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The objective of this paper is to address the challenges related to well control and highlight the successful implementation of deep transient tests (DTT) operations in an offshore well located in Southeast Asia that was carried out by PETRONAS with the help of a dynamic well control simulation platform. The paper aims to provide insights into the pre-job simulation process, which ensured a safer operation from a well control perspective. Additionally, a comparison between simulated and actual sensor measurements during the DTT operation will be presented. The latest DTT technology enables a higher volume of gas or hydrocarbon to be pumped into wellbore compared to formation tester (FT) operation. During the DTT operation, the pumped formation fluids are mixed with mud that is pumped from surface through a circulation sub into the annulus, and the mixture of fluids is then circulated out from annulus simultaneously to the surface during the drawdown period. To ensure well control safety, it is crucial to have a comprehensive understanding of the processes involved. Therefore, a dynamic multiphase flow simulator that takes into account the interactions between downhole pumped hydrocarbon and drilling fluids is important to better simulate the pressure downhole throughout the DTT operation. In this case study, simulations were conducted prior to the job execution, considering several sensitivities, to ensure that the operation stayed within a safe operating mud weight window while meeting the surface gas handling limits. During DTT execution, real time downhole measurements were sent to a cloud-based platform, where they were plotted on a graph alongside the simulation data for monitoring purposes. Any changes in observed formation fluid, downhole flow rates and mud circulation rates during the DTT operation were quickly reflected in the simulation, this enabled effective communication between the PETRONAS project and execution teams ensuring a safe well control condition throughout the operation. As a result, the DTT operation was conducted successfully and safely, with the measured data aligning well with the simulations. The accurate wellbore dynamics simulator allowed for quantification of changes in drilling fluid design, circulating rates, hydrocarbon composition, downhole pump rates, and pump duration for various formation testing design sequences. It also facilitated predictions of downhole well pressure, free-gas distribution along the well geometry, and gas rate on the surface. This valuable insight provides PETRONAS with more flexibility in understanding and planning advanced FT operations, while enabling larger volumes of hydrocarbons to be pumped downhole. Furthermore, adopting an advanced pressure transient testing method like DTT is in line with both industry and PETRONAS's efforts to reduce carbon dioxide emissions.
The objective of this paper is to address the challenges related to well control and highlight the successful implementation of deep transient tests (DTT) operations in an offshore well located in Southeast Asia that was carried out by PETRONAS with the help of a dynamic well control simulation platform. The paper aims to provide insights into the pre-job simulation process, which ensured a safer operation from a well control perspective. Additionally, a comparison between simulated and actual sensor measurements during the DTT operation will be presented. The latest DTT technology enables a higher volume of gas or hydrocarbon to be pumped into wellbore compared to formation tester (FT) operation. During the DTT operation, the pumped formation fluids are mixed with mud that is pumped from surface through a circulation sub into the annulus, and the mixture of fluids is then circulated out from annulus simultaneously to the surface during the drawdown period. To ensure well control safety, it is crucial to have a comprehensive understanding of the processes involved. Therefore, a dynamic multiphase flow simulator that takes into account the interactions between downhole pumped hydrocarbon and drilling fluids is important to better simulate the pressure downhole throughout the DTT operation. In this case study, simulations were conducted prior to the job execution, considering several sensitivities, to ensure that the operation stayed within a safe operating mud weight window while meeting the surface gas handling limits. During DTT execution, real time downhole measurements were sent to a cloud-based platform, where they were plotted on a graph alongside the simulation data for monitoring purposes. Any changes in observed formation fluid, downhole flow rates and mud circulation rates during the DTT operation were quickly reflected in the simulation, this enabled effective communication between the PETRONAS project and execution teams ensuring a safe well control condition throughout the operation. As a result, the DTT operation was conducted successfully and safely, with the measured data aligning well with the simulations. The accurate wellbore dynamics simulator allowed for quantification of changes in drilling fluid design, circulating rates, hydrocarbon composition, downhole pump rates, and pump duration for various formation testing design sequences. It also facilitated predictions of downhole well pressure, free-gas distribution along the well geometry, and gas rate on the surface. This valuable insight provides PETRONAS with more flexibility in understanding and planning advanced FT operations, while enabling larger volumes of hydrocarbons to be pumped downhole. Furthermore, adopting an advanced pressure transient testing method like DTT is in line with both industry and PETRONAS's efforts to reduce carbon dioxide emissions.
Well potential evaluation is key to reservoir development which can be estimated from petrophysical logs, mobility from wireline formation tester, Diagnostic Fracture Injection Test, or measured directly from drill stem tests, production well tests, or through extended well testing. All these data are having different coverage of the reservoir volume which represent the scale of the data from low scale core and log data to large scale from DFIT or DST. All of the extracted mobility and permeability data are correct in their scale and the objective of this paper is address the data scale through a comprehensive workflow to adopt all of them into a reservoir dynamic model to maximize the data utilization. Wide range of available permeability estimation from different source imposed the question of data reliability toward different analyses. The established workflow guides to analyze all individual data sources including NMR (nuclear magnetic resonance), pressure transient analysis from single probe points and sampling stations, after closure analysis from DFIT, and pressure transient analysis from pressure build-up tests. It also details out the scale of the data and their radius of investigation. The derived permeability from each scale is used in static model with their relevant scale. Finally, it explores an approach to use the highest data scale such as DFIT upscale for improve static model and dynamic model reliability and predictability. Additionally, the workflow addresses the permeability transformation from effective permeability for few data sources such as DFIT, DST to absolute permeability as a reference for comparison for all permeability measurements. Defining right tested interval for wireline formation tester and vertical extension of DFIT is one of the main challenges that is tackled through integration with image logs and implementing a single well model. The workflow was implemented in four wells that were all completed with frack-pack as sand control application. The DFIT analysis was showing a lower effective permeability in most of the wells due to saturated reservoir condition compared to core and log results which was showing very high absolute permeability. Calculated permeability from DFIT has been transformed to absolute permeability using post-production saturation from petrophysical logs with integration with relative permeability dataset from SCAL data and close estimation of absolute permeability is made from DFIT to core and log driven permeability. A comparison of all permeability data sources in one single plot on each well is made to confirm vertical permeability contrast and reservoir heterogeneity to build reliable dynamic model and this narrow down the uncertainty in the dynamic model and de-risk the project. No measured permeability data is wrong. As long as the right analysis is done, they are all correct and their difference lies under the nature of reservoir property variation laterally and vertically due to rock type change. The reflection of data scale in 3D dynamic model is an essential step to boost dynamic model reliability, as the conventional approach of using permeability from core/logs to populate the permeability is more statistical than measurement driven. This work illuminates embedding the big scale data specifically DFIT results into dynamic model to enhance model reliability and predictability.
Wellbore dynamics is one of the key factors in reservoir testing, acting as a bridge between the reservoir and surface measurements. The objective of this research is to address the challenges encountered in well control and highlight the outcomes of employing wellbore dynamic simulation to enhance the safety of formation tester (FT) sampling and deep transient tests (DTT) conducted in wells, with a special emphasis on pre-job simulations multi-parameter sensitivity analysis. This effort is geared towards advancing our comprehension of the interaction between hydrocarbons and wellbore mud during and following FT pump-out operations. The most recent advancement in DTT technology allows for the pumping of a larger volume of hydrocarbons into the wellbore, when compared to the operation of a conventional formation tester. While conducting DTT, formation fluids pumped from the well are mixed with drilling mud from the surface through a circulation sub into the annulus. This mixture of fluids is then circulated out from the annulus to the surface during the flowing period. It is imperative to possess a thorough comprehension of these procedures to ensure well control safety. Consequently, the utilization of a dynamic multiphase flow simulator that considers the interactions between downhole pumped hydrocarbons and drilling fluids becomes crucial to enhance the accuracy of pressure simulations during the DTT operation. Given the paramount importance of safety in oil and gas operations, a cloud-based wellbore dynamics simulator enables precise quantification of drilling fluid adjustments, circulation rates, hydrocarbon composition, downhole pump rates, well depth, hole diameter, overbalance pressure, and pump duration for various FT design sequences. This allows for accurate forecasting of downhole well pressure and the distribution of free gas throughout the well, adjusting these parameters as needed. Subsequently, we will explore scenarios with kick potential and risk mitigation strategies. This paper showcases a total of 15 case studies (different hydrocarbon types and overbalance scenarios), where cloud-based wellbore fluid simulations were performed for different flow rate scenarios, and to predict the potential well control situations. A special emphasis was given to the near critical hydrocarbon fluids such as condensate, volatile oil, and wet gas.
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