Combining gas logging, well logging and cuttings microbiota data to improve geosteering and flow profile prediction in a horizontal well

Drilling horizontal wells is known has a problem of ‘non-measurement’ zone of downhole logging devices. In this regard, there is a high probability of leaving the target interval when drilling horizontal wells, and this in turn is fraught with a reduction in the potential flow rate or productivity of the well. In such cases, the importance and necessity of thorough interpretation of gas logs conducted by the geological and technological research station increases. This method allows solving a whole range of tasks, namely: prompt identification of oil and gas promising reservoirs in the well section, study of their filtration-capacity properties and saturation character. At the same time, a special study of drill cuttings microbiota can serve as an additional source of information. DNA sequencing technology of drill cuttings microbiota is proposed as a technique to increase the informativeness of cuttings. Application of this method allows to identify natural biomarkers, as well as to monitor their presence and concentration in various technological processes of drilling and oil and gas production. A comparative analysis of practical application of gas logging and DNA sequencing technology of mud microbiota is presented. Verification of the used methods on the data of geophysical well survey and field geophysical survey is carried out. Identification and comparison of information during drilling of a well with the data obtained during its operation allows to determine with high reliability the source of watering and working oil-saturated intervals. Keywords: gas logging; geophysical surveys; gas chromatography; horizontal well drilling; drilling cuttings; DNA sequencing; geosteering.