Restricted or limited logging data acquisition can be caused by any number of operational issues. Limitations in the available logging data, such as that from wells in which only the gamma ray measurements were recorded, result in an incomplete and/or inadequate reservoir characterization and hydrocarbon identification. This paper presents the results of an advanced analysis of mud gas data. Mud gas data, in such cases, can be used to identify the presence of hydrocarbons, identify changes in fluid type as well as provide a qualitative formation evaluation.
Mud gas data is a common measurement during drilling operations. The gas data is able to reveal potential hydrocarbon zones and deliver insights to aid reservoir characterization. A recently developed advanced workflow, HC-Vision™ (Ritzmann et al., 2016) shows how additional information can be extracted from gas data. The result is an interpretation based on a data source that is independent from the formation evaluation logging data. To increase the accuracy of the interpreted gas data, rate-of-penetration (ROP) normalization and caliper correction of the chromatograph data is applied to account for effects due to changes in the drilling parameters.
The result of advanced mud-gas data analysis has shown at least 12 oil zones in the wells presented. Some of the identified intervals have been perforated and the hydrocarbon fluid types produced are in alignment with the mud gas data analysis. The gas ratio based permeability index has reliably identified zones with high productivity.
The result confirms that the advanced workflow supports the interpreted fluid composition and provides additional reservoir characterization for the permeable intervals that can be applied in the near real-time. Advanced analysis of mud gas data can also be applied to existing data from old wells to identify zones with bypassed hydrocarbons to prioritize potential zones for re-perforation.