2019 AAPG Annual Convention and Exhibition:

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Unconventional Development and Production Geochemistry - Oil, Natural Gas and Water Geochemical Data Provide Evaluation Workflows through the Lifecycle of a Well

Abstract

Prudent oil and gas operators understand the need to establish fluids geochemical baseline early during the development of a tight oil and gas play. Early evaluation of fluids geochemistry, whether helping to establish regulatory requirements or providing a chemical baseline of water, oil or gas composition, can be essential for petroleum systems analyses. Mud gas samples are often analyzed during drilling. Gas chromatography and isotope analyses are well-established geochemical tool that provides compositional analysis of the gases in the mud stream. This is often supplemented with additional evaluations conducted on gas dissolved in near surface waters or collection of the production gases for compositional and isotopic analyses. This baseline provides support for operational decisions that are required through the efficient production life of a well. The objective of this study is to investigate fluid geochemistry at multiple stages during the lifecycle of development and production of a horizontal well bore. Results are shown to exhibit the efficient use of fluids geochemistry to help in operational decisions throughout a life-cycle of a production well. Water is initially investigated during baseline geochemical analyses of near surface waters and continues through the flowback of operation fluids and months into production. A time-series of water samples are analyzed. Hydrogen and oxygen isotopes of water delineate frac fluids from native formation brines. Flowback timing is established. Hydrogen, oxygen and strontium isotopes can differentiate one formation brine from another more readily and completely than analysis of water ion chemistry alone. Separate formation water contributions to production are established. The gases dissolved in the near surface aquifer can be compared to the targeted production interval. Many variables can affect geochemical signature of production fluids. Carbon and hydrogen isotopes can act as natural tracers if baseline values are established. Migration and charge into specific reservoirs are established through a series of baseline whole oil GC analyses. Compartmentalization and communication during production of the wellbore is investigated. This study establishes baseline values in the Niobrara and Codell targets of Denver-Julesburg Basin production. Applying theses data to exploration, development, production and regulatory geological work evaluations provide a highly efficient and cost-saving method of evaluation. This study will demonstrate these work-processes in a demonstration of time-series analyses of fluids. Results are presented from isotopic analyses of waters, and oil-associated gases. Whole oil GC data of oil produced over time are presented to establish efficiency of horizontal well-spacing decisions.