavement in these areas, modified bagasse fiber combined with nano-TiO2 was used to improve the corrosion resistance of asphalt pavement in high-temperature and high-humidity salt environments. The micro-morphology, high-temperature oil absorption, high-temperature heat resistance, and hygroscopicity of bagasse fiber modified using three silane coupling agents combined with NaOH were compared, and the best silane coupling agent/NaOH modification scheme for bagasse fiber was found. Based on conventional physical tests (penetration, softening point, ductility), rheological property tests (rotational viscosity, dynamic shear rheological test, multi-stress creep recovery test, linear amplitude scanning test), and a four-point bending fatigue test of the asphalt mixture, the properties of modified bagasse fiber asphalt binder and mixture after cyclic dry-wet erosion under pure water and salt solution (NaCl, Na2SO4) were determined, and the effects of the erosion environment and fiber ratio on the basic physical and rheological properties of the asphalt were clarified. Compared with the silane coupling agents KH550 and KH590, the bagasse fiber modified with KH570/NaOH had a better high-temperature oil absorption capacity, heat stability capacity, and matrix asphalt compatibility. The worst erosion environment was Na2SO4, but the increase in test temperature and fiber content weakened the sensitivity of the asphalt binder performance in different erosion environments. The erosion capacity order was as follows: Na2SO4 > NaCl > pure water. In the worst erosion environment, 0.5% modified bagasse fiber/Nano-TiO2 asphalt binder (Bn-570-0.5) had the best corrosion resistance in a high-temperature and high-humidity salt environment. The penetration, softening point, creep recovery rate R3.2, non-recoverable creep compliance Jnr3.2, and fatigue life after long-term aging (with 5% strain) of Bn-570-0.5 were, respectively, increased by -16.9%, 37.5%, 37.95%, -27.86%, and 38.30% compared with unblended base asphalt binder (B). In addition, the four-point flexural fatigue life of Bn-570-0.5 was 169.2% higher than that of the unblended base mixture.

Experimental investigation of PAM/PEI polymer mud for reducing lost circulation in high-temperature formations

Lost circulation is a common and costly problem, especially in high-temperature oil and geothermal wells. Lost circulation materials, including polymeric solutions, are often used to remediate the problem. This study considers using thermoset polymeric gels in water-based drilling fluids as lost circulation materials (LCM) to mitigate the circulation loss in oil and geothermal wells at high temperatures of 150°C (302°F). Two polymers were considered, polyacrylamide (PAM), which serves as the base gel, and polyethyleneimine (PEI), an organic crosslinker. The rheological and sealing property of the PAM/PEI combination as lost circulation material was examined at 150°C (302°F) using a high temperature and high-pressure rheometer and a permeability plugging tester. The results showed the optimum gelation of the mud at 6% PAM and 1.25% PEI solution occurred at 17 minutes. The polymer mud tends to form an elastic-like solid at high concentrations of PAM and PEI. The PAM/PEI polymer mud reduced the fluid loss by 80% during the sealing treatment compared to the conventional LCM treatments with water-based mud. Also, details on effective mixing procedure and testing technique using 3D-printed tapered fracture discs are presented.

A coupling prediction model of annular pressure build-up for deepwater oil and gas wells during transient-state testing

To accurately predict annular pressure build-up of deepwater high pressure-high temperature oil and gas wells during the transient-state testing, a coupling prediction model of trapped & untrapped annular pressure build-up is proposed. For the short-term process of gas well transient testing, a wellbore transient heat transfer model has been established. Then the improved coupling model of trapped & untrapped annular pressure build-up is established, which is not only novelly considering fluid thermodynamic properties (isobaric expansion coefficient and isothermal compression coefficient) under high pressure-high temperature conditions and annulus fluid mass changes of untrapped annulus, but also considering annulus volume changes. For precise coupling calculating the annular pressure build-up, the annulus is divided into infinitesimal grid cells along well depth. The impact of different considering factors, testing times, testing production rates, formation permeability and cement sheath sealing positions on the annular pressure build-up in the model is investigated. The results show that conventional models (high pressure-high temperature properties and mass changes of the fluid are not considered) will greatly overestimate the annular pressure build-up; as the testing time increases, the impact of untrapped annulus fluid mass changes on the annular pressure build-up will gradually take the dominant role; reasonably optimizing the setting of untrapped annulus open hole section in high permeability formations and increasing the distance between cement sheath and the upper casing shoe can effectively relieve the increasing annular pressure build-up. These findings can achieve accurate prediction of trapped and untrapped annular pressure build-up, and play an important role in guaranteeing the wellbore integrity and safety of deepwater oil and gas wells during transient-state testing.

Optimizing Sour Gas Qualification Testing—Modeling the Effects of Temperature and Total Pressure on H2S Fugacity, Activity, and Solubility Coefficients up to 138 MPa and 204°C

Traditionally, the sour severities of high-pressure high-temperature (HPHT) oil and gas production wells were assessed by H2S partial pressure (PH2S): The mole fraction of H2S in the gas (yH2S) multiplied by the total pressure (PT). However, PH2S usually over-predicts the actual sour severity of HPHT systems, leading to suboptimal material selection choices. To reflect recent advances in thermodynamic modeling and to avoid over-conservatism, after careful deliberation, ANSI/NACE MR0175-2021/ISO 15156-2:2022 recently expanded the number of sour severity metrics to four: PH2S, fugacity (fH2S), chemical activity (aH2S), and dissolved concentration (CH2S) of the aqueous phase. The new metrics are often computationally derived and account for thermodynamic nonidealities, which are significant at HPHT conditions. Regardless of the preferred metric, quantifying the sensitivity of each metric to a wide range of temperatures and total pressures is critical when conducting H2S service assessments. In this article, the effect of increasing temperature and total pressure on the thermodynamically derived apparent H2S solubility (KH2S = CH2S/PH2S) was investigated. KH2S is a critical parameter for quantifying changes in H2S phase behavior/sour severity of HPHT systems. Apparent KH2S values were calculated by two different thermodynamic models and benchmarked to two publicly available H2S/H2O datasets up to 120°C and 10.3 MPa equilibrated in a brine containing 165,000 mg/L Cl−. The model that provided the best match to the experimental data was later used in a much broader thermodynamic sensitivity study of the H2S/CH4/H2O/NaCl “oilfield” system. For this sensitivity analysis, changes in fH2S, aH2S, CH2S, and KH2S were individually modeled between 4°C and 204°C, at total pressures up to 138 MPa, and in brines containing up to 25 wt% NaCl (180,000 mg/L Cl−). Lastly, a comparison of the predicted sour severity by pseudo-PH2S, fH2S, and CH2S metrics, over the same temperature and total pressure parameter space, is presented.

Study of a novel cross linked graft copolymer starch in water-based drilling fluid

In the drilling industry, the demand for environmentally friendly additives with high thermal stability is increasing due to the dual factors of increasing environmental pressure and high-temperature oil layers. However, commonly used non-toxic and biodegradable additives, such as etherified modified starch, cannot withstand temperatures higher than 150 °C. Additionally, natural polymers with better thermal stability obtained through graft modification with sulfonated monomers face challenges in meeting the standards of toxicity and biodegradability. To address these technical problems, a novel graft and crosslink copolymer, St-AA/AM/NVP/MBA (SAANM), was synthesized from corn starch by combining graft modification with a non-sulfonated monomer and cross-linking modification. Laboratory evaluation results confirm that the thermal stability of SAANM in a nitrogen atmosphere was close to 300 °C, and it exhibits excellent temperature resistance up to 170 °C in bentonite-based mud, while also retaining the non-toxic and biodegradable characteristics of starch. The water-based drilling fluid (WBDF), added with SAANM, demonstrated outstanding rheological properties, fluid loss control performance, and environmental friendliness after aging at 170 °C and being polluted by high concentrations of NaCl or CaCl2. The successful application of SAANM in a high-temperature directional well in an offshore oil field confirms its potential for borehole cleaning and wellbore stability.