A Universal Data Format for Wellbore Logs

In the formation evaluation industry, multiple data formats are used. Some of these are industry standards (for example, LAS and DLIS) and are often used for data interchange and archival, whereas others are proprietary. However, many of these industry-standard formats suffer from legacy issues: for example, limited metadata storage, inability to efficiently store complex data (or nonstandard extensions being required), or are unsuited for storing data from modern tools and interpretation results, especially multidimensional data (such as generated by azimuthal resistivity tools). This paper describes a proposed universal format for the storage of wellbore-centric formation evaluation data. The format is suitable for complex 3D data, for example, those generated by deep and extra-deep azimuthal resistivity tools, borehole acoustic reflection images, VSPs, borehole imaging tools, multifingered caliper logs, and depth of detection data. The format also naturally collapses down when utilized to store simple conventional logs that contain one value per depth in the wellbore. For this reason, it is a good standard for data exchange between applications. It is suitable for both field and interpreted data. The proposed format provides spatial details of every data point in the wellbore. The position of each data point is defined by reference back to the measure point of the sonde, which in turn is defined by the wellbore deviation survey and its coordinate reference system: both these can be natively included in the file so enabling the recorded data to be located in physical 3D space. Each data point in space may have an unrestricted number of parameters. An example might be horizontal and vertical resistivity, maximum value based on uncertainty, minimum value based on uncertainty, and a number of flags indicating if it is within the depths of detection of the logging tool defined by different criteria. Metadata such as tool information, acquisition parameters, well location, etc., can also be included in the file. The versatility of the proposed format gives the capability to store and exchange all data that is recorded and referenced to a defined location in a wellbore, including metadata. It is suitable to be used as a data interchange format between usually incompatible applications and as a long-term data archiving format. The proposed format requires a detailed definition so that computer scientists can implement it in applications used for subsurface modeling, and detailed standards can be defined. As many wellbore data formats compress very efficiently, concerns of size can be addressed by natively including data compression in the format specification