Spontaneous Potential Theory
Spontaneous potential as discussed is the potential difference that occurs naturally in the earth. If you plan to drill into the earth’s crust you need to have adequate knowledge on this theory. Do you believe you understand it clearly? If so then take up the test below and see if the results are in your favor. All the best!
- 1.The primary objective of logging the Spontaneous Potential (SP) is to determine:
- A.
True resistivity of the uninvaded formation (Rt)
- B.
A qualitative indicator of formation permeability
- C.
Mud filtrate resistivity (Rmf)
- D.
Formation porosity
- 2.Which of the following statements is true?
- A.
Electrokinetic processes relate to the movement of fluid at the borehole/formation interface, while electrochemical processes relate to ionic imbalances between fluids.
- B.
Electrokinetic processes relate to ionic imbalances between fluids, while electrochemical processes relate to the movement of fluid at the borehole/formation interface.
- 3.A majority of the deflection observed on an SP log is the result of
- A.
Electrokinetic potentials
- B.
Electrochemical potentials
- C.
Membrane potential
- D.
Liquid junction potential
- 4.Ionic exchange across the boundary of a permeable formation and an adjacent shale produces an electromotive force in the formation called the:
- A.
Membrane potential
- B.
Liquid junction potential
- C.
Electrokinetic potential
- 5.Ionic exchange across the interface between two fluids of different salinities produces an electromotive force in the formation called the:
- A.
Membrane potential
- B.
Liquid junction potential
- C.
Electrokinetic potential
- 6.The SP measurement is taken as a potential difference between:
- A.
A downhole electrode and a current return electrode, both located on the tool
- B.
A downhole electrode and casing
- C.
A downhole electrode and a reference electrode at the surface
- D.
A downhole electrode and the wireline
- 7.In which of the following conditions is the SP response valid?
- A.
Water-based mud
- B.
Cased hole
- C.
Air-drilled hole
- D.
Oil-based mud
- 8.Under what conditions is an electrokinetic potential created as fluid flows through the mud cake?
- A.
Borehole drilled with very heavy mud
- B.
Hydrostatic pressure in the borehole balances formation pressure
- C.
Borehole drilled with light mud
- D.
Hydrostatic pressure is less in the formation than in the borehole
- 9.Hydrostatic pressure is less in the formation than in the borehole
- A.
Rmf = Rw
- B.
Rmf > Rw
- C.
Rmf < Rw
- 10.Ionic exchange resulting from a pressure differential between the formation and the borehole produces an electromotive force called the:
- A.
Electrochemical potential
- B.
Electrokinetic potential
- C.
Membrane potential
- D.
Liquid junction potential
- 11.Select all of the potential applications of the SP measurement.
- A.
Determination of formation water resistivity (Rw)
- B.
Determination of volume of shale
- C.
Estimation of diameter of invasion
- D.
Well-to-well correlation
- E.
Determination of bed thickness
- 12.The spontaneous potential tool is designed to measure a natural – or spontaneous – current flow in the borehole and formation resulting from ionic imbalances that exist between different subsurface fluids and ionic movement near the borehole/formation interface.
- A.
True
- B.
False
- 13.The exchange in ions (primarily chlorine, Cl-, and sodium, Na+) between fluids of different salinities creates a _____ drop in a fluid-filled borehole.
- A.
Voltage
- B.
Resistivity
- C.
Current
- D.
Power
- 14.In which of the following conditions is the SP response not valid?
- A.
Water-based mud
- B.
Cased hole
- C.
Air-drilled hole
- D.
Oil-based mud
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