Page 129 - Origin and Prediction of Abnormal Formation Pressures

SMECTITE-ILLITE TRANSFORMATIONS Pore size 1.7-3.9 1.3-3.1 1.0-2.5 107
and pore size; average values Permeability (wm) mD) (2.7) (2.1) (1.6) 0.7-2.0 (1.3) 0.5-1.5 (0.8)

permeability (k\h) Porosity

Mixed-layer Traces Traces
(&,),
Contents of various clay minerals in the Apsheron Archipelago oilfields, variation with depth of porosity

Chlorite 5-10 (6.5) 0-10 (7.0) 5-15 (7.0) 0-10 (5.5) 0-15 (5.0) 0-10 (4.0)

Kaolinite 15-20 (1 7.5) 0-15 (13.0) 5-20 (7.0) 0-20 (12.5) 0-30 (15.5) 10-25 (15.5)
are shown in parentheses (after Buryakovsky et al., 1995, table 2, p. 208)

Hydromica 35-65 (43.5) 20-40 (35.0) 30-60 (42.0) 10-60 (38.0) 20-65 (39.0) 20-60 (37.5)

Clay-mineral content (%) Montmorillonite 10-45 (32.5) 35-70 (45.0) 15-50 (36.0) 15-70 (40.0) 5-65 (39.0) 5-70 (36.0)

TABLE 4-3 Depth range (m) 1000-2000 2000-3000 30004000 4000-5000 5000-6000 More than 6000 m