Quantitative evaluation Examine procedures in which data from

Quantitative evaluation Examine procedures in which data from 2 or more logs will be used to evaluate for the amount of hydrocarbon compared to pore water within a formation The proportion of pore space occupied by water is known as water saturation (Sw) e. g. if 65% of the formation is occupied by water and 35% by hydrocarbons the water saturation is 0. 65 (percent water saturation is 65%) Definition of the formation factor (F) F = Ro/Rw Where Ro is the resistivity of the total formation (rock matrix + fluids) saturated with water Rw is the resistivity of the water itself

q F= Formation factor is used to help calculate water saturation – function of porosity q Definition F = Ro/Rw q Definition for water saturation Sw RO = = √RO/RT RT (for a 100% saturated sand) q Substituting in the equations and rewriting for water saturation we have: RO = F. RW SW = F. RW/RT

QUANTITATIVE EVALUATION FOR HYDROCARBON POTENTIAL Archie equation (1942) … F = a/φm a m φ = = = constant which is lithology dependent empirically derived constant porosity (e. g. 30% enter as 0. 30) Actual values for a and m are lithology and region dependent Some examples F = 0. 82/φ uncompacted sands F = 1/ φ2 compacted formations, chalk F = 1/ φ2. 2 compacted clastic and oolitic rocks F = 0. 62/ φ2. 15 recrystallized carbonates (sucrosic texture) F = 1. 13/φ1. 73 generic value for large number of samples

Analysis for Hydrocarbon Potential Definition: Rwa = Rt / F q Rwa = apparent water resistivity q Rt is measured from a deeply focused induction log q F is calculated from the formula using log measured porosity value q est Sw (%) = q Rw = Rwa of a 100% water saturated formation. Measure from an obvious water-bearing formation q Rwa Analysis q Ratio Rwa < 2 No oil production q Ratio Rwa > 4 Oil production expected √Rw/ Rwax 100 Rwa/ Rw

Hydrocarbon potential Locations SP Resistivity ohm-m mv sh 1 2 3 4 5 Use F = 0. 83 / φ2 dp dp in. φ F Rwa est Sw % Rwa analysis Rwa/Rw Hydrocarbon Production y/n

READINGS AND CALCULATIONS Levels SP mv Resistivity ohm-m sh dp φ F Rwa dp in. est Sw % Rwa/ Rw Prod. y/n 1 - 62 0. 26 0. 20. 30 9 0. 02 100 1 N 2 - 45 7. 50 6. 70. 06 228 0. 03 82 1. 5 N 3 - 49 1. 50 0. 50. 23 16 0. 03 82 1. 5 N 4 - 18 1. 08 0. 98. 13 49 0. 02 100 1 N 5 - 15 0. 94 0. 8 0. 98. 26 12 0. 08 50 4 Y