Introduction
Cased hole logging is a specialized technique used to evaluate wellbore integrity after well completion phase. Cased hole logging concentrates on evaluating the well’s structural integrity and assessing of its subsurface contents, in contrast, to open-hole logging, which is carried out before completion phase.
- Production Logging Tool
Production logging is the measurement of fluid parameters and flow contributions on a zone-by-zone basis to yield information about the type and movement of fluids within and near the wellbore. This well-established production logging technique provides vital information about well performance and can help engineers to identify potential problems and take remedial action before production is interrupted. Production logging also helps production and reservoir engineers to understand where the various fluids enter the well. This enables them to identify optimal solutions, such as selecting which unwanted fluid entry zones should be shut off or which poorly producing layers require perforation and/or stimulation. The principal aim of production logging is to measure the performance of producing and injecting wells by gathering diagnostic data, for example, information indicating the efficiency of perforation. When extensive production logging campaigns are conducted as part of a reservoir monitoring or surveillance program, operating companies can use the data to assess the individual reservoir compartments and establish their contributions to oil and gas production or water cut. The information gained from production logging can be used to help companies in defining field economics and thus to make the most appropriate decisions for field development and reservoir management. However, traditional production-logging methods have limitations in many of today’s wells, wellbore conditions, and fluid types. Wellbore conditions have a large effect on the quality of the data obtained. In vertical wells with high fluid flow rates, the data acquired are accurate and reliable. However, multiphase flow conditions exist in many deviated and horizontal wells. In these wells, conventional production logging tools are often inadequate and may give misleading result. In the 1990s, the industry began to drill large numbers of deviated and horizontal wells, and so the need to understand and measure fluid flow within complex flow regimes became increasingly important and necessitated the development of new tools and techniques.
Production Logging Services
Calliper-Fullbore Flowmeter (CFF)
The Calliper-Fullbore Flowmeter combines a sensitive fullbore flowmeter with a dual-axis (X-Y) caliper measurement. This set of measurements enables the petroleum or reservoir engineer to compute an accurate volumetric flowrate at any given depth in the well. The flowmeter is of a unique design which allows the impeller to rotate even while the arms are partially closed. Therefore, a single flowmeter cage can be used from fully open to almost closed to log a range of tubular sizes. This brings considerable benefits in logistics, operations, capital expenditure, maintenance and data quality. The 1 11/16” tool is fitted with a cage suitable for up to 9 5/8” casing and the 1 3/8” tool has a cage for up to 7”.
Applications
- Measurement of linear and volumetric flowrates in production and injection wells;
- Detection of leaks and inflows;
- Detection of flowing/non-flowing perforations
Bowspring Fullbore Flowmeter (BFF)
Bowspring Fullbore Flowmeter surveys can be used for metering fluid flowrates within either cased or open hole wells. The velocity and direction of fluid movement in the borehole can be determined by the Bowspring Fullbore Flowmeter. Units of measurement are revolutions per second, which can be converted to barrels per day and percentage of full flow. The latter is usually presented in a flow profile derived from a log made with a stationary tool or a tool moving at constant speed.
Applications
•Injection and production profiles to indicate relative fluid movement from or into a zone of activity
•Locate points of increased production due to well treatment
•Detect the loss of production due to cross flow or thief zones
•Detect packer and plug leaks
•Detect zones of lost circulation in open holes
•Determine flow regime
In-Line Flowmeters (ILF)
The ILF – MPB’s are a range of In-Line Flowmeters with a fixed diameter, solid impellers which can be deployed with other tools both above and below. They are designed primarily for use in small diameter casings and tubing’s where conventional fullbore flowmeters cannot measure. The tools are available in body sizes of 1 3/8” and 1 11/16” mated with cages of 1 3/8”,1 11/16” and 2 1/8”. Larger or custom size cages are available on request.
Applications
• Measurement of Flow in Production and Injection wells;
• Detection of leaks and inflows in tubing;
• Backup flow measurement to fullbore flowmeter;
• Detection of flowing/non-flowing perforations
Radioactive Fluid Density
The Radioactive Fluid Density (RFD) Log is a radioactive log of the gamma ray type. While the Gamma Ray Log is a measurement of natural gamma rays, the Radioactive Fluid Density Log data are a record of the density difference between water, oil and gas, and are generated by use of a chemical gamma ray source. The density measurement is made by observing the relative absorption of gamma rays by the borehole fluid in a sampling channel. The basic unit of measure is a count of residual gamma rays. This counting rate is inversely proportional to the density of the sample and is a function of the activity of the gamma ray source. The log density data are recorded in grams per cubic centimeter.
Applications
•Locate entry of primary and secondary fluids in a 2- or 3-phase production flow
•Provide a density profile in a multiphase production flow
•Determine flow regime
•Locate borehole levels in static and flowing conditions
•Locate tubing and casing leaks when the leaks result in multiphase flow
•Check the operation of gas lift valves
GCT
The GCT tool is an short, all-in-one production logging tool, providing temperature, gamma ray and CCL sensors. The tool is designed to be used as a core element of a production logging tool or for GR/CCL depth correlations in perforating or setting operations. Use of a single combination tool increases reliability by minimizing electrical and mechanical connections, reduces rig up time, improves data quality through the close proximity of all sensors and brings the benefits of a smaller tool string. Semi-permanent metal seals are used to minimize maintenance. The GCT operates with GGT’s MPB (MonoPin Bus) interface and is fitted with GO Type A upper and lower heads. A separate High Speed Telemetry Cartridge (HSTC) or High-Capacity Memory Cartridge (HCMC) can be deployed directly with the PPL. For use with client-specific or third-party memory/telemetry protocols, an appropriate crossover can be supplied. The GCT is compatible with all other MPB tools including flowmeters, fluid density, pressure, water holdup and accelerometer. Designed for ease of maintenance and high reliability, the temperature and pressure ratings of the PPL make the tool suitable for a wide range of production logging operations.
Applications
- Production Monitoring
- Injection Monitoring
- Leak Detection
- Cement Channeling
- Water/Gas Ingress Detection
- Depth Correlation
- Well Testing
Temperature Log
The temperature sensor is a platinum resistance thermometer device, whose resistance varies with ambient temperature. The Temperature Log provides a continuous measurement of borehole fluid temperature. From the absolute borehole fluid temperature, a continuous differential temperature curve can be calculated at the surface.
Applications
- Locate points of gas entry in open and cased holes
- Distinguish zones that are producing from those that are non-producing
- Determine the geothermal gradient
- Determine injection points and under some conditions develop an injection profile
- Locate tubing and casing leaks, particularly when the leaking fluid is gas
Gamma Ray
When a natural gamma ray from the formation is incident on the Sodium Iodide (NaI) crystal, a photon of light is produced. The photon travels through the crystal and exits at the open end where it passes into the photomultiplier tube (PMT). In the PMT the photon hits a cathode which causes the release of an electron. The electron is accelerated along the PMT by the large potential across a number of dynode plates along its length. As the electron hits each plate a greater number of electrodes is released until the group of electrons hits the anode, when sufficient electrons have been produced to cause a small current pulse. This current pulse is amplified and counted. The count rate of current pulses is equal to the number of gamma rays entering the NaI crystal. This scintillation detector tool measures gamma radiation. It outputs counts scaled to be approximately one count per API unit. Both Memory and Surface Readout models are available. A variety of tool types ranging from 1 3/8″ to 1 11/16″ diameter are available to measure gamma radiation from the formation surrounding the wellbore or for particular applications. All models are compact, rugged and combine excellent sensitivity with high resolution for cased hole production logging applications. Tools can be combined for tracer work and, with the addition of a gamma source, used for gravel pack investigations.
Applications
- Lithology Identification
- Depth Correlation
- Identification of Radio Active Scale.
- Tracer Monitoring
- Gravel Pack Monitoring (with addition of a gamma source)
Quartz Pressure
The PWH provides combined quartz pressure and water hold-up sensors. The PWH-K/M is fitted with GGT’s MPB (MonoPin Bus) interface. The upper head is an MMC2 (GGT Multipin Connector 2), and the lower head a GO Type A incorporating pressure isolation. The PWH-K has an MMC5 upper head. The tool can be deployed with either a telemetry cartridge (HSTC) or a memory cartridge (HCMC) as part of a full production logging string or on its own for high accuracy pressure surveys. The single combination tool increases reliability by minimizing electrical and mechanical connections, reduces rig up time, improves data quality through the close proximity of sensors and brings the benefits of a smaller tool string. For high precision downhole pressure measurement, Asmary offers a quartz pressure gauge tool, employing an Industry standard quartz crystal pressure transducer. The tool provides both pressure and gauge temperature outputs.
Applications
- Data for P.I. and Nodal Analysis
- Draw-Down and Build-Up Pressure Transient Analysis
- Down-Hole Pressure Gradient Measurement
- Production Monitoring;
- Injection Monitoring;
- Well Testing;
- Pressure Gradients;
- Column Density;
Water Hold-up Indicator
The enhanced Capacitance Water Hold-up Tool operates in the same manner as a standard tool, but has improved circuitry. It therefore provides a better response to changes of fluid when the water-cut value is high. The improved design, in addition to providing greater discrimination in higher water cuts, also minimizes the “watering out” effect. This effect results in the tool output continuing to indicate water even though the surrounding fluid has been replaced by hydrocarbons.
Applications
- Multi-Phase Production Profiling
- Oil / Gas / Water Hold-up Calculations
- Qualitative Analysis of Water Loaded Up Wells
- Qualitative Analysis of High GOR, Water Free Wells
Gas Hold-up Indicator
The Sondex Gas Hold Up Tool was originally developed by Halliburton to provide a reliable, cross well bore means of measuring gas volume fraction in any flow regime and at any deviation. The tool response is representative of the entire cross section of the well bore within the casing and is almost completely independent of salinity, water cut and oil/water densities.
Applications
- Multi-phase Production Profiling
- Fluid Identification
- Bubble Point Determination
- Gas Entry Detection
Casing Inspection Tool
Casing inspection logs are a fundamental component of cased hole logging, serving as a critical tool in the assessment of casing integrity inspection. These specialized logs are designed to provide comprehensive insights into the condition of the casing, tubing and liner, and the surrounding geological formations. By shedding light on the integrity of the casing, these logs play a pivotal role in ensuring the longevity and reliability of oil and gas wells.
1. Electro Magnetic DefectoScop System (EMDS)
The EMDS tool detects the casing thickness, corrosion, deformation, cracks, … in tubing, inside and outside casing and indicating downhole string structure. Due to the unique structure and measurement principle, logging can be performed in the course of normal production of oil(water) wells. Using EMDS could reduce operating cost in inspection and increase efficiency and, determine the extent of damage of casing in time.
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2. Magnetic Thickness Tools (MTT)
Magnetic thickness tools are a vital component of cased hole logging, with their ability to accurately measure casing and tubing thickness. Their precision and capacity to detect corrosion, thinning, and wear make them indispensable for maintaining the structural integrity of oil and gas wells. By providing early warning of casing issues, these tools contribute significantly to well safety, and productivity, ensuring that well assets are effectively managed and maintained.
The sensor array is composed of 16 independent sensors. Each sensor can get a curve of casing thickness. Thinner pipe thickness and deformation is measured as well as outer pipe joint.
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3. Multi Finger Caliper (MFC)
Multifinger caliper logging is an essential tool for assessing the structural integrity of well casings in the oil and gas industry. By accurately measuring wellbore diameter, identifying casing deformities, and detecting holes or corrosion, this technique allows operators to make informed decisions regarding well maintenance and integrity management. It serves as a critical component in ensuring the safety, longevity, and productivity of cased wells, making it a cornerstone of cased hole logging practices.
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