Application of Formation Pressure While Drilling FPWD Technology in Challenging Low Mobility Environment – Case Study from Western Kazakhstan (Russian)
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Cited by 3 publications
References 4 publications
Influence of Permeable Wellbore on Formation Testing While Drilling and Mobility Inversion
Formation pressure and mobility represent two fundamental parameters that are essential for the development of oil and gas resources. These parameters can be obtained in real time through the process of formation testing while drilling (FTWD). It is highly probable that the drilling fluid will invade the formation during the FTWD process. Nevertheless, the prevailing theory regarding FTWD assumes that the wellbore is impermeable, thereby rendering its potential impact on FTWD and mobility inversion unclear. Therefore, to clarify the influence of the permeable wellbore on FTWD and mobility inversion, a mathematical model of FTWD seepage was first proposed by involving the permeable wellbore. Secondly, the finite element method was used to solve this model, and this model was verified by using the analytical models. The pressure response curves and isobaric surface near the FTWD probe were then compared for both the permeable and impermeable wellbores, and the influence of the permeable wellbore on the pressure response curves of FTWD was analyzed. Finally, the method of integral area was used to invert mobility, and the compressive influence of different factors on both the pressure response curves and mobility inversion was discussed for both the permeable and impermeable wellbores. The results indicated that the permeable wellbore has a significant impact on the pressure response curves and isobaric surface near the probe due to the limited pressure sweeping range around the probe and the invasion of drilling fluid. In the case of a permeable wellbore, the invasion of the drilling fluid into the formation can cause a supercharge effect around the well. This effect can cause an initial increase followed by a decrease in the pressure buildup phase. The pressure buildup always exceeds the original formation pressure, which can lead to an overestimation of the measured formation pressure compared to the original. Meanwhile, the permeable wellbore can also lead to an overestimation of the inversion mobility, but the impermeable wellbore has much less influence on the mobility inversion. To improve inversion accuracy, it is recommended to increase the rubber packer radius, lengthen the suction period, reduce the storage volume of the pipeline, and decrease the overbalanced pressure. However, these measures cannot mitigate the impact of the supercharge effect on formation pressure testing. This paper provides theoretical guidelines for the use of FTWD tools and data interpretation.
Influence of Permeable Wellbore on Formation Testing While Drilling and Mobility Inversion
Formation pressure and mobility represent two fundamental parameters that are essential for the development of oil and gas resources. These parameters can be obtained in real time through the process of formation testing while drilling (FTWD). It is highly probable that the drilling fluid will invade the formation during the FTWD process. Nevertheless, the prevailing theory regarding FTWD assumes that the wellbore is impermeable, thereby rendering its potential impact on FTWD and mobility inversion unclear. Therefore, to clarify the influence of the permeable wellbore on FTWD and mobility inversion, a mathematical model of FTWD seepage was first proposed by involving the permeable wellbore. Secondly, the finite element method was used to solve this model, and this model was verified by using the analytical models. The pressure response curves and isobaric surface near the FTWD probe were then compared for both the permeable and impermeable wellbores, and the influence of the permeable wellbore on the pressure response curves of FTWD was analyzed. Finally, the method of integral area was used to invert mobility, and the compressive influence of different factors on both the pressure response curves and mobility inversion was discussed for both the permeable and impermeable wellbores. The results indicated that the permeable wellbore has a significant impact on the pressure response curves and isobaric surface near the probe due to the limited pressure sweeping range around the probe and the invasion of drilling fluid. In the case of a permeable wellbore, the invasion of the drilling fluid into the formation can cause a supercharge effect around the well. This effect can cause an initial increase followed by a decrease in the pressure buildup phase. The pressure buildup always exceeds the original formation pressure, which can lead to an overestimation of the measured formation pressure compared to the original. Meanwhile, the permeable wellbore can also lead to an overestimation of the inversion mobility, but the impermeable wellbore has much less influence on the mobility inversion. To improve inversion accuracy, it is recommended to increase the rubber packer radius, lengthen the suction period, reduce the storage volume of the pipeline, and decrease the overbalanced pressure. However, these measures cannot mitigate the impact of the supercharge effect on formation pressure testing. This paper provides theoretical guidelines for the use of FTWD tools and data interpretation.
Challenges and Potentials for Sand Control Design and Management in Oil Reservoirs of Kazakhstan
Kazakhstan owns one of the largest global oil reserves (~3%). This paper aims at investigating the challenges and potentials for production from weakly-consolidated and unconsolidated oil sandstone reserves in Kazakhstan. We used the published information in the literature, especially those including comparative studies between Kazakhstan and North America. Weakly consolidated and unconsolidated oil reserves, in Kazakhstan, were studied in terms of the depth, pay-zone thickness, viscosity, particle size distribution, clay content, porosity, permeability, gas cap, bottom water, mineralogy, solution gas, oil saturation, and homogeneity of the pay zone. The previous and current experiences in developing these reserves were outlined. The stress condition was also discussed. Furthermore, geological condition, including the existing structures, layers and formations were addressed for different reserves. Weakly consolidated heavy oil reserves in shallow depths (less than 500 m) with oil viscosity around 500 cP and thin pay zones (less than 10 m) have been successfully produced using cold methods, however, thicker zones could be produced using thermal options. Sand management is the main challenge in cold operations, while sand control is the main challenge in thermal operations. Tectonic history is more critical in comparison to the similar cases in North America. The complicated tectonic history, necessitates the geomechanical models to strategize the sand control especially in cased and perforated completion. These models are usually avoided in North America due to the less problematic conditions. Further investigation has shown that Inflow Control Devices (ICDs) could be utilized to limit the water breakthrough, as water coning is a common problem, which initiates and intensifies the sanding. This paper provides a review on challenges and potentials for sand control and sand management in heavy oil reserves of Kazakhstan, which could be used as a guideline for service companies and operators. This paper could be also used as an initial step for further investigations regarding the sand control and sand management in Kazakhstan.
Strategic Reservoir Characterisation Manoeuvre in a Clay Sensitive, Pressure-Depleted and Geomechanically Complex Gas Reservoir in Offshore Peninsular Malaysia
Acquiring subsurface data in a highly unstable and geomechanically complex formation pose unusual challenges to adequately characterize the reservoir from production and completion perspective. The traditional way of acquiring data through LWD or wireline logging might be operationally constrained by severe hole break-out, mud losses and high differential sticking due to pressure depletion across the reservoirs. This condition warrants a specific and critical approach to optimally design the data acquisition plan to minimize subsurface uncertainties to meet the gas production target from the field. This paper will highlight customized techniques to successfully acquire good quality of subsurface logging and pressure data, technical and operational considerations involved and some of the best practice applied to operate within the threshold limit amidst the time-dependent hole instability culprit. Detailed technical plan, rigorous pre-job simulation and sensitivity analysis set the high tone to acquire critical subsurface log and pressure data prior to completion. Customizing LWD drilling dynamic parameters such as mud circulation rate, real time data transfer rate, pressure drawdown and build-up time, controlling the logging speed in ROP and optimizing the mud design are among the approaches taken to obtain fit-for-purpose data in a very narrow operating limit amidst the borehole instability issues. Acquiring real time image from LWD density tool enables fracture and break-out evaluation validating the existing geomechanical model in this field and enhance the understanding of causes for hole instability issues leading to real time well trajectory optimization and updating. Theoretically, open hole log data can be also complemented by cased hole pulsed neutron and production logging acquisition to formulate reservoir properties, gas water contact and estimated shut-in reservoir pressure through prolific log processing methodology and interpretation procedures. Post data acquisition activities along the problematic reservoir interval and incorporating all the interpretation outcomes, the reservoir connectivity and pressure communication are confirmed throughout the field area. Even though the main target reservoirs in the newly drilled well could not be completed and produced due to operational issues, the case presented in this paper will provide valuable lessons learned in designing and operating a well in the highly complex geomechanical area and strategizing data acquisition program to minimize the subsurface uncertainties. Best practices in customizing LWD open hole and wireline cased hole data acquisition to fully characterize the formation including downhole CO2 gas presence set the pioneering guideline in this region and become the critical benchmark for future well operation. In conclusion, securing adequate and reliable subsurface data in a highly unstable and geomechanically complex formation will justify for a strategic approach and customized plan to obtain much needed insights for sustainable gas production and delivery from the field. The first integrated and comprehensive approach combining both open hole and cased hole logging capabilities in Peninsular Malaysia region are presented in this paper setting a commendable runway for fit-for-purpose operation and optimization.
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