Drill-down

We must identify the specific mechanism or control loop to guarantee that there will be no uncontrollable buildup of any chemical component within the process (Downs drill). 

We recommend making a Downs drill table that lists each chemical component, its input, its generation or consumption, and its output. This table should specify how the control system will detect an imbalance in chemical components and what specific action it will take if an imbalance is detected. 

Carbonation is easy to detect and measure. A pH indicator, usually phenolphthalein in a solution of water and alcohol, will detect the change in pH across a freshly exposed concrete face. Phenolphthalein changes from colourless of low pH (carbonated zone) to pink at high pH (uncarbonated concrete). Measurements can be taken on concrete cores, fragments and down drilled holes. Care must be taken to prevent dust or water from contaminating the surface, is cheap and simple. Figure 3.1 shows a typical carbonation front in concrete with the pH of the concrete before and after carbonation, the pH threshold of corrosion for steel and the pH change of phenolphthalein taken from Parrott (1987). The measurement of the carbonation front is covered in Section 4.6. 

This term describes a situation whereby the drill string cannot be moved up or down or rotated anymore. The pipe can become stuck as a result of mechanical problems during... 

When drilling through normally pressured formations, the mud weight in the well is controlled to maintain a pressure greater than the formation pressure to prevent the influx of formation fluid. Atypical overbalance would be in the order of 200 psi. A larger overbalance would encourage excessive loss of mud Into the formation, slow down... 

Appraisal activity should be based upon the information required. The first step is therefore to determine what uncertainties appraisal is trying to reduce, and then what information is required to tie down those uncertainties. For example, if fluid contacts are a major source of uncertainty, drilling wells to penetrate the contacts is an appropriate tool seismic data or well testing may not be. Other examples of appraisal tools are ... 

The first function of a wellsite is to accommodate drilling operations. However, a wellsite must be designed to allow access for future operations and maintenance activity, and in many cases provide containment in the event of accidental emission. Production from a single wellhead or wellhead cluster is routed by pipeline to a gathering station, often without any treatment. In such a case the pipeline effectively becomes an extension of the production tubing. If a well is producing naturally or with assistance from a down... 

At core B2 a transverse crack going through from the surface down to the duct was found, as well as some weak Fig. 6 Drill core B2 reinforcement bars. Because both the crack and the bars could... 

Side drilled holes are widely used as reference reflectors, especially when angle beam probes are used (e.g. for weld testing). However, the distance law of side drilled holes is different to that of a flat bottomed hole. In the literature [2] a conversion formula is given which allows to convert the diameter of a side drilled hole into the diameter of a flat bottomed hole and vice versa, valid in the far field only, and for diameters greater than 1.5 times the wave length. In practical application this formula can be used down to approximately one nearfield length, without making big mistakes. Fig. 2 shows curves recorded from real flat bottomed holes, and the uncorrected and corrected DGS curves. 

Hole Drilling. Hole drilling is another popular way of using ECM. As indicated in Eigure 3 a tubular electrode is used as the cathode tool. Electrolyte is pumped down the central bore of the tool, and out through the side gap formed between the wall of the tool and the hole electrolyticaHy dissolved in the workpiece (2,9,10). 

Thixotropy and Other Time Effects. In addition to the nonideal behavior described, many fluids exhibit time-dependent effects. Some fluids increase in viscosity (rheopexy) or decrease in viscosity (thixotropy) with time when sheared at a constant shear rate. These effects can occur in fluids with or without yield values. Rheopexy is a rare phenomenon, but thixotropic fluids are common. Examples of thixotropic materials are starch pastes, gelatin, mayoimaise, drilling muds, and latex paints. The thixotropic effect is shown in Figure 5, where the curves are for a specimen exposed first to increasing and then to decreasing shear rates. Because of the decrease in viscosity with time as weU as shear rate, the up-and-down flow curves do not superimpose. Instead, they form a hysteresis loop, often called a thixotropic loop. Because flow curves for thixotropic or rheopectic Hquids depend on the shear history of the sample, different curves for the same material can be obtained, depending on the experimental procedure. 

Benzoic acid is also used as a down-hole drilling mud additive where it functions as a temporary plugging agent in subterranean formations. Since this is a secondary oil recovery appHcation, this use is heavily dependent on the price of cmde oil. 

Geologists can be thought of as the historians of the earth. Ffistory is important to exploration success. When a well is drilled, a number of devices are lowered down the well to log or identify the different formations that have been penetrated. The geologist uses the logs from many different wells to put together an interpretation of the geology between wells. A... 

Thread protectors should be used on pin and box when picking up or laying down the drill collars. 

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