Logging tool

Bottom hole assemblies and certain types of downhole equipment (e.g. logging tools, MWD tools) cost several US 100,000. Some logging tools will have radioactive sources which may need to be recovered or isolated for safety and legal reasons. However, prior to commencing fishing operations, a cost - benefit assessment will have to be made to establish that the time and equipment attributable to the fishing job is justified by the value of the fish or the cost of sidetracking the hole. 

A vast variety of logging tools are In existence and Section 5.4 will cover only those which enable the evaluation of essential reservoir parameters, specifically net reservoir thickness, lithology, porosity and hydrocarbon saturation. 

The formation density log is the main tool for measuring porosity. It measures the bulk density of a small volume of formation in front of the logging tool, which is a mixture of minerals and fluids. Providing the rock matrix and fluid densities are known the relative proportion of rock and fluid (and hence porosity) can be determined. 

The bulk density measured by the logging tool is the weighted average of the rock matrix and fluid densities, so that ... 

In practice the logging tools are often used to measure the resistivity of the formation rather than the conductivity and therefore the equation above is more commonly inverted and expressed as ... 

Permeable intervals can be identified from a number of logging tool measurements, the most basic of which is the caliper tool. The caliper tool is used to measure the borehole diameter which, in a gauge hole, is a function of the bit size and the mudcake thickness. Mudcake will only build up across permeable sections of the borehole where mud filtrate has invaded the formation and mud solids (which are too big to enter the formation pore system) plate out on the borehole wall. Therefore the presence of mudcake implies permeability. 

The arrangement of Figure 4-218 is common to all directional tools based on the earth s magnetic field for orientation MWD tools or wireline logging tools. 

Logging cable and wireline can part due to the logging tool becoming stuck. Such cable and wireline can be removed by special fishing tools. 

A wellbore fluid has been developed that has a nonaqueous continuous liquid phase that exhibits an electrical conductivity increased by a factor of 10 to 10 compared with conventional invert emulsion. 0.2% to 10% by volume of carbon black particles and emulsifying surfactants are used as additives. Information from electrical logging tools, including measurement while drilling and logging while drilling, can be obtained [1563]. 

Fig. 2.7.6 Left A representation of a Schlum- that dearly separate and correspond to the berger NMR well-logging tool [56], The long oil and water signals, respectively. The lower cylinder is the tool body and the shaded areas peak corresponds to the oil phase, the higher contain permanent magnets. The multiple peak corresponds to the water phase. Note that sensitivity regions are shown as the colored the T2 distribution of the oil and water peaks sheets that are outside the tool body. Right overlap significantly. From the map, a water...

Recovery well recharge test Dielectric well logging tool Optoelectronic sensor... 

At selected intervals during the drilling, generally before the casing is run or when formations with hydrocarbon indications are encountered, measurements may be taken of the characteristics of the borehole and surrounding strata. Wire line logging tools are used. 

Kleinberg et al. (2005) and Takayama et al. (2005) show that NMR-log measurement of sediment porosity, combined with density-log measurement of porosity, is the simplest and possibly the most reliable means of obtaining accurate gas hydrate saturations. Because of the short NMR relaxation times of the water molecules in gas hydrate, they are not discriminated by the NMR logging tool, and the in situ gas hydrates would be assumed to be part of the solid matrix. Thus the NMR-calculated porosity in a gas-hydrate-bearing sediment is apparently lower than the actual porosity. With an independent source of accurate in situ porosities, such as the density-log measurements, it is possible to accurately estimate gas hydrates saturations by comparing the apparent NMR-derived porosities with the actual reservoir porosities. Collett and Lee (2005) conclude that at relatively low gas... 

The estimated amount of hydrate by chloride anomalies had a mean value of 1.3 1.8 vol%, ranging to as high as 7% however, these values may be minimum because the baseline may have been lower than the actual interstitial water chlorinities. The logging tools indicate the presence of as much as 2.9 vol% hydrate, ranging as high as 9.5%. Recovered pieces of hydrate were concentrated in zones from 2 to 10 cm thick. However, most of the hydrate was disseminated... 

The estimated volume of hydrate via chlorinity had a mean value of 2.4 2.7 vol% ranging as high as 13.6 vol% again these are minimum values, perhaps caused by a low baseline. Logging tools indicated that hydrate occupied approximately 4 vol% of bulk sediments, ranging as high as approximately 11 vol%. 

Well logs from Hydrate Ridge indicated acceptably consistent estimates of hydrate occurrence, particularly water saturation, and RAB. Hydrate concentration data from logging tools have been confirmed and quantified by more direct core methods of IR sensing of temperature, gas evolution, and chlorinity decrease. 

An effective method to monitor corrosion in buried structures is to measure the pipe/soil potential along its span. With horizontal pipelines this is technically feasible however the access to data on the local CP performance in well casings is very limited and can only be obtained using expensive logging tools. 

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