Wellbore Stability Analysis and Guidelines for Efficient Shale Instability Management

Tan, C.P.; Rahman, Sheik S.; Chen, X.; Willoughby, D.R.; Choi, S.K.; Wu, Baichang

doi:10.2523/47795-ms

Cited by 4 publications

(5 citation statements)

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“…Thus, the formula of the equivalent pore pressure affected by chemical potential may be revised by adding a reflection coefficient (I n ) as follows: Tan (Tan et al, 1996;Chee and Brian, 1997;Tan et al, 1999;Tan et al, 1998) believed that the difference in total water potential is the fundamental cause of water flow. Total potential is the M A N U S C R I P T…”

Section: Total Water Absorption Methodsmentioning

confidence: 99%

A review of the shale wellbore stability mechanism based on mechanical–chemical coupling theories

et al. 2015

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A review of the shale wellbore stability mechanism based on mechanical-chemical coupling theories, Petroleum (2015), Abstract: Wellbore instability in hard brittle shale is a critical topic related to the effective exploitation of shale gas resources. This review first introduces the physical-chemical coupling theories applied in shale wellbore stability research, including total water absorption method, equivalent pore pressure method, elasticity incremental method of total water potential, and non-equilibrium thermodynamic method. Second, the influences of water activity, membrane efficiency, clay content, and drilling fluid on shale wellbore instability are summarized. Results demonstrate that shale and drilling fluid interactions can be the critical factors affecting shale wellbore stability. The effects of thermodynamics and electrochemistry may also be considered in the future, especially the microscopic reaction of shale and drilling fluid interactions. An example of this reaction is the chemical reaction between shale components and drilling fluid.

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Section: Total Water Absorption Methodsmentioning

confidence: 99%

A review of the shale wellbore stability mechanism based on mechanical–chemical coupling theories

et al. 2015

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“…Hence, the instability events didn't occur immediately after drilling the section but a few days after it was open. In case of time-dependent instability, the key mitigation measures include optimizing the mud chemical properties including mud type and mud salinity (Tan et al 1998) and minimizing the time the section is open. Evidence of time-dependent instability is also shown in Fig.…”

Section: Time-dependent Instabilitymentioning

confidence: 99%

Using Wellbore Stability Analysis to Improve Drilling Performance: Case Study from the Western Desert, Egypt

Steene

Povstyanova

Al-Attar³

et al. 2010

All Days

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Multiple wellbore stability projects in the Western Desert of Egypt identified a strong sensitivity of the breakout gradient to wellbore inclination and a weak sensitivity to wellbore azimuth, from the Abu Roash to the Alam El Bueib formations. The breakdown gradient shows strong sensitivity to both wellbore inclination and wellbore azimuth. Tensile failures are a problem only in high deviation wells (deviation more than 55-60°) where the breakdown gradient will in general be lower. For highly deviated wells, the occurrence of tensile failure can be reduced by drilling close to the minimum horizontal stress direction.Breakout can be tolerated to some extent, so planning the drilling mud weight to completely eliminate it is not necessary. The extent to which breakout can be tolerated depends on the well deviation, as cuttings become more difficult to evacuate as the well deviation increases.As losses are very common in most of the Western Desert formations, the optimum drilling mud weight should be formulated as a balance between the risks caused by breakout and mud loss.Understanding the main causes of rock failure and applying the recommended failure mitigation measures resulted in successfully drilling four deviated wells in the area. IntroductionThe Western Desert of Egypt is a mature hydrocarbon province. Wells with increasing deviation are being drilled to maximize the hydrocarbon recovery. This leads, however, to a rise in the severity of the borehole instability events. The Western Desert is a tectonically active region where the drilling problems range from mud losses in natural fracture networks or fault zones to time-dependent instability and tight pulls or sticking events. Depleted reservoirs are also encountered, lowering the fracture gradient.Wellbore stability analysis is an important tool to anticipate drilling problems and mitigate failure. We use a systematic approach: first, we analyze drilling reports in offset wells to gather the evidence for borehole failure. Then we develop a geomechanical model and calibrate it until it accurately predicts the observed borehole failures. After model calibration, we can make borehole failure predictions for any wellbore trajectory, regardless of the well deviation or azimuth, and assess the instability risks associated with a particular trajectory. This analysis assures that we choose the optimum drilling mud weight.Applying this process to several wells in one of Gupco's fields in the Western Desert resulted in four successful new wells.

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“…Evidence of time-dependent instability is that tight spots are both reported in wellbores drilled with lower mud weight and in wellbores drilled with higher mud weights (for similar mud type and borehole deviation). In case of time-dependent instability, the key mitigation measures include optimizing the mud chemical properties including mud type and mud salinity (Tan et al 1998), as well as minimizing the time the section is open. The mud weight should be kept low but sufficient to avoid generating excessive shear failure in the weaker zones.…”

Section: Fig 8 Stable and Safe Mud Weight Window Sensitivity With Bomentioning

confidence: 99%

Improving Drilling Efficiency Through Wellbore Stability Analysis in the Gulf of Suez, Egypt

Steene

Dutta

Fotoh

2009

Middle East Drilling Technology Conference &Amp; Exhibition

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An increasing number of deviated wells are being drilled to maximize production and hydrocarbon recovery in the mature reservoirs of the Gulf of Suez (GoS). Successfully drilling a high-angle well in a tectonically disturbed and structurally complex area like the GoS is very challenging, especially in depleted reservoirs. Selecting the optimal mud weight is absolutely essential. Stress orientation and magnitude also have a major impact on wellbore stability.The region poses significant drilling challenges that vary widely from reactive shale and salt creep to stress-related instability. From the findings of multiple wellbore stability projects we conducted in the GoS, we review the dominant mechanisms of wellbore instability in the GoS. We provide a summary of the failure mitigation measures and an overview of stress magnitude and orientation in the region, demonstrating how it impacts the knowledge of the most stable drilling direction.Understanding the main causes of rock failure in the GoS resulted in improved drilling efficiency and reduced drilling costs. We show an example, where a new, nearly horizontal (86º) well was successfully drilled through the Asl formation with less than half a day of non productive time during the entire drilling process.We conclude that acquisition of new, high-quality data would considerably reduce the uncertainty surrounding drilling complex wells in the area and reduce their cost. IntroductionThe Gulf of Suez (GoS) is a mature hydrocarbon region of Egypt. Most of the wells were drilled several decades ago, but, to optimize the hydrocarbon recovery, operators are now drilling increasingly deviated wells. This has led to a rise in the severity of borehole instability events, adding to the complexity of drilling in the area. In this tectonically active area, numerous drilling problems are present. They range from salt creep to mud losses in natural fracture networks or subseismic fault zones, without mentioning borehole failure linked to formation/fluid interactions. Highly depleted reservoirs are encountered, with sometimes a high uncertainty in the current pore pressure, leading to high uncertainty on the fracture gradient or the mud loss gradient.The available data is, however, usually scarce because most of the fields were developed a long time ago. Essential data like sonic compressional and shear logs can be missing. Mechanical properties from core are rarely available to calibrate the rock mechanical properties. Little direct information is available about stress magnitudes, as leakoff tests (LOT), extended LOT (XLOT), and hydraulic fracturing are rarely conducted.Wellbore stability analysis can, however, deliver crucial information to mitigate failure in complex new well trajectories. A systematic approach in analysing the causes of borehole instability is necessary to forecast the risks associated with drilling new wells and to recommend mitigation measures. First, the evidence for formation and borehole failure needs to be gathered and analyzed from drilling reports. Th...

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Wellbore Stability Analysis and Guidelines for Efficient Shale Instability Management

Cited by 4 publications

References 0 publications

A review of the shale wellbore stability mechanism based on mechanical–chemical coupling theories

A review of the shale wellbore stability mechanism based on mechanical–chemical coupling theories

Using Wellbore Stability Analysis to Improve Drilling Performance: Case Study from the Western Desert, Egypt

Improving Drilling Efficiency Through Wellbore Stability Analysis in the Gulf of Suez, Egypt

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