North GOM Petroleum Systems: Modeling the Burial and Thermal History, Organic Maturation, and Hydrocarbon Generation and Expulsion Roger J. Barnaby 2006 GCAGS MEETING
Previous studies of northern GOM crude oils: composition, 13 C, document Type II algal kerogen in Smackover major source Objectives Evaluate source rock hydrocarbon potential and maturity Smackover geochemistry (TOC, kerogen) Model burial history Model thermal history Model hydrocarbon maturation, generation and expulsion Key controls Timing and burial depths Volumes of oil and gas Assess secondary hydrocarbon migration
MONROE UPLIFT N. LA SALT BASIN Primary control for basin modeling 140 key wells (red) 44 sample wells (blue) 30 additional wells being analyzed CRETACEOUS SHELF MARGIN 50 mi
Burial History: Depositional and Erosion Events Geological time scale: Berggren et al. 1995 Formation ages: Salvador 1991 Galloway et al. 2000 Mancini and Puckett 2002; 2003 Mancini et al 2004
Hosston Wilcox Miocene Oligocene Cotton Valley
Burial History Reconstructed from present-day sediment thickness after correcting for compaction Compaction due to sediment loading Maximum paleo water depths < few 100 meters, no correction for water loading Paleobathymetry Sea level through time
depth (ft) Porosity-Depth Relationships 0 porosity 0.00 0.10 0.20 0.30 0.40 0.50 0.60 Limestone Shale 5000 10000 Exponential Compaction f = f 0 exp (-Kz) 15000 Sandstone Where: f = porosity f 0 = Initial porosity K = compaction factor z = depth 20000
depth (ft) Burial History: Decompaction Present-day depths 3 t1 Remove 2 & 3 Decompact 1 1 y 1 y 2 t2 Add 2 Partially compact 1 2 t3 Add 3 Compact 2 and 1 3 2 1 2 y 1 y 2 1 porosity 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0 1 5000 10000 15000 20000
Burial History: Compacted vs Non-compacted Depth (ft) Time (Ma) 200 150 100 50 0 0 5000 Non-compacted 10000 Compacted 15000 20000
Lithology (Wilcox) CALCULATE DECOMPACTION -lithology from digital logs End member lithologies -SS, SH, LS, ANH Log-derived lithology -mixture of end members Compaction parameters for mixed lithology weighted arithmetic average
Lithology (Upper Glen Rose)
Hosston Wilcox Miocene Oligocene Cotton Valley
Burial History
2 Miocene Oligocene Hosston Wilcox Cotton Valley
Burial History
Thermal History Modeling formation temperature Heat flow approach: temperature function of basement heat flow, thermal conductivity overlying sediment Present-day heat flow Well BHTs Surface temp = 20 o C Thermal conductivity Porosity and lithology are major variables controlling thermal conductivity In-situ thermal conductivity computed by BasinMod
Heat Flow Calculation W meters 2 = T 2 -T 1 (10 3. deg K) y 2 -y 1 (meters) x W meter (10 3. deg K) T 1, y 1 Heat Flow Temperature Gradient Thermal Conductivity T 2, y 2
Calculated vs Measured BHTs BHTs Calculated Heat Flow = 50 mw/m 2
Thermal History: Paleoheat Flow Constant vs. rift model Heat Flow (mw/m2) b = 2.0 100 170130026300 90 b = 1.75 80 b = 1.5 b = 1.25 70 60 50 Litho=120 Litho=96 Litho=80 Litho=68 Litho=60 b = 1.0 40 150 100 50 0 30 Time (Ma) Moho b = 2 Crust Aesthenosphere Subcrustal lithosphere 30 km 120 km N. LA Beta 1.25 b 2.0 Nunn et al 1984 Dunbar & Sawyer 1987
Thermal History: Lithospheric Stretching b = 1.25 Dunbar and Sawyer 1987 b = 2.0
170152065500 170612011700 MONROE UPLIFT Depth (ft) 170152087800 17067006100 171190136200 Thermal History Late K Igneous Event 170692007200 170692023300 0 2000 %Ro (measured) 0.10 1.00 10.00 Surface %Ro (expected) 4000 6000 17067006100 8000 10000 170612011700 50 mi 12000 14000
Moody (1949)
Heat Flow History and Thermal Maturity, Monroe Uplift Late K thermal event 170670006100 (J-2) 6000 ft Optimum match between BHTs and %Ro and modeled values using rift model with Late Cretaceous thermal event
Heat Flow: 170 Ma
Heat Flow: 119 Ma
Heat Flow: 95 Ma
Heat Flow: 17 Ma
Maturity Modeling Thermal maturity (%Ro) calculated using kinetic model from LLNL Standard type II kerogen 1D steady-state heat flow at model base, heat transfer from conduction 170692023300
48 mw/m2, rift model, modeled maturity reasonably matches TAI and %Ro Thermal History: Paleoheat Flow Thermal maturity constrained by %Ro 170692023300
171190164100 170152087800 170812037000 170812042100 170692008800 170692007200
%Ro (calc) Calculated %Ro vs. Measured 2.50 2.00 y = 1.0162x R 2 = 0.7036 1.50 1.00 0.50 0.00 0.00 0.50 1.00 1.50 2.00 2.50 %Ro (meas)
Smackover Maturity Present-day 95 Ma Present-day
N Hydrocarbon Generation & Expulsion Smackover: oil-prone Type II kerogen TOC data updip wells only Extrapolated downdip Ran models with range TOC 20 15 10 5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 2.0 3.0 4.0 TOC (%)
RELATIVE PERMEABILITY: OIL/WATER 100 OIL-WATER SYSTEM WATER-WET LITHOLOGIES 10 K Sw irr OIL SOURCE ROCKS OIL INCREASINGLY MOBILE 1 PHASES EQUALLY MOBILE 0.1 Ex: saturation threshold = 0.20 WATER INCREASINGLY MOBILE 0.01 0.7 0.4 0.0 OIL SATURATION Pepper (1991)
Oil Expulsion Volumetrics 10 9 bbls oil
cum. billion bbls Expulsed Oil Volumetrics 1500 1250 Constant heat flow (present-day) 1000 750 Series1 Series4 Rift heat flow model 500 peak expulsion (108 to 103 my) (late Early Cretaceous) 250 175 150 125 100 75 50 25 0 0 M.a. TOC = 2 x RKZ Saturation Threshold = 0.15
Gas Generation and Expulsion Primary gas Secondary gas Average GOR, North Louisiana = 12,500, up to 500,000 or more
Expelled Gas (Primary + Secondary) TOC = 2%, saturation threshold = 0.2, rift heat flow w/ K event
Cumulative Expulsed Gas Fraction Timing of gas expulsion Saturation threshold = 0.2 TOC = 1% Heat flow model with rifting and late K event 1.00 0.80 0.60 0.40 0.20 140 120 100 80 M.a. 60 40 20 0.00 0
N. LA Petroleum System 200 150 100 50 Jurassic Cretaceous Tertiary E M L E L Time Scale Petroleum Systems Events Source Rock oil gas Reservoir Rocks Overburden Rocks Uplift Generation-Expulsion Secondary Migration Trap Salt Critical Moments
Conclusions Geochemical data and basin modeling indicate that Smackover mature for oil and gas Peak oil expulsion late Early Cretaceous, persisted into Late Cretaceous Most gas is secondary Peak gas expulsion early to middle Tertiary Cumulative production accounts for less than 1.0% of total expulsed volumes of oil and gas Estimates in published literature 1-3%