What Physical Properties Best Indicate the Presence of Petroleum in Rock Formations?
high resistance to the flow of electric current. Petroleum gas is more resistive then liquid crude. Water on the other hand is less resistive then oil and gas. Thus by measuring the resistivity of the formation and fluid, it is relatively easy to infer the presence of petroleum in the formation. A water bearing formation underlying a petroleum bearing formation will be an easy find because the resistivity contrast between the two zones will be vividly clear. The water bearing formation will show relatively low resistivity and the petroleum bearing formation will show very high resistivity. Low resistivity means high conductivity and vice versa. Wireline service companies have various resistivity measuring devices. Some examples are induction and laterolog devices. Application of each device depends very much on the bore hole fluid and formation salinity. Salinity is a measure of the amount of chlorides in the bore hole and formation fluid. When the presence of petroleum in indicated by
