Spontaneous Potential Log: Principais Usos e Aplicações

Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade Universidade Federal do Oeste do Para 14 de junho de 2022 Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SUMARIO 1 INTRODUC AO 2 SP PRINCIPALS 3 USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log INTRODUC AO To explain how Spontaneous potential SP is created in the formation borehole How SP is measured Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log The spontaneous potential tool measures natural electrical potentials occur in boreholes Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log SP distinguishes porous permeable sandstones from intervening shales The natural batteryis caused when the use of drilling mud with a different salinity from the formation waters causes two solutions to be in contact that have different ion concentrations Ions diffuse from the more concentrated solution typically formation water to the more dilute The ion flow constitutes electrical current which generates a small natural potential measured by the SP tool in millivolts Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SUMARIO 1 INTRODUC AO 2 SP PRINCIPALS 3 USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP Principals The direction of an electric current Current is defined as moves in the same direction as the positive charge flow The charge carriers electrons are negative Current is in the opposite direction as the electrons Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP Principals The direction of an electric current Current is defined as moves in the same direction as the positive charge flow The charge carriers electrons are negative Current is in the opposite direction as the electrons Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP Principals The direction of an electric current Current is defined as moves in the same direction as the positive charge flow The charge carriers electrons are negative Current is in the opposite direction as the electrons Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Spontaneous potential SP is used To Detect permeable zones Detect boundaries Determine formation Rwater Determine Vshale in permeable beds Well to well correlation Property Measures formation voltage Passive measurement Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Must have waterbased mud Mudformation water salinity difference causes battery effect Battery effect components Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP Principals Electrochemical Liquid Junction Potential Diffusion Ej In permeable region Anions more mobile than cations Membrane Effect Em Shale acts as membrane Repels anions passes cations Electrokinetic due to P Usually minor disregarded Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Origin of SP SP is a naturally occurring potential in the borehole which Is sum of The membrane potential between the shale and the sand The liquid junction potential The electro Kinetic effect is sometimes observed but is rare and shortlived Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Electrochemical Potential The electrochemical potential sensed in the borehole is generated by the sum of two potentials known as The membrane potential Em The liquid junction potential Ej Ec Em Ej 1 Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Liquid Junction Potential Ej In a permeable sand if the formation water is more saline than the mud filtrate then the salt ions Na and Cl will diffuse towards the mud filtrate The Cl ions are more mobile than the Na ions Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Electrokinetic potential To be able to control the formation pressure there is always a positive pressure from the mud to the formation overbalance Saline mud filtrate will penetrate the sand The Movement of saline mud filtrate create an electrokinetic potential difference between the formation and the mud Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Measuring SP in the borehole The SP measurement is taken as a potential difference between a downhole electrode and a reference electrode at the surface The mud column in front of the sandstone behaves as a resistor in the SP loop Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Static SP SSP SSP is the total potential drop along a line of current flow The deflections of SP curve are a measure of only potential drop in the borehole resulting from SP current SP is a fraction of the total potential drop Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Static SP SSP SSP is the sum of the membrane Em and junction potential Ej SSP Em Ej Isprm rt rsh rxo 2 Where ISP is the SP current r is the resistance The SP we measure is the change in potential from one point in the well bore to another It is developed across the resistance of the mud column Rm from one point to another due to the SP current ISP SP Isprm 3 Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Static SP SSP In front of a thik permeable water bearing clean sand The SP will be flat This is called static SP or sand baseline Most SP interpretation is based on the comparison between sand and shale baselines Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP Currents Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Determination of SSP Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Determination of SSP Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Determination of SSP Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Measure SP value is affected by Bed thickness Bed resistivity Borehole diameter Invasion Shale content and The ratio of Rmf to Rw Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Typical SP responses Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SUMARIO 1 INTRODUC AO 2 SP PRINCIPALS 3 USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Uses of SP log Identify permeable zones Define bed boundaries Compute shale content Depositional Environment from the SP Determine values of formation water resistivity Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 1Identify permeable zones Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 1Identify permeable zones The negative abnormal on SP curve usually indicates the permeable zone the higher abnormal range the more permeable of the formation Since invasion can only occur in permeable formations deflections of SP can be used to identify permeable formations Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 1Identify permeable zones SP alone can not tell the whole story Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 2 Definition of bed boundaries Half of abnormal amplitude point will be boundaries of shale and sand The bed thickness is the interval between two boundaries The vertical resolution of SP is poor and often the permeable bed must be 30 ft or more to achieve a static flat baseline SP Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 2 Definition of bed boundaries Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 2 Definition of bed boundaries Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 3 Compute shale content The presence of shale in a permeable formation reduces the SP deflection In waterbearing zones the amount of SP reduction is related to the amount of shale in the formation The SP response of shales is relatively constant and follows a straight line called a shale baseline The SP value of the shale baseline is assumed to be zero and SP curve deflections are measured from this baseline Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 3 Compute shale content Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Base Line Drift Over long intervals several hundreds to thousands of feet the SP baseline can drift either in the positive or negative direction This characteristic is commonly observed in shallow sections Caused by increases in relative oxidation of the rocks that are close to the land surface This may introduce errors if the SP magnitude is being calculated over that long interval especially by means of a computer The baseline drift can be removed many programs have such editing routines so that the SP baseline retains a constant value usually set to zero over the length of the logged interval Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Base Line Drift Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Shale Content Presence of shale in the formation will reduce the static SP Shale lattice will slow the migration of chlorine ions and assist the flow of sodium ions decreasing Ej This reduces SSP to a pseudostatic value PSP Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Shale Content Example1 Determine the volume of shale in zone B Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Shale Content Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Shale Content Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Shale Content Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 4 Determination of Formation Water Resistivity from SP Log The most direct way of finding water resistivity Rw is to obtain a sample of formation water and measure its resistivity Formation water samples if available are invariably contaminated by mud filtrate Rw is therefore usually calculated Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 4 Determination of Formation Water Resistivity from SP Log Determine formation temperature Find Rmf at formation temperature Convert Rmf at formation temperature to Rmfe value Compute the Rwe Convert Rwe at formation temperature to Rw Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log 4 Determination of Formation Water Resistivity from SP Log Induction electric log with an SP curve from a Pennsylvanian upper Morrow sandstone in Beaver County Oklahoma Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP shapes and Depositional Sequence Since shales and clays are generally finergrained than sands a change in SP suggests a change in grain size SP deflections can indicate depositional sequences where either sorting grain size or cementation change with depth and produce characteristic SP shapes These shapes are referred to as bells funnels or cylinders Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log SP shapes and Depositional Sequence Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Factors Affecting the SP Response Hydrocarbons reduce the SP deflection Shaliness reduces the SP deflection Bed thickness thin beds do not develop a full SP deflection Permeability low permeability zones will have a very high invasion diameter so it may be impossible to read the Junction Potential hence SP readings may be low Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Passive Log Correlation GR SP and Caliper Often correlate Different measurements Different reasons Correlation helps GR instead of SP in oil base mud Easier detection of shales Facilitates zonation Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Passive Log Correlation Spontaneous Potential Log Prof a Zoraida Roxana Tejada da Piedade INTRODUC AO SP PRINCIPALS USES OF SP LOG 1Identify permeable zones 2 Definition of bed boundaries 3 Compute shale content 4 Determination of Formation Water Resistivity from SP Log Obrigada