Fault traps

The efforts to classify every conceivable trapping configuration finds its culmination in the paper by Wilhelm (1945). He subdivided reservoirs into five groups convex traps, permeability traps, pinch-out traps, fault traps and piercement traps. He constructed a set of diagrams illustrating all the various basic types (Fig. 10) and their numerous combinations (Fig. 11). With this classification, we can consider the recognition of trap types as... 

Level high in reboiler instrument/inlet or exit pipe nozzle too small/wrong nozzle orientation/steam trap fault, see Section 5.1/steam trap is above the reboiler. 

Fault traps which are the result of brittle crustal deformations... 

In many oil and gas fields throughout the world hydrocarbons are found in fault bound anticlinal structures. This type of trapping mechanism is called a combination trap. 

Even if all of the elements described so far have been present within a sedimentary basin an accumulation will not necessarily be encountered. One of the crucial questions in prospect evaluation is about the timing of events. The deformation of strata into a suitable trap has to precede the maturation and migration of petroleum. The reservoir seal must have been intact throughout geologic time. If a leak occurred sometime in the past, the exploration well will only encounter small amounts of residual hydrocarbons. Conversely, a seal such as a fault may have developed early on in the field s history and prevented the migration of hydrocarbons into the structure. 

A secondary feature is the development of rollover anticlines which form as a result of the downward movement close to the fault plane which decreases with increasing distance from the plane. Rollover anticlines may trap considerable amounts of hydrocarbons. 

Oil reservoirs are layers of porous sandstone or carbonate rock, usually sedimentary. Impermeable rock layers, usually shales, and faults trap the oil in the reservoir. The oil exists in microscopic pores in rock. Various gases and water also occupy rock pores and are often in contact with the oil. These pores are intercoimected with a compHcated network of microscopic flow channels. The weight of ovedaying rock layers places these duids under pressure. When a well penetrates the rock formation, this pressure drives the duids into the wellbore. The dow channel size, wettabiUty of dow channel rock surfaces, oil viscosity, and other properties of the cmde oil determine the rate of this primary oil production. 

Figure 6.35 Trapped energy distribution of a large feeding source during a fault clearing by a current-limiting device...

When there is no dedicated transformer and these circuits are connected on the system bus directly a large inductor will be essential at the incoming of the static circuits, sufficient to absorb the trapped charge within the transformer and the interconnecting cables up to the converter unit. The size of the inductor can be calculated depending on the size (kVA) of the distribution transformer, its fault level and the characteristics of its current limiting protective device. An inductor sufficient to absorb //, L of the transformer and the cables may be provided at the incoming of the sialic circuits. 

Structural traps result from deformation of rock formations. Such deformations are the result of folding or faulting. 

Fault traps—involve the movement of the reservoir rock formation to a position where the formation across the fault plane provides a seal preventing further migration of hydrocarbons (see Figure 2-48). 

Combination tra/ s—sedimentary trap features that result from both stratigraphic and structural mechanisms. There can be many combinations for stratigraphic and structural traps. An example of such a trap would be a reef feature overlaying a porous and permeable sandstone, but in which the sequence has been faulted (see Figure 2-54). Without the fault, which has provided an impregnable barrier, the hydrocarbons would have migrated further up dip within the sandstone. 

Any small amount of vapour which might enter through faults in the vapour harrier should he encouraged to pass through the inner (cold side) skin of the structure to the coil, rather than he trapped within the insulation. It follows that, if the vapour harrier is at all suspect, the inner wall coating should he more porous. In traditional construction, this was provided hy an inner lining of cement plaster or asbestos cement sheet, hoth of which transmit vapour. The modern use of impervious materials on hoth skins requires meticulous attention to the sealing of any joints. 

All automated algorithms require extensive tests and traps to detect unusual and fault conditions, such as failure of the X-ray source, grossly misaligned samples, and even perfectly aligned samples ... 

Solubility trapping refers to the C02 that dissolves into the brine. The C02-brine solution has a density greater than brine alone, preventing buoyant flow of the C02 toward the surface, even along high-permeability vertical pathways such as faults. 

Fig. I. Types of natural gas reservoirs and entrapments (a) anticlinal trap (b) coral reef trap (c) stratigraphic trap (d) fault trap and (e) unconformity...

Another type of structural trap is the fault trap. A fault is a fracture in the earth s crust along which movement has occurred such that a porous rock layer is offset by a nonporous layer. The oil moving along a porous stratum is dammed or blocked by an impermeable shale or limestone. See Fig. 3, Examples of fields of this type occur along the Mexia fault zone of East-Central Texas. 

Fig. 3. Example of a fault structural trap. The oil is confined in traps like this because of the tilt of the rock layers and faulting...

Lithology may exercise a primary control of hydrate deposition, resulting from permeability, faults, and traps. 

Migration (secondary) the movement of the hydrocarbons as a single, continuous fluid phase through water-saturated rocks, fractures, or faults followed by accumulation of the oil and gas in sediments (traps, q.v.) from which further migration is prevented. 

When considering the results obtained in the present investigation, it seems quite difficult to account for the occurrence of stacking faults in the framework of pentasils simply by the different molecular size of the tetralkylammonium cations trapped within the pores. In fact, the phenomenon occurs in the presence of tetrabutylammonium or tetramethylammonium cations which have the largest and the smallest molecular size, respectively, among the organic bases investigated. It is possible that crystallization kinetics or hydrophilicity of the quaternary ammonium cations play some role. In any case, additional experiments are needed to provide a reasonable explanation. 

Another contribution to variations of intrinsic activity is the different number of defects and amount of disorder in the metallic Cu phase. This disorder can manifest itself in the form of lattice strain detectable, for example, by line profile analysis of X-ray diffraction (XRD) peaks [73], 63Cu nuclear magnetic resonance lines [74], or as an increased disorder parameter (Debye-Waller factor) derived from extended X-ray absorption fine structure spectroscopy [75], Strained copper has been shown theoretically [76] and experimentally [77] to have different adsorptive properties compared to unstrained surfaces. Strain (i.e. local variation in the lattice parameter) is known to shift the center of the d-band and alter the interactions of metal surface and absorbate [78]. The origin of strain and defects in Cu/ZnO is probably related to the crystallization of kinetically trapped nonideal Cu in close interfacial contact to the oxide during catalyst activation at mild conditions. A correlation of the concentration of planar defects in the Cu particles with the catalytic activity in methanol synthesis was observed in a series of industrial Cu/Zn0/Al203 catalysts by Kasatkin et al. [57]. Planar defects like stacking faults and twin boundaries can also be observed by HRTEM and are marked with arrows in Figure 5.3.8C [58],... 

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