Category Archives: Registros Electricos
MUD LOGGING | DRILLING FLUIDS
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.1. Rate of Penetration and Lag
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:
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.
3. Collecting Samples
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
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.
RESISTIVITY LOGS
The resistivity depends on the salt dissolved in the fluids in the pores of the rocks. Provides evidence of fluid content in rocks. If the pores of a formation containing salt water present high conductivity and thus the resistivity will be low, but if oil or gas filled with low conductivity and therefore the resistivity is high. Compact slightly porous rocks such as massive limestones have high resistivities.
There are two main types of resistivity profiles: Side Profile (Laterolog) and the Profile of Induction (Induction Log). The side profile is used in conductive mud (mud salty) and the profile of induction is used in resistive sludge (fresh or oil-based mud).
Within Induction Resistivity Profiles are:
a) SFL = Spherical Induction Log. For shallow depths (0.5 – 1.5 ‘). The resistivity log measures the resistivity of the washing area (Rxo).
b) MIL = LIM = Medium Induction Log. For medium distances (1.5 – 3.0 ‘)
c) DIL = ILD = Deep Induction Log. For depths greater than 3.0. ” The resistivity log measures the formation resistivity (Rt).
Within the Lateral Resistivity logs are:
a) MSFL = Microspheric Laterolog. For nearby (1.0 and 6.0”). Read the resistivity of the washing area (Rxo).
b) MLL = LLM = Micro Laterolog. For nearby (1.0 and 6.0”)
c) SLL = LLS = Someric Laterolog. For shallow depths (0.5 and 1.5 ‘)
d) DLL = LLD = Deep Laterolog. For depths greater than 3.0. ” Measure formation resistivity (Rt).
Read from left to right, on a logarithmic scale. The unit of measurement for profiles of resistivity is the ohm-m with a range of values ranging from 0.2 to 2000 ohm-m.
Resistivity logs are used to estimate oil-water contacts, to calculate the formation water resistivity (Rw) and training erdadera resistivity (Rt). Read from left to right.
ENCICLOPEDIA DE REGISTROS DE POZOS
A sugerencia de Alirio posteo esta Enciclopedia que hasta ahora desconocía y que veo será de gran utilidad por la amplia cobertura especializada de temas en lo que a registros de pozos se refiere:
Well logging during drilling
Measurements using drilling mud
Measurements in cuttings
Downhole measurements
WIRELINE WELL LOGGING
LOGGING EQUIPMENT AND TECHNIQUES
Calibration of sondes, secondary porosity and shaly formations
ELECTRIC AND DIELECTRIC WELL LOGGING
Spontaneous polarization
Induction measurements
Laterolog (LL3 LL7 LL8), Dual laterolog, Spherically Focused Log (SFL),6FF40 sonde, Dual Induction Laterolog 8 (DIL), Microlog, Microlaterolog, Proximity Logs, Micro SFL Log (MSFL)
Dielectric sondes
Gamma-Ray Logs, Neutron Logs, Cilindrical tools
Nuclear magnetic resonance log (NML), CNL Neutron
Acoustic Well Logging
CBL measurements, Cement evaluation tool (CET)
Dipmeter survey, Fracture Identification Log (FIL), Stratigraphic dipmeter (SHDT)
Vertical seismic profile (VSP)
ULSEL
Caliper logging
Cased-hole interpretation
Sidewall sampling and testing
Repeat formation tester (RFT)
WIRELINE COMPLETION OPERATIONS
Production logging
Basket and packer flowmeter
Gradiomanometer, Water detector
Logging in relief wells
Geothermal logging
LOGGING FOR CIVIL ENGINEERING
Logging in oil muds
MEASUREMENT WHILE DRILLING (MWD)
PROGRAMS AND COSTS OF WELL LOGGING
REGISTROS DE RESISTIVIDAD
Son registros inducidos. La resistividad es la capacidad que tienen las rocas de oponerse al paso de corriente eléctrica inducida y es el inverso de la conductividad.Existen dos tipos principales de perfiles de resistividad: el Perfil Lateral (Laterolog) y el Perfil de Inducción (Induction Log). El perfil lateral se utiliza en lodos conductivos (lodo salado) y el perfil de inducción se utiliza en lodos resistivos (lodo fresco o base aceite).
Dentro de los Perfiles de Resistividad de Inducción tenemos:
a) SFL = Spherical Induction Log. Para profundidades someras (0.5 – 1.5’). Este registro de resistividad mide la resistividad de la zona lavada (Rxo).
b) MIL = LIM = Medium Induction Log. Para distancias medias (1.5 – 3.0’)
c) DIL = ILD = Deep Induction Log. Para profundidades de más de 3.0’. Este registro de resistividad mide la resistividad de la formación (Rt).
Dentro de los Registros de Resistividad Laterales tenemos:
a) MSFL = Microspheric Laterolog. Para las proximidades (1.0 y 6.0’’). Lee la resistividad de la zona lavada (Rxo).
b) MLL = LLM = Micro Laterolog. Para las proximidades (1.0 y 6.0’’)
c) SLL = LLS = Someric Laterolog. Para profundidades someras (0.5 y 1.5’)
d) DLL = LLD = Deep Laterolog. Para profundidades de más de 3.0’. Miden resistividad de la formación (Rt).
Se lee de izquierda a derecha, en escala logarítmica. La unidad de medida para los perfiles de resistividad es el ohm-m, con un rango de valores que va desde 0.2 hasta 2000 omh-m.
Los registros de resistividad se utilizan para estimar contactos agua–petróleo, para calcular la resistividad del agua de formación (Rw) y la resistividad erdadera de la formación (Rt). Se lee de izquierda a derecha.
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
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.
* 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
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.
