Deepwater Drilling Research Articles

Application of Mode Superposition Method in the Recoil Response of Deepwater Drilling Risers after Emergency Disconnection

Summary How to effectively control the recoil response after an emergency disconnection is one of the core technical problems in ensuring the safe and reliable operation of a deepwater drilling riser. Currently, the theoretical analysis is based on a discretization model or numerical simulation, which ignores the continuity of the riser system and the coupling effects of load acting on the riser. To address this problem further, in this paper, we establish a mechanical model and control equation with infinite degree of freedom for riser recoil response, where the heave motion of the floating drilling platform, seawater damping, and the viscous resistance of drilling fluid discharge were taken into account. In addition, the correctness of the model and solving approach are verified against the Orcaflex software. On this basis, the influence of wave period, wave height, initial phase angle, and tension coefficient on the recoil characteristics are discussed. The success of riser emergency disconnection is related to the clearance between the lower marine riser package (LMRP) and the blowout preventer (BOP) and the axial force distribution of the riser. The influence of the above-mentioned factors on the riser recoil response is also complicated. On the basis of the assumptions put forward and the model established, some quantitative conclusions are drawn. This study is of reference significance for safety control of riser emergency disconnection operation.

A kick monitoring method for deepwater open-circuit drilling based on convolutional neural network

In the case of shallow drilling in deepwater without installation of riser and subsea BOP, open-circuit drilling is usually used. In the process of open-circuit drilling, drilling fluid is directly returned to the seabed. Therefore, observing the return of seabed drilling fluid through Remotely Operated Vehicle (ROV) has become one of the main methods for monitoring the kick in open-circuit drilling. However, the current ROV monitoring method only relies on the professional technical personnel to observe the video screen, which is difficult to identify the kick quickly and accurately in the early stage. In view of this problem, an intelligent kick monitoring method based on deep learning image recognition technology is proposed in this paper. By collecting the actual video image data shot by ROV and simulating the drilling fluid return morphology under different gas influx using Ansys Fluent software, a typical sample database is constructed. Then, the pretrained GoogLeNet neural network model is used for transfer learning, and the video images shot by ROV on site are used to test the trained model. The results show that this method can identify the kick more quickly and accurately, and the model has good robustness. Using this method can greatly reduce the economic losses in the process of deepwater open-circuit drilling, and provides technical support for safe and efficient drilling of deepwater open-circuit drilling.

Calculation method of deep-water surface conductor bearing capacity based on jetting operation parameters

The surface conductor bears the weight of the Christmas tree, a blowout preventer (BOP), and casings from various layers, and is subject to immense force. It is also affected by the coupling effect of the drilling platform and wellhead load for a long time. The accurate characterization of its bearing capacity is an important guarantee for the safety of deepwater drilling operations. Through the analysis of the installation process, mechanical characteristics, and the theoretical bearing capacity model of the surface conductor, three important stages of jet drilling, lifting up jet string, and running jet string are selected. Carry out the jet operation parameters and vertical force analysis for each stage, reveal the relationship between jet operation parameters and vertical friction of the surface conductor, and establish the real-time bearing capacity calculation model of the surface conductor of each stage. From the operation efficiency and economy, an analysis method of bearing capacity based on an actively pressing downward experiment is established when the well is located in a new block or a shallow block with complex geology. The coefficient of each model is corrected by the known well data, and the adaptability of the bearing capacity checking methods in different stages is evaluated. The results show that the calculation accuracy of the surface conductor bearing capacity model based on jetting operation parameters is more than 85%, and the error is reduced by 20% compared with the conventional model. The calculation accuracy is higher when the calculation is based on the upper friction parameter or lower friction parameter. The calculation method of deep-water surface conductor bearing capacity based on jetting operation parameters has been successfully applied in most deep wells in the South China Sea in recent two years and has become an important method for deep-water surface conductor design, which ensures the stability of the wellhead of deep-water oil and gas wells.

High Performance Aqueous Fluids in Deepwater Operation

An exploration drilling in Gambia deepwater with water depth of 965m. well total depth drilled at measured depth 3,457m, the maximum inclination angle 34.6º and the horizontal section depth 1000m. The top-hole section was drilled with seawater and Guar GUM Sweep and the conductor casing set at 1053m. After the 26’’ hole was drilled with seawater and GUAR GUM sweep at TD the well was displaced to pad mud (KCl/polymer Mud) the 20’’ casing run and cemented. The intermediate and landing section was drilled with High Performance Water-based mud which was provide by one of leading servicing provider. This is where it was first deployed in Deepwater operation in West Africa (Gambia) and it shows good cutting and shale inhibitive performance, good hole cleaning, and wellbore stability, it allows the MWD tools to performed at high ROP, the rheological properties were stable with little treatment, the gives good lubrication and good cutting carrying to surface. According to Pearson, J.R.A [1], that the important rheological requirements are that they should have a low an apparent viscosity as possible, consistent with drilled cutting back to the surface during circulation.
 In deepwater operation we may encountered some extremely reactive formations that can incur lot of cost, well lost hole pack off and lost of drilling tools (BHA) which will require sidetrack. Also, with the glamour for the clean energy in the world, there are a lot of environmental restriction now and high cost of waste disposal. This high-performance Water based mud is an option to address the above concerns much attractive in drilling operation.
 In this study, the rheological preparties of the mud will be compare with Oil based mud to see the way they performed downhole. The hole cleaning ability and the number of cutting waste that will be generated which will translate to the cost of disposal.
 This result show that high performance water-based mud is more effective in term of cost, solved environmental concern and performed as oil – based mud that is wildly used in the region.

Study of the Relationships among the Reverse Torque, Vibration, and Input Parameters of Mud Pumps in Riserless Mud Recovery Drilling

Compared with traditional deepwater drilling, riserless mud recovery (RMR) drilling technology has the advantages of improving drilling efficiency, reducing risks, and minimizing environmental effects. Therefore, RMR drilling technology has been widely applied in recent years. This study primarily investigates the relationships among reverse torque, vibration, and input parameters of mud pumps in riserless mud recovery drilling. Firstly, the operating principle and the structure of the mud pump module are analyzed, and an analytical model for the reverse torque and the vibration of the mud pump is established. Secondly, relevant data are derived from theoretical calculations and experiments, and the relationships among the reverse torque, vibration, and input parameters of the mud pump are analyzed using ANSYS (Version 2020 R1) software. Furthermore, the SVR (support vector regression) algorithm is employed to predict and analyze the amplitude of the mud pump’s vibration. Finally, the conclusions are drawn based on the findings of the relationships among the reverse torque, vibration, and input parameters of the mud pump. The findings show that the reverse torque of the mud pump increases approximately linearly with an increase in rotational speed, and the vibration of the mud pump increases and then decreases with an increase in rotational speed. The predicted values obtained through the prediction algorithm closely match the actual values. The findings provide a valuable reference for the application of RMR technology.

Experimental study on ultrasonic wave propagation characteristics of gas-liquid two-phase flow in riser annulus

Deepwater drilling projects face challenges such as delays in gas kick monitoring and a high risk of well control failure. How to monitor gas kicks as early and accurately as possible is one of the keys to preventing significant accidents such as well blowouts. Monitoring gas kicks at risers is a promising method for early monitoring of gas kicks in deepwater drilling. In this paper, by constructing an experimental device for ultrasonic gas kicks monitoring of the riser, the response law of the ultrasonic signal to the gas-liquid two-phase flow was tested under different air intake, drill pipe rotation speeds, and liquid flow rates. This was done by constructing an experimental riser ultrasonic gas kick monitoring device. The signal-to-noise ratio and the root-mean-square error are used as measurement standards, and the wavelet threshold noise reduction method is used to reduce noise-containing signals. The ultrasonic sensitivity characteristics of the gas-liquid two-phase flow are demonstrated by analyzing the signal in the time domain and frequency domain: peak amplitude, attenuation coefficient, wave velocity, and fundamental frequency. A non-linear relationship exists between peak amplitude, fundamental frequency, and air intake, whereas an approximately linear relationship is evident between the attenuation coefficient and wave velocity with air intake. A quantitative characterization relationship between ultrasonic characteristic parameters and air intake was obtained by conducting a multiple regression analysis using the least-squares method on the attenuation coefficient, wave velocity, fundamental frequency, and air intake. Experiments demonstrate that the relative error between the actual air intake of 86.4 % of the test data group and the theoretical air intake determined based on the quantitative characterization relationship is less than 10 %.

Influence of Auxiliary Pipelines of the Deepwater Drilling Riser on the Dynamic Characteristics of the Subsea Wellhead

During deepwater drilling, the subsea wellhead will be subjected to dynamic loads transmitted from the marine environment, floating drilling platform, riser, and blowout preventer (BOP). Therefore, complex dynamic responses will be induced, which will seriously affect the safety of the subsea wellhead. In this paper, considering the effect of auxiliary pipelines on the riser, a novel entire mechanical model of the floating platform–riser–BOP–subsea wellhead is established. By using the finite-difference method, the governing equations are solved. Finally, the dynamic bending moment and stress distribution of the subsea wellhead are obtained. Moreover, the model is verified by numerical simulation in Orcaflex. On this basis, the influence of the wave height, wave period, sludge height of the subsea wellhead, rotational stiffness of the lower flexible joint, and wall thickness of the conductor on the dynamic characteristics of the subsea wellhead is discussed. Analysis results show that the theoretical analysis results are in good agreement with the numerical simulation. The auxiliary pipelines have important influence on the dynamic characteristics of the subsea wellhead. Wave period is the most important factor affecting the mechanical behavior of the subsea wellhead. Wave height, wall thickness of the conductor, and sludge height are secondary factors affecting the mechanical behavior of the subsea wellhead. The rotational stiffness of the lower flexible joint has little influence on the mechanical behavior of the subsea wellhead. By solving the optimized mechanical model proposed in this paper, the dynamic characteristic of the subsea wellhead conforms more to the actual deepwater drilling conditions. This study has reference significance for the design and mechanical control of the subsea wellhead in deepwater drilling.

Lateral bearing characteristics of subsea wellhead assembly in the hydrate trial production engineering

Conductor and suction anchor are the key equipment providing bearing capacity in the field of deep-water drilling or offshore engineering, which have the advantages of high operation efficiency and short construction period. In order to drill a horizontal well in the shallow hydrate reservoir in the deep water, the suction anchor wellhead assembly is employed to undertake the main vertical bearing capacity in the second round of hydrate trial production project, so as to reduce the conductor running depth and heighten the kick-off point position. However, the deformation law of the deep-water suction anchor wellhead assembly under the moving load of the riser is not clear, and it is necessary to understand the lateral bearing characteristics to guide the design of its structural scheme. Based on 3D solid finite element method, the solid finite element model of the suction anchor wellhead assembly is established. In the model, the seabed soil is divided into seven layers, the contact between the wellhead assembly and the soil is simulated, and the vertical load and bending moment are applied to the wellhead node to simulate the riser movement when working in the deep water. The lateral bearing stability of conventional wellhead assembly and suction anchor wellhead assembly under the influence of wellhead load is discussed. The analysis results show that the bending moment is the main factor affecting the lateral deformation of the wellhead string; the anti-bending performance from increasing the outer conductor diameter is better than that from increasing the conductor wall thickness; for the subsea wellhead, the suction anchor obviously improves the lateral bearing capacity and reduces the lateral deformation. The conduct of the suction anchor wellhead assembly still needs to be lowered to a certain depth that below the maximum disturbed depth to ensure the lateral bearing stability, Thus, a method for the minimum conductor running depth for the suction anchor wellhead assembly is developed. The field implementations show that compared with the first round of hydrate trial production project, the conductor running depth is increased by 9.42 m, and there is no risk of wellhead overturning during the trial production. The method for determining the minimum conductor running depth in this paper is feasible and will still play an important role in the subsequent hydrate exploration and development.

Quantitative Analysis of the Stability of a Mud-Return Circulation System in a Riserless Mud-Recovery Drilling System

Riserless mud-recovery (RMR) drilling technology was widely applied in recent years. Compared with traditional deepwater drilling, RMR drilling can improve drilling efficiency, reduce risks, and minimize environmental effects. This paper focuses primarily on the stability of a mud-return circulation system in an RMR system. First, various factors that affect the stability of a mud-return circulation system are analyzed. An analytical model for the skid-and-mud-return line is established. Second, relevant data are derived from theoretical calculations and experiments. ABAQUS software is used to analyze the effects of each factor on the stability of the mud-return circulation system. The influencing patterns of each factor on the stability of the mud-return circulation system are summarized. Furthermore, the stability of the system under different operating conditions is analyzed based on the coupling of multiple factors. The support vector regression with derivative significance weight analysis (SVR-DWSA) algorithm is employed to perform a weight analysis of the effect on the system’s stability. Finally, based on the research findings on the stability of the mud-return circulation system, relevant conclusions and recommendations are drawn. The results of this study provide valuable references for the application of RMR technology.

Research on the Stability of the Spacer Fluid Interface in Dual-Layer Pipe Dual-Gradient Drilling

Dual-layer pipe dual-gradient drilling technology is an emerging technology for solving the problem of the narrow safety density window in deepwater drilling. The unstable spacer fluid interface in this technology directly affects the dual-gradient pressure system in the annulus, causing changes in the drilling mud performance and affecting the control of bottom hole pressure and rock removal with drilling mud. Therefore, the key to the stable operation of dual-layer pipe dual-gradient drilling technology is to maintain the stability of the spacer fluid interface. Based on this, a seawater-spacer fluid-drilling mud annular flow model was established in this study, with a bottom hole pressure control step of 0.2 MPa, and the spacer fluid height after a single control was used as the evaluation index to study the influence of annular flow velocity, the spacer fluid properties, and the drill string rotation speed on the stability of the spacer fluid interface. The results show that in the determined conditions of the seawater and drilling mud system, the annular fluid flow rate and the physical parameters of the spacer fluid are the main factors affecting the stability of the spacer fluid interface. When the annular fluid flow rate increased within the range of 0.04~0.2 m/s, the liquidity index of the spacer fluid increased between 0.5 and 0.9, the consistency coefficient increased in the range of 0.6 to 1.4 Pa⋅sn, and the stability of the spacer fluid interface decreased. However, the stability of the spacer fluid interface increased with the increase in its density in the range of 1100~1500 kg/m3. The results obtained in this study can provide a reference for selecting the operating parameters to ensure the stable operation of dual-gradient pressure systems.

Eco-Friendly Drilling Fluid: Calcium Chloride-Based Natural Deep Eutectic Solvent (NADES) as an All-Rounder Additive

Designing an effective drilling mud is a critical aspect of the drilling process. A well-designed drilling mud should not only provide efficient mud hydraulics but also fulfill three important functions: enhancing mud rheology, inhibiting hydrate formation in deepwater drilling, and suppressing shale swelling when drilling through shale formations. Achieving these functions often requires the use of various additives, but these additives are often expensive, non-biodegradable, and have significant environmental impacts. To address these concerns, researchers have explored the potential applications of ionic liquids and deep eutectic solvents in drilling mud design, which have shown promising results. However, an even more environmentally friendly alternative has emerged in the form of natural deep eutectic solvents (NADES). This research focuses on an in-house-prepared NADES based on calcium chloride and glycerine, with a ratio of 1:4, prepared at 60 °C, and utilizes it as a drilling mud additive following the API 13 B-1 standards and checks its candidacy as a rheology modifier, hydrates, and shale inhibitor. The findings of the study demonstrate that the NADES-based mud significantly improves the overall yield point to plastic viscosity ratio (YP/PV) of the mud, provides good gel strength, and inhibits hydrate formation by up to 80%. Additionally, it has shown an impressive 62.8% inhibition of shale swelling while allowing for 84.1% improved shale recovery. Moreover, the NADES-based mud exhibits a 28% and 25% reduction in mud filtrate and mud cake thickness, respectively, which is further supported by the results of XRD, zeta potential, and surface tension. Based on these positive outcomes, the calcium chloride–glycerine NADES-based mud is recommended as a versatile drilling mud additive suitable for various industrial applications. Furthermore, it presents a more environmentally friendly option compared to traditional additives, addressing concerns about cost, biodegradability, and environmental impact in the drilling process for an ultimate global impact.

Iso-propyl caprylate and iso-propyl linolenate synthetic fluids as novel alternatives in deep-water drilling operations: Critical fluid properties and aerobic biodegradability assessments

Present drilling fluids for deep water wells have severe degenerative effect on the environment with high operational and disposal costs. Thus, making them less desirable in recent times. Ester synthetic drilling fluid provides a novel environmentally friendly alternative but conventional ester-based drilling fluids exhibit high viscosities in deep-water wells causing excessive equivalent circulating density (ECD) and increased risk of lost circulation owing to narrow mud density window. This study experimentally investigates the critical fluid properties and aerobic biodegradability potentials of two newly developed deep-water synthetic ester drilling fluids namely: iso-propyl caprylate (COIPE) and iso-propyl linolenate (LOIPE) synthetic fluids and their comparison with synthetic-paraffin (SP-SBF) and isomerized-olefin (IO-SBF) synthetic hydrocarbon fluids. The esters of iso-propyl caprylate and iso-propyl linolenate were produced from the isolation of ester mixtures that were obtained from the homogeneous catalytic transesterification of coconut and linseed plant oil biomass respectively. The COIPE was isolated from the coconut oil iso-propyl ester mixture by low-pressure fractional distillation technique. While fractional distillation and crystallization were used to isolate the LOIPE ester from the linseed oil iso-propyl ester mixture. Meanwhile, the aerobic biodegradation investigation was conducted by a modified oxygen consumption respirometry technique. The GC-MS analysis of the COIPE and LOIPE showed that the former contains essentially of lower saturated carbon compounds (C8). Whereas the latter contains higher molecular weight and unsaturated carbon compounds (C18+). The COIPE and LOIPE kinematic viscosity values are in good agreement with that of the reference synthetic hydrocarbon fluid samples (SP-SBF and IO-SBF). Although, the COIPE synthetic ester has lower viscosity value owing to the presence of shorter chain and saturated carbon atoms (C8 esters). Similarly, the linolenic oil iso-propyl ester has excellent cold flow characteristics for deep-water well drilling owing to lower values of cloud and pour points as a result of higher concentration of poly-unsaturated linolenic esters. The iso-propyl caprylate and the iso-propyl linolenate ester synthetic fluids are readily biodegradable in the sea water inoculum under aerobic condition. However, the iso-propyl caprylate is inherently biodegradable because its degradation level and that of the reference chemical sample were already above 60% during the 10-day window period. The SP-SBF and the IO-SBF synthetic fluids have lower aerobic biodegradation values because they contain little quantity of poly aromatic hydrocarbons as evident in their GC-MS profiles. Finally, esters and unsaturated synthetic-based fluid are more rapidly biodegradable than paraffinic synthetic fluids and the rate of biodegradation of organic compounds decreases as molecular weight increases

Loads Calculation and Strength Calculation of Landing String during Deepwater Drilling

As an important drilling tool, the landing string will be directly exposed to seawater during surface riserless drilling operations, and it will undergo complex deformation under the action of environmental loads such as ocean currents and waves and the displacement, heave and vibration of the drilling platform. At the same time, with the increase in water depth, the floating weight of drill pipe and casing also increases significantly, and the landing string will bear great tensile loads, which can easily cause accidents. Therefore, in this paper, based on ANSYS software, the finite element analysis models of three stages of the landing string lowering operation were established, and finite element simulations under different combinations of working conditions were carried out. Through theoretical analysis and numerical simulation, the ultimate load and stress distribution of the string under different operating sea conditions were obtained, and the external force requirements for restraining the lateral displacement of the string were proposed according to the existing standards of the industry. Thereby, the recommended safe operating time, safe operating conditions window and the required restraint reaction force of the support mechanism are given for landing string lowering operation throughout the year.

Effects of Salty Additives in Drilling Fluids on Hydrate Formation Dynamics and Phase Equilibrium

In the drilling process for deepwater and hydrate formations, adding salty components to drilling fluids is an important way to avoid secondary generation of hydrates in the annulus, and the effect of salt solutions on the hydrate generation lays a basis for drilling fluid design. In this study, an evaluation device for the effect of drilling fluid additives on hydrate formation and phase equilibrium is designed based on their interaction characteristics. In addition, hydrate generation experiments were carried out for pure water and three commonly used salty additives for drilling fluids. As such, the hydrate phase equilibrium equations under different conditions are established, and the hydrate phase change latent heat is further calculated. The results show that hydrate formation can be divided into four stages, i.e., gas dissolution, hydrate crystal nucleation, hydrate particle mass aggregation, and stabilization. Compared with pure water, sodium chloride and potassium formate solutions can effectively inhibit hydrate formation. At lower ambient temperature, the higher the concentration of potassium formate, the lower the phase equilibrium pressure. On the contrary, at higher ambient temperature, the higher the concentration of potassium formate, the higher the phase equilibrium pressure. The incomplete presence of sodium silicate in water in the form of ions is found to promote methane hydrate formation. Based on the experimental results of methane hydrate generation in potassium formate and sodium silicate solutions with different mass concentrations, the phase equilibrium calculation models for methane hydrate in both salt solutions were finally established. The latent heat of the phase change distribution of hydrate under different conditions was further calculated. The results of this paper can provide a theoretical basis for the study of deepwater drilling fluid systems and multicomponent annular flow.

Scheme optimization of deepwater dual gradient drilling based on the fuzzy comprehensive evaluation method

Offshore drilling is facing a series of difficulties in deepwater and ultra-deepwater environments, such as harsh operating environments and complex downhole geological conditions. How to achieve full management of the wellbore pressure during deepwater drilling has become one of the main concerns. The dual gradient drilling technology realizes wellbore pressure management by applying multiple pressure gradients in the annulus. It also enables the managed pressure drilling technology, such as constant bottomhole pressure drilling and mud cap drilling, to be applicable for deepwater conditions. However, the decision-making of deepwater dual gradient drilling scheme is always affected by many factors, which brings confusion for scheme optimization of deepwater drilling. In this work, according to the characteristics of four typical dual gradient drilling technologies, the fuzzy comprehensive evaluation method is applied to determine the most effective one from the aspects of drilling capacities and equipment requirements in a particular scenario. The fuzzy comprehensive evaluation results show that the subsea mud lifting pump system has better applicability in this case.

An improved coupled model for axial dynamic analysis of deepwater drilling risers under a soft hang-off mode

ABSTRACT Soft hang-off is an emergency operation for drilling risers to survive under harsh environments. Buckling of the suspended riser and overstroke of the tensioner piston rod would probably occur. Conventional analysis methods usually ignored the dynamic interaction of the riser and tension fluctuation. This paper is devoted to developing an improved coupled model for the axial dynamic analysis of the riser under soft hang-off mode. In the developed model, the mathematical model of the tensioner was established considering gas state variations, internal friction and pressure loss, the mechanical model of the riser considering axial hydrodynamic load was developed, and the two models were coupled through the kinematic variables. A case study is carried out to analyse the axial dynamic characteristics of the riser under soft hang-off mode, and the comparison showed that the conventional tensioner models will underestimate the axial dynamic response of the riser in soft hang-off mode.

Field data analysis and risk assessment of shallow gas hazards based on neural networks during industrial deep-water drilling

Field data analysis and risk assessment of shallow gas hazards based on neural networks during industrial deep-water drilling

Slope Instability Analysis of the Qiongdongnan Basin in the Northern Part of the South China Sea: Implications for the Risk Evaluation of Deepwater Drilling

Slope Instability Analysis of the Qiongdongnan Basin in the Northern Part of the South China Sea: Implications for the Risk Evaluation of Deepwater Drilling

Analysis of large deformation of deep water drilling riser considering vortex-induced vibration

In this study, a dynamic model for large deformation of deepwater drilling riser considering vortex-induced vibration (VIV) and actual ocean load was established. Nonlinear Van der Pol equation was used to simulate the VIV. The model was discretized by finite element method and solved by Newmark-β method. The dynamic characteristics of the riser under different marine environments and working conditions were analyzed. Results show that the force on the flow direction of the riser adds the pulsating drag term, which increases the riser deformation, after VIV is considered. The riser deflection and bending moment increase with the rise in surface velocity, decrease with the increment in top tension, and slightly change with the increase in wind speed and drilling fluid displacement. The rise in surface wind speed will increase the vibration mode and frequency of riser flow direction, while the increment in top tension will decrease the vibration mode and keep the vibration frequency unchanged. Wind speed and drilling fluid displacement slightly influence the riser deflection.

Research on the Formation and Plugging Risk of Gas Hydrate in a Deepwater Drilling Wellbore: A Case Study

At present, the formation mechanism of gas hydrate (hereinafter referred to as hydrate) plugging in the wellbore during deepwater drilling is not clear, so there are problems such as the overuse of hydrate inhibitors and the low utilization efficiency of inhibitors. Therefore, in view of the risk of hydrate formation and plugging under different working conditions during deepwater drilling, research was carried out on the wellbore hydrate formation area and wellbore hydrate deposition and plugging. Taking an atmospheric well in the South China Sea as an example, the wellbore annulus temperature field under different working conditions was combined with the hydrate formation phase curve to analyze the hydrate formation plugging risk under different working conditions during deepwater drilling, and the hydrate formation risk region of the wellbore under different working conditions was obtained. The effects of the drilling fluid circulation rate, injection temperature and drilling fluid viscosity in the wellbore annulus on the risk zone and subcooling of the wellbore hydrate formation were predicted. A deepwater drilling wellbore hydrate deposition plugging model was developed, based on which the dynamic deposition of the hydrate in the wellbore was predicted quantitatively. The results of the study showed that: (1) Increasing the circulation rate of drilling fluid, drilling fluid inlet temperature and drilling fluid viscosity during deepwater drilling can effectively reduce the hydrate formation region and subcooling, thus reducing the hydrate formation. (2) The risk of plugging by hydrate formation basically does not occur during normal drilling. (3) Under the condition of using seawater bentonite slurry drilling fluid, the safe operating time for stopping drilling is 20 h, and the safe operating time for shutting in and killing the well is 30 h.