Formation Factor-Porosity Relation Derived From Well Log Data

Data derived from deep induction-density log combination in shallow invaded water sands has been averaged and combined to define an in place formation factor-porosity relation. A total of 2295 formation factors were calculated and plotted. Data from eleven wells from the offshore California Pliocene and four wells from the offshore Texas-Louisiana Miocene were used. The 1575 formation factors calculated from the California Pliocene indicate an in place formation factor-porosity relation of: F = 2.45 / (porosity^1.08)The 720 formation factors calculated from the Gulf Coast Miocene indicate an in place formation factor-porosity relation of:F = 1.97 / (porosity^1.29)Plots are presented of data from all wells from the Pliocene and Miocene. A combination data plot from all wells in each geological province is also represented. It is concluded that reliable formation factor-porosity relations can be defined using well log data. Care should be exercised in the transfer of these relations from one geological province to another.