Malleswar Yenugu. Miguel Angelo. Prof. Kurt J Marfurt. School of Geology and Geophysics, University of Oklahoma. 10 th November, 2009

Transcription

1 Integrated Studies of Seismic Attributes, Petrophysics and Seismic Inversion for the characterization of Mississippian Chat, Osage County, Northeast Oklahoma By Malleswar Yenugu 10 th November, 2009 Miguel Angelo Prof. Kurt J Marfurt School of Geology and Geophysics, University of Oklahoma

2 Objective: 1. To better understand the seismic and petrophysical properties of Mississippian Chat, which is a good oil/gas producer in Oklahoma, Kansas, West Texas, California etc 2. To Drive away the Misconception of Geoscientists who often treat Chat with Carbonates 3. To better understand the fault compartmentalization of the reservoir with different porosity and permeability distribution and calibrating with production data 2

3 Geological Setting: 3

4 Seismic Attributes: TWT structural map of MC 4 RMS amplitude extraction map along MC

5 Most Negative curvature along MC 5 Most Positive curvature along MC

6 Post stact Acoustic Impedance Inversion: Petrophysical properties of Well-1 6 Amplitude and Frequency spectra of extracted wavelet

7 Synthetic vs Seismic Correlation Correlation : 78% Seismic amplitude section superimposed on Impedance section along well-1 7

8 Cross plot between Impedance and Neutron porosity of the well-1 8 Acoustic Impedance slice extracted along the MC

9 Laboratory Petrophysical Measurements: Integration of seismic to petrophysical measurements Rock Physics properties Porosity Permeability Vp and Vs Acoustic impedance MINERALOGY HELIUM POROSITY MERCURY INJECTION NUCLEAR MAGNETIC RESONANCE TOTAL ORGANIC CARBON ULTRASONIC VELOCITY Samples 9

10 MC-Mineralogy Mineralogy is carried out using transmission Fourier Transform Infrared Spectroscopy. Mid infrared energy is absorbed by molecules when they vibrate at their characteristic frequencies. Combinations of absorption peaks on the spectra represent certain minerals in the sample, (Sondergeld and Rai, 1993) Obtained spectra is inverted using Beer s law i 1 Quantitative inversion resolves 16 minerals. n A bki c i The organic matter in samples is removed by oxidation using a low temperature plasma asher, before measurement, as organic matter can mask the mineral spectrum. 10 FTIR spectra (After Sontergeld and Rai, 1993)

11 Mineralogy Discussion qtz qtz qtz qtz 11

12 NMR Nuclear Magnetic Resonance measurements were done using a 2MHz Oxford- Maran Ultra Spectrometer. 10 scans seconds Based on the transverse relaxation time (T2) for H in water and hydrocarbons, petrophysical properties of rocks like porosity, bound volume/free fluid index can be estimated. Distribution 23,000 22,500 22,000 21,500 21,000 20,500 20,000 19,500 19,000 18,500 18,000 17,500 17,000 16,500 16,000 15,500 15,000 14,500 14,000 13,500 13,000 12,500 12,000 11,500 11,000 10,500 10,000 9,500 9,000 8,500 8,000 7,500 7,000 6,500 6,000 5,500 5,000 4,500 4,000 3,500 3,000 2,500 2,000 1,500 1, ,000 10, ,000 1,000,000 10,000,000 Time (us) A sample NMR T2 distribution from spectral inverson. 12

13 Cum por, % NMR Results T2_Cutoff Cum curves T2 Cutoff: 67ms (desat) inc poro incr poro(desat) T2, ms Nuclear Magnetic Resonance signals were observed in sample The measured T2 cutoff is 67 ms not the accepted value of 93 ms. This means S wir is less and the inferred permeabilities are different. 13

14 Hg Injection Capillary pressure curves and pore throat distribution are obtained using High Pressure Mercury Injection. Mercury is forced into a sample up to 60,000 psi and the incremental volume that enters the sample is measured as a function of pressure. The pore throat radii can be determined from the capillary pressure data using Washburn s equation: P c 2g cosq r P c = Capillary pressure q = Contact angle g =Surface tension r = Pore radius 14

15 Hg Injection Mercury Injection Capillary Pressure Curves show 3 distinct groupings Intrusion between 5,000 and 20,000 psi corresponding to mixed carbonates. Incomplete intrusion even after 59,000 psi corresponding to clay rich zones. 59,000psi 20000psi 15 Clay rich zones show an average pore throat diameter of less than.05 um or 50 nm Samples where intrusion occurs between 5 and 20,000 psi show an average pore throat diameter of.1um or 100 nm. 5000psi

16 Vp-Vs Pulse transmission method (Birch, 1960) This technique, generates ultrasonic pulses by an electrical pulse generator and converted into mechanical vibration by an ultrasonic piezoelectric transducer. Velocity can be calculated by: V L t L= Sonic wave travel distance through the sample (length) Δt = Sonic wave travel time through the sample. t t t total endcap P, S1, S2 500psi,700psi,5000psi 16

17 Velocity, km/sec Velocity, km/sec Velocity, km/sec Velocity, km/sec Vp-Vs Fluid effect O2934W_42_wet_8/27/2009 O2934_42_dry_8/27/ Vp Vs1 Vs Vp Vs1 Vs2 Pressure, psi Pressure, psi O2925W_52_wet_8/27/2009 O2925_52_dry_8/27/ Vp Vs1 Vs Vp Vs1 Vs2 Pressure, psi Pressure, psi 17

18 Vp, km/sec Vp Summary vp_sum_ 08/27/ Pressure, psi Note: Flat behavior of the curve suggests pore geometry to be circular cracks are not a major influence at this scale 18

19 MC-Porosity/Perm/Grain density Grain density was obtained using the Helium porosimeter Helium porosity was calculated from grain and bulk volumes as: V V g Vb= Sample bulk volume V Vg = Sample grain volume b Permeability was measured 1 in. diameter samples (when available) using the AP-608 automated permeameter (CoreTest Systems, Inc.) b 19 AP-608 device used to measure porosity and permeability. (University of Oklahoma (OU-IC 3 ))

20 Porosity vs Perm and Density plots Porosity Vs Density Porosity Vs Perm Porosity vs permeability and density show three groups of lithology 20

21 Work Plan for 2010: Image logs to better understand the fractures within the reservoir zone The lithofacies distribution of Miss. Chat vis a vis to the distribution of fractures and the understanding of porosity for the further drilling of wells Elastic Impedance Inversion with multiple angle gathers The relation between fractures and the production rate of the individual wells 21