Permeability is the cornerstone to any reservoir-flow modeling, leading to field development and production management. Typical sources of permeability include cores, logs, wireline formation tests or mini-DSTs, and conventional drill-stem tests or DSTs., Integrating various sources of permeability at different scales is problematic. Anchored in mini-DST-derived permeability, this study endeavors to integrate various sources of permeability, leading to reservoir description in a trubidite sandstone reservoir in the Sabah Basin, Malaysia.Pressure-transient test data recorded during a mini-DST operation differ significantly from those gathered during a conventional DST. In the case of this well, although the test quality is excellent, interpretation challenges are numerous. The paper llustrates the planning and integration of Mini-DST data with multidisciplinary information from side-wall cores, MDT, NMR, and FMI image logs. This case study demonstrates that, in this particular setting, the use of mini-DSTs was cost-effective and yielded the necessary subsurface information required to plan field development options.

Summary Permeability is the cornerstone of any reservoir-flow modeling that leads to field development and production management. Typical sources of permeability include cores, logs, wireline formation tests [or minidrillstem tests (mini-DSTs)], and conventional DSTs. However, integrating various sources of permeability at different scales is problematic. Anchored in mini-DST-derived permeability, this study endeavors to integrate various sources of permeability, leading to reservoir description in a turbidite sandstone reservoir in the Sabah basin, Malaysia. Ordinarily, pressure-transient-test data recorded during a mini-DST operation differ significantly from data gathered during a conventional DST. Even though test quality was excellent, interpretation challenges were numerous in this well. Consequently, multidisciplinary information was brought to bear for integration of data derived from mini-DSTs. Other sources of information included sidewall cores, spot pressure measurements, nuclear magnetic resonance (NMR), and microelectrical imaging logs. This case study demonstrates that, in this particular setting, the use of mini-DSTs was cost-effective and yielded the subsurface information required to plan field-development options.

Shales account for 75% of the formations drilled worldwide, while drilling troubles associated with shale represents 90% of wellbore stability problems reported. In this paper, a traditional wellbore stability study has been implemented at an onshore gas field in a tectonically active region. Despite following the program however, the drilling experienced significant challenges, particularly in the shales where the sonic logs have shown high velocity and therefore high rock strength. To investigate the root cause, several mechanisms for the wellbore instabilities have been investigated, such as overpressure, weak bedding plane, chemical activity, insufficient mud weight, and fractured shales. The cavings collected and preserved from the wells, as big as several inches in size, have undergone XRD, SEM, thin-section, and strength tests. While most mechanisms have been ruled out, focus has turned to the fractured shales. With the evidence from the lab and collaborated with drilling experience in the field, it has found the troublesome shale formation has been extensively fractured during past and present tectonic movements. The presence of the fissure network becomes so significant that it dominates rock mechanical behavior and wellbore stability. More interestingly, it seems the sonic logs have overlooked the existence of fissures and still shown the response from a typical strong rock. Based on those findings, modified drilling strategies have been suggested and implemented in the region. The field case presents a new challenge to the log-based wellbore stability interpretation routinely implemented in current drilling society. Being openminded, closely monitoring and testing cavings, and updating the model with drilling experience may be as important as the model development itself.