Abstract

Development of new fields of hard-to-recover hydrocarbons has led to the necessity of using new expanded and more informative logging suites. We have started to develop fields with more complex geological structure (seismic faults, several transitional areas in the section, etc.) and more complex lithology of formations. Currently there is a need to drill horizontal wells in demanding geological conditions. Now a standard set of methods is not enough and there is a growing necessity to improve the LWD suite. The conventional gamma-ray logging is continuously supplemented with new methods – density neutron logging, array resistivity logging, spectral gamma-ray logging, boundary mapper, and acoustic logging.

Horizontal drilling with geosteering is more often preferred, as drilling with pre-approved profile may be ineffective in demanding geological conditions. It is important to timely receive comprehensive information of the reservoir properties, when using geosteering in unconventional formations. Therefore it is necessary to use the most appropriate logging suite for evaluation of the lithology, and permeability and porosity properties, depending on the geological situation.

Our company successfully performs horizontal drilling in fields with high degree of reservoir uncertainty (facies replacement, lateral heterogeneities, etc.), drilling for shale oil and gas (including equivalents of Bazhenov formation in the USA). The main target is the maximum exposing of the reservoir producing section, and this task is successfully performed.

This study is an overview of practice in the application of expanded LWD suite for intelligent drilling of horizontal wells. For the first time ever we have the possibility to determine the rock natural radioactivity spectrum while drilling using the three-component analysis of Th, K, U. This helps to determine the nature of rocks radioactivity and to effectively drill horizontal wells in unconventional reservoirs with increased natural radioactivity.

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