Production allocation and time lapse changes
The Cretaceous Eagle Ford Shale in south eastern Texas, USA, is an economically important tight oil and shale gas play. It has been the target of extensive exploration activity since 2008 using a highly developed directional (non-vertical) drilling technology. However, it is not always clear which part(s) of a hydraulically fractured shale formation has actually been tapped during production. In part, this may be due to the heterogeneous nature and complexity of the formation itself. The in-situ fluids in a “shale oil play” display compositional signatures, both laterally and vertically, which are tied to facies, lithofacies and maturity. To allocate production to distinct zones within the shale formation we need to deconvolute produced fluid compositions in terms of the contributions from different completed zones or contribution from unwanted zones. A second important issue is the compositional change of the produced fluids with production time.
Objectives and Goals
- Delineate reservoir heterogeneity at the metre scale
We characterise cored shale and immediately juxtaposed sequences using high frequency geochemical analyses. Compositional profiling of the organic matter is done based on standard tools in organic geochemistry (MPLC, GC-MS) and on FT-ICR MS (Fourier transform-ion cyclotron resonance mass spectrometry). Developing FT-ICR MS into a practical and powerful “geoforensic” tool is a major thrust, with a focus on high molecular weight organic species.
- Characterise time lapse changes in produced fluids
Bulk fluids of different maturities as well as of a time lapse series from the same production well will be characterised using whole oil-GC, MPLC, GC-MS, and FT-ICR-MS.
- Determine degree of mixing – deconvolute produced fluids
For a given maturity level, the detailed high frequency profiling will be used to assess the contribution of the various shale organofacies to the bulk produced petroleum, and thereby assess mixing.
- Stefanie Poetz
- Brian Horsfield