Automated compilation of depth-corrected and drilling-parameter normalized logs of oil and gas shows in drilling mud

Research output: ThesisMaster's ThesisResearch

Authors

Abstract

This thesis represents the first part of a project within the company RAG to use the installed real-time chromatographic gas show measurements in combination with a RAG proprietary OILFINDER system for reservoir interpretation. The aim of this Master Thesis was to analyze and evaluate the effect of drilling parameters on the gas show measurements provided by the company used equipment. The Thesis is therefore split in three main parts. In a first part, the theory of mud logging including the measurement principle and different sources of gas show signals is explained. Based on definitions commonly used in mud logging industry and in the literature, the different sources of a gas-show signal are explained. The second part focuses on the conversion from a time-based gas-show measurement into a depth based mud-log. For this purpose the measurement principle within the company used system is summarized, including a description of the installed equipment and real-time data acquisition. Moreover the integrated depth conversion, using data of the installed real-time data software will be explained and evaluated. Simplifications and potential weaknesses found are investigated by sensitivity analysis, which show error margins and limitations of the system. In the last part, influences on the quality of volatile gas-show signals are determined Starting from the hydrocarbon release downhole up to the final measurements on surface. Based on a simplified model, the signal is normalized to distinct drilling parameters that mainly influence the quantity of released formation fluid into the mud. This procedure enhances gas-show interpretations and allows a comparison of different wells. On site tests have been performed to determine the effects of different drilling parameters as the fluid travels along the annulus. Influences of extraction efficiencies of different gas traps are discussed based on several pub-lications throughout the industry, raising the concern, that the installed gas trap shows insuf-ficient efficiency for heavier hydrocarbon (C3 to C6) fractions for the use of reservoir fluid recombination. Based on laboratory fluid data the significance of this information is carried out by determining the molar distributions under atmospheric pressure and different mud temperatures. Finally, besides natural occurring dependencies the mudlog can be affected by gas events like tripping gas and/or connection gas. The theory behind these gas events are explained shortly and the basis for an automated algorithm is created to determine possible gas events, enhancing mud-log interpretation.

Details

Translated title of the contributionAutomatisierte Erstellung von teufenkorrigierten und bohrparameternormierten Öl- und Gasanzeichenlogs
Original languageEnglish
QualificationDipl.-Ing.
Supervisors/Advisors
Award date14 Dec 2012
Publication statusPublished - 2012