The Application of the Combination of NMR Logging and NMR Measurements at RSWC Samples at the Well Site To Identify Producible Oil in Tight Rocks
- Anton Nikitin (Shell International Exploration and Production) | Sean Dolan (Shell International Exploration and Production) | Arcady Reiderman (Ecotek Inc.) | Rahul Grover (Schlumberger) | Aidan Blount (Shell Exploration and Production)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- SPWLA 58th Annual Logging Symposium, 17-21 June, Oklahoma City, Oklahoma, USA
- Publication Date
- Document Type
- Conference Paper
- 2017. copyright held jointly by the Society of Petrophysicists and Well Log Analysts (SPWLA) and the submitting authors
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- 343 since 2007
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The process by which fluid is lost from a core during retrieval to the surface by hydrocarbon expansion in tight rocks mimics hydrocarbon production under depletion drive in these reservoirs. Therefore, a comparison of hydrocarbon saturation in situ with that of a core sample at standard conditions provides a measure of producible hydrocarbons in tight rocks. From the point of view of hydrocarbon recovery, the core plug can be considered as a reservoir depleted to 1 atm pressure. This of course cannot be achieved physically and hence the difference between the residual hydrocarbon saturation in the plug and that in situ should be regarded as an upper bound on producible hydrocarbon.
The concentration of fluids present in the formation can be directly quantified using NMR T2 measurements. The same measurements can be performed on side wall core samples, at the well site, to quantify the concentration of residual fluid in the core. Thus the two can be compared. Here we will present the results of the analysis of downhole NMR logs and NMR T2 data acquired on side wall samples to identify producible hydrocarbon intervals in a light tight oil formation. The former dataset was acquired using a CMR logging tool by Schlumberger. The latter dataset, NMR measurements on side wall samples, were acquired using an Ecotek SWC-A relaxometer optimized to perform comparable measurements with those of the CMR tool. The comparison of these datasets, at the well site, provides an assessment of in situ producible hydrocarbon in the formation.
The primary objective of this work is to demonstrate how the combination of downhole NMR T2 measurements and NMR T2 measurements on core samples can be used to identify producible hydrocarbons (HC) in Light Tight Oil (LTO) formations. The data used in this study were acquired on an undercharged liquid-rich Organic Rich Shale (ORS) formation, from West Texas, i.e., ORS formations where the volume of HC generated was not sufficient to replace all the water originally deposited in matrix pores.
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