Horizontal drilling

Carbonate rocks are more frequently fractured than sandstones. In many cases open fractures in carbonate reservoirs provide high porosity / high permeability path ways for hydrocarbon production. The fractures will be continuously re-charged from the tight (low permeable) rock matrix. During field development, wells need to be planned to intersect as many natural fractures as possible, e.g. by drilling horizontal wells. 

Suggestions have been made recently to drill horizontal branches in the horizontal portion of the horizontal wells. If this technique is developed, the drainage capacity of horizontal w ells will be even better. 

DSS Feed System. The DSS feed system consisted of an agitated, 55-gallon polyethylene supply tank for the sewage sludge and standard piping and pumps. The feed system supplied two air-sparged tubes located 25 cm and 46 cm above the distributor plate in the EHE. Each tube contained six, 2.36 mm diameter holes drilled horizontally (3 on each side) through which DSS and air were fed. Because the clay and lime additives used in the study had a tendency to settle out in the supply tank, a recirculation line was also installed. 

Fig. 6. Typical lithofacies of the Namorado Sandstone. Fine- and very fine.grained sandstones arranged as turbidite cycles, each capped by shale and siltstone. Pervasively calcite-cemented beds resulted from concretion coalescence. Both individual concretions and calcite-cemented beds are discontinuous on the lateral scale as indicated by core analysis of a recently drilled horizontal well. Concretions show variable shapes and intensity of cementation, and a gradual vertical transition to partially cemented and porous intervals.

Although certain coal deposits can be strip-mined without the use of explosives, some means of breaking the overburden is often necessary. This is usually accomplished by drilling horizontal or vertical blast holes (up to 14 in., 36 cm, diameter) into the overburden whereupon explosive charges are employed to break the rock fragments for subsequent easy removal. This latter part of the operation can be achieved by the use of a dragline (Figure 5.12), power shovel, excavators, bucket wheels, and trucks. 

Tunnelling by drilling and blasting, (a) Full-fece, (b) top heading and bench and (c) lop heading. Bench drilled horizontally. 

A group of four fuel assemblies, surrounding a cruciform control rod, makes up a core module unit. The control rod blades and control rod drives for the BWR 90 are of a well-proven design. The cruciform rod is based on solid steel blades that are welded together. Holes filled with B4C as neutron absorber are drilled horizontally in the blades. In the top of the rod, the absorber consists of Hafnium which makes the rod tip more "grey" and provides for a long service life. 

Directional drilling — Technologies such as steerable downhole motor assembhes and measurement-while-drilling tools allow driUing to occur on the horizontal. The three variations of directional drilhng are extended-reach drilling horizontal drilhng and multiple laterals. 

Example 15-4. Simulating-while-drilling horizontal gas wells through a dome-shaped reservoir. ... 

Use of borate-cross-linked starch in clayless drilling fluids for drilling horizontal, deviated holes in sandstone, and carbonate reservoirs benefits include good filtration, rheology, lubrication, and biological... 

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