2014 Rocky Mountain Section AAPG Annual Meeting

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The importance of high-resolution geochemistry in downspacing evaluations of unconventional plays


Downspacing studies are emerging as the most important geological evaluations to fully understand the economic potential of North American tight oil and gas plays. Understanding fluid communication or compartmentalization in high-density well fields can optimize well spacing and orientation of laterals. This can be achieved through baseline fluid and gas characterization during well-drilling, followed by routine monitoring of production fluids and gases. Baseline geochemical evaluations can be made using a variety of samples: mudstream gases, gases desorbed from cuttings or cores, source rock extracts, and early production fluids or gases. While standard geochemical analyses, such as traditional gas chromatography, provide useful characterization data, they may lack the precision for tracking communication between wells. Emerging technologies, specifically two-dimensional gas chromatography (GCxGC), are now more economically viable for upstream applications. The analytical capabilities of GCxGC flame ionization detection (FID) and time of flight mass spectrometry (TOF-MS) have been proven in tracing degraded, oil-associated compounds in environmental quality assessments. In upstream applications, they have the potential to offer unprecedented resolution for distinguishing between production fluids. Furthermore, using subtraction algorithms, well-coordinated GCxGC analyses can diminish the influence of oil based drilling fluids in baseline well field studies. This presentation will discuss unconventional hydrocarbon characterization using GCxGC, as well as single and triple quadrupole mass spectrometry (GCMS & GCMS/MS). Highlighted will be the values and limitations of these technologies for determining optimal well spacing and achieving maximum production.