Dielectric Dispersion Logging A New Petrophysical Measurement for the Permian Basin

Transcription

1 Dielectric Scanner Dielectric Dispersion Logging A New Petrophysical Measurement for the Permian Basin James Hemingway Petrophysics Advisor Physics Dielectric Permittivity Permittivity is: a physical quantity that describes how an electric field affects, and is affected by a dielectric medium, and is determined by the ability of a material to polarize in response to the field, and thereby reduce the total electric field inside the material. Thus, permittivity relates to a material's ability to transmit (or "permit") an electric field.

2 Dielectric Polarization Mechanism Medium Characteristic Oil, Rock ε ~ 2, 5-9 r Water ε r ~ Hence, we can discriminate water from hydrocarbons, whatever its salinity Textural Effect? Interfacial polarization Molecular orientation Electronic polarization Dielectric as function of frequency Pore fluid analysis Formation matrix analysis 1e+5 1e+6 1e+7 1e+8 1e+9 1e+10 (Hz) Principle of Dielectric Measurement Change in Amplitude Phase Change Transmitter frequency - Vacuum - Medium ω Amplitude A φ Spacing r f 1 ε σ Receiver Permittivity = f ( ω, ε, σ, r) = Ae We convert a collection of amplitude and phase measurements into Phase Conductivity Dielectric Constant, is complex with two components one real and one imaginary * ε = ε r + i σ ωε 0 V * iφ ε and σ

3 Defining fresh formation water This is an environmentally friendly oil field waste product Kern River water ppm Variable Formation Water Salinity Standard logs SP GR Caliper 6 16 X-plot Porosity Micro-Resistivity Neutron Porosity 0 1 Deep Resistivity Density Porosity 0 X100 Moved Oil? High deep resistivity and high porosity Invasion from shallow resitivity Heavy oil X200 X300 X400 X500 X600 Water zone X700 X800

4 Variable Formation Water Salinity Dielectric-Scanner real time answer SP GR 150 Oil Salinity Caliper Sw 1 Hydrocarbon 1 Micro-Resistivity DS Water Porosity 0 1 Deep Resistivity X-plot Porosity 0 X100 Fresh Water Dielectric water filled porosity overlays with total porosity X200 X300 X400 Heavy oil X500 X600 Water zone X700 X800 Thin Beds Analysis Dielectric-Scanner real time answers 0 SP 100 Oil 0 GR Sw Ait 1 Salinity Static FMI 0 6 Caliper Image 16 0 Sw 30 1 Hydrocarbon 1 Horizontal Micro-Resistivity Resistivity DS Water Porosity 0 1 Vertical Deep Resistivity X-plot Porosity 0 Dielectric shows thin beds and a lot more oil than Induction XX10 XX15 Interpretation is confirmed by FMI images and with vertical and horizontal resistivities from Rt- Scanner XX20 XX25 XX30 Venezuela SPE (2008)

5 Thin Bed Analysis Thinly bedded sands, conductive clay beds High viscosity oil Objectives Hydrocarbon volume Reservoir quality Dielectric Scanner high resolution water-filled porosity Correct hydrocarbon volume (uninvaded zone) Sand count & net pay Identify potential high sand quality Comparison of 3 Laminated Sand Analysis methods XX95 XX00 XX05 XX10 XX15 XX20 XX30 Water volume - dielectric Water volume conventional (black) & triaxial induction (orange) Venezuela SPE (2008) & SPE (2010) Permian Basin Dielectric Scanner Example West Texas High Water Cut Carbonate - The goal is to identify higher oil saturations and improve economics. - The result in this case using the Dielectric Scanner was identification of lower water saturations and higher oil cut than standard Elan. - The oil cut was up to 15%, out-performing the offsets - Another result was better water resistivity calculation in the shallow portion of the well.

6 Main Zone of interest Perfs 840 bbl/day 10-15% oil cut Zone with low salinity Salinity RW used in Elan (constant green curve) ADT RW xo

7 Variable M & Rwa Sw from Variable MN & Rwa from ADT Delaware Basin Wolfbone Using ADT to reduce water-cut and decrease Drilling & Completion Costs Conventional processing of data shows a productive zone at the bottom of the well. This is incorrect as shown by the Elan/Dielectric and is verified PL results. The cost to drill and stimulate these unproductive zones is approximately $750K/well. With 60+ wells drilled to date, the client has spent in excess of $45M drilling and completing zones that have contributed nothing but excess water. Lost opportunity costs associated with the 7-10 days it takes to drill through the lower 2 zones coupled with $750k savings on all future wells has changed client s outlook on SLB logs. Savings by using SLB is about 20-25% of well cost and versus only 2% added well cost to use SLB for logging the ADT.

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