In extended reach or long horizontal wells, it is imperative to maintain borehole quality & borehole stability to ensure efficient drilling and to facilitate the running and installation of completion equipment. Hence managing the risk of the degrading borehole is evolving as an important aspect of well planning process. The quality of the borehole is affected primarily by geomechanical or drilling related problems, which can significantly impact the life cycle of a well. Recent technological advances in visualisation now enable the management of the aforementioned risks before, during and after drilling. We show examples of how recently available, high-resolution, acoustic logging-while-drilling (LWD) borehole image logs have enabled detailed characterisation of borehole shape to the extent that we can visualise and analyse the root causes of occurrence. LWD logging also enables the use of time-lapse logging; comparing images from the drilling first pass and then repeated at later stages in drilling to look for worsening conditions of the borehole shape. These data can be used for several new or existing critical applications that can be split into two main categories: drilling hazards and completions hazards. These applications are realised by the use of a tabulated characterisation of all ranges of borehole trajectory, borehole shape and image artefact features for coding of the well during drilling. The realisations are then combined with a geomechanics-centric integrated risk management workflow. The workflow focuses on providing an improved well planning process by identifying potential drilling and geological risks in each of the planed well sections. The combination of the pre-drill risk identification and the visual verification of the borehole condition enables quick decision making for drilling and potential de-risking of the wireline logging and completions operations.


Borehole stability during drilling and completion operations is of paramount importance for safety, time and cost constraints. The recent development of high-resolution acoustic imaging for logging-while-drilling (LWD) applications has enabled the visualisation of borehole shape characteristics to an extent that was not previously possible. The high-resolution acoustic images now available for LWD and can be acquired in both water-based mud (WBM) and oil-based mud (OBM) and give critical information about borehole shape and potential failure mechanisms in a time-frame that is useful for making critical decisions during drilling and completions operations. The scale of borehole shape features seen in acoustic image logs forms only a part of a larger-scale spectrum of borehole trajectory, shape and wall surface features, all of which can be applied as zonation schemes to the well.

We use data acquired in a test well to prove the concept of the scheme to describe borehole shape characteristics and to test geomechanical models created to capture the stability and borehole shape properties and comprising only data acquired by LWD. In addition to high-resolution acoustic images, the dataset included the availability of high-resolution electrical images, standard resolution density, caliper and gamma image logs and additional omni-directional resistivity and other logs. LWD data were compared in a composite well log, and a geomechanical model was created to characterise the stability of the well, taking into account the predicted and measured occurrences of borehole stability features (breakout in this case).

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