The article presents a brief description of the controlled pressure method, which is one of the effective approaches for drilling wells in a narrow range of drilling fluid densities. This method has been successfully applied to the exploration and development of offshore fields, with a significant reduction in operational risks and well costs. To implement this method, it is necessary to conduct staff training and impose increased requirements on the management of operations.
The article presents a well management matrix in the event of an inflow, as well as various contingency actions in response to unforeseen events, downhole equipment failures and surface equipment failures.
Keywords: offshore drilling, high pressure and high temperatures, mud density, managed pressure drilling method, risk, control matrix.
With the exploration and development of high pressure and high temperature (HPHT) areas, the drilling fluid density (MW) safe window is narrowing, resulting in increased drilling time with an increased risk of potential drilling incidents in the well, and sometimes even shutting down the well .
Methods. The controlled pressure method (MPD) is a drilling process that uses surface back pressure (SBP)  at normal hydrostatic pressure in the column, which allows drilling complex formations with narrow MW windows while maintaining a constant bottom hole pressure . The loss of equivalent circulation density (ECD) is equivalently compensated for by the SBP, and thus continuous drilling operations can be performed while remaining within the pore pressure gradient window at all times. An automated MPD system with SBP manipulation should not violate the mud density window in case of inflow or loss detection. MPD is one of the effective approaches to solving the complex problem of safe operation in a narrow MW drilling window . In addition, the rate of penetration increases and the formation pollution decreases.
MPD has been successfully applied to the exploration and development of offshore HPHT fields, such as the North Sea basin and the Gulf of Mexico basin, with a significant reduction in operational risks and well costs [5,8].
Since MPD is a non-standard operation that includes many operations such as well control, pipe connection and tripping, it must take into account compliance with special operating standards.
Results and Discussion. In the offshore conditions with HPHT, MPD operations face additional challenges due to limited platform space (e.g. escape routes and preparation areas). As a result, detailed procedures such as staff training and operations management are required. In addition, personnel should be aware of their roles and responsibilities in the wellsite training program and be educated in pre-designed emergency procedures . Therefore, it is noted that the human factor and safety training of personnel should reduce operational risks during offshore MPD operations [1,11,12,14].
In order to reduce the risk and teach safety in marine operations, the MPD in fig. 1 shows the information flow among the personnel involved in MPD operations.
Fig. 1. The flow of information among the staff during the MPD operations 
Drilling Supervisor (DS), Drilling Rig Manager (DRM) and MPD Supervisor.
The DS is the «key person» in monitoring the safe operation of the MPD. In addition to their normal roles and responsibilities, the DS is responsible for coordinating and ensuring overall smooth and safe operation throughout the MPD operation, ensuring that all rig personnel are aware of the operation of the MPD as compared to conventional drilling.
The drilling crew (DC) is responsible for shutting in the well and performing well control operations using the rig's well control system. DRM is the head of the drilling crew, as well as a key person in overseeing the safe execution of the MPD operation. The Drilling Foreman (DF) is responsible for ensuring that the drilling operations and associated site activities are managed in such a way as to ensure safe drilling. The driller (D) is the person in charge of personnel supervision, and his main task is to ensure that instructions are carried out completely and safely. The driller must accurately understand his responsibilities under the MPD and inform supervisors of any indication of an abnormal event during the operation of the MPD. The Driller Assistant (DA) replaces the driller and must be able to take on the same duties as the driller and therefore be qualified.
The MPD Supervisor (SMPD) is another key person in overseeing the safe operation of the MPD. He is responsible for training all key personnel to ensure they are fully trained and understand the operation of the MPD, discusses MPD related issues with the SD, and ensures that the entire MPD operation runs smoothly and safely. The MPD Engineer (EMPD) is responsible for ensuring that the well is drilled in accordance with the MPD program, monitoring the state of the well to ensure the conditions of the MPD. The rotary wellhead operator (RWHO) works alongside a supervisor to ensure the entire operation runs smoothly and safely. The throttle operator (OT) is solely responsible for the overall operation of the throttle and hardware and must be present at all times to monitor the condition of the necessary parts and evaluate any alarms. The throttle operator maintains and operates the throttle manifold and ensures that all necessary parts are in place and that all equipment is operating in accordance with design criteria. The drilling site training program consists of two parts, which must also be carried out at the drilling site prior to the start of MPD operations .
A successful project in the HPHT environment starts with a clear plan; therefore, it is necessary to plan emergency procedures during MPD. Changes in pressure and flow patterns indicate what is happening in the well.
Well flow is the most common occurrence. an unexpected drilling event that occurs during times of extreme high pressure offshore and, if not handled properly, can cause a major blowout that can destroy the rig and result in death of personnel, resulting in well shut-in [4,15].
On the fig. 2 presents the well management matrix for the inflow MPD, as well as various contingency actions in response to unforeseen events, downhole equipment failures and surface equipment failures.
Fig. 2. Well control matrix 
Conclusions. The operating procedures of the MPD include the roles and responsibilities of key personnel during MPD operations, so staff training is required.
If the well control matrix is followed, then the MPD technology will significantly increase the operational efficiency and safety in offshore drilling of HPHT wells with narrow mud density windows.
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