Drilling Challenge of Unstable Hole: Condition in Kilo Field: A Case Study in Southeast Asia

Tobing, Jerry; Tanjung, Erwindo

doi:10.2118/165338-ms

Cited by 2 publications

References 5 publications

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Mud Weight Evaluation Based on Safe Mud Window in Drilling Well “X-1” to Overcome Caving and Partial Loss Problems in The Oil Field

Wibowo

Julianto

Buntoro

et al. 2021

IOP Conf. Ser.: Earth Environ. Sci.

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Drilling of Well X-1 in the North Sumatra Basin at a depth of 2887-3186 m TVD occurred partial loss, and caving at a depth of 500-1650m TVD. To overcome this problem, it is necessary to use the safe mud window concept. Drilling mud density planning must be greater than the pore pressure and shear failure gradient but not more than the minimum horizontal stress and fracture pressure. The purpose of this paper is to make an accurate subsurface pressure analysis and to overcome problems caused by the mud weight planning errors used based on the safe mud window, and can be used as a reference for further drilling of wells that have field conditions and stratigraphy such as the Well X-1. In conducting safe mud window analysis, there are several parameters that need to be estimated in order to make a safe mud window, namely formation pressure, formation fracture pressure, minimum horizontal stress, maximum horizontal stress, vertical stress / overburden pressure, and shear failure gradient. From the results of the safe mud window on Well X-1, the actual mud weight data used during drilling is entered. After being analyzed, at a depth of 500-1050 m TVD caving occurs because the density value used is smaller than the shear failure gradient, while at a depth of 1050-1600m there is kaolinite mineral which causes caving. At a depth of 2829-3281 m TVD the density value is greater than minimum horizontal stress (SHmin). Here, caving occurs if the density value used is smaller than shear failure gradient and partial loss occurs if the density used is greater than SHmin. Based on the safe mud window, the optimal mud weight for drilling at a depth of 36-354.2 meter on a 20” route is 9.2-9.4 ppg. At a depth of 354.2-948 meter on a 16” route is 14.49-15.33ppg. At a depth of 948-1619 meter on a 13 3/8” route is 15.45-17.65ppg. At a depth of 1619-2829 meter on a 9 5/8” route is 17.36-17.76ppg. At a depth of 2829-3281 meter on a 7” route is 16.57-16,7ppg. And at a depth of 3281-3796.1 meter is 13.49-13.74ppg in order to avoid partial loss and caving problems.

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Mud Weight Evaluation Based on Safe Mud Window in Drilling Well “X-1” to Overcome Caving and Partial Loss Problems in The Oil Field

Wibowo

Julianto

Buntoro

et al. 2021

IOP Conf. Ser.: Earth Environ. Sci.

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Geomechanics Improves Drilling Operations and Reduces Non-Productive Times (NPT) in Kilo Field, Offshore Northwest Java

et al. 2015

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Recent drilling of moderately to highly deviated development wells in the Kilo Field has proven to be extremely challenging. Numerous lost-time incidents including stuck pipe, pack-off, and difficulties in running casing were experienced, particularly when drilling through the Main-Massive Formation. Earlier analyses pointed to mud material quality issues, but drilling performance benchmarking with other nearby fields ruled out this explanation. Faced with continually high NPTs, a geomechanical study was initiated to mitigate the wellbore instability problems. The recommendations arising from the comprehensive geomechanical and drilling experience analyses have been implemented to improve performance during subsequent development drilling. The field-wide geomechanical model indicates the Kilo Field is characterized by a state of stress that is transitional between a normal and strike-slip faulting regimes. The combination of relatively large differential stress and relatively weak rocks means the field is potentially subject to stress-induced wellbore instability problems. However, observations of numerous time-dependent failures imply secondary influences must also be considered to arrive at possible remediation strategies. A systematic ranking process has been developed to delineate the primary causal mechanism of wellbore instability. This process suggests that the major contributor to the time-dependent deterioration process is rising pore pressure caused by the invasion of drilling fluid into micro-fractured formations, and then exacerbated by less-than-optimal drilling practices. This finding, together with the improved geomechanical understanding of the Kilo Field, provides the basis for optimizing mud weights and wellbore trajectories as well as formulating appropriate drilling strategies to maintain the mud hydrostatic support (overbalance) in future drilling. The finding also highlights the importance of integrating geomechanics with drilling practices when developing strategies to mitigate unstable hole problems. This paper presents a comprehensive, ordered workflow that integrates the disparate data available in a mature field to identify the most likely causative mechanisms of the time-delayed wellbore instabilities. This knowledge was then used to develop strategies for optimizing future drilling operations in the Kilo Field.

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Drilling Challenge of Unstable Hole: Condition in Kilo Field: A Case Study in Southeast Asia

Cited by 2 publications

References 5 publications

Mud Weight Evaluation Based on Safe Mud Window in Drilling Well “X-1” to Overcome Caving and Partial Loss Problems in The Oil Field

Mud Weight Evaluation Based on Safe Mud Window in Drilling Well “X-1” to Overcome Caving and Partial Loss Problems in The Oil Field

Geomechanics Improves Drilling Operations and Reduces Non-Productive Times (NPT) in Kilo Field, Offshore Northwest Java

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