New Technologies Applied to Well Drilling Evaluation Using High-Resolution Oil and Gas Biomarker and Isotopic Logging (HRGWD): Examples from Offshore Brazil
High resolution biomarker and isotopic logging is a technique that utilizes oil and gas samples taken from cutting samples and gas flow lines during drilling to identify, characterize and quantify the yield of oil and gas and measure biomarkers and carbon isotopes on C1 to C4 gases whenever possible. The goal of HRGWD is to aid assessment of potential oil and gas zones, particularly those drilled with oil based muds (OBM). This technique utilizes well known biomarkers and carbon isotopic techniques applied toward exploration well evaluation, bypassed pay zones, and reservoir compartmentalization issues. This is the most modern approach to determine and assess: oil yield, oil type, oil maturity, oil quality, oil cracking, oil mixing, reservoir heterogeneities and oil-water contact. Also, it allows to determine whether gas is thermogenic (economic) or biogenic (usu. non-economic), whether shows are “true” or “false” (e.g., gas kicks due to overpressure), efficiency of seals, extent of thermogenic gas mixing, extent of biogenic-thermogenic gas mixing, gas thermal evolution and possibility of down-dip gas pay. Such data are critical to evaluate the well during drilling in order to take exploratory decisions about bypassed pay zones and the possibility of down-dip pay. Examples from wells drilled offshore Brazil will be discussed.