04.sp log

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WELL LOGGING ANALYSIS.WELL LOGGING ANALYSIS.

04.Spontaneous 04.Spontaneous Potential.Potential.

Mustoto Mustoto Moehadi Moehadi ..HP. 085814457579 HP. 085814457579

[email protected]

5MT – Oil & Gas Business Series.

5MT - Oil & Gas Business Course.

Spontaneous Potential.

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Dihasilkan dari adanyaperbedaan tegangan dari

suatu elektroda yangberjalan didalam lubang bor

dengan elektroda yang

tetap dipermukaan, dimana

elektroda tersebut melewati

berbagai jenis batuan yang

berbeda sifat serta isi yang

terkandung didalamnya,

dalam satuan millivolt.

SPONTANECOUS POTENTIAL LOG SPONTANECOUS POTENTIAL LOG



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What is SP?What is SP? (Spontaneous Potential) (Spontaneous Potential)

A Voltage measurement between a down-

hole Electrode and a Surface Electrode (also

called a Fish)

SP Voltage was discovered by accidentwhen an Engineer running an Electrical Tool

was pulling out the Tool (without any Tool

Power applied) and forgot to STOP the Log

recording

SP Voltage is an extremely SMALL voltage

and develops in Open Hole with Water based

Muds only (due to differences in

concentration of Ions between Drilling Mudand Formation Water)



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What causes the SP voltage? What causes the SP voltage?

Electro-chemical (Ec) sources (Primary reason, produces > 95% ofthe Total SP signal)

Electro-kinetic (Ek) sources (rare and small signal)

Electro-Chemical (Ec)

sources are further

divided into

a. Liquid Junction

Potential (E j)

b. Membrane Potential

(Em)

OREc = E j + Em

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Liquid Junction Potential Liquid Junction Potential

Chloride Ions Cl- are more mobile, therefore they

quickly migrate from Higher concentration C1 tolower concentration C2, leaving the Sodium Ions

Na+ behind

This results in charge imbalance and a Potential to

appear at the Liquid Juncti on



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Membrane Potential Membrane Potential

Shales have negative charge on their crystal lattice frame,therefore they attract Sodium Na+ ions and repel Chloride Cl-ions and act like Ion filters

These Na+ ions then migrate thru the Shale and accumulate onthe Borehole Shale boundary.



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Combining the Two effects Combining the Two effects

If we now pass an electrode past the formation we would see negativedeflection in front of the permeable zone and a positive deflection in

front of the Shale The magnitude of the deflection will depend on the contrast of salinitiesof the two liquids

We measure the Total deflection from the Shale Base line

++

+ _ _ _ _ _

Shale

base

line



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SHALE LINE dan SAND LINE

Adalah gambaran kurva SP terhadap lapisanshale yang pada umumnya konstan dan akanmengikuti suatu garis lurus.

Sedang untuk lapisan yang porouspermeable defleksinya akan menjauhi shalebase li ne pada lapisan yang tebal .Penyimpangan ini mencapai suatu hargadef leksi yang konstan yang biasa disebutsebagai “ Sand Line”.

Peny impangan kurva SP b isa kearah k irimaupun kanan tergantung pada salinitasrelatif dari air formasi dan filtrate sumur.


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Magnitude and Polarity of Sp deflectionMagnitude and Polarity of Sp deflection

depends on the Contrast in Salinities depends on the Contrast in Salinities



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KURVA SP AKAN

TERBENTUK BILA.

Terdapat shale dan lapisan

yang permeable.

Adanya perbedaan salin itasantara air formasi (Rw) dan

filtrat lumpur (Rmf).

Terjadi invasi dari fi ltrat.

Fluida didalam sumur

konduktif.

Sumur tidak diselubungi pipa.

Kontrak elektrik terjadi antara

elektroda acuan dengan

elektroda dalam sumur.




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STATIK SPONTANEOUS POTENSIAL.

Apabila pengukuran SP melalui lapisan batuan yang cukup

tebal serta dengan kondisi bersih, maka defleksi kurva SP

akan mencapai maksimum, bila defleksi SP tidak dipengaruhioleh kandungan shale yang ada dalam batuan tersebut.


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Membedakan lapisan/batuan impermeable (shale)

dengan permeable (non-shale).

Menentukan batas litologi dan ketebalan batuan.

Membantu untuk menentukan lingkungan

pengendapan.

Kwalitatif; banyak shale pada lapisan batuan

permeable.

Kwantitatif; menentukan Rw.

Korelasi antar sumur-sumur geologi.

Kegunaan Kegunaan SP Log.SP Log.



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FACTORS AFFECTING THE SP RESPONSE FACTORS AFFECTING THE SP RESPONSE

Hydrocarbons: reduce the SP deflection.

Shaliness: reduces the SP deflection.

Bed thickness: thin beds do not develop a full SPdeflection.

Permeability: low permeability zones will have a veryhigh invasion diameter, so it may be impossible to

read the Junction Potential, hence SP readings may

be low



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Dibawah ini adalah sejumlah pembatasan darikehandalan metode ini:

1. Komponen elektrokinetik dari SP diabaikan.

2. Contoh Rmf yang buruk (contoh filtrasi lumpur yang tidak baik).

3. Hubungan antara Rwe-Rw dan Rmfe-Rmf,khususnya pada Rw yang tinggi.

Sehingga penggunaan SP untuk menentukan Rwhanya boleh dilakukan bila metode lain tidakberlaku.

Ketidak Ketidak Pastian Pastian SP Log.SP Log.



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SP Applications SP Applications

Depth correlation (SP curve behaves very

much like the Gamma Ray curve)

Identify ing Bed boundaries

Lithology Indicator (Shale or non-Shale)Permeability Indicator

Volume of Shale (Vsh) indicator

Rw Calculation

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Problems recording SP Problems recording SP

Drum Magnetism, Measuring Head Magnetism

causes cyclic SP

Cable conductor leakage

Running water on SP Fish

Welding or any heavy Electrical activity at Rig

Stray ground currents and voltages

Bi-metallism



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SP LOG SAMPLE and The Effect Magnetism on SP SP LOG SAMPLE and The Effect Magnetism on SP



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1. Baca harga Ssp.

2. Tentukan Rmfe. Jika Rmf pada 75 deg F>0.1 Ohm, maka Rmfe=0.85XRmf.

Jika Rmf pada 75 deg F

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10.SP 10.SP



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11.Sp 11.Sp



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11.SP 11.SP

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12.SP 12.SP



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12.SP 12.SP



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13.Rmf/Rwe f/ SP 13.Rmf/Rwe f/ SP



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13.Rmf/Rwe 13.Rmf/Rwe

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14.Rw 14.Rw



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14.Rw 14.Rw



31 5MT - Oil & Gas Business Course.


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MOUNCE & RUST;

Mempelajari rantai aliran dari suatu sistim yang terdiri dari

2 elektrolit dengan konsentrasi berbeda dengan shale.Ternyata arus yang mengalir dalam sistim tergantung padakonsentrasi kedua elektrolit. Gambar jo lali


04.sp log

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