Category Archives: Registros Electricos

POTENTIAL SPONTANEOUS LOG



The SP is a record of the terrestrial natural potential, which occur between a moving electrode into the well (A) and a fixed electrode on the surface (B).
SP Register

Registro SP

The deflections of the SP curve from the electric currents flowing in the mud pit.

The SP has 2 components: a component Electrokinetic and Electrochemical.

a) Electrokinetic Component.
This component is also known as current or potential potential of electro-filtration. Occurs when an electrolyte flows because a solution is forced by differential pressure to flow through a porous medium, non-metallic permeable (membrane).

b) Electrochemical Component
This potential is produced by contact with solutions of different salinities. Contact can be direct or through a semi-permeable membrane such as shale. According to the type of contact may be potential: Potential for contact with liquid or membrane potential.

* Liquid Contact Potential

Takes place at the boundary between the area washed and unspoiled, no shale separating the two solutions. Both anions and cations can move from one solution to another.

Because the formation water salinity is higher, both the cations Na + and Cl-anions will migrate towards the mud filtrate. The Na + ion is comparatively higher and drag water molecules 4.5. Cl-ion is smaller and carries only 2.5 molecules of water. Hence, the Cl-migrate more easily than Na + ions.
The result is an increase of positive charges left in the formation water, these charges restrict the migration of Cl-washed into the area this equates to a conventional current flow in the opposite direction.

* Membrane Potential

Because of the layered structure of clay and the loads on the blades, the shales are permeable to cations Na + but impermeable to anions Cl-, ie act as selective membranes so the potential across the shale is called potential membrane.


SP CURVE
Spontaneous potential curve (SP) is a record of physical phenomena that occur naturally in the rocks of a given formation or reservoir.

SP curve records the electrical potential produced by the interaction between the formation water, drilling fluid (conductive) and shales, this voltage is the result of a continuous stream that is generated in these edges by the difference in salinity.

The slope of the SP curve is proportional to the current intensity of SP in the mud of the well at that level, these currents are the maximum limits of permeable formations.

The shape of the curve of the SP and the amplitude of the deflection in front of the permeable layer depends on several factors.

FACTORS AFFECTING THE CURVE SP

Factors affecting the distribution of SP streamlines and potential declines taking place in each of these means through which current flows of SP are:

* Type used drilling fluid (mud), ie know the characteristics of salinity.
* Diameter of invasion from the contaminated area with dirt.
* Layer thickness h.
* True resistivity Rt permeable layer (formation).
* Low permeability.
* Shale inclusions are present as spots within the permeable layer.
* Diameter of the hole.
* Temperature.
* Fractures and faults.

USES OF SPONTANEOUS POTENTIAL CURVE

* Determine Rw values (resistivity of formation water).
* Select permeable zones, only qualitatively not provide a value of K, and compare permeabilities.
* Estimate the clay content of the reservoir rock.
* Correlate lithologic units and helps to define depositional models.
* Identifying the steps of failure.
* Helps define drained sands.

DIPMETER LOG REGISTER



DIP LOG

(1) A well log from which formation dip magnitude and azimuth can be determined. The resistivity dipmeter includes three or four (sometimes eight) micro-resistivity readings made using sensors distributed in azimuth about the logging sonde and a measurement of the azimuth of one of these; a measurement of the hole deviation or drift angle and its bearing; and one or two caliper measurements. The azimuth, deviation, and relative bearing are measured by a system similar to that described for the poteclinometer. The microresistivity curves are correlated to determine the difference in depth of bedding markers on different sides of the hole. See also high-resolution dipmeter and poteclinometer.

(2) Other types of dipmeters use three SP curves, three wall scratchers, etc. to produce logs.

(3) A log showing the formation dips calculated from the above, such as a tadpole plot or stick plot. See illustration of dip patterns at dip.

Registro Dip meter

DIPMETER TOOL

A downhole tool used to make a dipmeter log or dip log.

CURSO: INTERPRETACION DE REGISTROS ELECTRICOS



La promoción Ing. Edwin Mendioloza Bazaldúa de la Escuela de Ingeniería Geológica de la Universidad Nacional Mayor de San Marcos (Lima – Perú) llevará a cabo este Jueves 14 y Viernes 15 deOctubre el Curso: INTERPRETACION DE REGISTROS ELECTRICOS

Los expositores que se encargarán de dicho evento son los Ingenieros Angel Meso y Rubén Cárdenas Calderón, ambos pertenecientes al área de Wireline de la Compañía Weatherford.

Entre los puntos a tratar en el curso se encuentran:

  • Principios básicos de los registros eléctricos y convenciones petrofísicas.
  • Herramientas de resistividad (resistivas y conductivas).
  • Métodos de Evaluación de Litología.
  • Cálculo de Saturación.
  • Interpretación de registros de cementación CBL-VDL
  • Nuevas tecnologías en registros eléctricos: Compact, Shuttle, TBL, etc.

El curso se llevará a cabo en el Auditorio de Telemática de la Universidad Nacional Mayor de San Marcos; más detalles concernientes a la inscripción en el afiche adjunto.

Los costos son en dólares.

MUD LOGGING | FLUIDOS DE PERFORACION

As the drill bit cuts through the different formations, the cuttings are brought to the surface by the drilling mud. Traces of oil or gas may also be brought up in the mud. The practice of mud logging tries to identify, record, and/or evaluate lithology, drilling parameters, and hydrocarbon shows. The information obtained by the mud logger is presented in the form of various logs such as the driller’s log, the cuttings log, or the show evaluation log. The mud logger takes this information, correlates it with data from other wells, and determines whether the well may be able to produce hydrocarbons in commercial quantities. In addition, the mud logger monitors the wellbore for stability to prevent blowouts or kicks.
To comprehend all of the information available, we need to understand four important areas of mud logging; rate of penetration and lag, gas detection, formation evaluation arid sample collection, and show evaluation.

1. Rate of Penetration and Lag

Rate of penetration (ROP) is the oldest and most common way of measuring and evaluating formation characteristics and drilling efficiency. The formation’s lithology (rock type and hardness), porosity, and pressure affect the ROP. The drilling parameters that affect ROP include the weight on the bit, the bit’s speed (rpm), the drillstring configuration, the type of bit selected and its condition, and hydraulics.

2. Gas Detection

Gases extracted from the mud system are usually the first indication that hydrocarbons are present downhole.

Gas enters the drilling fluid from one of three sources:

(1) a gas-bearing formation, (2) a formation feeding gas into the mud, or (3) contamination.

As the bit drills through a formation, it opens or exposes some of the pores. Fluid from these opened pores mixes with the drilling mud. This gas, along with cuttings, or piece, from the drilled formation, is pumped back up toward the surface. As the gas and cuttings rise, the pressure drops and more gas comes out of the pores in the cuttings. This “liberated gas” is an important piece of data por log interpretations.

If the hydrostatic pressure is less than the formation pressure, even more gas can flow into the wellbore. The amount of flow from the formation into the borehole depends upon the pressure differential (the difference between the hydrostatic pressure and the formation pressure), the porosity and permeability, the properties of the formation’s fluids, and the length of time this condition lasts. When the formation fluids enter continuously, the well is said to kick. Swabbing (lifting the drillstring rapidly) also encourages formation fluids to flow in the well because the wellhore pressure drops.

Engineers can identify this gas that enters the borehole during swabbing, called connection gas, and can use the data to enhance formation evaluation and improve well safety-occasionally gas is introduced into the drilling fluid from a source other than the formation, particularly when oil-based drilling fluids are used. This is called contamination gar.

3. Collecting Samples

One of the most important jobs of the mud logger is to collect a representative sample of drill cuttings from the shale shakers and prepare it for lithological identification and hydrocarbon show evaluation.

When the cuttings arrive at the shale shaker, they are covered in mud, unsorted by size, and generally unidentifiable. The shale shaker sifts or separates the larger cuttings from the drilling fluids and finer—microscopic or dust-sized pieces of formation. The fluid is filtered for reuse, and the cuttings arc routed to the reserves pit. The mud logger collects some of the cuttings before they arc routed to the reserve pit and lost.

Once the samples are collected, the logger can examine them unwashed and wet, washed and wet, or washed and dried. The unwashed samples arc collected directly from the shale shakers and are untreated. They are placed in labeled sample bags and are shipped to a laboratory. Washed samples are also collected from the shale shaker; however, the excess drilling mud is flushed away and then the samples are sieved to remove the coarser cavings (formation fragments that originate from the sides, nor the bottom, of the borehole) before they are put in sample bags. Washed and dried samples go through the same steps as washed samples. Before they are bagged, though, they are air dried or dried in ovens. It is from this set of samples that cuttings are taken for microscopic analysis for lithology identification and to observe oil shows.

4. Show Evaluation

A show is the presence of hydrocarbons in a sample over and above background levels. Show evaluation is the complete analysis of the hydrocarbon-bearing formation with respect to lithology and type of hydrocarbon present. A complete show evaluation identifies the presence and type of hydrocarbon, determines the depth and thickness of the show, assesses the porosity and permeability, and assigns a show value that indicates the potential productivity of the formation.

Two types of shows are recognized: gas and oil. A gas show is hard to identify, but the mud logger may see a significant increase in gas levels. An oil show is an increase in heavier-than-methane gas levels as well as a physical indication of oil.

REGISTRO CBL

Antes de empezar este post me gustaría saludar a mis amigos El Father, Talara y Goofy quienes son asiduos visitantes del blog y constantemente me manifiestan sus observaciones.

HISTORIA DEL REGISTRO CBL
  • El registro CBL (REGISTRO DE ADHERENCIA DE CEMENTO O CEMENT BOND LOG) se ha utilizado desde la década de 1960. Aún es ampliamente utilizado y se prefiere a menudo a muchos otros instrumentos de evaluación más reciente de cemento.
  • A mediados de 1980 herramientas de transductor ultrasónico fueron introducidas como el CET y las herramientas de PET.

APLICACIONES DEL REGISTRO CBL

Entre las variadas aplicaciones del registro CBL se encuentran:

  • Determinar la calidad del cemento vínculo entre el cemento y el casing así como también entre el cemento y la formación para la zona de aislamiento.
  • Correlacionar registros a hueco abierto (open hole logs) con registros de pozo entubado (cased hole logs) utilizando el Casing Collar Locator (CCL) y la herramienta de Gamma Ray.
  • Una indicación de la resistencia a la compresión del cemento. Estas herramientas (CET, PET) también miden el espesor de casing, micro anillo y la canalización del cemento, pero no miden los ingresos de cemento a la formación.

MEDICION A TRAVES DEL REGISTRO CBL

Operación del Registro CBL

registro cbl
Representación esquemática de la herramienta CBL-VDL

Una vez que un pozo ha sido determinado para ser producido, el casing es corrido en el agujero abierto y el cemento se bombea al exterior para sellarlo a la pared del pozo.

Un registro de adherencia del cemento (CBL) se ejecuta para inspeccionar la integridad del cemento de sellado de la envoltura y la formación. Esto garantizará que los fluidos de la formación fluirán en la cubierta cuando la zona productiva esté perforada y no hacia la parte exterior del casing.

La herramienta CBL es similar en funcionamiento a la herramienta Sónica (sonic tool) a hueco abierto. Consta de un transmisor y dos receptores a distancias de 3 y 5 pies del transmisor. Al igual que con la herramienta Sonic las ondas compresionales u ondas P se utilizan para medir el tiempo de viaje desde el transmisor al receptor. La herramienta CBL no es compensada a diferencia de la herramienta Sonic a hueco abierto. La centralización de la CBL es esencial para garantizar su operación. Con este fin, un centralizador Gemoco de diámetro exterior que coincida con el diámetro interior de la carcasa debe estar siempre colocado en la herramienta CBL.

La señal 3-pie (3-foot signal) desde el emisor hacia el primer receptor, principalmente medirá el la adherencia del cemento al casing. Si hay poco o ningún vínculo, la amplitud de la señal será muy grande. Si hay buena adherencia, la amplitud será muy pequeña. Esto se conoce comúnmente como el TT3 (Tiempo de viaje de 3 pies) o señal CBL (Registro CBL de Adherencia del cemento).

Una onda de compresión similar se medirá con la señal de 5-pie desde el emisor hasta el segundo receptor. La señal sin embargo leerá más profundamente en la formación. Predominante medirá la adherencia del cemento a la formación. Al igual que para el TT3, una amplitud grande de la onda indicará una mala adherencia mientras que una amplitud lo contrario. Se conoce comúnmente como el TT5 (Tiempo de viaje de 5 pies) o señal VDL (Registro de Densidad Variable VDL).

CALIBRACION DEL CBL

correcion del perfil cbl
Típica tabla de Calibración CBL

Limitación del registro CBL

El hoyo debe tener líquido en el pozo con el fin de que el acoplamiento acústico que se produzca.

MUESTRA DEL PERFIL CBL (CBL LOG SAMPLE)

esquema del registro perfil cbl
Típica representación del perfil de adherencia de cemento CBL

PRESENTACION DEL PERFIL CBL (REGISTRO CBL – CBL LOG)

La presentación CBL no ha cambiado en muchos años. De la figura anterior:

Track 1:

  • La medida Gamma Ray para la correlación en huecos abiertos.
  • El CCL (Localizador Collar Magnético) que resalta los picos de de cada casing.
  • El tiempo de viaje TT3 como función del tamaño del casing.

Track 3:

  • Amplitud del CBL (3 pies) en mV. Para bajas amplitudes (mejor adherencia del cemento); las curvas 0-20mV entra en la pantalla para una medición precisa.

Track 4:

  • Señal TT5 es mostrada en una presentación de firma. Esto muestra el tren de ondas entero.

Track 5:

  • Señal TT5 es mostrada en la pseudo-estándar presentación del VDL. Se trata de una “vista de pájaro” de la onda TT5 ‘sobre’ el umbral.

El propósito de interpretar el registro CBL es asegurar el aislamiento de una buena zona sobre una formación productiva. Al ver la presentación de registro CBL un análisis cualitativo de la adherencia del cemento puede ser determinado.