Drilling depth

Much of the Yilgarn ( 70%) is under transported cover and exploration has relied heavily on geochemical sampling either at surface or from depth (drilling). Two broad regions (north and south) are... 

ControUed-depth drilling has the advantage that standard innerlayer processing is used, including foil stacking. ControUed-depth drilling has several limitations ... 

There is no aspect ratio limitation and the need for controlled-depth drilling is completely eUminated.To be able to driU bUnd vias prior to lamination, a clad outer stack-up is required. One side of the outer component layer is patterned prior to lamination, while the other is patterned after lamination.This means that when the blind via is metallized, the unpattemed side is blanket-metallized. This is true for either pattern plate or panel plate. This outside layer is metalUzed again when the holes in the finished ML-PWB are metallized. The result can be very thick plating on the exterior of a bUnd via board. To minimize this problem, the fabricator should plate the blind via iimerlayer with the minimum possible current density on the blanket-metaUized side. 

PITCH DIA. MINOR DIA. LENGTH BORE DEPTH DRILL DIA. BORE DIA. C BORE DIA. C BORE DEPTH ANGLE... 

For shallow water depths, drilling is preferably performed from a jack-up platform. See Figure B.IO. 

In standard PCB fabrication, metallized drilled holes provide an electrical connection between any two layers. However, through vias utilize board real estate on all layers whether an interconnection is required on a particular layer or not. The number of layers not connected by through vias can be significantly reduced through the use of controlled-depth drilled vias and the sequential lamination of pre-drilled core layers (blind internal layer vias). While the use of blind vias (vias that connect individual circuit layers) increases board utilization it may significantly add cost. Additive board layer processes and micro-via formation methods provide alternative solutions to mechanically-drilled holes. Figure 2A, shows an example of inner-layer (buried vias) and outer-layer (blind vias). 

This first information about the reservoir is recorded, as a function of depth, in the form of several columns. Although rather qualitative in many respects, mudlogging is an important data gathering technique. It is of importance as a basis for operational decisions, e.g. at what depth to set casing, or where to core a well. Mudlogging is also cheap, as data is gathered while the normal drilling operations go on. 

Estimated cost casing drilling operation well equipment TOTAL Estimated rig time 000 200 2000 400 2600 28 days Type of well Deviated, oil, development Drilling rig Jolly Roger-1 Datum Level DFE 88ft above MSL Sea Bed 250ft Total Depth 3700ft Conductor No No.8 ... 

If we consider a well trajectory from surface to total depth (TD) it is sensible to look at the shallow section and the intermediate and reservoir intervals separately. The shallow section, usually referred to as top hole consists of rather unconsolidated sediments, hence the formation strength is low and drilling parameters and equipment have to be selected accordingly. 

Not surprisingly, costs are several times higher than conventional wells. Nevertheless, overall project economics may favour ERD over other development options. For example, BP developed the offshore part of the Wytch Farm Oilfield (which is located under Poole Harbour in Dorset, UK) from an onshore location. The wells targeted the reservoir at a vertical depth of 1,500 meters with a lateral displacement of over 8,000 meters (Fig. 3.20). The alternative was to build a drilling location on an artificial island in Poole Bay. ERD probably saved a considerable amount of money and advanced first oil by several years. 

Sometimes primary cementations are not successful, for instance if the cement volume has been wrongly calculated, if cement is lost into the formation or if the cement has been contaminated with drilling fluids. In this case a remedial or secondary cementation is required. This may necessitate the perforation of the casing a given depth and the pumping of cement through the perforations. 

Considerable effort will be made to predict the onset of overpressures ahead of the drill bit. The most reliable indioations are gas readings, porosity - depth trends, rate of penetration and shale density measurements. 

Actual contracts often involve a combination of the above. For instance, an operator may agree to pay footage rates to a certain depth, day rates below that depth, and standby rates for days when the rig is on site, but not drilling. 

The sidewall sampling tool (Sl/VS) can be used to obtain small plugs (2 cm diameter, 5 cm length, often less) directly from the borehole wall. The tool is run on wireline after the hole has been drilled. Some 20 to 30 individual bullets are fired from each gun (Fig. 5.35) at different depths. The hollow bullet will penetrate the formation and a rock sample will be trapped inside the steel cylinder. By pulling the tool upwards, wires connected to the gun pull the bullet and sample from the borehole wall. 

Data transmission rate per foot is a function of both pulse frequency and rate of penetration. Sensors acquire and transmit data samples at fixed time intervals and therefore the sampling per foot is a function of rate of penetration. Current tools allow a real time sampling and transmission rate similar to wireline tools as long as the penetration rate does not exceed about 100 ft/h. If drilling progresses faster or if there are significant variations in penetration rate, resampling by depth as opposed to time intervals may be required. 

Steel piled jackets are the most common type of platform and are employed in a wide range of sea conditions, from the comparative calm of the South China Sea to the hostile Northern North Sea. Steel jackets are used in water depths of up to 150 metres and may support production facilities a further 50 metres above mean sea level. In deep water all the process and support facilities are normally supported on a single jacket, but in shallow seas it may be cheaper and safer to support drilling, production... 

In Lakestani (10) modelling work performed within the PISC III project is validated against experiments. Figure 1 shows the pulse echo response from the lower edge of a 10 mm vertical strip-like crack at centre depth 55 mm. The probe has the size 20 mm by 22 ram, is of SV type with angle 45 and has centre frequency 2.2 MHz and an assumed bandwidth of 2 MHz. The calibration is perfomed by a side-drilled hole of diameter 9.5 mm and centre depth 60 mm (the... 

The first example refers to the detection of a 1mm side drilled hole at a depth of 45 mm in a polyethylene plastic material. Due to the high sound absorption in plastics, a low operating frequency is chosen. A probe having a 1 MHz element of 24 mm diameter was selected for this example. The echo pattern of a conventional probe with a PZT transducer is pre-... 

Accidentially, one of the drills (core B2, Fig. 6) hit a duct. The depth of the duct was 15cm with a diameter of 3cm. According to these parameters and the geometry, which former studies [Ref 1] concluded, the dectection of a defect (here the duct) under these conditions would be possible if at least one dimension of the defect exceeds 4cm. Since the duct s diameter was only 3 cm, whereas the parameter of the testing-system was 4cm, possibly more than one drill would be needed to hit a duct. 

Echo directivity was experimentally studied for surface SH Wave probes and SH Wave angle probes. Frequencies used in the experiment were 5MHz and 2MHz, the angles of refraction 90°and 70°, the crystal size 10X 10mm and 5X5mm. The echo directivity was evaluated, using side drilled holes of various depths. The experimental results showed consistency with the calculation based on a point sound source assumption on the test surface in different phases. 

The laser can be used as a finely focused beam that, with each pulse, drills deeper and deeper into the specimen to give a depth profile. Alternatively, the beam can be defocused and moved over an area at lower power to explore only surface features of a specimen. 

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