Application of NMR for Evaluation of Tight Oil Reservoirs

Transcription

1 Application of NMR for Evaluation of Tight Oil Reservoirs Rick Lewis & Erik Rylander Iain Pirie Stacy Reeder, Paul Craddock, Ravi Kausik, Bob Kleinberg & Drew Pomerantz

2 Lots of oil in place what is pay?

3 Organic Shale Pore System Diameter (nm) 0.38 Methane Molecule 0.38 to 10 Oil Molecule 4 to 70 Pore Throat 15 to 200 Virus 5 to 750 Organic Pore 10 to 2000 Inter/Intra Particle Pores 200 to 2000 Bacteria Shale Size Particle (mean)

4

5 Evolution of organic fractions of shale with increasing thermal maturity.

6 NMR T 2 Time Distribution (Conventional vs. Organic Shale) 1 1 T 2 T 2 bulk 1 T T 2 T 2 T 2 bulk surface 1 1 ~ T 2 T 2 surface

7 Porosity (p.u.) Porosity (p.u.) sity (p.u.) 0.1 Porosity (p.u.) ity (p.u.) Porosity (p.u.) 0.1 Comparison of 1 Core 10 NMR 100 to 1000 Log NMR: T investigate expelled 2 (ms) fluids re Depth 9198 ft Core CMR CMR Porosity: 9.9 p.u. Core NMR Porosity: 9.1 p.u. Core Depth 9198 ft Shifted T - Core TOil - - Core 2 2 Oil - CMR T 2 - CMR T Oil CMR CMR Water T 2 (ms) m T Shifte - Core 2 Oil - C T 2 - CMR Water T 2 (ms) T 2 (ms) T 2 (ms) T (ms) Shifted Oil - Core Oil - Core Oil Oil - CMR - CMR Shifted Oil - Core Oil - CMR

8 T2 distribution (pu) T 2 Cutoff ~ 9.4 ms T 2 -cutoff = 9.4 ms xx99 ft 10.1 pu xx10 ft 10 pu xx23 ft 13 pu xx33 ft 8.8 pu xx40 ft 5.8 pu xx58 ft 10.5 pu xx65 ft 7.5 pu xx81 ft 8.1 pu xx93 ft 9.9 pu xx02 ft 7.1 pu T 2 (ms)

9 Bulk Relaxivity

10 Kerogen Light oil Bitumen Pore Water Clay bound water Shale Constituents by Volume Tight Oil Reservoir Eff Phi Mineral matrix Total Phi

11 Pore Distribution Clay-Bound Water Bitumen Cap-Bound Water Cap-Bound Oil (OM Pores) Cap-Bound Water Free Oil (Larger OM Pore > 250 nm) Producible Fluids Oil and Water (Water wet pores)

12 BOPM Eagle Ford Oil Producer Mar-00 Jun-00 Oct-00 Jan-01 Apr-01

13 BOPM Eagle Ford Oil Producer Mar-00 May-00 Jun-00 Aug-00 Oct-00

14 Tmax Data

15 T 2 relaxation of native and re-saturated shale

16 T 2 relaxation of native and re-saturated shale

17 T 2 relaxation of native and re-saturated shale Native state porosity Resaturated oil porosity

18 Rock Eval Pyrolysis Measurements of S1: oil in the sample S2: potential oil and gas S3: CO 2 S4: residual hydrocarbon Tmax: maturity indicator TOC

19 The Importance of Oil Saturation Index (OSI) Jarvie, 2012: As much as mg Oil / g TOC is sorbed to Kerogen An OSI > 100 mg Oil / g TOC may produce oil

20 Oil Saturation Index (OSI) Free Water Bound Water Matrix Kerogen Bitumen Oil TOC S 1 OSI = S1 TOC = Kerogen Oil Bitumen Oil Jarvie, 2012: As much as mg Oil / g TOC is sorbed to Kerogen An OSI > 100 mg Oil / g TOC may produce oil

21 Shale-Oil Systems Hybrid Shale Juxtaposed organic-rich and organic-lean intevals Bakken is end member OSI provides method to ID contribution of organic-lean intervals in finely juxtaposed system

22 TOC standard workflows Estimating TOC from logs: - Schmoker (density) - Δ log R (Sonic-Resistivity) - Uranium - NMR-PHIA deficit Based on indirect measurements Require calibration to core data Specific to a particular formation All are kerogen-only TOC

23 Elements from Spectroscopy TOC from Carbon workflow Carbon Direct measurement from Inelastic Spectra Si, Ca, Mg, S, Fe, K, Minerals Na, Mn,P, etc. TIC = 0.120*Calcite *Dolomite *Siderite *Ankerite

24 Carbon Saturation Index CSI W c oil W c organics W c oil CSI W W c oil NMR Carbon SaturationIndex (unitless, 0 to1) c organics bitumen BVW oil bulk OilWeight fraction of carbon in light hydrocarbon (w/w) Total NMR porosity (v/v) Volume bitumen (v/v) Oildensity (g/cm NMR bitumen Bulk density (g/cm ) ) Total organiccarbon content,directly from geochemical log(w/w) Bulk volume water,from petrophysi cal model or dielectric(v/v) 3 3 BVW oil bulk

25 Reservoir Producibility Index Account for Porosity Differences RPI where CSI CSI W W c W c c oil oil organics CSI Carbon Saturation Index (unitless, 0 to1) W W c oil c organics Oil Weight fraction of carbon in light hydrocarbon, may require correction for bitumen (w/w) Log generated index Total organic carbon (TOCj) content, directly from Litho Scanner (w/w) Circumvents problems associated with recovery and analysis of hydrocarbons from cuttings and/or core OSI of 100 ~ RPI of 0.1 (fc of porosity)

26 BOPM RPI Good Well Mar-00 Jun-00 Oct-00 Jan-01 Apr-01

27 BOPM RPI - Poor Well Mar-00 May-00 Jun-00 Aug-00 Oct-00

28 BBL or MCF RPI, Woodford (VRo ~ 0.7)

29 RPI, Bakken (VRo ~ 1.0)

30 T 2 Distribution of Native Shale Sample Plotted Together with Formation Oil and Brine Re-saturated Shale

31 Pore Fluids from T 1 /T 2 Differentiate between hydrocarbon and waterfilled pores Two pore system model Organic with hydrocarbon Inorganic with water T 1 /T 2 ratio higher for oilsaturated pores Core work performed by OU on Barnett Shale

32 T 1 /T 2 maps of Eagle Ford Shale at various depths

33 Universal T 1 -T 2 picture for shale at 2MHz

34 WT(1) WT(2) WT(3) WT(4) CPMG(1) CPMG(2) CPMG(3) CPMG(4) WT(4) WT(1) WT(2) WT(3) M z = M 0 [1 - exp(-t/t 1 ) ] t

35 Potential for T 1 -T 2 in Tight Oil Differentiate and potentially quantify bitumen Differentiate and quantify OM and IP pores Limit from 2 to ~30ms Initial Observations Can not differentiate between hydrocarbon and water in IP pores All bitumen may not be quantified due to short relaxation time

36 Conclusions Non-producible hydrocarbons are common constituent in liquid producing shales One type of non-producible hydrocarbon is viscous source rock bitumen Another type of non-producible hydrocarbon are oils sorbed to organic pore walls RPI methodology can be used to characterize producible zones, and it takes porosity and pore water into account It recognizes hybrid reservoirs T 1 /T 2 shows potential to differentiate bitumen and OM vs. IP pore fluids Application of these metrics to landing point selection has had dramatic positive impact to productivity in shale wells!