Report On Well Logging.docx 67244t

WELL LOGGING Well Logging is the technique of making petro physical measurements with respect to depth in the sub-surface earth formations in order to determine both the physical and chemical properties of rocks and the fluids they contain.

Log: The record of comprehensive information about the formation in a well during logging process. Also print of all the data acquired in his well.

• The objective is to locate, define, and produce from a given reservoir Wire line well logging operations provide continious measurements of bore hole and petro physical properties at accurately measured depth.

Log measurements can define or at least infer these formation properties such as porosity, shale volume, lithology, and water, oil, or gas saturation. Estimation of permeability, prediction of water cut and selection of over pressure zones can also be made. Log analysis is primarily used to describe formation properties in a single well.

Quite normally, log and core data are often compared and used in conjunction to define reservoir properties. When cores are not available, log data are often used as extension from core analysis and log comparisons on other wells.

Introduction to well logging •The first electrical log was introduced in 1927 in using stationed resistivity method. •The first commercial electrical resistivity tool in 1929 was used in Venezuela, USA and Indones ia. •SP was run along with resistivity first time in 1931 •Schlumberger developed the first continuous recording in 1931 •GR and Neutron logs was started in 1941 1|Page

•Microresistivity array dipmeter and lateralog were first time introduced in 1950’s •The first induction tool was used in 1956 followed by Formation tester in 1957, Fomation Dens ity in 1960’s, Electromagnetic tool in 1978 and most of Imaging logs were developed in 1980’s •Advanced formation tester was commercialized in early 1990’s.

Advantages and limitations of well logging Advantages: Continuous measurements -Easy and quick to work with -Short time acquisition -Better resolution than seismic data -Economical

Limitations: -Indirect measurements -Limited by tool specification -Affected by environment -Varying resolution

Different types of logging 1.Wireline logging a) open hole logging b) cased hole logging

2.Logging while drilling

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3.Mud logging 4.Coring

Open Hole: A borehole drilled in the formation, usually available immediately after drilling – All basic petro physical measurements for Formation Evaluation

Cased Hole: A borehole wherein steel casing pipes have been placed and cemented suitably – Measurements mostly concern with Reservoir Development & Production

TYPES OF LOGGING UNITS 1. Land logging unit 2. Offshore logging unit

In land logging unit Logging Unit : A specialized truck installed with a full computer system for data acquisition & processing

• Logging cable or the Wireline – An electro-mechanical cable reel mounted on the truck and operated by the truck hydraulics

• Logging Tool or Sonde – An electronic instrument containing sensors and processing circuitry for data acquisition and transmission. The logging tool is lowered into the wellbore by means of the logging cable or wireline. The wireline also connects the logging tool electrically to the surface computer system. Data acquired by the tool are transmitted to the surface system over the logging cable using digital telemetry. The surface computer records, processes and plots these data as a function of well depth and produces what is called a “log” or “well log”. This is normally called the Wireline Logging Technique in onshore

Offshore logging unit In this the unit is pressurized when compared to outside is also known as purge unit. To restrict the flow of gasses with the help og sensors 3|Page

offshore units meet MMS requirements and zone classifications and are built to comply with DNV Rules for Certification of Lifting. All units include emergency lighting to be used in case of power outage, emergency shut-off with loss of purge, and an audible alarm indicating positive pressure loss. Units include a Gaitronics or equivalent microphone/speaker voice system with exterior hook-up for connection to the rig intercom system. All units are configured to interface with rig services and utilities prior to being deployed. offshore units consist of three rack mounted computer systems. These include: PC-1 data acquisition, PC-2 data storage and offline communications, and PC-3 chromatograph analysis. All PCs and critical equipment are powered by a UPS system for emergency power Geolograph is used to measure the depth of the bore hole

Difference between wireline logging and logging while drilling Comparison between the LWD and wireline services covering some of the important services that both can provide, advantages, and disadvantages, and will conclude with few points about why it is still not time to replace wireline with LWD.

Logging while drilling is the operations of acquiring data in real time while drilling using mud telemetry. On the other hand, the wireline service is the operation of acquiring data, but after finishing drilling an interval, a section, or a well.

Let's start the comparison by listing the main advantages and disadvantages of both, the LWD and wireline services:

Advantages: Logging while drilling:

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Acquiring data after less time after drill ed wich means less affected by mud invasion

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Critical for geological decisions while drilling

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More capable in tough environment (deviated wells, horizontal wells, unstable borehole)

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Well placement Wireline:

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Smaller, Lighter and delicate

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Accurate depth

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high data speeds due to wire usage

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good borehole

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Communication and Powered using cable

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Cased hole logging

Disadvantages:

Logging whie drilling:

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big, heavy and tough Data variety depends on speed telemetry limited control (Programmed before run in hole, unlink wireline where you can make 2 ways communications with the tools)

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Powered using batteries and/or mud turbine

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Vibrations & stick and slip Wireline:

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takes time

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Measurements are taken after long time of finished drilling

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specific coverage (as the tools don't rotate)

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problem at high deviation (Tough logging condition is needed)

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susceptible to hole condition

There are three suits in Open hole logging services. 1. Suit 1: Gamma Ray, SP, Caliper. 2. Suit 2: Sonic, Neutron, Density, Gamma Ray. 3. Suit 3: R.F.T, Side wall sampler, Dip meter. These three suits provide the information about Lithology, Porosity and Resistivity of the Formations in the Bore hole. In these logs GR and SP provides the information about lithology. So these are called as lithology logs. Some other logs infer the porosity and resistivity. Lithology logs: GR and SP. Porosity logs: Neutron, Formation density, Sonic. Resistivity logs: Conventional, Focused, Induction, Micro resistivity logs.

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Wireline logging: In practice the open hole wire line logging tools are used to measure the various parameters that influences the porosity, permeability and saturation of the formation. Various types of logging methods are used to determine the formation properties. The logging tools are classified along with logging methods based on the measurement principle. There are four principle logging methods are in use: Electrical logging, Radio Active logging, Sonic logging, and Miscellaneous logging.

Caliper log: Caliper Logs record the diameter of the hole. It is very useful in relaying information about the quality of the hole and hence reliability of the other logs. An example includes a large hole where dissolution, caving or falling of the rock wall occurred, leading to errors in other log responses. Most caliper logs are run with GR logs and typically will remain constant throughout. Borehole geometry is controlled by: ➢ Lithology ➢ Mud type ➢ Formation Properties ➢ In-situ stresses Borehole size can be determined from caliper log. Caliper log can be an indication to one of the following cases: 1) Gauged hole: diameter of hole is about equal to the bit size Hard well consolidated and impermeable formation. borehole diameter = drill bit size 2) Increased borehole diameter which means:

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a) Washout: general drilling wear, especially in shaly zones and dipping beds, both caliper larger than bit size, considerable vertical extent. b) Keyseat: asymmetric oval holes, formed by wear against the drill string at points where the borehole inclination changes (doglegs). c) Breakout: similar to keyseat but not due to doglegs, small brittle fractures due to existing stress regime of the country rock.

Unconsolidated formation borehole diameter > drill bit size 3) Decreased borehole diameter means: a) Generally due to formation of mud cake Mud cake thickness = (bit size diameter – caliper diameter reading)/2 b) mud cake formation indicates permeability and involves loss of mud filtrate into a permeable formation – invasion Permeable formation borehole diameter < drill bit size

GAMMA RAY: It measures the natural radioactivity of the formation. In sedimentary formations its reading reflects the shale content of the formation.

Principle: The gamma rays are emitted by the radioactive elements like U, Th, K in the formations, and detected by the suitable gamma ray sensor (typically scintillation detector, 8 to 12 inches in active length). The detector gives a discrete electrical pulse for each gamma ray detected. The parameter recorded is the number of pulses recorded per unit of time by the detector.

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In cased holes, gamma ray log is used as a depth control. Also, it is used to position the formation testers and sidewall core guns. It is also used in radioactive tracer operations to locate pipe leaks, channeling behind casing.

Uses: 1. Correlation 2. Mineral analyses. 3. Records radioactivity of a formation 4. Shales have high gamma radioactive response 5. Gamma ray logs are most commonly used logs for sequence stratigraphic analysis 6. Gamma ray log is measurement of natural radioactivity in formation versus depth. 7. GR log reflects shale or clay content. 8. Clean formations have low radioactivity level.

Density log: The density log belongs to the group of active nuclear tools, which contains a radioactive source and two detectors. Density logs measure the bulk electron density of the formation, and is measured in kilograms per cubic meter (gm/cm3 or kg/m3). PRINCIPLE Thus, the density tool emits gamma radiation which is scattered back to a detector in amounts proportional to the electron density of the formation. The higher the gamma ray reflected, the greater the porosity of the rock. Electron density is directly related to the density of the formation (except in evaporates) and amount of density of interstitial fluids. Helpful in distinguishing lithology, especially between dolomite and limestone. A short-range detector. This detector is very similar to the detectors used in the natural gamma ray tools, and is placed 7 inches from the source. 9|Page

A long-range detector. This detector is identical to the short-range detector, and is placed 16 inches from the source. Formation bulk density is a function of matrix density, porosity and formation fluid density. Common values of matrix density (in g/cm³) are: i.

Quartz sand - 2.65

ii.

Limestone - 2.71

iii.

Dolomite - 2.87

Applications: 1. This method is usually used for measuring the bulk density of formation in bore hole. 2. This method is the most reliable porosity indicator for sandstones and limestones because their density is well-known. 3. On the other hand, the density of clay minerals such as mudstone is highly variable, depending on depositional environment, overburden pressure, type of clay mineral and many other factors. SONIC TOOL: A sonic tool consists of a transmitter that emits a sound-pulse and different spacing receivers that picks up and records the pulse as it es and calculate travel time through the formation and reaches to receiver.

Principle: A transmitter sends compressional or longitudinal waves into the borehole fluid. The compressional wave incident on wall gets refracted into the formation. Acoustic pulse sent into the borehole mud received by the receiver is measured. These waves do not reach the receivers at the same time, but at different times depending upon the path traversed and the velocity of the medium. It records full wave form with the help of 8 receiver array. Sonic log measures the porosity of the rock. Hence, they measure the travel time of an elastic wave through a formation. Intervals containing greater pore space will result in greater travel time and vice versa for non-porous sections. 10 | P a g e

Sonic logs are used to determine: 1) Determine porosity of reservoir rock 2) Improve correlation and interpretation of seismic records 3) Assist in identifying lithology 4) Estimate secondary pore space 5) Estimate rock permeability Must be used in combination with other logs, particularly gamma rays and resistivity, thereby allowing one to better understand the reservoir petro physical properties.

Resistivity log: There are two general types of resistivity tools: 

Electrode: forces a current through the rock and measures resistivity.

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Induction: Uses a fluctuating electro-magnetic field to induce electrical currents in the rock; it measures conductivity which is converted to resistivity.

Generally, induction type is used in nonconductive muds Response of the normal device in beds more resistive than the surrounding formations. The upper part shows the response in a thick bed (h= 10 AM). The curve is symmetrical and a maximum is observed at the center of the bed, where the reading is almost equal to Rt. The apparent bed thickness is less than actual bed thickness by an amount equal to the spacing.

DUAL LATRO LOG (DLL): The dual latro log is a set of record of resistivity, there are two records: DLL (latro log deep) and LLS (latro log shallow). Its response is mostly dependent upon the true formation resistivity. However, LLS reading is useful to get true resistivity from LLD reading, and most of the times LLD is very close to the true resistivity.

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Uses: 1. Estimation of true resistivity 2. Identification of diameter of invasion. MICROLATRO LOG (MLL):

The micro latro log is a record of measured resistivity of the flushed zone, Rxo, and to delineate permeable beds by detecting the presence of mud cake. Response of MLL depends upon the Rxo/Rmc ratio as current is prevented from flowing into mud cake. The depth of investigation of this tool is three to five inches, so even if invasion is low or moderate, MLL responds to invaded zone. Effect of mud cake is negligible up to cake thickness of 3/8 inches but increase rapidly with greater thickness of cake. MLL measurements are not preferred where mud cake thickness is (greater than 3/8 inches).

Uses: 3. Identification of permeable beds. 4. Information of flushed zone resistivity.

Resistivity analysis:  Qualitative: 

High Resistivity deflection: o Porous Rock (Fresh water or Hydrocarbon). o Dry Rock (Anhydrite, Dolomite or Limestone)

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Low Resistivity: o Shale o Porous rock bearing Saline water.

 Quantitative Resistivity of 

shale 0.1:1

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Sand from 2.5

Advanced resistivity tool 12 | P a g e

Formation micro imager To increase the vertical resolution this tool is four pads. On each pad there are there are 16 electrodes .The FMI full bore formation microimager provides real-time microresistivity formation images and dip data in water-base mud. With 80% borehole coverage in 8-in boreholes and 0.2-in image resolution in the vertical and azimuthal directions, imaging with the FMI microimager is the preferred approach for determining net pay in laminated sediments of fluvial and turbidite depositional environments.

Applications 

Fractures detection

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Beds identification

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Faults identification

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Lithology

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Resistivity of the formation

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dipmeter

Neutron log: Principle The Neutron log measurement of the slowdown neutron counts. The neutron collides with formation, after sufficient number of collisions the neutron will reach a lower energy state where upon they are captured by formation nuclei. When a nucleus captures a thermal neutron, it dissipates the energy and slows down. The neutron tool responds to porosity but they are also influenced by other parameters and certain environmental effects: borehole fluid type, density, salinity, borehole size, mud cake, standoff temperature and pressure. Special application: In cased hole it is used for correlation and depth control for perforation Depending on the device, these measurements may be made either in open or cased holes.

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Two types of neutron logs are commonly used 1. Single Neutron Pad log (SNP) 2. Compensated Neutron Log (CNL)

Sidewall Neutron Porosity log (SNP) • Tools: Pad-type single detector. • Detects: Epithermal neutrons. • Depth interval: Shallow, 8”

Compensated Neutron Log (CNL) • Tool: Mandrel-type 2 detectors. • Detects: Thermal Neutrons • Depth interval: Deeper, 12”

Applications: 1. Determination of porosity / Lithology. 2. Delineation of porous formations. 3. CNL can be used in cased hole 14 | P a g e

Unit: Neutron log is measured in count/minute

Limitations: 1. In shale there is weak hydrogen bonding, so neutrons are captured by hydrogen and loss of neutron occurred. This limitation overcomes by knowledge of seismic log. 2. In case of gas in reservoir rock the gas molecules are too far from one another so neutron is not lost shows low porosity then the actual porosity. This limitation is overcome by the density log identify the presence of gas. 3. In case of gypsum (CaSO4 .2H2O), water molecule is present in gypsum. So, neutron is captured by hydrogen shows more neutron log value but there is no fluid in the formation.

LOGGING WHILE DRILLING

Mud Motor A mud motor (or drilling motor) is a progressive cavity positive displacement pump (PD) placed in the drill string to provide additional power to the bit while drilling. The PD pump uses drilling fluid(commonly referred to as drilling mud, or just mud) to create eccentric motion in the power section of the motor which is transferred as concentric power to the drill bit (well). The mud motor uses different rotor and stator configurations to provide optimum performance for the desired drilling operation, typically increasing the number of lobes and length of power assembly for greater horsepower. In certain applications, compressed air, or other gas, can be used for mud motor input power. Normal rotation of the bit while using a mud motor can be from 60 rpm, to over 100 rpm. Based on the principle developed by Rene Moineau, the theory states that a helical rotor with one or more lobes will rotate eccentrically when the stator contains more lobes than the rotor. The flow of the fluid transmits power allowing the assembly to rotate and turn the bit.

Advantages: ● Extremely hard rock formations can be drilled with motors using diamond or PDC bits. ● High penetration rates can be achieved since rotation speeds are high.

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● Will allow circulation of the borehole regardless of the horsepower or torque produced by the motor.

Major disadvantage in oilfield application: The PD stator, which is a major component of the pump, is usually lined with an elastomer. Most of PD pump failures are due to this elastomer part. However, the operating conditions and environment should not degrade or induce mechanical failure of the elastomer part for the life of the equipment. Unfortunately, the industry does not have elastomers that can last longer, resisting abrasive fluids and solids, and withstand deflections in operating temperatures. The most common elastomer grades used for this application are the NBR (nitrile or acrylonitrile butadiene rubber) grades, which perform moderately well. There is definitely a need for better elastomer compounds to reach areas which are not currently accessible by PDs and also improve the life of current products. Bit speeds can be very high as such bit selection is important. The high speeds may limit the use of certain types of bits. Special pump requirements may be needed as particular pressures and flow rates may be needed to maintain proper and efficient motor operation. If used for directional control the down-hole assembly may be long and this may take time to assemble on the rig floor. The mud motor may be sensitive to fouling agents. This means that certain types of drilling fluids or additives may ruin the motor or lower its performance. One particular example, as mentioned above, would be the use of oil based mud with the mud motor. Over time the oil degrades the elastomers and the seals in the motor.

Telescope The telescope high speed telemetry while drilling service is one of the next generation scope that are setting new standards for data quality and rapid transmission of real time information while drilling. The telescope service and it's Orion telemetry platform effectively leverage the principles of mud pulse telemetry to enhance signal detection and effective data transmission rates. These two advantages significantly increase the amount of information available in real time and enable transmission from great depths. The telescope service can transmit measurements and data from multiple tools, giving comprehensive downhole information that can reduce drilling risks and improve time efficiencies while drilling.

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The telescope service provides the electrical power for, transmits data from, other downhole measurement services. It maximises the amount of information available in real time and make it possible to log before sections in greater detail. The telescope service provides accurate static and continuous directional and inclination measurements. A combination of these measurements and formation evaluation data acquired close to the bit by other services make it possible to land wells on target in less time.

SADN tool . Density and neutron sensors are mounted within dedicated stabilizer blades (of 12 and 11 in diameter respectively) for standoff minimization and increased depth of investigation. In addition, azimuthal technology delivers density and photoelectric factor(Pe) measurements in sixteen individual sectors. Combined, the azimuthal data provide images that can be used for complex interpretation and structural dip information, in both real-time and memory. Density measurement is based on dual detectors to compensate for any residual standoff. The image derived density alogorithm ensures the best possible density data even in the most difficult environments. The porosity measurement is also based on short and long spacing arrays. The tool is equipped with a pair of ultrasonic sensors, that measure standoff in eight individual radial sectors. The 4-axis caliper information can be transmitted in real-timreto produce a 3D image of the borehole while drilling. The adnVISION azimuthal density neutron service provides realtime apparent neutron porosity, formation bulk density, and photoelectric factor data to characterize formation porosity and lithology while drilling. These nuclear measurements are borehole compensated for improved accuracy. Tool sizes include 8 1/4-in (stabilized or slick), 6 3/4-in, and 4 3/4-in. Azimuthal measurements of rock and fluid properties in all quadrants provide more accurate formation evaluation, better identification of reserves, and new diagnostic capabilities. Potential pay zones can be detected and quantified early. Gas/oil and other fluid s can be determined in real time while drilling. Downhole gas influxes can also be detected earlier with an ultrasonic caliper. This wireline retrievability reduces environmental concerns and improves safety.

ARC tool The arcVISION service is available in a full tool size range from 3 1/8 to 9 in. This compensated resistivity service provides real-time resistivity, gamma ray, inclination, and annular pressurewhile-drilling measurements (APWD) that help produce and evaluate reservoirs. The tools can withstand a high sand content and high mud flow rates which ensure maximum power transfer. Annular pressure, near-bit, and multiple depth resistivity measurements are transmitted to the surface simultaneously in real time to maintain accurate trajectory control. Multiple depths of investigation enable you to monitor invasion and other borehole changes over time. Measurements are compensated to remove rugosity effects and electronics drift.

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Ecoscope tool EcoScope multifunction LWD integrates a full suite of formation evaluation, well placement, and drilling optimization measurements into a single collar that can be deployed faster than conventional LWD tools. Multiple near-bit sensors offer a compact design that eliminates the need for an americium beryllium (AmBe) chemical source in LWD nuclear porosity logging, substantially reducing transportation and wellsite risks. Formation evaluation measurements include azimuthal natural gamma ray, a resistivity array, and a nuclear section with neutron porosity, sigma, spectroscopy, and an azimuthal density and photoelectric factor from a sideloaded cesium source. Designed around a pulsed neutron generator (PNG), the EcoScope service uses technology developed by Schlumberger and Japan Oil, Gas and Metals National Corporation to deliver a full suite of formation evaluation, well placement, and drilling optimization measurements, including APWD annular pressure while drilling, caliper, and shock. Because multiple LWD sensors are integrated into a single collar and located closer to the bit, flat time associated with making up and breaking down the BHA is reduced. Having fewer connections also reduces the number of tools needed in the BHA assembly, minimizing the amount of rathole that must be drilled to provide comprehensive formation evaluation measurements and improving well placement and production and reserves calculations.

Cased hole logging and production logging 1. Gamma ray 2. Casing collar locator 3. Cement bond log and variable density log 4. Cased hole formation resistivity 5. Cased hole formation density

Gamma ray: Gamma ray tool in cased hole is used for depth correlation with in the well and between the wells. It is also used cased hole perforation depth control and lithology identification in the reservoir.

Casing collar locator: The tool is comprised of a coil mounted between two opposing permanent magnets. As the tool es a collar, the lines of magnetic flux between the magnets are disturbed, inducing a low frequency voltage in the coil. A signal is transmitted to surface equipment that provides a screen 18 | P a g e

display and printed log enabling the output to be correlated with previous logs and known casing features such as pup ts installed for correlation purposes.

CEMENT BOND LOG VARIABLE AND DENSITY LOG CBL measures casing to the cement VDL measures cement to the formation It depends on travel time and amplitude of sonic wave. The loss/attenuation of signal is related to quality of cementation. If it is having less amplitude good cementation is done and vice-versa. The loss/attenuation of signal is related to quality of cementation. In variable density log after transmitter fires the wave form arrives sensors different paths via casing formation and mud. Arrival times are the function of density of the medium. The wave form recorded at each sensor is combination of all arrivals present. Variable density having wave display of 5ft receiver and displayed light and dark stripes. if there is good bond the waves from the formation will disturb. If the waves are in chevron pattern then there is indication of casing collar or some disturbance in tool

UltraSonic Imaging Tool: Rotating transducer (provides full casing coverage) emits and records sound waves that bounce of borehole walls •  Acoustic amplitude and travel time are recorded and processed into images •  If the tool is off-center the travel times may be too long (top) or too short (bottom). •  Some parts of the borehole are not even imaged because reflected sound wave does not return to transducer. Each firing measures internal radius, thickness and acoustic impedance of annular material for cement evaluation 19 | P a g e

•  Measurement provides •  Cement evaluation •  Casing corrosion and wear

Cased Hole Formation Resistivity Principle Tool injects current into the casing, most of the current remains in the casing but a very small portion escapes to the formation. The measuring electrodes measures the potential difference created by the leaked current which is proportional to conductivity of the formation. As the resistance of casing is a few tens of 𝑚𝑖𝑐𝑟𝑜𝑜ℎ𝑚𝑠 and the leaked current is typically on the order of a few milliamperes, hence the measured potential difference is in nanovolts. Applications •  Resistivity measurement behind casing in new or old wells •  Reservoir monitoring •  Location of byed hydrocarbons •  Determination of residual oil saturation •  Contingency logging in wells where open hole logs could not be run •  Primary evaluation where open hole logging is not possible Resistivity Logging

Cased hole Formation Density It makes accurate formation density measurements in cased wells. It uses chemical gamma ray source and three-detector measurement system to make measurements in a wide range of casing and borehole sizes. The density measurement made by the three-detector system is corrected for casing and cement thickness. Applications •  Porosity determination •  Lithology analysis and identification of minerals •  Gas detection •  Hydrocarbon density determination •  Shaly sand interpretation

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Free point locator

The FPIT free-point indicator tool with combined back off shot determines the free point in stuck drillpipe, drill collars, tubing, or casing and then provides the force that frees the stuck assembly. The FPIT tool provides accurate information about the stuck assembly, saving you both time and money because you can make immediate and informed decisions. Causes of pipe sticking    

  Differential sticking caused by heavy mud and/or highly deviated wells Key seated pipe caused by dog legs Unconsolidated formations collapsing around the pipe Sloughing or swelling of shales

String shot puncture and cutter tools are used to release from the stuck pipe after getting free point locator

Bridge plug is used to isolate the zones in the casing .it is one type of packer arrangement, if the casing is not clean it might not set properly so before instillation of plug it should be cleaned by using junk basket tool . it will collect the junk present in casing

Production logging Flow meter Measures the fluid flow inside the well-bore. There are two types of flowmeters Full bore flow meter Flow diverter flow meter A continuous flowmeter was run in a well. When the flow meter vanes rotates means the fluid is ing through it , when it rotates in clockwise direction the flow is from below and vice versa. If it is 3rps there is no flow in the borehole and if it is 15rps there is 100 percent flow. Temperature Measures the temperature in the well Pressure

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Measures the total pressure due to well-bore column & reservoir

Wire line formation tester Wireline Formation testing allows determination of pressure of mobile fluid in the reservoir and its identification through fluid analysis/sampling It is pad based tool having probes. When the probe is set in the wellbore, a short test, which is called a pretest, is conducted to measure the formation pressure. Usually up to20 cm3 of fluid is withdrawn from the formation during the pretest. At the end of the drawdown period, the pretest chamber is full and the buildup period starts. Generally in first cycle mud will come and after that it is repeated to several cycles to estimate the formation pressure

Basic tool modules Electrical power •Hydraulic power •Single probe •Sample chambers Optional tool modules Dual-probe •Flow-control •Dual-packer •Multisample •MPSR 450 cc PVT •SPMC 250 cc Single Phase •Pump out •Optical Fluid Analyzer This tool is having different types of probes to collect the based on their applications Different types of probes Extra-large diameter module Quicksilver module Minifrac tester if the formation is less permeable

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Pump out module is used to pump the formation fluid into the borehole. After collecting sample it is stored different types of chambers like normal chamber and PVT chamber for reservoir conditions. After the sample is collected it should be analyzed by live fluid analyzer or condensate fluid analyzer Just as you would hold a test tube of oil up to a light to look at its color that is what the Fluid Analysis with MDT does downhole. Every fluids are having different optical densities depending on that to know which fluid type. It can also differentiate between oil based mud and reservoir fluids with the help of channels. In the case of gases reservoirs the rays are fully reflected and no refraction so that wellbore fluid is full of gas. Downhole Fluid Analysis benefits •Improve sampling •Fluid Identification Stations, to complement gradient interpretation •Define Compositional hydrocarbon grading/ compartmentalization • Transition zone and Gas Injection breakthroughs

Perforations In cased hole completions (the majority of wells), once the completion string is in place, the final stage is to make a connection between the wellbore and the formation. This is done by running perforation guns to blast holes in the casing or liner to make a connection. Modern perforations are made using shaped explosive charges. Establishes fluid communication between well bore and formation for production/injection Types Of Perforating

• Bullet

Propellant driven bullets shot through casing, cement & formation

• Hydro

High pressure water jet or slurry

• Jet

Uses high explosives and metal liners in shaped charges

The delivery system for placing the shaped charges at the proper location in the well via wireline may be categorized as

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RETRIEVABLE, consisting of a cylindrical, hollow steel charge carrier SEMIEXPENDABLE, where the charges are conveyed into the well on a retrievable metal strip or wire carrier (used in through-tubing operations where gun size is an important factor) FULLY EXPENDABLE, where the charge cases and carrier linkage disintegrate and only the wireline is retrieved (again, used in through-tubing operations).

Perforating under balance is the technique of choice for maximizing productivity. (Initial wellbore pressure < pore pressure) Over balanced perforating is damaging. (Initial wellbore pressure > pore pressure)

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